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Journal Cover Microorganisms
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  This is an Open Access Journal Open Access journal
   ISSN (Online) 2076-2607
   Published by MDPI Homepage  [151 journals]
  • Microorganisms, Vol. 5, Pages 35: Free and Nanoencapsulated Tobramycin:
           Effects on Planktonic and Biofilm Forms of Pseudomonas

    • Authors: Eulalia Sans-Serramitjana, Marta Jorba, Ester Fusté, José Pedraz, Teresa Vinuesa, Miguel Viñas
      First page: 35
      Abstract: Cystic fibrosis (CF) is a genetic disorder in which frequent pulmonary infections develop secondarily. One of the major pulmonary pathogens colonizing the respiratory tract of CF patients and causing chronic airway infections is Pseudomonas aeruginosa. Although tobramycin was initially effective against P. aeruginosa, tobramycin-resistant strains have emerged. Among the strategies for overcoming resistance to tobramycin and other antibiotics is encapsulation of the drugs in nanoparticles. In this study, we explored the antimicrobial activity of nanoencapsulated tobramycin, both in solid lipid nanoparticles (SLN) and in nanostructured lipid carriers (NLC), against clinical isolates of P. aeruginosa obtained from CF patients. We also investigated the efficacy of these formulations in biofilm eradication. In both experiments, the activities of SLN and NLC were compared with that of free tobramycin. The susceptibility of planktonic bacteria was determined using the broth microdilution method and by plotting bacterial growth. The minimal biofilm eradication concentration (MBEC) was determined to assess the efficacy of the different tobramycin formulations against biofilms. The activity of tobramycin-loaded SLN was less than that of either tobramycin-loaded NLC or free tobramycin. The minimum inhibitory concentration (MIC) and MBEC of nanoencapsulated tobramycin were slightly lower (1–2 logs) than the corresponding values of the free drug when determined in tobramycin-susceptible isolates. However, in tobramycin-resistant strains, the MIC and MBEC did not differ between either encapsulated form and free tobramycin. Our results demonstrate the efficacy of nanoencapsulated formulations in killing susceptible P. aeruginosa from CF and from other patients.
      PubDate: 2017-06-26
      DOI: 10.3390/microorganisms5030035
      Issue No: Vol. 5, No. 3 (2017)
  • Microorganisms, Vol. 5, Pages 36: Reply to the Comment on “Melanisation
           of Aspergillus terreus—Is Butyrolactone I Involved in the Regulation of
           Both DOPA and DHN Types of Pigments in Submerged Culture'
           Microorganisms 2017, 5, 22”

    • Authors: Elina Palonen, Sheetal Raina, Annika Brandt, Jussi Meriluoto, Tajalli Keshavarz, Juhani Soini
      First page: 36
      Abstract: n/a
      PubDate: 2017-07-04
      DOI: 10.3390/microorganisms5030036
      Issue No: Vol. 5, No. 3 (2017)
  • Microorganisms, Vol. 5, Pages 37: Antifungal Microbial Agents for Food
           Biopreservation—A Review

    • Authors: Marcia Leyva Salas, Jérôme Mounier, Florence Valence, Monika Coton, Anne Thierry, Emmanuel Coton
      First page: 37
      Abstract: Food spoilage is a major issue for the food industry, leading to food waste, substantial economic losses for manufacturers and consumers, and a negative impact on brand names. Among causes, fungal contamination can be encountered at various stages of the food chain (e.g., post-harvest, during processing or storage). Fungal development leads to food sensory defects varying from visual deterioration to noticeable odor, flavor, or texture changes but can also have negative health impacts via mycotoxin production by some molds. In order to avoid microbial spoilage and thus extend product shelf life, different treatments—including fungicides and chemical preservatives—are used. In parallel, public authorities encourage the food industry to limit the use of these chemical compounds and develop natural methods for food preservation. This is accompanied by a strong societal demand for ‘clean label’ food products, as consumers are looking for more natural, less severely processed and safer products. In this context, microbial agents corresponding to bioprotective cultures, fermentates, culture-free supernatant or purified molecules, exhibiting antifungal activities represent a growing interest as an alternative to chemical preservation. This review presents the main fungal spoilers encountered in food products, the antifungal microorganisms tested for food bioprotection, and their mechanisms of action. A focus is made in particular on the recent in situ studies and the constraints associated with the use of antifungal microbial agents for food biopreservation.
      PubDate: 2017-07-08
      DOI: 10.3390/microorganisms5030037
      Issue No: Vol. 5, No. 3 (2017)
  • Microorganisms, Vol. 5, Pages 38: Strategies for Pathogen Biocontrol Using
           Lactic Acid Bacteria and Their Metabolites: A Focus on Meat Ecosystems and
           Industrial Environments

    • Authors: Patricia Castellano, Mariana Pérez Ibarreche, Mariana Blanco Massani, Cecilia Fontana, Graciela Vignolo
      First page: 38
      Abstract: The globalization of trade and lifestyle ensure that the factors responsible for the emergence of diseases are more present than ever. Despite biotechnology advancements, meat-based foods are still under scrutiny because of the presence of pathogens, which causes a loss of consumer confidence and consequently a fall in demand. In this context, Lactic Acid Bacteria (LAB) as GRAS organisms offer an alternative for developing pathogen-free foods, particularly avoiding Listeria monocytogenes, with minimal processing and fewer additives while maintaining the foods’ sensorial characteristics. The use of LAB strains, enabling us to produce antimicrobial peptides (bacteriocins) in addition to lactic acid, with an impact on quality and safety during fermentation, processing, and/or storage of meat and ready-to-eat (RTE) meat products, constitutes a promising tool. A number of bacteriocin-based strategies including the use of bioprotective cultures, purified and/or semi-purified bacteriocins as well as their inclusion in varied packaging materials under different storage conditions, have been investigated. The application of bacteriocins as part of hurdle technology using non-thermal technologies was explored for the preservation of RTE meat products. Likewise, considering that food contamination with L. monocytogenes is a consequence of the post-processing manipulation of RTE foods, the role of bacteriocinogenic LAB in the control of biofilms formed on industrial surfaces is also discussed.
      Citation: Microorganisms
      PubDate: 2017-07-11
      DOI: 10.3390/microorganisms5030038
      Issue No: Vol. 5, No. 3 (2017)
  • Microorganisms, Vol. 5, Pages 14: Identification and Characterization of
           Spontaneous Auxotrophic Mutants in Fusarium langsethiae

    • Authors: Olga Gavrilova, Anna Skritnika, Tatiana Gagkaeva
      First page: 14
      Abstract: Analysis of 49 strains of Fusarium langsethiae originating from northern Europe (Russia, Finland, Sweden, UK, Norway, and Latvia) revealed the presence of spontaneous auxotrophic mutants that reflect natural intraspecific diversity. Our investigations detected that 49.0% of F. langsethiae strains were auxotrophic mutants for biotin, and 8.2% of the strains required thiamine as a growth factor. They failed to grow on vitamin-free media. For both prototrophic and auxotrophic strains, no growth defect was observed in rich organic media. Without essential vitamins, a significant reduction in the growth of the auxotrophic strains results in a decrease of the formation of T-2 toxin and diacetoxyscirpenol. In addition, all analysed F. langsethiae strains were distinguished into two subgroups based on PCR product sizes. According to our results, 26 and 23 strains of F. langsethiae belong to subgroups I and II respectively. We determined that the deletion in the intergenic spacer (IGS) region of the rDNA of F. langsethiae belonging to subgroup II is linked with temperature sensitivity and causes a decrease in strain growth at 30 °C. Four thiamine auxotrophic strains were found in subgroup I, while 21 biotin auxotrophic strains were detected in subgroups II. To the best of our knowledge, the spontaneous mutations in F. langsethiae observed in the present work have not been previously reported.
      PubDate: 2017-03-31
      DOI: 10.3390/microorganisms5020014
      Issue No: Vol. 5, No. 2 (2017)
  • Microorganisms, Vol. 5, Pages 15: Approaches to Dispersing Medical

    • Authors: Derek Fleming, Kendra Rumbaugh
      First page: 15
      Abstract: Biofilm-associated infections pose a complex problem to the medical community, in that residence within the protection of a biofilm affords pathogens greatly increased tolerances to antibiotics and antimicrobials, as well as protection from the host immune response. This results in highly recalcitrant, chronic infections and high rates of morbidity and mortality. Since as much as 80% of human bacterial infections are biofilm-associated, many researchers have begun investigating therapies that specifically target the biofilm architecture, thereby dispersing the microbial cells into their more vulnerable, planktonic mode of life. This review addresses the current state of research into medical biofilm dispersal. We focus on three major classes of dispersal agents: enzymes (including proteases, deoxyribonucleases, and glycoside hydrolases), antibiofilm peptides, and dispersal molecules (including dispersal signals, anti-matrix molecules, and sequestration molecules). Throughout our discussion, we provide detailed lists and summaries of some of the most prominent and extensively researched dispersal agents that have shown promise against the biofilms of clinically relevant pathogens, and we catalog which specific microorganisms they have been shown to be effective against. Lastly, we discuss some of the main hurdles to development of biofilm dispersal agents, and contemplate what needs to be done to overcome them.
      PubDate: 2017-04-01
      DOI: 10.3390/microorganisms5020015
      Issue No: Vol. 5, No. 2 (2017)
  • Microorganisms, Vol. 5, Pages 16: Insights on Klebsiella pneumoniae
           Biofilms Assembled on Different Surfaces Using Phenotypic and Genotypic

    • Authors: Maria Bandeira, Vítor Borges, João Gomes, Aida Duarte, Luisa Jordao
      First page: 16
      Abstract: Klebsiella pneumoniae is a prominent etiological agent of healthcare associated infections (HAIs). In this context, multidrug-resistant and biofilm-producing bacteria are of special public health concern due to the difficulties associated with treatment of human infections and eradication from hospital environments. Here, in order to study the impact of medical devices-associated materials on the biofilm dynamics, we performed biofilm phenotypic analyses through a classic and a new scanning electron microscopy (SEM) technique for three multidrug-resistant K. pneumoniae isolates growing on polystyrene and silicone. We also applied whole-genome sequencing (WGS) to search for genetic clues underlying biofilm phenotypic differences. We found major differences in the extracellular polymeric substances (EPS) content among the three strains, which were further corroborated by in-depth EPS composition analysis. WGS analysis revealed a high nucleotide similarity within the core-genome, but relevant differences in the accessory genome that may account for the detected biofilm phenotypic dissimilarities, such as genes already associated with biofilm formation in other pathogenic bacteria (e.g., genes coding haemogglutinins and haemolysins). These data reinforce that the research efforts to defeat bacterial biofilms should take into account that their dynamics may be contingent on the medical devices-associated materials.
      PubDate: 2017-04-03
      DOI: 10.3390/microorganisms5020016
      Issue No: Vol. 5, No. 2 (2017)
  • Microorganisms, Vol. 5, Pages 17: Probiotic Microorganisms: A Closer Look

    • Authors: Julio Villena, Haruki Kitazawa
      First page: 17
      Abstract: n/a
      PubDate: 2017-04-08
      DOI: 10.3390/microorganisms5020017
      Issue No: Vol. 5, No. 2 (2017)
  • Microorganisms, Vol. 5, Pages 18: High Prevalence of blaNDM-1, blaVIM,
           qacE, and qacEΔ1 Genes and Their Association with Decreased
           Susceptibility to Antibiotics and Common Hospital Biocides in Clinical
           Isolates of Acinetobacter baumannii

    • Authors: Fatma Gomaa, Zeinab Helal, Mazhar Khan
      First page: 18
      Abstract: The objective of this study was to evaluate the susceptibility of metallo-β-lactamase (MBL)-producing Acinetobacter baumannii (A. baumannii) clinical isolates to biocides. We also determined the prevalence and correlation of efflux pump genes, class 1 integron and MBL encoding genes. In addition, blaVIM, blaNDM-1, qacE and qacEΔ1 nucleotide sequence analysis was performed and compared to sequences retrieved from GenBank at the National Center for Biotechnology Information database. A. baumannii had a resistance rate to carbapenem of 71.4% and 39.3% and was found to be a MBL producer. The minimum inhibitory concentrations (MICs) of chlorhexidine and cetrimide were higher than the recommended concentrations for disinfection in 54.5% and 77.3% of MBL-positive isolates respectively and their MICs were significantly higher among qac gene-positive isolates. Coexistence of qac genes was detected in 68.1% and 50% of the isolates with blaVIM and blaNDM-1 respectively. There was a significant correlation between the presence of qac genes and MBL-encoding blaVIM and blaNDM-1 genes. Each of the blaNDM-1, blaVIM, qacE and qacEΔ1 DNA sequences showed homology with each other and with similar sequences reported from other countries. The high incidence of Verona integron-encoded metallo-β-lactamases (VIM) and New-Delhi-metallo-β-lactamase (NDM) and qac genes in A. baumannii highlights emerging therapeutic challenges for being readily transferable between clinically relevant bacteria. In addition reduced susceptibility to chlorhexidine and cetrimide and the potential for cross resistance to some antibiotics necessitates the urgent need for healthcare facilities to periodically evaluate biocides efficacy, to address the issue of antiseptic resistance and to initiate a “biocidal stewardship”.
      PubDate: 2017-04-12
      DOI: 10.3390/microorganisms5020018
      Issue No: Vol. 5, No. 2 (2017)
  • Microorganisms, Vol. 5, Pages 19: The Status of Biofilms in Penile

    • Authors: Matthew Faller, Tobias Kohler
      First page: 19
      Abstract: Erectile dysfunction is prevalent among men and will continue to become more so with the aging population. Of the available treatment options, implantable prosthetic devices are typically thought of as a third line treatment even though they have the highest satisfaction rate and continually improving success rates. Infection and mechanical failure are the most common reasons for implant revision in the past. Since the development of more reliable devices, bacterial biofilms are coming to the forefront of discussion as causes of required revision. Biofilms are problematic as they are ubiquitous and exceedingly difficult to prevent or treat.
      PubDate: 2017-04-18
      DOI: 10.3390/microorganisms5020019
      Issue No: Vol. 5, No. 2 (2017)
  • Microorganisms, Vol. 5, Pages 20: Tellurite and Tellurate Reduction by the
           Aerobic Anoxygenic Phototroph Erythromonas ursincola, Strain KR99 Is
           Carried out by a Novel Membrane Associated Enzyme

    • Authors: Chris Maltman, Lynda Donald, Vladimir Yurkov
      First page: 20
      Abstract: Erythromonas ursincola, strain KR99 isolated from a freshwater thermal spring of Kamchatka Island in Russia, resists and reduces very high levels of toxic tellurite under aerobic conditions. Reduction is carried out by a constitutively expressed membrane associated enzyme, which was purified and characterized. The tellurite reductase has a molecular weight of 117 kDa, and is comprised of two subunits (62 and 55 kDa) in a 1:1 ratio. Optimal activity occurs at pH 7.0 and 28 °C. Tellurite reduction has a Vmax of 5.15 µmol/min/mg protein and a Km of 3.36 mM. The enzyme can also reduce tellurate with a Vmax and Km of 1.08 µmol/min/mg protein and 1.44 mM, respectively. This is the first purified membrane associated Te oxyanion reductase.
      PubDate: 2017-04-19
      DOI: 10.3390/microorganisms5020020
      Issue No: Vol. 5, No. 2 (2017)
  • Microorganisms, Vol. 5, Pages 21: Hyperbaric Oxygen Therapy is Ineffective
           as an Adjuvant to Daptomycin with Rifampicin Treatment in a Murine Model
           of Staphylococcus aureus in Implant-Associated Osteomyelitis

    • Authors: Nis Jørgensen, Kasper Hansen, Caroline Andreasen, Michael Pedersen, Kurt Fuursted, Rikke Meyer, Eskild Petersen
      First page: 21
      Abstract: Implant-associated infections caused by bacterial biofilms are difficult to treat. Surgical intervention is often necessary to cure the patient, as the antibiotic recalcitrance of biofilms renders them untreatable with conventional antibiotics. Intermittent hyperbaric oxygen treatment (HBOT) has been proposed as an adjuvant to conventional antibiotic treatment and it has been speculated that combining HBOT with antibiotics could improve treatment outcomes for biofilm infections. In this study we addressed whether HBOT could improve treatment outcomes of daptomycin and rifampicin combination therapy. The effect of HBOT on the treatment outcomes of daptomycin and rifampicin against implant-associated osteomyelitis was quantified in a murine model. In total, 80 mice were randomized into two groups receiving antibiotics, either alone or in combination with daily intermittent HBOT (304 kPa for 60 min) following injection of antibiotics. Treatment was initiated 11 days after animals were infected with Staphylococcus aureus and treatment duration was 14 days. We found that HBOT did not improve the cure rate and did not reduce the bacterial load on the implant surface or in the surrounding tissue. Cure rates of daptomycin + rifampicin were 40% in infected tibias and 75% for implants while cure rates for HBOT-daptomycin + rifampicin were 50% and 85%, respectively, which were not significantly higher (Fisher’s exact test). While it is encouraging that the combination of daptomycin and rifampicin is very effective, our study demonstrates that this efficacy cannot be improved by adjuvant HBOT.
      PubDate: 2017-04-25
      DOI: 10.3390/microorganisms5020021
      Issue No: Vol. 5, No. 2 (2017)
  • Microorganisms, Vol. 5, Pages 22: Melanisation of Aspergillus terreus—Is
           Butyrolactone I Involved in the Regulation of Both DOPA and DHN Types of
           Pigments in Submerged Culture'

    • Authors: Elina Palonen, Sheetal Raina, Annika Brandt, Jussi Meriluoto, Tajalli Keshavarz, Juhani Soini
      First page: 22
      Abstract: Pigments and melanins of fungal spores have been investigated for decades, revealing important roles in the survival of the fungus in hostile environments. The key genes and the encoded enzymes for pigment and melanin biosynthesis have recently been found in Ascomycota, including Aspergillus spp. In Aspergillus terreus, the pigmentation has remained mysterious with only one class of melanin biogenesis being found. In this study, we examined an intriguing, partially annotated gene cluster of A. terreus strain NIH2624, utilizing previously sequenced transcriptome and improved gene expression data of strain MUCL 38669, under the influence of a suggested quorum sensing inducing metabolite, butyrolactone I. The core polyketide synthase (PKS) gene of the cluster was predicted to be significantly longer on the basis of the obtained transcriptional data, and the surrounding cluster was positively regulated by butyrolactone I at the late growth phase of submerged culture, presumably during sporulation. Phylogenetic analysis of the extended PKS revealed remarkable similarity with a group of known pigments of Fusarium spp., indicating a similar function for this PKS. We present a hypothesis of this PKS cluster to biosynthesise a 1,8-dihydroxynaphthalene (DHN)-type of pigment during sporulation with the influence of butyrolactone I under submerged culture.
      PubDate: 2017-05-04
      DOI: 10.3390/microorganisms5020022
      Issue No: Vol. 5, No. 2 (2017)
  • Microorganisms, Vol. 5, Pages 23: Lactic Fermentation as an Efficient Tool
           to Enhance the Antioxidant Activity of Tropical Fruit Juices and Teas

    • Authors: Amandine Fessard, Ashish Kapoor, Jessica Patche, Sophie Assemat, Mathilde Hoarau, Emmanuel Bourdon, Theeshan Bahorun, Fabienne Remize
      First page: 23
      Abstract: Tropical fruits like pineapple, papaya, mango, and beverages such as green or black teas, represent an underestimated source of antioxidants that could exert health-promoting properties. Most food processing technologies applied to fruit beverages or teas result in an impairment of inherent nutritional properties. Conversely, we hypothesise that lactic acid fermentation may constitute a promising route to maintain and even improve the nutritional qualities of processed fruits. Using specific growth media, lactic acid bacteria were selected from the fruit phyllosphere diversity and fruit juice, with the latter undergoing acidification kinetics analyses and characterised for exopolysaccharide production. Strains able to ferment tropical fruit juices or teas into pleasant beverages, within a short time, were of particular interest. Strains Weissella cibaria 64 and Leuconostoc mesenteroides 12b, able to increase antioxidant activity, were specifically studied as potential starters for lactic fermented pineapple juice.
      PubDate: 2017-05-10
      DOI: 10.3390/microorganisms5020023
      Issue No: Vol. 5, No. 2 (2017)
  • Microorganisms, Vol. 5, Pages 24: Dairy Propionibacteria: Versatile

    • Authors: Houem Rabah, Fillipe Rosa do Carmo, Gwénaël Jan
      First page: 24
      Abstract: Dairy propionibacteria are used as cheese ripening starters, as biopreservative and as beneficial additives, in the food industry. The main species, Propionibacterium freudenreichii, is known as GRAS (Generally Recognized As Safe, USA, FDA). In addition to another dairy species, Propionibacterium acidipropionici, they are included in QPS (Qualified Presumption of Safety) list. Additional to their well-known technological application, dairy propionibacteria increasingly attract attention for their promising probiotic properties. The purpose of this review is to summarize the probiotic characteristics of dairy propionibacteria reported by the updated literature. Indeed, they meet the selection criteria for probiotic bacteria, such as the ability to endure digestive stressing conditions and to adhere to intestinal epithelial cells. This is a prerequisite to bacterial persistence within the gut. The reported beneficial effects are ranked according to property’s type: microbiota modulation, immunomodulation, and cancer modulation. The proposed molecular mechanisms are discussed. Dairy propionibacteria are described as producers of nutraceuticals and beneficial metabolites that are responsible for their versatile probiotic attributes include short chain fatty acids (SCFAs), conjugated fatty acids, surface proteins, and 1,4-dihydroxy-2-naphtoic acid (DHNA). These metabolites possess beneficial properties and their production depends on the strain and on the growth medium. The choice of the fermented food matrix may thus determine the probiotic properties of the ingested product. This review approaches dairy propionibacteria, with an interest in both technological abilities and probiotic attributes.
      PubDate: 2017-05-13
      DOI: 10.3390/microorganisms5020024
      Issue No: Vol. 5, No. 2 (2017)
  • Microorganisms, Vol. 5, Pages 25: Microbial Diversity in Extreme Marine
           Habitats and Their Biomolecules

    • Authors: Annarita Poli, Ilaria Finore, Ida Romano, Alessia Gioiello, Licia Lama, Barbara Nicolaus
      First page: 25
      Abstract: Extreme marine environments have been the subject of many studies and scientific publications. For many years, these environmental niches, which are characterized by high or low temperatures, high-pressure, low pH, high salt concentrations and also two or more extreme parameters in combination, have been thought to be incompatible to any life forms. Thanks to new technologies such as metagenomics, it is now possible to detect life in most extreme environments. Starting from the discovery of deep sea hydrothermal vents up to the study of marine biodiversity, new microorganisms have been identified, and their potential uses in several applied fields have been outlined. Thermophile, halophile, alkalophile, psychrophile, piezophile and polyextremophile microorganisms have been isolated from these marine environments; they proliferate thanks to adaptation strategies involving diverse cellular metabolic mechanisms. Therefore, a vast number of new biomolecules such as enzymes, polymers and osmolytes from the inhabitant microbial community of the sea have been studied, and there is a growing interest in the potential returns of several industrial production processes concerning the pharmaceutical, medical, environmental and food fields.
      PubDate: 2017-05-16
      DOI: 10.3390/microorganisms5020025
      Issue No: Vol. 5, No. 2 (2017)
  • Microorganisms, Vol. 5, Pages 26: Adding Value to Goat Meat: Biochemical
           and Technological Characterization of Autochthonous Lactic Acid Bacteria
           to Achieve High-Quality Fermented Sausages

    • Authors: Miriam Nediani, Luis García, Lucila Saavedra, Sandra Martínez, Soledad López Alzogaray, Silvina Fadda
      First page: 26
      Abstract: Quality and safety are important challenges in traditional fermented sausage technology. Consequently, the development of a tailored starter culture based on indigenous microbiota constitutes an interesting alternative. In the present study, spontaneously fermented goat meat sausages were created and analyzed using a physicochemical and microbiological approach. Thereafter 170 lactic acid bacteria (LAB) strains were isolated and preliminary characterized by phenotypic assays. The hygienic and technological properties, and growth and fermentative potential of isolates using a goat-meat-based culture medium were evaluated. All strains proved to have bioprotective features due to their acidogenic metabolism. Almost all grew optimally in meat environments. LAB isolates presented proteolytic activity against meat proteins and enriched amino acid contents of the goat-meat-based model. The most efficient strains were four different Lactobacillus sakei isolates, as identified by genotyping and RAPD analysis. L. sakei strains are proposed as optimal candidates to improve the production of fermented goat meat sausages, creating a new added-value fermented product.
      PubDate: 2017-05-17
      DOI: 10.3390/microorganisms5020026
      Issue No: Vol. 5, No. 2 (2017)
  • Microorganisms, Vol. 5, Pages 27: From Genome to Phenotype: An Integrative
           Approach to Evaluate the Biodiversity of Lactococcus lactis

    • Authors: Valérie Laroute, Hélène Tormo, Christel Couderc, Muriel Mercier-Bonin, Pascal Le Bourgeois, Muriel Cocaign-Bousquet, Marie-Line Daveran-Mingot
      First page: 27
      Abstract: Lactococcus lactis is one of the most extensively used lactic acid bacteria for the manufacture of dairy products. Exploring the biodiversity of L. lactis is extremely promising both to acquire new knowledge and for food and health-driven applications. L. lactis is divided into four subspecies: lactis, cremoris, hordniae and tructae, but only subsp. lactis and subsp. cremoris are of industrial interest. Due to its various biotopes, Lactococcus subsp. lactis is considered the most diverse. The diversity of L. lactis subsp. lactis has been assessed at genetic, genomic and phenotypic levels. Multi-Locus Sequence Type (MLST) analysis of strains from different origins revealed that the subsp. lactis can be classified in two groups: “domesticated” strains with low genetic diversity, and “environmental” strains that are the main contributors of the genetic diversity of the subsp. lactis. As expected, the phenotype investigation of L. lactis strains reported here revealed highly diverse carbohydrate metabolism, especially in plant- and gut-derived carbohydrates, diacetyl production and stress survival. The integration of genotypic and phenotypic studies could improve the relevance of screening culture collections for the selection of strains dedicated to specific functions and applications.
      PubDate: 2017-05-19
      DOI: 10.3390/microorganisms5020027
      Issue No: Vol. 5, No. 2 (2017)
  • Microorganisms, Vol. 5, Pages 28: Regulatory and Safety Requirements for
           Food Cultures

    • Authors: Svend Laulund, Anette Wind, Patrick Derkx, Véronique Zuliani
      First page: 28
      Abstract: The increased use of food cultures to ferment perishable raw materials has potentiated the need for regulations to assess and assure the safety of food cultures and their uses. These regulations differ from country to country, all aimed at assuring the safe use of food cultures which has to be guaranteed by the food culture supplier. Here we highlight national differences in regulations and review a list of methods and methodologies to assess the safety of food cultures at strain level, at production, and in the final product.
      PubDate: 2017-05-23
      DOI: 10.3390/microorganisms5020028
      Issue No: Vol. 5, No. 2 (2017)
  • Microorganisms, Vol. 5, Pages 29: Toxin Variability Estimations of 68
           Alexandrium ostenfeldii (Dinophyceae) Strains from The Netherlands Reveal
           a Novel Abundant Gymnodimine

    • Authors: Helge Martens, Urban Tillmann, Kirsi Harju, Carmela Dell’Aversano, Luciana Tartaglione, Bernd Krock
      First page: 29
      Abstract: Alexandrium ostenfeldii is a toxic dinoflagellate that has recently bloomed in Ouwerkerkse Kreek, The Netherlands, and which is able to cause a serious threat to shellfish consumers and aquacultures. We used a large set of 68 strains to the aim of fully characterizing the toxin profiles of the Dutch A. ostenfeldii in consideration of recent reports of novel toxins. Alexandrium ostenfeldii is known as a causative species of paralytic shellfish poisoning, and consistently in the Dutch population we determined the presence of several paralytic shellfish toxins (PST) including saxitoxin (STX), GTX2/3 (gonyautoxins), B1 and C1/C2. We also examined the production of spiroimine toxins by the Dutch A. ostenfeldii strains. An extensive liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis revealed a high intraspecific variability of spirolides (SPX) and gymnodimines (GYM). Spirolides included 13-desMethyl-spirolide C generally as the major compound and several other mostly unknown SPX-like compounds that were detected and characterized. Besides spirolides, the presence of gymnodimine A and 12-Methyl-gymnodimine A was confirmed, together with two new gymnodimines. One of these was tentatively identified as an analogue of gymnodimine D and was the most abundant gymnodimine (calculated cell quota up to 274 pg cell−1, expressed as GYM A equivalents). Our multi-clonal approach adds new analogues to the increasing number of compounds in these toxin classes and revealed a high strain variability in cell quota and in toxin profile of toxic compounds within a single population.
      PubDate: 2017-05-26
      DOI: 10.3390/microorganisms5020029
      Issue No: Vol. 5, No. 2 (2017)
  • Microorganisms, Vol. 5, Pages 30: Table Olive Fermentation Using Starter
           Cultures with Multifunctional Potential

    • Authors: Stamatoula Bonatsou, Chrysoula Tassou, Efstathios Panagou, George-John Nychas
      First page: 30
      Abstract: Table olives are one of the most popular plant-derived fermented products. Their enhanced nutritional value due to the presence of phenolic compounds and monounsaturated fatty acids makes olives an important food commodity of the Mediterranean diet. However, despite its economic significance, table olive fermentation is mainly craft-based and empirically driven by the autochthonous microbiota of the olives depending on various intrinsic and extrinsic factors, leading to a spontaneous process and a final product of variable quality. The use of microorganisms previously isolated from olive fermentations and studied for their probiotic potential and technological characteristics as starter cultures may contribute to the reduction of spoilage risk resulting in a controlled fermentation process. This review focuses on the importance of the development and implementation of multifunctional starter cultures related to olives with desirable probiotic and technological characteristics for possible application on table olive fermentation with the main purpose being the production of a health promoting and sensory improved functional food.
      PubDate: 2017-05-28
      DOI: 10.3390/microorganisms5020030
      Issue No: Vol. 5, No. 2 (2017)
  • Microorganisms, Vol. 5, Pages 31: Changes in Microbial (Bacteria and
           Archaea) Plankton Community Structure after Artificial Dispersal in
           Grazer-Free Microcosms

    • Authors: Hera Karayanni, Alexandra Meziti, Sofie Spatharis, Savvas Genitsaris, Claude Courties, Konstantinos Kormas
      First page: 31
      Abstract: Microbes are considered to have a global distribution due to their high dispersal capabilities. However, our knowledge of the way geographically distant microbial communities assemble after dispersal in a new environment is limited. In this study, we examined whether communities would converge because similar taxa would be selected under the same environmental conditions, or would diverge because of initial community composition, after artificial dispersal. To this aim, a microcosm experiment was performed, in which the temporal changes in the composition and diversity of different prokaryoplankton assemblages from three distant geographic coastal areas (Banyuls-sur-Mer in northwest Mediterranean Sea, Pagasitikos Gulf in northeast Mediterranean and Woods Hole, MA, USA in the northwest Atlantic), were studied. Diversity was investigated using amplicon pyrosequencing of the V1–V3 hypervariable regions of the 16S rRNA. The three assemblages were grown separately in particle free and autoclaved Banyuls-sur-mer seawater at 18 °C in the dark. We found that the variability of prokaryoplankton community diversity (expressed as richness, evenness and dominance) as well as the composition were driven by patterns observed in Bacteria. Regarding community composition, similarities were found between treatments at family level. However, at the OTU level microbial communities from the three different original locations diverge rather than converge during incubation. It is suggested that slight differences in the composition of the initial prokaryoplankton communities, resulted in separate clusters the following days even when growth took place under identical abiotic conditions.
      PubDate: 2017-06-03
      DOI: 10.3390/microorganisms5020031
      Issue No: Vol. 5, No. 2 (2017)
  • Microorganisms, Vol. 5, Pages 32: Interaction of Candida Species with the

    • Authors: Andreas Kühbacher, Anke Burger-Kentischer, Steffen Rupp
      First page: 32
      Abstract: The human skin is commonly colonized by diverse fungal species. Some Candida species, especially C. albicans, do not only reside on the skin surface as commensals, but also cause infections by growing into the colonized tissue. However, defense mechanisms at the skin barrier level are very efficient, involving residential non-immune and immune cells as well as immune cells specifically recruited to the site of infection. Therefore, the skin is an effective barrier against fungal infection. While most studies about commensal and pathogenic interaction of Candida species with host epithelia focus on the interaction with mucosal surfaces such as the vaginal and gastrointestinal epithelia, less is known about the mechanisms underlying Candida interaction with the skin. In this review, we focus on the ecology and molecular pathogenesis of Candida species on the skin and give an overview of defense mechanisms against C. albicans in this context. We also discuss new research avenues in dermal infection, including the involvement of neurons, fibroblasts, and commensal bacteria in both mouse and human model systems.
      PubDate: 2017-06-07
      DOI: 10.3390/microorganisms5020032
      Issue No: Vol. 5, No. 2 (2017)
  • Microorganisms, Vol. 5, Pages 33: Purine Acquisition and Synthesis by
           Human Fungal Pathogens

    • Authors: Jessica Chitty, James Fraser
      First page: 33
      Abstract: While members of the Kingdom Fungi are found across many of the world’s most hostile environments, only a limited number of species can thrive within the human host. The causative agents of the most common invasive fungal infections are Candida albicans, Aspergillus fumigatus, and Cryptococcus neoformans. During the infection process, these fungi must not only combat the host immune system while adapting to dramatic changes in temperature and pH, but also acquire sufficient nutrients to enable growth and dissemination in the host. One class of nutrients required by fungi, which is found in varying concentrations in their environmental niches and the human host, is the purines. These nitrogen-containing heterocycles are one of the most abundant organic molecules in nature and are required for roles as diverse as signal transduction, energy metabolism and DNA synthesis. The most common life-threatening fungal pathogens can degrade, salvage and synthesize de novo purines through a number of enzymatic steps that are conserved. While these enable them to adapt to the changing purine availability in the environment, only de novo purine biosynthesis is essential during infection and therefore an attractive antimycotic target.
      PubDate: 2017-06-08
      DOI: 10.3390/microorganisms5020033
      Issue No: Vol. 5, No. 2 (2017)
  • Microorganisms, Vol. 5, Pages 34: Comment on: “Melanisation of
           Aspergillus terreus—Is Butyrolactone I Involved in the Regulation of
           Both DOPA and DHN Types of Pigments in Submerged Culture'
           Microorganisms 2017, 5, 22”

    • Authors: Elena Geib, Matthias Brock
      First page: 34
      Abstract: A recent article by Palonen et al. describes the effect of butyrolactone I on the expression of a secondary metabolite biosynthesis gene cluster from Aspergillus terreus that shows similarities to fusarubin biosynthesis gene clusters from Fusarium species. The authors claim that two different types of pigments are formed in Aspergillus terreus conidia, whereby one pigment is termed a DOPA-type melanin and the second a DHN-type melanin. Unfortunately, the terminology of the classification of melanin-types requires revision as Asp-melanin present in A. terreus conidia is clearly distinct from DOPA-melanins. In addition, some hypotheses in this manuscript are based on questionable data published previously, resulting in incorrect conclusions. Finally, as biochemical data are lacking and metabolite production is only deduced from bioinformatics and transcriptomic data, the production of a second pigment type in A. terreus conidia appears highly speculative.
      PubDate: 2017-06-21
      DOI: 10.3390/microorganisms5020034
      Issue No: Vol. 5, No. 2 (2017)
  • Microorganisms, Vol. 5, Pages 2: Acknowledgement to Reviewers of
           Microorganisms in 2016

    • Authors: Microorganisms Editorial Office
      First page: 2
      Abstract: n/a
      PubDate: 2017-01-11
      DOI: 10.3390/microorganisms5010002
      Issue No: Vol. 5, No. 1 (2017)
  • Microorganisms, Vol. 5, Pages 3: Using Network Extracted Ontologies to
           Identify Novel Genes with Roles in Appressorium Development in the Rice
           Blast Fungus Magnaporthe oryzae

    • Authors: Ryan Ames
      First page: 3
      Abstract: Magnaporthe oryzae is the causal agent of rice blast disease, the most important infection of rice worldwide. Half the world’s population depends on rice for its primary caloric intake and, as such, rice blast poses a serious threat to food security. The stages of M. oryzae infection are well defined, with the formation of an appressorium, a cell type that allows penetration of the plant cuticle, particularly well studied. However, many of the key pathways and genes involved in this disease stage are yet to be identified. In this study, I have used network-extracted ontologies (NeXOs), hierarchical structures inferred from RNA-Seq data, to identify pathways involved in appressorium development, which in turn highlights novel genes with potential roles in this process. This study illustrates the use of NeXOs for pathway identification from large-scale genomics data and also identifies novel genes with potential roles in disease. The methods presented here will be useful to study disease processes in other pathogenic species and these data represent predictions of novel targets for intervention in M. oryzae.
      PubDate: 2017-01-17
      DOI: 10.3390/microorganisms5010003
      Issue No: Vol. 5, No. 1 (2017)
  • Microorganisms, Vol. 5, Pages 4: Phylogenetic Heatmaps Highlight
           Composition Biases in Sequenced Reads

    • Authors: Sulbha Choudhari, Andrey Grigoriev
      First page: 4
      Abstract: Due to advancements in sequencing technology, sequence data production is no longer a constraint in the field of microbiology and has made it possible to study uncultured microbes or whole environments using metagenomics. However, these new technologies introduce different biases in metagenomic sequencing, affecting the nucleotide distribution of resulting sequence reads. Here, we illustrate such biases using two methods. One is based on phylogenetic heatmaps (PGHMs), a novel approach for compact visualization of sequence composition differences between two groups of sequences containing the same phylogenetic groups. This method is well suited for finding noise and biases when comparing metagenomics samples. We apply PGHMs to detect noise and bias in the data produced with different DNA extraction protocols, different sequencing platforms and different experimental frameworks. In parallel, we use principal component analysis displaying different clustering of sequences from each sample to support our findings and illustrate the utility of PGHMs. We considered contributions of the read length and GC-content variation and observed that in most cases biases were generally due to the GC-content of the reads.
      PubDate: 2017-01-24
      DOI: 10.3390/microorganisms5010004
      Issue No: Vol. 5, No. 1 (2017)
  • Microorganisms, Vol. 5, Pages 5: Fluorescence Lectin Bar-Coding of
           Glycoconjugates in the Extracellular Matrix of Biofilm and Bioaggregate
           Forming Microorganisms

    • Authors: Thomas Neu, Ute Kuhlicke
      First page: 5
      Abstract: Microbial biofilm systems are defined as interface-associated microorganisms embedded into a self-produced matrix. The extracellular matrix represents a continuous challenge in terms of characterization and analysis. The tools applied in more detailed studies comprise extraction/chemical analysis, molecular characterization, and visualisation using various techniques. Imaging by laser microscopy became a standard tool for biofilm analysis, and, in combination with fluorescently labelled lectins, the glycoconjugates of the matrix can be assessed. By employing this approach a wide range of pure culture biofilms from different habitats were examined using the commercially available lectins. From the results, a binary barcode pattern of lectin binding can be generated. Furthermore, the results can be fine-tuned and transferred into a heat map according to signal intensity. The lectin barcode approach is suggested as a useful tool for investigating the biofilm matrix characteristics and dynamics at various levels, e.g. bacterial cell surfaces, adhesive footprints, individual microcolonies, and the gross biofilm or bio-aggregate. Hence fluorescence lectin bar-coding (FLBC) serves as a basis for a subsequent tailor-made fluorescence lectin-binding analysis (FLBA) of a particular biofilm. So far, the lectin approach represents the only tool for in situ characterization of the glycoconjugate makeup in biofilm systems.  Furthermore, lectin staining lends itself to other fluorescence techniques in order to correlate it with cellular biofilm constituents in general and glycoconjugate producers in particular.
      PubDate: 2017-02-10
      DOI: 10.3390/microorganisms5010005
      Issue No: Vol. 5, No. 1 (2017)
  • Microorganisms, Vol. 5, Pages 6: Effects of Dietary Yogurt on the Healthy
           Human Gastrointestinal (GI) Microbiome

    • Authors: Daniel Lisko, G. Johnston, Carl Johnston
      First page: 6
      Abstract: The gastrointestinal (GI) tract performs key functions that regulate the relationship between the host and the microbiota. Research has shown numerous benefits of probiotic intake in the modulation of immune responses and human metabolic processes. However, unfavorable attention has been paid to temporal changes of the microbial composition and diversity of the GI tract. This study aimed to investigate the effects of yogurt consumption on the GI microbiome bacteria community composition, structure and diversity during and after a short-term period (42 days). We used a multi-approach combining classical fingerprinting techniques (T-RFLPs), Sanger analyses and Illumina MiSeq 16S rRNA gene amplicon sequencing to elucidate bacterial communities and Lactobacilli and Bifidobacteria populations within healthy adults that consume high doses of yogurt daily. Results indicated that overall GI microbial community and diversity was method-dependent, yet we found individual specific changes in bacterial composition and structure in healthy subjects that consumed high doses of yogurt throughout the study.
      PubDate: 2017-02-15
      DOI: 10.3390/microorganisms5010006
      Issue No: Vol. 5, No. 1 (2017)
  • Microorganisms, Vol. 5, Pages 7: Presence of Calcium Lowers the Expansion
           of Bacillus subtilis Colony Biofilms

    • Authors: Eisha Mhatre, Anandaroopan Sundaram, Theresa Hölscher, Mike Mühlstädt, Jörg Bossert, Ákos Kovács
      First page: 7
      Abstract: Robust colony formation by Bacillus subtilis is recognized as one of the sessile, multicellular lifestyles of this bacterium. Numerous pathways and genes are responsible for the architecturally complex colony structure development. Cells in the biofilm colony secrete extracellular polysaccharides (EPS) and protein components (TasA and the hydrophobin BslA) that hold them together and provide a protective hydrophobic shield. Cells also secrete surfactin with antimicrobial as well as surface tension reducing properties that aid cells to colonize the solid surface. Depending on the environmental conditions, these secreted components of the colony biofilm can also promote the flagellum-independent surface spreading of B. subtilis, called sliding. In this study, we emphasize the influence of Ca2+ in the medium on colony expansion of B. subtilis. Interestingly, the availability of Ca2+ has no major impact on the induction of complex colony morphology. However, in the absence of this divalent ion, peripheral cells of the colony expand radially at later stages of development, causing colony size to increase. We demonstrate that the secreted extracellular compounds, EPS, BslA, and surfactin facilitate colony expansion after biofilm maturation. We propose that Ca2+ hinders biofilm colony expansion by modifying the amphiphilic properties of surfactin.
      PubDate: 2017-02-16
      DOI: 10.3390/microorganisms5010007
      Issue No: Vol. 5, No. 1 (2017)
  • Microorganisms, Vol. 5, Pages 8: Genome Sequence of Rhodoferax antarcticus
           ANT.BRT; A Psychrophilic Purple Nonsulfur Bacterium from an Antarctic
           Microbial Mat

    • Authors: Jennifer Baker, Carli Riester, Blair Skinner, Austin Newell, Wesley Swingley, Michael Madigan, Deborah Jung, Marie Asao, Min Chen, Patrick Loughlin, Hao Pan, Yuankui Lin, Yaqiong Li, Jacob Shaw, Mindy Prado, Chris Sherman, Joseph Tang, Robert Blankenship, Tingting Zhao, Jeffrey Touchman, W. Sattley
      First page: 8
      Abstract: Rhodoferax antarcticus is an Antarctic purple nonsulfur bacterium and the only characterized anoxygenic phototroph that grows best below 20 °C. We present here a high-quality draft genome of Rfx. antarcticus strain ANT.BRT, isolated from an Antarctic microbial mat. The circular chromosome (3.8 Mbp) of Rfx. antarcticus has a 59.1% guanine + cytosine (GC) content and contains 4036 open reading frames. In addition, the bacterium contains a sizable plasmid (198.6 kbp, 48.4% GC with 226 open reading frames) that comprises about 5% of the total genetic content. Surprisingly, genes encoding light-harvesting complexes 1 and 3 (LH1 and LH3), but not light-harvesting complex 2 (LH2), were identified in the photosynthesis gene cluster of the Rfx. antarcticus genome, a feature that is unique among purple phototrophs. Consistent with physiological studies that showed a strong capacity for nitrogen fixation in Rfx. antarcticus, a nitrogen fixation gene cluster encoding a molybdenum-type nitrogenase was present, but no alternative nitrogenases were identified despite the cold-active phenotype of this phototroph. Genes encoding two forms of ribulose 1,5-bisphosphate carboxylase/oxygenase were present in the Rfx. antarcticus genome, a feature that likely provides autotrophic flexibility under varying environmental conditions. Lastly, genes for assembly of both type IV pili and flagella are present, with the latter showing an unusual degree of clustering. This report represents the first genomic analysis of a psychrophilic anoxygenic phototroph and provides a glimpse of the genetic basis for maintaining a phototrophic lifestyle in a permanently cold, yet highly variable, environment.
      PubDate: 2017-02-21
      DOI: 10.3390/microorganisms5010008
      Issue No: Vol. 5, No. 1 (2017)
  • Microorganisms, Vol. 5, Pages 9: Microbial Biofilms and Chronic Wounds

    • Authors: Amin Omar, J. Wright, Gregory Schultz, Robert Burrell, Patricia Nadworny
      First page: 9
      Abstract: Background is provided on biofilms, including their formation, tolerance mechanisms, structure, and morphology within the context of chronic wounds. The features of biofilms in chronic wounds are discussed in detail, as is the impact of biofilm on wound chronicity. Difficulties associated with the use of standard susceptibility tests (minimum inhibitory concentrations or MICs) to determine appropriate treatment regimens for, or develop new treatments for use in, chronic wounds are discussed, with alternate test methods specific to biofilms being recommended. Animal models appropriate for evaluating biofilm treatments are also described. Current and potential future therapies for treatment of biofilm-containing chronic wounds, including probiotic therapy, virulence attenuation, biofilm phenotype expression attenuation, immune response suppression, and aggressive debridement combined with antimicrobial dressings, are described.
      PubDate: 2017-03-07
      DOI: 10.3390/microorganisms5010009
      Issue No: Vol. 5, No. 1 (2017)
  • Microorganisms, Vol. 5, Pages 10: Lactobacillus gasseri PA-3 Uses the
           Purines IMP, Inosine and Hypoxanthine and Reduces their Absorption in Rats

    • Authors: Naruomi Yamada, Chizuru Saito-Iwamoto, Marie Nakamura, Misato Soeda, Yoshika Chiba, Hiroshi Kano, Yukio Asami
      First page: 10
      Abstract: Excessive intake of purine-rich foods elevates serum levels of uric acid. Animal and fish meats contain high amounts of inosine and its related purines, and the reduction of taking those purines is crucial for the improvement of serum uric acid levels. We previously showed that Lactobacillus gasseri PA-3 (PA-3) incorporates adenosine and its related purines and that oral treatment with PA-3 reduced adenosine absorption in rats. This study investigated whether PA-3 also incorporates IMP (inosine 5′-monophosphate), inosine, and hypoxanthine, and whether it reduces their absorption in rats. PA-3 was incubated in vitro with radioisotope (RI)-labeled IMP, inosine, and hypoxanthine, and the incorporation of these compounds by PA-3 was evaluated. In addition, rats were orally administered PA-3 along with RI-labeled inosine 5′-monophosphate, inosine, or hypoxanthine, and the ability of PA-3 to attenuate the absorption of these purines was determined. PA-3 incorporated all three purines and displayed greater proliferation in the presence than in the absence of these purines. Oral administration of PA-3 to rats reduced the absorption of IMP, inosine, and hypoxanthine. These results indicate that PA-3 reduces the absorption of purines contained in foods and it is expected that PA-3 contributes attenuation of the excessive intake of dietary purines.
      PubDate: 2017-03-08
      DOI: 10.3390/microorganisms5010010
      Issue No: Vol. 5, No. 1 (2017)
  • Microorganisms, Vol. 5, Pages 11: The Food Production Environment and the
           Development of Antimicrobial Resistance in Human Pathogens of Animal

    • Authors: Manjusha Lekshmi, Parvathi Ammini, Sanath Kumar, Manuel F. Varela
      First page: 11
      Abstract: Food-borne pathogens are a serious human health concern worldwide, and the emergence of antibiotic-resistant food pathogens has further confounded this problem. Once-highly-efficacious antibiotics are gradually becoming ineffective against many important pathogens, resulting in severe treatment crises. Among several reasons for the development and spread of antimicrobial resistance, their overuse in animal food production systems for purposes other than treatment of infections is prominent. Many pathogens of animals are zoonotic, and therefore any development of resistance in pathogens associated with food animals can spread to humans through the food chain. Human infections by antibiotic-resistant pathogens such as Campylobacter spp., Salmonella spp., Escherichia coli and Staphylococcus aureus are increasing. Considering the human health risk due to emerging antibiotic resistance in food animal–associated bacteria, many countries have banned the use of antibiotic growth promoters and the application in animals of antibiotics critically important in human medicine. Concerted global efforts are necessary to minimize the use of antimicrobials in food animals in order to control the development of antibiotic resistance in these systems and their spread to humans via food and water.
      PubDate: 2017-03-14
      DOI: 10.3390/microorganisms5010011
      Issue No: Vol. 5, No. 1 (2017)
  • Microorganisms, Vol. 5, Pages 12: Transcriptomic Complexity of Aspergillus
           terreus Velvet Gene Family under the Influence of Butyrolactone I

    • Authors: Elina Palonen, Sheetal Raina, Annika Brandt, Jussi Meriluoto, Tajalli Keshavarz, Juhani Soini
      First page: 12
      Abstract: Filamentous fungi of the Ascomycota phylum are known to contain a family of conserved conidiation regulating proteins with distinctive velvet domains. In Aspergilli, this velvet family includes four proteins, VeA, VelB, VelC and VosA, and is involved in conidiation and secondary metabolism along with a global regulator LaeA. In A. terreus, the overexpression of LaeA has been observed to increase the biogenesis of the pharmaceutically-important secondary metabolite, lovastatin, while the role of the velvet family has not been studied. The secondary metabolism and conidiation of A. terreus have also been observed to be increased by butyrolactone I in a quorum-sensing manner. An enlightenment of the interplay of these regulators will give potential advancement to the industrial use of this fungus, as well as in resolving the pathogenic features. In this study, the Aspergillus terreus MUCL 38669 transcriptome was strand-specifically sequenced to enable an in-depth gene expression analysis to further investigate the transcriptional role of butyrolactone I in these processes. The sequenced transcriptome revealed intriguing properties of the velvet family transcripts, including the regulator laeA, and uncovered the velC gene in A. terreus. The reliability refining microarray gene expression analysis disclosed a positive regulatory role for butyrolactone I in laeA expression, as well as an influence on the expression of the canonical conidiation-regulating genes under submerged culture. All of this supports the suggested regulative role of butyrolactone I in A. terreus secondary metabolism, as well as conidiation.
      PubDate: 2017-03-14
      DOI: 10.3390/microorganisms5010012
      Issue No: Vol. 5, No. 1 (2017)
  • Microorganisms, Vol. 5, Pages 13: Immune Response to Coccidioidomycosis
           and the Development of a Vaccine

    • Authors: Natalia Castro-Lopez, Chiung-Yu Hung
      First page: 13
      Abstract: Coccidioidomycosis is a fungal infection caused by Coccidioides posadasii and Coccidioides immitis. It is estimated that 150,000 new infections occur in the United States each year. The incidence of this infection continues to rise in endemic regions. There is an urgent need for the development of better therapeutic drugs and a vaccine against coccidioidomycosis. This review discusses the features of host innate and adaptive immune responses to Coccidioides infection. The focus is on the recent advances in the immune response and host-pathogen interactions, including the recognition of spherules by the host and defining the signal pathways that guide the development of the adaptive T-cell response to Coccidioides infection. Also discussed is an update on progress in developing a vaccine against these fungal pathogens.
      PubDate: 2017-03-16
      DOI: 10.3390/microorganisms5010013
      Issue No: Vol. 5, No. 1 (2017)
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