Open AccessCommunication
Markers of Microbial Translocation and Immune Activation Predict Cognitive Processing Speed in Heavy-Drinking Men Living with HIV
Microorganisms 2017, 5(4), 64; doi:10.3390/microorganisms5040064 -
Abstract
HIV infection and alcohol use disorder are associated with deficits in neurocognitive function. Emerging evidence points to pro-inflammatory perturbations of the gut-brain axis as potentially contributing to neurocognitive impairment in the context of HIV and chronic heavy alcohol use. This study examined whether
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HIV infection and alcohol use disorder are associated with deficits in neurocognitive function. Emerging evidence points to pro-inflammatory perturbations of the gut-brain axis as potentially contributing to neurocognitive impairment in the context of HIV and chronic heavy alcohol use. This study examined whether plasma markers of microbial translocation (LPS) from the gastrointestinal tract and related immune activation (sCD14, EndoCAb) were associated with neurocognition in 21 men living with HIV who were virally suppressed on antiretroviral therapy. All participants met federal criteria for heavy drinking and were enrolled in a randomized controlled trial (RCT) of a brief alcohol intervention. This secondary analysis utilized blood samples and cognitive scores (learning, memory, executive function, verbal fluency, and processing speed) obtained at baseline and three-month follow-up of the RCT. In generalized estimating equation models, LPS, sCD14, and EndoCAb individually were significant predictors of processing speed. In a model with all biomarkers, higher LPS and sCD14 both remained significant predictors of lower processing speed. These preliminary findings suggest that inflammation stemming from HIV and/or alcohol could have negative effects on the gut-brain axis, manifested as diminished processing speed. Associations of microbial translocation and immune activation with processing speed in heavy-drinking PLWH warrant further investigation in larger-scale studies. Full article
Open AccessArticle
Diagnostic Value of Endotracheal Aspirates Sonication on Ventilator-Associated Pneumonia Microbiologic Diagnosis
Microorganisms 2017, 5(3), 62; doi:10.3390/microorganisms5030062 -
Abstract
Microorganisms are able to form biofilms within respiratory secretions. Methods to disaggregate such biofilms before utilizing standard, rapid, or high throughput diagnostic technologies may aid in pathogen detection during ventilator associated pneumonia (VAP) diagnosis. Our aim was to determine if sonication of endotracheal
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Microorganisms are able to form biofilms within respiratory secretions. Methods to disaggregate such biofilms before utilizing standard, rapid, or high throughput diagnostic technologies may aid in pathogen detection during ventilator associated pneumonia (VAP) diagnosis. Our aim was to determine if sonication of endotracheal aspirates (ETA) would increase the sensitivity of qualitative, semi-quantitative, and quantitative bacterial cultures in an animal model of pneumonia caused by Pseudomonas aeruginosa or by methicillin resistant Staphylococcus aureus (MRSA). Material and methods: P. aeruginosa or MRSA was instilled into the lungs or the oropharynx of pigs in order to induce severe VAP. Time point assessments for qualitative and quantitative bacterial cultures of ETA and bronchoalveolar lavage (BAL) samples were performed at 24, 48, and 72 h after bacterial instillation. In addition, at 72 h (autopsy), lung tissue was harvested to perform quantitative bacterial cultures. Each ETA sample was microbiologically processed with and without applying sonication for 5 min at 40 KHz before bacterial cultures. Sensitivity and specificity were determined using BAL as a gold-standard. Correlation with BAL and lung bacterial burden was also determined before and after sonication. Assessment of biofilm clusters and planktonic bacteria was performed through both optical microscopy utilizing Gram staining and Confocal Laser Scanning Microscopy utilizing the LIVE/DEAD®BacLight kit. Results: 33 pigs were included, 27 and 6 from P. aeruginosa and MRSA pneumonia models, respectively. Overall, we obtained 85 ETA, 69 (81.2%) from P. aeruginosa and 16 (18.8%) from MRSA challenged pigs. Qualitative cultures did not significantly change after sonication, whereas quantitative ETA cultures did significantly increase bacterial counting. Indeed, sonication consistently increased bacterial burden in ETAs at 24, 48, and 72 h after bacterial challenge. Sonication also improved sensitivity of ETA quantitative cultures and maintained specificity at levels previously reported and accepted for VAP diagnosis. Conclusion: The use of sonication in ETA respiratory samples needs to be clinically validated since sonication could potentially improve pathogen detection before standard, rapid, or high throughput diagnostic methods used in routine microbial diagnostics. Full article
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Open AccessArticle
Microbial Community Structure and Functions in Ethanol-Fed Sulfate Removal Bioreactors for Treatment of Mine Water
Microorganisms 2017, 5(3), 61; doi:10.3390/microorganisms5030061 -
Abstract
Sulfate-rich mine water must be treated before it is released into natural water bodies. We tested ethanol as substrate in bioreactors designed for biological sulfate removal from mine water containing up to 9 g L−1 sulfate, using granular sludge from an industrial
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Sulfate-rich mine water must be treated before it is released into natural water bodies. We tested ethanol as substrate in bioreactors designed for biological sulfate removal from mine water containing up to 9 g L−1 sulfate, using granular sludge from an industrial waste water treatment plant as inoculum. The pH, redox potential, and sulfate and sulfide concentrations were measured twice a week over a maximum of 171 days. The microbial communities in the bioreactors were characterized by qPCR and high throughput amplicon sequencing. The pH in the bioreactors fluctuated between 5.0 and 7.7 with the highest amount of up to 50% sulfate removed measured around pH 6. Dissimilatory sulfate reducing bacteria (SRB) constituted only between 1% and 15% of the bacterial communities. Predicted bacterial metagenomes indicated a high prevalence of assimilatory sulfate reduction proceeding to formation of l-cystein and acetate, assimilatory and dissimilatory nitrate reduction, denitrification, and oxidation of ethanol to acetaldehyde with further conversion to ethanolamine, but not to acetate. Despite efforts to maintain optimal conditions for biological sulfate reduction in the bioreactors, only a small part of the microorganisms were SRB. The microbial communities were highly diverse, containing bacteria, archaea, and fungi, all of which affected the overall microbial processes in the bioreactors. While it is important to monitor specific physicochemical parameters in bioreactors, molecular assessment of the microbial communities may serve as a tool to identify biological factors affecting bioreactor functions and to optimize physicochemical attributes for ideal bioreactor performance. Full article
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Open AccessArticle
Bioprospecting for Exopolysaccharides from Deep-Sea Hydrothermal Vent Bacteria: Relationship between Bacterial Diversity and Chemical Diversity
Microorganisms 2017, 5(3), 63; doi:10.3390/microorganisms5030063 -
Abstract
Many bacteria biosynthesize structurally diverse exopolysaccharides (EPS) and excrete them into their surrounding environment. The EPS functional features have found many applications in industries such as cosmetics and pharmaceutics. In particular, some EPS produced by marine bacteria are composed of uronic acids, neutral
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Many bacteria biosynthesize structurally diverse exopolysaccharides (EPS) and excrete them into their surrounding environment. The EPS functional features have found many applications in industries such as cosmetics and pharmaceutics. In particular, some EPS produced by marine bacteria are composed of uronic acids, neutral sugars, and N-acetylhexosamines, and may also bear some functional sulfate groups. This suggests that they can share common structural features with glycosaminoglycans (GAG) like the two EPS (HE800 and GY785) originating from the deep sea. In an attempt to discover new EPS that may be promising candidates as GAG-mimetics, fifty-one marine bacterial strains originating from deep-sea hydrothermal vents were screened. The analysis of the EPS chemical structure in relation to bacterial species showed that Vibrio, Alteromonas, and Pseudoalteromonas strains were the main producers. Moreover, they produced EPS with distinct structural features, which might be useful for targeting marine bacteria that could possibly produce structurally GAG-mimetic EPS. Full article
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Open AccessArticle
Proteomic Characterization of Armillaria mellea Reveals Oxidative Stress Response Mechanisms and Altered Secondary Metabolism Profiles
Microorganisms 2017, 5(3), 60; doi:10.3390/microorganisms5030060 -
Abstract
Armillaria mellea is a major plant pathogen. Yet, the strategies the organism uses to infect susceptible species, degrade lignocellulose and other plant material and protect itself against plant defences and its own glycodegradative arsenal are largely unknown. Here, we use a combination of
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Armillaria mellea is a major plant pathogen. Yet, the strategies the organism uses to infect susceptible species, degrade lignocellulose and other plant material and protect itself against plant defences and its own glycodegradative arsenal are largely unknown. Here, we use a combination of gel and MS-based proteomics to profile A. mellea under conditions of oxidative stress and changes in growth matrix. 2-DE and LC-MS/MS were used to investigate the response of A. mellea to H2O2 and menadione/FeCl3 exposure, respectively. Several proteins were detected with altered abundance in response to H2O2, but not menadione/FeCl3 (i.e., valosin-containing protein), indicating distinct responses to these different forms of oxidative stress. One protein, cobalamin-independent methionine synthase, demonstrated a common response in both conditions, which may be a marker for a more general stress response mechanism. Further changes to the A. mellea proteome were investigated using MS-based proteomics, which identified changes to putative secondary metabolism (SM) enzymes upon growth in agar compared to liquid cultures. Metabolomic analyses revealed distinct profiles, highlighting the effect of growth matrix on SM production. This establishes robust methods by which to utilize comparative proteomics to characterize this important phytopathogen. Full article
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Open AccessArticle
Effect of Environmental Factors on Intra-Specific Inhibitory Activity of Carnobacterium maltaromaticum
Microorganisms 2017, 5(3), 59; doi:10.3390/microorganisms5030059 -
Abstract
Carnobacterium maltaromaticum is frequently associated with foods having extended shelf-life due to its inhibitory activity to other bacteria. The quantification of such inhibition interactions affected by various environmental factors is limited. This study investigated the effect of environmental factors relevant to vacuum-packaged beef
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Carnobacterium maltaromaticum is frequently associated with foods having extended shelf-life due to its inhibitory activity to other bacteria. The quantification of such inhibition interactions affected by various environmental factors is limited. This study investigated the effect of environmental factors relevant to vacuum-packaged beef on inhibition between two model isolates of C. maltaromaticum, D0h and D8c, specifically D8c sensitivity to D0h inhibition and D0h inhibitor production. The effects of temperature (−1, 7, 15, 25 °C), atmosphere (aerobic and anaerobic), pH (5.5, 6, 6.5), lactic acid (0, 25, 50 mM) and glucose (0, 0.56, 5.55 mM) on D8c sensitivity (diameter of an inhibition zone) were measured. The effects of pH, glucose, lactic acid and atmosphere on D0h inhibitor production were measured at 25 °C. Sensitivity of D8c was the highest at 15 °C, under aerobic atmosphere, at higher concentrations of undissociated lactic acid and glucose, and at pH 5.5 (p < 0.001). pH significantly affected D0h inhibitor production (p < 0.001), which was the highest at pH 6.5. The effect of lactic acid depended upon pH level; at relatively low pH (5.5), lactic acid decreased the production rate (arbitrary inhibition unit (AU)/mL/h). This study provides a quantitative description of intra-species interactions, studied in in vitro environments that are relevant to vacuum-packaged beef. Full article
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Open AccessArticle
The Skin Bacterium Propionibacterium acnes Employs Two Variants of Hyaluronate Lyase with Distinct Properties
Microorganisms 2017, 5(3), 57; doi:10.3390/microorganisms5030057 -
Abstract
Hyaluronic acid (HA) and other glycosaminoglycans are extracellular matrix components in the human epidermis and dermis. One of the most prevalent skin microorganisms, Propionibacterium acnes, possesses HA-degrading activity, possibly conferred by the enzyme hyaluronate lyase (HYL). In this study, we identified the
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Hyaluronic acid (HA) and other glycosaminoglycans are extracellular matrix components in the human epidermis and dermis. One of the most prevalent skin microorganisms, Propionibacterium acnes, possesses HA-degrading activity, possibly conferred by the enzyme hyaluronate lyase (HYL). In this study, we identified the HYL of P. acnes and investigated the genotypic and phenotypic characteristics. Investigations include the generation of a P. acneshyl knockout mutant and HYL activity assays to determine the substrate range and formed products. We found that P. acnes employs two distinct variants of HYL. One variant, HYL-IB/II, is highly active, resulting in complete HA degradation; it is present in strains of the phylotypes IB and II. The other variant, HYL-IA, has low activity, resulting in incomplete HA degradation; it is present in type IA strains. Our findings could explain some of the observed differences between P. acnes phylotype IA and IB/II strains. Whereas type IA strains are primarily found on the skin surface and associated with acne vulgaris, type IB/II strains are more often associated with soft and deep tissue infections, which would require elaborate tissue invasion strategies, possibly accomplished by a highly active HYL-IB/II. Full article
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Open AccessArticle
Rapid and Highly Sensitive Non-Competitive Immunoassay for Specific Detection of Nodularin
Microorganisms 2017, 5(3), 58; doi:10.3390/microorganisms5030058 -
Abstract
Nodularin (NOD) is a cyclic penta-peptide hepatotoxin mainly produced by Nodularia spumigena, reported from the brackish water bodies of various parts of the world. It can accumulate in the food chain and, for safety reasons, levels of NOD not only in water
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Nodularin (NOD) is a cyclic penta-peptide hepatotoxin mainly produced by Nodularia spumigena, reported from the brackish water bodies of various parts of the world. It can accumulate in the food chain and, for safety reasons, levels of NOD not only in water bodies but also in food matrices are of interest. Here, we report on a non-competitive immunoassay for the specific detection of NOD. A phage display technique was utilized to interrogate a synthetic antibody phage library for binders recognizing NOD bound to an anti-ADDA (3-Amino-9-methoxy-2,6,8-trimethyl-10-phenyldeca-4(E),6(E)-dienoic acid) monoclonal antibody (Mab). One of the obtained immunocomplex binders, designated SA32C11, showed very high specificity towards nodularin-R (NOD-R) over to the tested 10 different microcystins (microcystin-LR, -dmLR, -RR, -dmRR, -YR, -LY, -LF, -LW, -LA, -WR). It was expressed in Escherichia coli as a single chain antibody fragment (scFv) fusion protein and used to establish a time-resolved fluorometry-based assay in combination with the anti-ADDA Mab. The detection limit (blank + 3SD) of the immunoassay, with a total assay time of 1 h 10 min, is 0.03 µg/L of NOD-R. This represents the most sensitive immunoassay method for the specific detection of NOD reported so far. The assay was tested for its performance to detect NOD using spiked (0.1 to 3 µg/L of NOD-R) water samples including brackish sea and coastal water and the recovery ranged from 79 to 127%. Furthermore, a panel of environmental samples, including water from different sources, fish and other marine tissue specimens, were analyzed for NOD using the assay. The assay has potential as a rapid screening tool for the analysis of a large number of water samples for the presence of NOD. It can also find applications in the analysis of the bioaccumulation of NOD in marine organisms and in the food chain. Full article
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Open AccessComment
Comments to Article by Willetts A. et al., Microorganisms 2016, 4, 38
Microorganisms 2017, 5(3), 54; doi:10.3390/microorganisms5030054 -
Abstract
We would like to comment on recent work published in your journal in October 2016 by Willetts A. et al. [1].[...] Full article
Open AccessReview
Lactobacillus sakei: A Starter for Sausage Fermentation, a Protective Culture for Meat Products
Microorganisms 2017, 5(3), 56; doi:10.3390/microorganisms5030056 -
Abstract
Among lactic acid bacteria of meat products, Lactobacillus sakei is certainly the most studied species due to its role in the fermentation of sausage and its prevalence during cold storage of raw meat products. Consequently, the physiology of this bacterium regarding functions involved
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Among lactic acid bacteria of meat products, Lactobacillus sakei is certainly the most studied species due to its role in the fermentation of sausage and its prevalence during cold storage of raw meat products. Consequently, the physiology of this bacterium regarding functions involved in growth, survival, and metabolism during meat storage and processing are well known. This species exhibits a wide genomic diversity that can be observed when studying different strains and on which probably rely its multiple facets in meat products: starter, spoiler, or protective culture. The emerging exploration of the microbial ecology of meat products also revealed the multiplicity of bacterial interactions L. sakei has to face and their various consequences on microbial quality and safety at the end of storage. Full article
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Open AccessReply
Reply to the Comment by Littlechild and Isupov
Microorganisms 2017, 5(3), 55; doi:10.3390/microorganisms5030055 -
Abstract
I thank Drs. Littlechild and Isupov for their recent comments, which are considered below. Before addressing these specifically, their correspondence raises two more general issues which require initial clarification.[...] Full article
Open AccessArticle
Multiple Antibiotic-Resistant, Extended Spectrum-β-Lactamase (ESBL)-Producing Enterobacteria in Fresh Seafood
Microorganisms 2017, 5(3), 53; doi:10.3390/microorganisms5030053 -
Abstract
Members of the family Enterobacteriaceae include several human pathogens that can be acquired through contaminated food and water. In this study, the incidence of extended spectrum β-lactamase (ESBL)-producing enterobacteria was investigated in fresh seafood sold in retail markets. The ESBL-positive phenotype was detected
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Members of the family Enterobacteriaceae include several human pathogens that can be acquired through contaminated food and water. In this study, the incidence of extended spectrum β-lactamase (ESBL)-producing enterobacteria was investigated in fresh seafood sold in retail markets. The ESBL-positive phenotype was detected in 169 (78.60%) isolates, with Escherichia coli being the predominant species (53), followed by Klebsiella oxytoca (27), and K. pneumoniae (23). More than 90% of the isolates were resistant to third generation cephalosporins, cefotaxime, ceftazidime, and cefpodoxime. Sixty-five percent of the isolates were resistant to the monobactam drug aztreonam, 40.82% to ertapenem, and 31.36% to meropenem. Resistance to at least five antibiotics was observed in 38.46% of the isolates. Polymerase Chain Reaction (PCR) analysis of ESBL-encoding genes detected blaCTX, blaSHV, and blaTEM genes in 76.92%, 63.3%, and 44.37% of the isolates, respectively. Multiple ESBL genes were detected in majority of the isolates. The recently discovered New Delhi metallo-β-lactamase gene (blaNDM-1) was detected in two ESBL+ isolates. Our study shows that secondary contamination of fresh seafood with enteric bacteria resistant to multiple antibiotics may implicate seafood as a potential carrier of antibiotic resistant bacteria and emphasizes an urgent need to prevent environmental contamination and dissemination of such bacteria. Full article
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Open AccessReview
Insight into the Genome of Staphylococcusxylosus, a Ubiquitous Species Well Adapted to Meat Products
Microorganisms 2017, 5(3), 52; doi:10.3390/microorganisms5030052 -
Abstract
Staphylococcus xylosus belongs to the vast group of coagulase-negative staphylococci. It is frequently isolated from meat products, either fermented or salted and dried, and is commonly used as starter cultures in sausage manufacturing. Analysis of the S. xylosus genome together with expression in
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Staphylococcus xylosus belongs to the vast group of coagulase-negative staphylococci. It is frequently isolated from meat products, either fermented or salted and dried, and is commonly used as starter cultures in sausage manufacturing. Analysis of the S. xylosus genome together with expression in situ in a meat model revealed that this bacterium is well adapted to meat substrates, being able to use diverse substrates as sources of carbon and energy and different sources of nitrogen. It is well-equipped with genes involved in osmotic, oxidative/nitrosative, and acidic stress responses. It is responsible for the development of the typical colour of cured meat products via its nitrate reductase activity. It contributes to sensorial properties, mainly by the the catabolism of pyruvate and amino acids resulting in odorous compounds and by the limiting of the oxidation of fatty acids, thereby avoiding rancidity. Full article
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Open AccessReview
The Sea as a Rich Source of Structurally Unique Glycosaminoglycans and Mimetics
Microorganisms 2017, 5(3), 51; doi:10.3390/microorganisms5030051 -
Abstract
Glycosaminoglycans (GAGs) are sulfated glycans capable of regulating various biological and medical functions. Heparin, heparan sulfate, chondroitin sulfate, dermatan sulfate, keratan sulfate and hyaluronan are the principal classes of GAGs found in animals. Although GAGs are all composed of disaccharide repeating building blocks,
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Glycosaminoglycans (GAGs) are sulfated glycans capable of regulating various biological and medical functions. Heparin, heparan sulfate, chondroitin sulfate, dermatan sulfate, keratan sulfate and hyaluronan are the principal classes of GAGs found in animals. Although GAGs are all composed of disaccharide repeating building blocks, the sulfation patterns and the composing alternating monosaccharides vary among classes. Interestingly, GAGs from marine organisms can present structures clearly distinct from terrestrial animals even considering the same class of GAG. The holothurian fucosylated chondroitin sulfate, the dermatan sulfates with distinct sulfation patterns extracted from ascidian species, the sulfated glucuronic acid-containing heparan sulfate isolated from the gastropode Nodipecten nodosum, and the hybrid heparin/heparan sulfate molecule obtained from the shrimp Litopenaeus vannamei are some typical examples. Besides being a rich source of structurally unique GAGs, the sea is also a wealthy environment of GAG-resembling sulfated glycans. Examples of these mimetics are the sulfated fucans and sulfated galactans found in brown, red and green algae, sea urchins and sea cucumbers. For adequate visualization, representations of all discussed molecules are given in both Haworth projections and 3D models. Full article
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Open AccessReview
Bacterial Contaminants of Poultry Meat: Sources, Species, and Dynamics
Microorganisms 2017, 5(3), 50; doi:10.3390/microorganisms5030050 -
Abstract
With the constant increase in poultry meat consumption worldwide and the large variety of poultry meat products and consumer demand, ensuring the microbial safety of poultry carcasses and cuts is essential. In the present review, we address the bacterial contamination of poultry meat
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With the constant increase in poultry meat consumption worldwide and the large variety of poultry meat products and consumer demand, ensuring the microbial safety of poultry carcasses and cuts is essential. In the present review, we address the bacterial contamination of poultry meat from the slaughtering steps to the use-by-date of the products. The different contamination sources are identified. The contaminants occurring in poultry meat cuts and their behavior toward sanitizing treatments or various storage conditions are discussed. A list of the main pathogenic bacteria of concern for the consumer and those responsible for spoilage and waste of poultry meat is established. Full article
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Open AccessArticle
Transcriptional Analysis Allows Genome Reannotation and Reveals that Cryptococcus gattii VGII Undergoes Nutrient Restriction during Infection
Microorganisms 2017, 5(3), 49; doi:10.3390/microorganisms5030049 -
Abstract
Cryptococcus gattii is a human and animal pathogen that infects healthy hosts and caused the Pacific Northwest outbreak of cryptococcosis. The inhalation of infectious propagules can lead to internalization of cryptococcal cells by alveolar macrophages, a niche in which C. gattii cells can
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Cryptococcus gattii is a human and animal pathogen that infects healthy hosts and caused the Pacific Northwest outbreak of cryptococcosis. The inhalation of infectious propagules can lead to internalization of cryptococcal cells by alveolar macrophages, a niche in which C. gattii cells can survive and proliferate. Although the nutrient composition of macrophages is relatively unknown, the high induction of amino acid transporter genes inside the phagosome indicates a preference for amino acid uptake instead of synthesis. However, the presence of countable errors in the R265 genome annotation indicates significant inhibition of transcriptomic analysis in this hypervirulent strain. Thus, we analyzed RNA-Seq data from in vivo and in vitro cultures of C. gattii R265 to perform the reannotation of the genome. In addition, based on in vivotranscriptomic data, we identified highly expressed genes and pathways of amino acid metabolism that would enable C. gattii to survive and proliferate in vivo. Importantly, we identified high expression in three APC amino acid transporters as well as the GABA permease. The use of amino acids as carbon and nitrogen sources, releasing ammonium and generating carbohydrate metabolism intermediaries, also explains the high expression of components of several degradative pathways, since glucose starvation is an important host defense mechanism. Full article
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Open AccessReview
Phosphate Acquisition and Virulence in Human Fungal Pathogens
Microorganisms 2017, 5(3), 48; doi:10.3390/microorganisms5030048 -
Abstract
The ability of pathogenic fungi to acquire essential macro and micronutrients during infection is a well-established virulence trait. Recent studies in the major human fungal pathogens Candida albicans and Cryptococcus neoformans have revealed that acquisition of the essential macronutrient, phosphate, is essential for
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The ability of pathogenic fungi to acquire essential macro and micronutrients during infection is a well-established virulence trait. Recent studies in the major human fungal pathogens Candida albicans and Cryptococcus neoformans have revealed that acquisition of the essential macronutrient, phosphate, is essential for virulence. The phosphate sensing and acquisition pathway in fungi, known as the PHO pathway, has been extensively characterized in the model yeast Saccharomyces cerevisiae. In this review, we highlight recent advances in phosphate sensing and signaling mechanisms, and use the S. cerevisiae PHO pathway as a platform from which to compare the phosphate acquisition and storage strategies employed by several human pathogenic fungi. We also explore the multi-layered roles of phosphate acquisition in promoting fungal stress resistance to pH, cationic, and oxidative stresses, and describe emerging roles for the phosphate storage molecule polyphosphate (polyP). Finally, we summarize the recent studies supporting the necessity of phosphate acquisition in mediating the virulence of human fungal pathogens, highlighting the concept that this requirement is intimately linked to promoting resistance to host-imposed stresses. Full article
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Open AccessArticle
MALDI-TOF MS for the Identification of Cultivable Organic-Degrading Bacteria in Contaminated Groundwater near Unconventional Natural Gas Extraction Sites
Microorganisms 2017, 5(3), 47; doi:10.3390/microorganisms5030047 -
Abstract
Groundwater quality and quantity is of extreme importance as it is a source of drinking water in the United States. One major concern has emerged due to the possible contamination of groundwater from unconventional oil and natural gas extraction activities. Recent studies have
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Groundwater quality and quantity is of extreme importance as it is a source of drinking water in the United States. One major concern has emerged due to the possible contamination of groundwater from unconventional oil and natural gas extraction activities. Recent studies have been performed to understand if these activities are causing groundwater contamination, particularly with respect to exogenous hydrocarbons and volatile organic compounds. The impact of contaminants on microbial ecology is an area to be explored as alternatives for water treatment are necessary. In this work, we identified cultivable organic-degrading bacteria in groundwater in close proximity to unconventional natural gas extraction. Pseudomonas stutzeri and Acinetobacter haemolyticus were identified using matrix-assisted laser desorption/ionization-time-of-flight-mass spectrometry (MALDI-TOF MS), which proved to be a simple, fast, and reliable method. Additionally, the potential use of the identified bacteria in water and/or wastewater bioremediation was studied by determining the ability of these microorganisms to degrade toluene and chloroform. In fact, these bacteria can be potentially applied for in situ bioremediation of contaminated water and wastewater treatment, as they were able to degrade both compounds. Full article
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Open AccessArticle
Culturing Toxic Benthic Blooms: The Fate of Natural Biofilms in a Microcosm System
Microorganisms 2017, 5(3), 46; doi:10.3390/microorganisms5030046 -
Abstract
A microcosm designed for culturing aquatic phototrophic biofilms on artificial substrata was used to perform experiments with microphytobenthos sampled during summer toxic outbreaks of Ostreopsis cf. ovata along the Middle Tyrrhenian coast. This dynamic approach aimed at exploring the unique and complex nature
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A microcosm designed for culturing aquatic phototrophic biofilms on artificial substrata was used to perform experiments with microphytobenthos sampled during summer toxic outbreaks of Ostreopsis cf. ovata along the Middle Tyrrhenian coast. This dynamic approach aimed at exploring the unique and complex nature of O. cf. ovata bloom development in the benthic system. Epibenthic assemblages were used as inocula for co-cultures of bloom organisms on polycarbonate slides at controlled environmental conditions. Biofilm surface adhesion, growth, and spatial structure were evaluated along with shifts in composition and matrix production in a low disturbance regime, simulating source habitat. Initial adhesion and substratum colonisation appeared as stochastic processes, then community structure and physiognomy markedly changed with time. Dominance of filamentous cyanobacteria and diatoms, and dense clusters of Amphidinium cf. carterae at the mature biofilm phases, were recorded by light and confocal microscopy, whilst O. cf. ovata growth was visibly limited in the late culture phases. Life-form strategies, competitiveness for resources, and possibly allelopathic interactions shaped biofilm structure during culture growth. HPLC (High Performance Liquid Chromatography) analysis of exopolysaccharidic matrix revealed variations in sugar total amounts and composition. No toxic compounds were detected in the final communities tested by LC-MS (Liquid Chromatography- Mass Spectrometry) and MALDI-TOF MS (Matrix Assisted Laser Desorption Ionization Time OF Flight Mass Spectroscopy) techniques. Full article
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Open AccessArticle
Growth and Photosynthetic Characteristics of Toxic and Non-Toxic Strains of the Cyanobacteria Microcystis aeruginosa and Anabaena circinalis in Relation to Light
Microorganisms 2017, 5(3), 45; doi:10.3390/microorganisms5030045 -
Abstract
Cyanobacteria are major bloom-forming organisms in freshwater ecosystems and many strains are known to produce toxins. Toxin production requires an investment in energy and resources. As light is one of the most important factors for cyanobacterial growth, any changes in light climate might
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Cyanobacteria are major bloom-forming organisms in freshwater ecosystems and many strains are known to produce toxins. Toxin production requires an investment in energy and resources. As light is one of the most important factors for cyanobacterial growth, any changes in light climate might affect cyanobacterial toxin production as well as their growth and physiology. To evaluate the effects of light on the growth and physiological parameters of both toxic and non-toxic strains of Microcystis aeruginosa and Anabaena circinalis, cultures were grown at a range of light intensities (10, 25, 50, 100, 150 and 200 µmol m−2 s−1). The study revealed that the toxic strains of both species (CS558 for M. aeruginosa and CS537 and CS541 for A. circinalis) showed growth (µ) saturation at a higher light intensity compared to the non-toxic strains (CS338 for M. aeruginosa and CS534 for A. circinalis). Both species showed differences in chlorophyll a, carotenoid, allophycocyanin (APC) and phycoerythrin (PE) content between strains. There were also differences in dark respiration (Rd), light saturated oxygen evolution rates (Pmax) and efficiency of light harvesting (α) between strains. All other physiological parameters showed no statistically significant differences between strains. This study suggest that the different strains respond differently to different light habitats. Thus, changes in light availability may affect bloom intensity of toxic and nontoxic strains of cyanobacteria by changing the dominance and succession patterns. Full article
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