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Enzymatic synthesis of 6'-sialyllactose, a dominant sialylated human milk oligosaccharide, by a novel exo-α-sialidase from Bacteroides fragilis NCTC9343.
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Enzymatic synthesis of 6'-sialyllactose, a dominant sialylated human milk oligosaccharide, by a novel exo-α-sialidase from Bacteroides fragilis NCTC9343.

Appl Environ Microbiol. 2018 Apr 20;:

Authors: Guo L, Chen X, Xu L, Xiao M, Lu L

Abstract
Gut bacteria provide a rich source of glycosidases that can recognize and/or hydrolyze glycans for nutritions. Interestingly, some glycosidases are also found to catalyze transglycosylation reactions in vitro and thus can be used for oligosaccharide synthesis. In this work, six putative and one known exo-α-sialidase genes, including three from Bacteroides fragilis NCTC9343, three from Clostridium perfringens ATCC13124, and one known from Bifidobacterium bifidum JCM1254, were subjected to gene cloning and heterogeneous expression in Escherichia coli The recombinant enzymes were purified, characterized for substrate specificity, and screened for transglycosylation activity. A sialidase, named BfGH33C, from B. fragilis NCTC9343 was found to possess excellent transglycosylation activity for the synthesis of sialylated human milk oligosaccharide. The native BfGH33C was a homodimer with a molecular weight of 113.6 kDa. The Km and kcat values for 4-methylumbelliferyl N-acetyl-α-d-neuraminic acid and sialic acid dimer were determined to be 0.06 mM and 283.2 s-1, and 0.75 mM and 329.6 s-1, respectively. The enzyme was able to transfer sialyl from sialic acid dimer or oligomer to lactose with high efficiency and strict α2-6 regioselectivity. The influences of initial substrate concentration, pH, temperature, and reaction time on the transglycosylation were investigated in detail. Using 40 mM sialic acid dimer (or 40 mg/ml oligomer) and 1 M lactose (pH 6.5) at 50 °C for 10 min, BfGH33C could specifically produce 6'-sialyllactose, a dominant sialylated human milk oligosaccharide, at a maximal conversion ratio above 20%. It provided a promising alternative to the current chemical and enzymatic methods for obtaining sialylated oligosaccharides.IMPORTANCE Sialylated human milk oligosaccharides are significantly beneficial for the neonate, as they play important roles in supporting resistance to pathogens, gut maturation, immune function, brain and cognitive development. Therefore, access to the sialylated oligosaccharides has attracted increasing attention either for the study of saccharide functions or for the development of infant formulas that could mimic the nutritional value of human milk. Nevertheless, nine-carbon sialic acids are rather complicated for the traditional chemical modifications that require multiple protection and deprotection steps to achieve a specific glycosidic bond. Here, the exo-α-sialidase BfGH33C synthesized 6'-sialyllactose in a simple step with high transglycosylation activity and strict regioselectivity. Additionally, it could utilize oligosialic acid as glycosyl donor, which was newly prepared in a facile, economical way to reduce the substrate cost. All these studies laid a foundation for the practical use of BfGH33C in large-scale synthesis of sialylated oligosaccharides in the future.

PMID: 29678922 [PubMed - as supplied by publisher]




A repeating sulfated galactan motif resuscitates dormant Micrococcus luteus.
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A repeating sulfated galactan motif resuscitates dormant Micrococcus luteus.

Appl Environ Microbiol. 2018 Apr 20;:

Authors: Böttcher T, Szamosvári D, Clardy J

Abstract
Only a small fraction of bacteria can autonomously initiate growth on agar plates. Non-growing bacteria typically enter a metabolically inactive dormant state and require specific chemical trigger factors or signals to exit this state and resume growth. Micrococcus luteus has become a model organism for this important yet poorly understood phenomenon. So far, only few resuscitation signals have been described and all of them are produced endogenously by bacterial species. We report the discovery of a novel type of resuscitation signal that allows M. luteus to grow on agar but not on agarose plates. Fractionation of the agar polysaccharide complex and sulfation of agarose allowed to identify the signal as highly sulfated saccharides found in agar or carrageenans. Purification of hydrolyzed κ-carrageenan ultimately led to the identification of the signal as a small fragment of a large linear polysaccharide - an oligosaccharide of five or more sugars with a repeating disaccharide motif containing d-galactose-4-sulfate (G4S) 1,4-linked to a 3,6-anhydro-α-d-galactose (DA) unit - G4S-[DA-G4S]n≥2Importance Most environmental bacteria cannot initiate growth on agar plates, but they can flourish on the same plates once growth is initiated. While there are a number of names for and manifestations of this phenomenon, the underlying cause appears to be the requirement for a molecular signal indicating safe growing conditions. Micrococcus luteus has become a model organism for studying this growth initiation process, often called resuscitation, because of its apparent connection with the persistent or dormant form of Mycobacterium tuberculosis, an important human pathogen. In this report we identify a highly sulfated saccharide from agar or carrageenans that robustly resuscitates dormant M. luteus on agarose plates. We identified and characterized the signal as a small repeating disaccharide motif. Our results indicate that signals inherent to or absent from the polysaccharide composition of solid growth media can have major effects on bacterial growth.

PMID: 29678921 [PubMed - as supplied by publisher]




Imidacloprid decreases honey bee survival but does not affect the gut microbiome.
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Imidacloprid decreases honey bee survival but does not affect the gut microbiome.

Appl Environ Microbiol. 2018 Apr 20;:

Authors: Raymann K, Motta EVS, Girard C, Riddington IM, Dinser JA, Moran NA

Abstract
Accumulating evidence suggests that pesticides have played a role in the increased rate of honeybee colony loss. One of the most commonly used pesticides in the US is the neonicotinoid imidacloprid. Although the primary mode of action of imidacloprid is the insect nervous system, it has also been shown to cause changes insects' digestive physiology, and alter the microbiota of Drosophila melanogaster larvae. The honey bee gut microbiome plays a major role in bee health. Although many studies have shown that imidacloprid affects honey bee behavior, its impact on the microbiome has not been fully elucidated. Here we investigated the impact of imidacloprid on the gut microbiome composition, survivorship of honey bees, and susceptibility to pathogens. Consistent with other studies, we show that imidacloprid exposure results in elevated mortality of honey bees in the hive and increases susceptibility to infection by pathogens. However, we did not find evidence that imidacloprid affects the gut bacterial community of honey bees. Our in vitro experiments demonstrated that honey bee gut bacteria can grow in the presence of imidacloprid, and we found some evidence that imidacloprid can be metabolized in the bee gut environment. However, none of the individual bee gut bacterial species tested could metabolize imidacloprid, suggesting that the observed metabolism of imidacloprid in vitro bee gut cultures is not caused by the gut bacteria. Overall, our results indicate that imidacloprid causes increased mortality in honey bees, but this mortality does not appear to be linked to the microbiome.Importance Growing evidence suggests that the extensive use of pesticides has played a large role in the increased rate of honey bee colony loss. Despite extensive research on the effects of imidacloprid on honey bees, it is still unknown whether it impacts the community structure of the gut microbiome. Here we investigated the impact of imidacloprid on the gut microbiome composition, survivorship of honey bees, and susceptibility to pathogens. We found that exposure to imidacloprid resulted in elevated mortality of honey bees, and increased susceptibility to infection by opportunistic pathogens. However, we did not find evidence that imidacloprid affects the gut microbiome of honey bees. We found some evidence that imidacloprid can be metabolized in the bee gut environment in vitro, but because it is quickly eliminated from the bee it is unlikely that this metabolism occurs in nature. Thus, imidacloprid causes increased mortality in honey bees, but this does not appear to be linked to the microbiome.

PMID: 29678920 [PubMed - as supplied by publisher]




Investigating the central metabolism of Clostridium thermosuccinogenes.
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Investigating the central metabolism of Clostridium thermosuccinogenes.

Appl Environ Microbiol. 2018 Apr 20;:

Authors: Koendjbiharie JG, Wiersma K, van Kranenburg R

Abstract
Clostridium thermosuccinogenes is a thermophilic anaerobic bacterium able to convert various carbohydrates to succinate and acetate as main fermentation products. Genomes of the four publicly available strains have been sequenced and the genome of the type-strain has been closed. The annotated genomes were used to reconstruct the central metabolism, and enzyme assays were used to validate annotations and to determine co-factor specificity. Genes for the pathways to all fermentation products were identified, as well as for the Embden-Meyerhof-Parnas pathway, and the pentose phosphate pathway. Notably, a candidate transaldolase was lacking and also transcriptomics during growth on glucose versus xylose did not provide any leads to potential transaldolase genes or alternative pathways connecting the C5 with the C3/C6 metabolism. Enzyme assays showed xylulokinase to prefer GTP over ATP, which could be of importance for engineering xylose utilization in related, thermophilic species of industrial relevance. Furthermore, the gene responsible for malate dehydrogenase was identified via heterologous expression in E. coli and subsequent assays with the cell-free extract, which has proven to be a simple and powerful method for basal characterization of thermophilic enzymes.Importance Running industrial fermentation processes at elevated temperatures has several advantages, including reduced cooling requirements, increased reaction rates and solubilities, and a possibility to perform simultaneous saccharification and fermentation of pretreated biomass. Most studies with thermophiles so far have focussed on bioethanol production. C. thermosuccinogenes seems an attractive production organism for organic acids, succinic acid in particular, from lignocellulosic biomass-derived sugars. This study provides valuable insights in its central metabolism and GTP and PPi co-factor utilization.

PMID: 29678919 [PubMed - as supplied by publisher]




Impact of currently marketed tampons and menstrual cups on Staphylococcus aureus growth and TSST-1 production in vitro.
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Impact of currently marketed tampons and menstrual cups on Staphylococcus aureus growth and TSST-1 production in vitro.

Appl Environ Microbiol. 2018 Apr 20;:

Authors: Nonfoux L, Chiaruzzi M, Badiou C, Baude J, Tristan A, Thioulouse J, Muller D, Prigent Combaret C, Lina G

Abstract
Fifteen currently marketed intravaginal protection products (11 types of tampon and four menstrual cups) were tested by the modified tampon sac method to determine their effect on Staphylococcus aureus growth and toxic shock toxin 1 (TSST-1) production. Most tampons reduced S. aureus growth and TSST-1 production, with differences based on brand and composition, and S. aureus growth was higher in de-structured than in unaltered tampons. We observed higher S. aureus growth and toxin production in menstrual cups than in tampons, potentially due to the additional air introduced to the bag by cups, with differences based on cup composition and size.Importance Menstrual toxic shock syndrome is a rare but severe disease. It occurs in healthy women vaginally colonized by Staphylococcus aureus producing toxic shock syndrome toxin 1 using intravaginal protection such as tampons or menstrual cups. Intravaginal protection induces TSS production by collecting catamenial products which act as a growth medium for S. aureus Previous studies have evaluated the impact of tampon composition on S. aureus producing toxic shock syndrome toxin 1, but they are not recent and did not include menstrual cups. This study demonstrates that highly reproducible results for S. aureus growth and TSST-1 production can be obtained using a simple protocol that reproduces the physiological conditions of tampon and cup usage as closely as possible, providing recommendations for tampon or cup use to both manufacturers and consumers. Notably, our results do not show that menstrual cups are safer than tampons and suggest that they require similar precautions.

PMID: 29678918 [PubMed - as supplied by publisher]




Genomic inference of recombination-mediated evolution in Xanthomonas euvesicatoria and X. perforans.
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Genomic inference of recombination-mediated evolution in Xanthomonas euvesicatoria and X. perforans.

Appl Environ Microbiol. 2018 Apr 20;:

Authors: Jibrin MO, Potnis N, Timilsina S, Minsavage GV, Vallad GE, Roberts PD, Jones JB, Goss EM

Abstract
Recombination is a major driver of evolution in bacterial populations because it can spread and combine independently evolved beneficial mutations. Recombinant lineages of plant bacterial pathogens are typically associated with colonization of novel hosts and emergence of new diseases. Here, we show that recombination between evolutionarily and phenotypically distinct plant pathogenic lineages generated recombinant lineages with unique combinations of pathogenicity and virulence factors. X. euvesicatoria (Xe) and X. perforans (Xp) are two closely related lineages causing bacterial spot disease on tomato and pepper worldwide. We sequenced the genome of atypical strains collected from tomato in Nigeria and observed recombination in the type III secretion system and effector genes, which showed alleles from both Xe and Xp Wider horizontal gene transfer was indicated by the lipopolysaccharide cluster of one strain being most similar to that of a distantly related Xanthomonas pathogen of barley. This strain and others have experienced extensive genomewide homologous recombination and both species exhibited dynamic open pangenomes. Variation in effector gene repertoires within and between species must be taken into consideration when breeding tomatoes for disease resistance. Resistance breeding strategies that target specific effectors must consider possibly dramatic variation in bacterial spot populations across global production regions, as illustrated by the recombinant strains observed here.Importance The pathogens that cause bacterial spot of tomato and pepper are extensively studied models of plant-microbe interactions and cause problematic disease worldwide. Atypical bacterial spot strains collected from tomato in Nigeria, and other strains from Italy, India, and Florida, showed evidence of genomewide recombination that generated genetically distinct pathogenic lineages. The strains from Nigeria and Italy were found to have a mix of type III secretion system genes from X. perforans and X. euvesicatoria, and effectors from X. gardneri These genes and effectors are important in the establishment of disease and effectors are common targets of resistance breeding. Our findings point to global diversity in the genomes of bacterial spot pathogens that is likely to affect the host-pathogen interaction and influence management decisions.

PMID: 29678917 [PubMed - as supplied by publisher]




Identification of LaoABCR as a novel system for the oxidation of long-chain alcohols derived from SDS- and alkane-degradation in Pseudomonas aeruginosa.
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Identification of LaoABCR as a novel system for the oxidation of long-chain alcohols derived from SDS- and alkane-degradation in Pseudomonas aeruginosa.

Appl Environ Microbiol. 2018 Apr 20;:

Authors: Panasia G, Philipp B

Abstract
The opportunistic pathogen Pseudomonas aeruginosa strain PAO1 is able to use a variety of organic pollutants as growth substrates including the anionic detergent sodium dodecyl sulfate (SDS) and long-chain alkanes. While the enzymes initiating SDS and alkane degradation are well known, the following enzymatic steps for degradation of the derived primary long-chain alcohols have not been identified yet. By evaluating genes specifically induced during growth with SDS, a gene cluster encoding a putative alcohol dehydrogenase (PA0364/LaoA), a probable inner membrane protein (PA0365/LaoB) and a presumable aldehyde dehydrogenase (PA0366/LaoC) were identified and designated as Lao (long-chain-alcohol/aldehyde-oxidation) system. Growth experiments with deletion mutants with SDS, 1-dodecanol and alkanes revealed that LaoA/B are involved in the degradation of primary long-chain alcohols. Moreover, detection of 1-dodecanol oxidation in cell extracts by activity staining revealed an interdependency of LaoA and LaoB for efficient 1-dodecanol oxidation. An in silico analysis yielded no well-characterized homologue proteins for LaoA/B. Furthermore, a gene adjacent to the lao gene cluster encodes a putative transcriptional regulator (PA0367/LaoR). A laoR deletion mutant exhibited constitutive expression of LaoA/B indicating that LaoR is a repressor for the expression of laoABC Taken together, these results showed that the proteins LaoA/B constitute a novel oxidation system for long-chain alcohols derived from toxic substrates.IMPORTANCE The versatile and highly adaptive bacterium Pseudomonas aeruginosa is able to colonize a variety of habitats including anthropogenic environments, where it is often challenged with toxic compounds. Its ability to degrade such compounds and to use them as growth substrates can significantly enhance spreading of this opportunistic pathogen in hygienic settings, such as clinics or water distribution systems. Thus, knowledge about the metabolism of P. aeruginosa can contribute to novel approaches for its preventing growth and reducing nosocomial infections. As the lao-system is important for the degradation of two different classes of toxic compounds, the identification of these novel enzymes can be a useful contribution for developing effective antibacterial strategies.

PMID: 29678916 [PubMed - as supplied by publisher]




Ralstonia eutropha's Poly(3-hydroxybutyrate)(PHB) polymerase PhaC1 and PHB depolymerase PhaZa1 are phosphorylated in vivo.
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Ralstonia eutropha's Poly(3-hydroxybutyrate)(PHB) polymerase PhaC1 and PHB depolymerase PhaZa1 are phosphorylated in vivo.

Appl Environ Microbiol. 2018 Apr 20;:

Authors: Jüngert JR, Patterson C, Jendrossek D

Abstract
In this study, we screened PHB synthase PhaC1 and PHB depolymerase PhaZa1 of Ralstonia eutropha for the presence of phosphorylated residues during the PHB accumulation and PHB degradation phase. Thr373 of PHB synthase PhaC1 was phosphorylated in the stationary growth phase but was not modified in the exponential and PHB accumulation phases. Ser35 of PHB depolymerase PhaZa1 was identified in phosphorylated form both in the exponential and in the stationary growth phase. Additional phosphosites were identified for both proteins in sample-dependent forms. Site-directed mutagenesis of the codon for Thr373 and other phosphosites of PhaC1 revealed a strong negative impact on PHB synthase activity. Modification of Thr26 and Ser35 of PhaZa1 reduced the ability of R. eutropha to mobilize PHB in the stationary growth phase. Our results show that phosphorylation of PhaC1 and PhaZa1 can be important for modulation of the activities of PHB synthase and PHB depolymerase.Importance Polyhydroxybutyrate (PHB) and related polyhydroxyalkanoates (PHAs) are important intracellular carbon and energy storage compounds in many prokaryotes. The accumulation of PHB or PHAs increases the fitness of cells during periods of starvation and other stress conditions. The simultaneous presence of poly(3-hydroxybutyrate) (PHB) synthase (PhaC1) and PHB depolymerase (PhaZa1) on synthesized PHB granules in Ralstonia eutropha (alternative designation Cupriavidus necator) has been previously shown in several laboratories. These findings imply that the activities of PHB synthase and PHB depolymerase should be regulated to avoid a futile cycle of simultaneous synthesis and degradation of PHB. Here, we addressed this question by identifying phosphorylation sites on PhaC1 and PhaZa1 and by site-directed mutagenesis of identified residues. Furthermore, we conducted in vitro and in vivo analysis of PHB synthase activity and PHB contents.

PMID: 29678915 [PubMed - as supplied by publisher]




Cross-talk between calcium and ROS regulates hyphal branching and ganoderic acids biosynthesis in Ganoderma lucidum under copper stress.
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Cross-talk between calcium and ROS regulates hyphal branching and ganoderic acids biosynthesis in Ganoderma lucidum under copper stress.

Appl Environ Microbiol. 2018 Apr 20;:

Authors: Gao T, Shi L, Zhang T, Ren A, Jiang A, Yu H, Zhao M

Abstract
Ganoderma lucidum is among the best known medicinal basidiomycetes due to its production of many pharmacologically active compounds. To study the regulatory networks involved in its growth and development, we analyzed the relationship between reactive oxygen species (ROS) and Ca2+ signaling in the regulation of hyphal branching and ganoderic acid (GA) biosynthesis after Cu2+ treatment. Our results revealed that Cu2+ treatment decreased the distance between hyphal branches and increased the GAs content and the intracellular levels of ROS and Ca2+ Further research revealed that the Cu2+-induced changes in hyphal branch distance, GAs content, and cytosolic Ca2+ level were dependent on increases in cytosolic ROS. Our results also showed that increased cytosolic Ca2+ could reduce cytosolic ROS by activating antioxidases and modulating Cu2+ accumulation, resulting in feedback to adjust hyphal growth and GAs biosynthesis. These results indicated that cytosolic ROS and Ca2+ levels exert important cross-talk in the regulation of hyphal growth and GAs biosynthesis induced by Cu2+ Taken together, our results provide a reference for analyzing the interactions among different signal transduction pathways with regard to the regulation of growth and development in other filamentous fungi.ImportanceGanoderma lucidum, which is known as an important medicinal basidiomycete, is gradually becoming a model organism for studying environmental regulation and metabolism. In this study, we analyzed the relationship between reactive oxygen species (ROS) and Ca2+ signaling in the regulation of hyphal branching and ganoderic acids (GAs) biosynthesis under Cu2+ stress. The results revealed that the Cu2+-induced changes in the hyphal branch distance, GAs content, and cytosolic Ca2+ level were dependent on increases in cytosolic ROS. Furthermore, the results indicated that increased cytosolic Ca2+ could reduce cytosolic ROS by activating antioxidases and modulating Cu2+ accumulation. The results in this manuscript indicated that there was important cross-talk between cytosolic ROS and Ca2+ levels in the regulation of hyphal growth and GAs biosynthesis induced by Cu2.

PMID: 29678914 [PubMed - as supplied by publisher]




Long-term Survival and Thermal Death Kinetics of Enterohemorrhagic Escherichia coli Serogroups O26, O103, O111 and O157 in Wheat Flour.
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Long-term Survival and Thermal Death Kinetics of Enterohemorrhagic Escherichia coli Serogroups O26, O103, O111 and O157 in Wheat Flour.

Appl Environ Microbiol. 2018 Apr 20;:

Authors: Forghani F, den Bakker M, Futral AN, Diez-Gonzalez F

Abstract
Wheat flour has been associated with outbreaks of enterohemorrhagic Escherichia coli (EHEC), but little is known on EHEC's survival during storage and thermal processing. The objectives of this study were to determine long-term viability and thermal inactivation kinetics of serogroups O26, O103, O111 and O157. Wheat flour samples were inoculated with a cocktail of five strains of a single serogroup and stored at 23 and 35 °C. Inoculated samples were heated at 55, 60, 65 and 70 °C. Viability was determined by plate counting. D- and δ-values were calculated with Log-linear and Weibull models, respectively. At 23 °C, EHEC counts declined gradually for 84 days and samples tested positive from 84 to 280 days. The D- and δ-values ranged from 7.5 to 8.2 and 3.1 to 5.3 days, respectively, but no significant difference among serogroups (p ≤ 0.05). At 35 °C EHEC were not quantifiable by day seven and no positive samples were detected after 49 days. Heating at 55 and 65 °C resulted in δ-value ranges of 15.6-39.7 min and 3.0-3.9 min, respectively, with no significant difference among serogroups, either. Z-values were 12.6, 6.7, 10.2 and 13.4 °C for O26, O103, O111 and O157, respectively. Thermal death kinetics of EHEC in flour were better described using Weibull model. Survival and inactivation rates of four serogroups were remarkably similar. These findings indicated that all EHEC serovars tested remained viable for at least 9 months at room temperature and survived for up to 60 min at 70 °C in wheat flour.IMPORTANCE Enterohemorrhagic Escherichia coli (EHEC) and Salmonella have recently caused several gastroenteritis outbreaks and recalls of wheat flour. Because EHEC can cause illness with very low doses and there is very scarce information regarding their ability to survive storage and heating in flour, the present study was undertaken to assess the long-term survival of EHEC serogroups O26, O103, O111 and O157 in flour. These findings are relevant as we report that EHEC can survive for more than 9 months in wheat flour during storage. In addition, results obtained suggest that thermal inactivation at 65 °C for 30 min or two months of storage at 35 °C may be feasible strategies to mitigate the risk of most EHEC serovars in wheat flour.

PMID: 29678913 [PubMed - as supplied by publisher]




Characterizing the ecology of Vibrio in the Neuse River Estuary, North Carolina using heat shock protein 60 (hsp60) next-generation amplicon sequencing.
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Characterizing the ecology of Vibrio in the Neuse River Estuary, North Carolina using heat shock protein 60 (hsp60) next-generation amplicon sequencing.

Appl Environ Microbiol. 2018 Apr 20;:

Authors: Jesser KJ, Noble RT

Abstract
Of marine eubacteria, the genus Vibrio is intriguing because member species are relevant to both marine ecology and human health. Many have touted the relationships of Vibrio to environmental factors, especially temperature and salinity, to predict total Vibrio abundance, but these studies lacked the taxonomic resolution to identify relationships among species and key drivers of Vibrio dynamics. In order to improve NGS surveys of Vibrio, we have conducted both 16S small subunit ribosomal RNA (rRNA) and heat shock protein 60 (hsp60) amplicon sequencing of water samples collected at two well-studied locations in the Neuse River Estuary, NC. Samples were collected between May and December 2016 with enhanced sampling efforts in response to two named storms. Using hsp60 sequences, 21 Vibrio species were identified, including the potential human pathogens V. cholerae, V. parahaemolyticus, and V. vulnificus. Changes in the Vibrio community mirrored seasonal and storm-related changes in the water column, especially in response to an influx of nutrient-rich freshwater to the estuary after Hurricane Matthew which initiated dramatic changes in the overall Vibrio community. Individual species dynamics were wide-ranging, indicating that individual Vibrio taxa have unique ecologies and that total Vibrio predictors are insufficient for risk assessments of potentially pathogenic species. Positive relationships between Vibrio, dinoflagellates, and Cyanobacteria were identified, as were intra-species associations which further illuminated the interactions of co-occurring Vibrio taxa along environmental gradients.IMPORTANCE The objective of this research was to utilize a novel approach to improve sequence-based surveys of Vibrio communities and to demonstrate the usefulness of this approach by presenting an analysis of Vibrio dynamics in context of environmental conditions, with a particular focus on species which cause disease in humans and storm effects. The methods presented here allowed for the analysis of Vibrio dynamics with excellent taxonomic resolution, and could be incorporated into future ecological studies and risk prediction strategies for potentially pathogenic species. Next-generation sequencing of hsp60 and other innovative sequence-based approaches are valuable tools and show great promise for studying Vibrio ecology and associated public health risks.

PMID: 29678912 [PubMed - as supplied by publisher]




Food-spoilage-associated Leuconostoc, Lactococcus, and Lactobacillus species display different survival strategies in response to competition.
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Food-spoilage-associated Leuconostoc, Lactococcus, and Lactobacillus species display different survival strategies in response to competition.

Appl Environ Microbiol. 2018 Apr 20;:

Authors: Andreevskaya M, Jääskeläinen E, Johansson P, Ylinen A, Paulin L, Björkroth J, Auvinen P

Abstract
Psychrotrophic lactic acid bacteria (LAB) are the prevailing spoilage organisms in packaged cold-stored meat products. Species composition and metabolic activities of such LAB spoilage communities are determined by the nature of meat product, storage condition and interspecies interactions. Our knowledge of systems-level responses of LAB during such interactions is very limited. To expand it, we studied interactions between three common psychrotrophic spoilage LAB (Leuconostoc gelidum, Lactococcus piscium and Lactobacillus oligofermentans) by comparing their time-course transcriptome profiles obtained during their growth in individual, pairwise and triple cultures. The study revealed how these LAB employed different strategies to cope with the consequences of interspecies competition. The fastest growing bacterium, Le. gelidum, attempted to enhance its nutrient-scavenging and growth capabilities in the presence of other LAB through upregulation of the carbohydrate catabolic pathways, pyruvate fermentation enzymes and ribosomal proteins. Whereas, the slower growing Lc. piscium and Lb. oligofermentans downregulated these functions. These findings may explain the competitive success and predominance of Le. gelidum in a variety of spoiled foods. Peculiarly, interspecies interactions induced overexpression of prophage genes and restriction-modification systems (mechanisms of DNA exchange and protection against it) in Lc. piscium and Lb. oligofermentans, but not in Le. gelidum Co-cultivation induced also overexpression of the numerous putative adhesins in Lb. oligofermentans. These adhesins might contribute to the survival of this slowly growing bacterium in actively growing meat spoilage communities.Importance Despite the apparent relevance of LAB for biotechnology and human health, interactions between members of LAB communities are not well known. Knowledge of such interactions is crucial for understanding how these communities function and, consequently, whether there is any possibility to develop new strategies to interfere with the growth and to postpone spoilage of packaged and refrigerated foods. With the help of controlled experiments detailed regulation events can be observed. This study gives an insight into the system-level interactions and the different competition-induced survival strategies related to enhanced uptake and catabolism of carbon sources, overexpression of adhesins and putative bacteriocins, and to the induction of exchange of genetic material. Even though this experiment dealt only with three LAB strains in vitro, these findings agreed well with the relative abundance patterns typically reported for these species in natural food microbial communities.

PMID: 29678911 [PubMed - as supplied by publisher]




Serotype diversity and antimicrobial resistance among Salmonella enterica isolated from patients at an equine referral hospital.
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Serotype diversity and antimicrobial resistance among Salmonella enterica isolated from patients at an equine referral hospital.

Appl Environ Microbiol. 2018 Apr 20;:

Authors: Leon IM, Lawhon SD, Norman KN, Threadgill DS, Ohta N, Vinasco J, Scott HM

Abstract
Although Salmonella enterica can produce life-threatening colitis in horses, certain serotypes are more commonly associated with clinical disease. Our aim was to evaluate the proportional morbidity attributed to different serotypes, as well as phenotypic and genotypic antimicrobial resistance (AMR) of Salmonella isolated from patients at an equine referral hospital in the southern United States. Two-hundred-fifty-five Salmonella isolates were obtained from clinical samples of patients admitted to the hospital between 2007 and 2015. Phenotypic resistance to 14 antibiotics surveilled by the U.S. National Antimicrobial Resistance Monitoring System was determined using a commercially available panel. Whole genome sequencing was used to identify serotypes and genotypic AMR. The most common serotypes were Newport (18%), Anatum (15.2%) and Braenderup (11.8%). Most (n=219) of the isolates were pansusceptible, while 25 were multidrug resistant (≥3 antimicrobial classes). Genes encoding beta-lactams resistance such as blaCMY-2, blaSHV-12, blaCTX-M-27 and blaTEM-1B were detected. The qnrB2 and aac(6')-Ib-cr genes were present in isolates with reduced susceptibility to ciprofloxacin. Genes encoding gentamicin resistance (aph(3' )-Ia, aac(6')-IIc), streptomycin (strA and strB), sulfonamides (sul1), trimethoprim (dfrA), phenicols (catA), tetracyclines (tet(A) and tet(E)), and macrolides (ere(A)) also were identified. The main predicted incompatibility plasmid type was I1 (10%). Core-genome-based analyses revealed phylogenetic associations between isolates of common serotypes. The presence of AMR Salmonella in equine patients increases the risk of unsuccessful treatment and causes concern for potential zoonotic transmission to attending veterinary personnel, animal caretakers, and horse owners. Understanding the epidemiology of Salmonella in horses admitted to referral hospitals is important for the prevention, control, and treatment of salmonellosis.IMPORTANCE In horses, salmonellosis is a leading cause of life-threatening colitis. At veterinary teaching hospitals, nosocomial outbreaks can increase the risk of zoonotic transmission, lead to restrictions on admissions, impact hospital reputation, and interrupt educational activities. The antimicrobials most often used in horses are included in the 5th revision of the World Health Organization's list of Critically Important Antimicrobials for human medicine. Recent studies have demonstrated an increasing trend in bacterial resistance to drugs commonly used to treat Salmonella infections. In this study, we identify temporal trends in the distribution of Salmonella serotypes and their mechanisms of antimicrobial resistance; further, we are able to determine the likely origin of several temporal clusters of infection by using whole genome sequencing. These data can be used to focus strategies to better contain the dissemination and enhance the mitigation of Salmonella infections, and to provide evidence-based policies and guidelines to steward antimicrobial use in veterinary medicine.

PMID: 29678910 [PubMed - as supplied by publisher]