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Environmental Microbiology

Wed, 04/10/2019 - 10:02
Summary Dickeya is a genus of phytopathogenic enterobacterales causing soft rot in a variety of plants (e.g. potato, chicory, maize). Among the species affiliated to this genus, Dickeya aquatica, described in 2014, remained particularly mysterious because it had no known host. Furthermore, while D. aquatica was proposed to represent a deep‐branching species among Dickeya genus, its precise...
Wed, 04/10/2019 - 10:02
Summary Dickeya is a genus of phytopathogenic enterobacterales causing soft rot in a variety of plants (e.g. potato, chicory, maize). Among the species affiliated to this genus, Dickeya aquatica, described in 2014, remained particularly mysterious because it had no known host. Furthermore, while D. aquatica was proposed to represent a deep‐branching species among Dickeya genus, its precise...
Mon, 04/01/2019 - 12:01
Summary Early gut microbial colonization is important for postnatal metabolic and immune development. However, little is known about the effects of different feeding modes (suckling versus bottle‐feeding) or microbial sources on this process in farm animals. We found that suckled and bottle‐fed newborn lambs had their own distinct gut microbiota. Results from 16S rRNA gene sequencing and qPCR...
Mon, 04/01/2019 - 12:01
Summary Early gut microbial colonization is important for postnatal metabolic and immune development. However, little is known about the effects of different feeding modes (suckling versus bottle‐feeding) or microbial sources on this process in farm animals. We found that suckled and bottle‐fed newborn lambs had their own distinct gut microbiota. Results from 16S rRNA gene sequencing and qPCR...
Mon, 03/18/2019 - 11:00
Summary Type VI secretion systems (T6SSs) are widespread, tightly regulated, protein delivery apparatuses used by Gram‐negative bacteria to outcompete their neighbors. The pathogen, Vibrio parahaemolyticus, encodes two T6SSs. These T6SSs are differentially regulated by external conditions. T6SS1, an antibacterial system predominantly found in pathogenic isolates, requires warm marine‐like...
Mon, 03/18/2019 - 11:00
Summary Type VI secretion systems (T6SSs) are widespread, tightly regulated, protein delivery apparatuses used by Gram‐negative bacteria to outcompete their neighbors. The pathogen, Vibrio parahaemolyticus, encodes two T6SSs. These T6SSs are differentially regulated by external conditions. T6SS1, an antibacterial system predominantly found in pathogenic isolates, requires warm marine‐like...
Wed, 03/13/2019 - 11:47
Summary Vibrio parahaemolyticus, the leading cause of seafood‐associated gastroenteritis worldwide, requires the two type‐III secretion systems (T3SS1 and T3SS2) and a thermostable direct hemolysin (encoded by tdh1 and tdh2) for full virulence. The tdh genes and the T3SS2 gene cluster constitute an 80 kb pathogenicity island known as Vp‐PAI located on the chromosome II. Expression of T3SS1 and...
Wed, 03/13/2019 - 11:47
Summary Blackleg and soft rot are devastating diseases on potato stem and tuber caused by Pectobacterium and Dickeya pectinolytic enterobacteria. In European potato cultures, D. dianthicola and D. solani species successively emerged in the past decades. Ecological traits associated to their settlement remain elusive, especially in the case of the recent invader D. solani. In this work, we...
Wed, 03/13/2019 - 11:47
Summary The patulin biosynthesis is one of model pathways in an understanding of secondary metabolite biology and network novelties in fungi. However, molecular regulation mechanism of patulin biosynthesis and contribution of each gene related to the different catalytic enzymes in the biochemical steps of the pathway remain largely unknown in fungi. In this study, the genetic components of...
Wed, 03/13/2019 - 11:47
Summary Vibrio parahaemolyticus, the leading cause of seafood‐associated gastroenteritis worldwide, requires the two type‐III secretion systems (T3SS1 and T3SS2) and a thermostable direct hemolysin (encoded by tdh1 and tdh2) for full virulence. The tdh genes and the T3SS2 gene cluster constitute an 80 kb pathogenicity island known as Vp‐PAI located on the chromosome II. Expression of T3SS1 and...
Wed, 03/13/2019 - 11:47
Summary Blackleg and soft rot are devastating diseases on potato stem and tuber caused by Pectobacterium and Dickeya pectinolytic enterobacteria. In European potato cultures, D. dianthicola and D. solani species successively emerged in the past decades. Ecological traits associated to their settlement remain elusive, especially in the case of the recent invader D. solani. In this work, we...
Wed, 03/13/2019 - 11:47
Summary The patulin biosynthesis is one of model pathways in an understanding of secondary metabolite biology and network novelties in fungi. However, molecular regulation mechanism of patulin biosynthesis and contribution of each gene related to the different catalytic enzymes in the biochemical steps of the pathway remain largely unknown in fungi. In this study, the genetic components of...
Thu, 10/25/2018 - 11:38
Summary To date, no demonstration of a direct correlation between the presence of mycoviruses and the quantitative or qualitative modulation of mycotoxins has been shown. In our study, we transfected a virus‐free ochratoxin A (OTA)‐producing isolate of Aspergillus ochraceus with purified mycoviruses from a different A. ochraceus isolate and from Penicillium aurantiogriseum. Among the mycoviruses...
Thu, 10/25/2018 - 11:38
Summary To date, no demonstration of a direct correlation between the presence of mycoviruses and the quantitative or qualitative modulation of mycotoxins has been shown. In our study, we transfected a virus‐free ochratoxin A (OTA)‐producing isolate of Aspergillus ochraceus with purified mycoviruses from a different A. ochraceus isolate and from Penicillium aurantiogriseum. Among the mycoviruses...
Fri, 01/19/2018 - 04:10
Summary Adaptation to bile is the ability to endure the lethal effects of bile salts after growth on sublethal concentrations. Surveys of adaptation to bile in Salmonella enterica ser. Tyhimurium reveal that active efflux is essential for adaptation while other bacterial functions involved in bile resistance are not. Among S. enterica mutants lacking one or more efflux systems, only strains...
Wed, 01/10/2018 - 02:00
Summary Bacteria have evolved different mechanisms to catabolize carbon sources from nutrient mixtures. They first consume their preferred carbon source, before others are used. Regulatory mechanisms adapt the metabolism accordingly to maximize growth and to outcompete other organisms. The human pathogen Campylobacter jejuni is an asaccharolytic Gram-negative bacterium that catabolizes amino...
Thu, 12/21/2017 - 06:12
Summary Proton-pumping rhodopsins provide an alternative pathway to photosynthesis by which solar energy can enter the marine food web. Rhodopsin genes are widely found in marine bacteria, also in the Arctic, and were recently reported from several eukaryotic lineages. So far, little is known about rhodopsin expression in Arctic eukaryotes. In this study, we used metatranscriptomics and 18S rDNA...
Wed, 12/13/2017 - 06:51
Summary Vibrio vulnificus has the highest death rate (>35%) and per-case economic burden ($3.3 million) of any foodborne pathogen in the US. Infections occur via open wounds or following ingestion of contaminated seafood, most infamously oysters. We isolated a 1000th generation descendant, designated NT, that exhibited increased biofilm and aggregate formation relative to its parent. We...
Thu, 12/07/2017 - 05:21
Abstract Photosynthetic picoeukaryotes contribute a significant fraction of primary production in the upper ocean. Micromonas pusilla is an ecologically relevant photosynthetic picoeukaryote, abundantly and widely distributed in marine waters. Grazing by protists may control the abundance of picoeukaryotes such as M. pusilla, but the diversity of the responsible grazers is poorly understood. To...
Tue, 11/21/2017 - 02:11
Summary Arsenic, a highly cytotoxic and cancerogenic metalloid, is brought into the biosphere through geochemical sources and anthropogenic activities. A global biogeochemical arsenic biotransformation cycle exists in which inorganic arsenic species are transformed into organoarsenicals, which are subsequently mineralized again into inorganic arsenic compounds. Microorganisms contribute to this...
Fri, 10/27/2017 - 05:55
Abstract The flagella of various Gram-negative bacteria are decorated with diverse glycan structures, amongst them nonulosonic acids related to the sialic acid family. Although nonulosonic sugar biosynthesis pathways have been dissected in various pathogens, the enzymes transferring the sugars onto flagellin are still poorly characterized. The deletion of genes coding for Motility associated...
Fri, 10/13/2017 - 01:55
Summary Vibrio vulnificus is a Gram-negative aquatic bacterium first isolated by the United States (US) Centers for Disease Control and Prevention (CDC) in 1964. This bacterium is part of the normal microbiota of estuarine waters and occurs in high numbers in molluscan shellfish around the world, particularly in warmer months. Infections in humans are derived from consumption of seafood produce...
Mon, 09/11/2017 - 10:57
Abstract Campylobacter jejuni, the most frequent cause of food-borne bacterial gastroenteritis worldwide, is a microaerophile that has to survive high environmental oxygen tensions, adapt to oxygen limitation in the intestine and resist host oxidative attack. Here, oxygen-dependent changes in C. jejuni physiology were studied at constant growth rate using carbon (serine)-limited continuous...
Tue, 08/15/2017 - 07:15
Summary Clostridium botulinum produces the most potent natural toxin, the botulinum neurotoxin (BoNT), probably to create anaerobiosis and nutrients by killing the host, and forms endospores that facilitate survival in harsh conditions and transmission. Peak BoNT production coincides with initiation of sporulation in C. botulinum cultures, which suggests common regulation. Here we show that Spo0A...
Fri, 07/28/2017 - 07:27
SUMMARY Vibrio cholerae is a natural resident of the aquatic environment, where a common nutrient is the chitinous exoskeletons of microscopic crustaceans. Chitin utilization requires chitinases, which degrade this insoluble polymer into soluble chitin oligosaccharides. These oligosaccharides also serve as an inducing cue for natural transformation in Vibrio species. There are 7 predicted...
Fri, 07/28/2017 - 07:23
Summary Zoonotic thermophilic Campylobacter and nontyphoidal Salmonella enterica are a major cause of foodborne human gastroenteritis worldwide. There is little information about reservoirs of these zoonotic agents in Africa. Thus, chicks of kelp gulls (Larus dominicanus, n=129) and greater crested terns (Thalasseus bergii, n=100) were studied at five colonies on the Western Cape coast (South...
Fri, 07/28/2017 - 07:21
Abstract In children from developing countries 5 to 10 per cent of acute diarrhea (AD) episodes develop into persistent diarrhea (PD) defined by > 14 days of diarrhea duration. PD represents a major health burden leading to growth faltering. It is also associated with half of all diarrhea mortality. A rational intervention is thus crucial, but depends on an understanding of the pathogenesis of...
Tue, 06/20/2017 - 00:10
Abstract Indirect readout mechanisms of transcription control rely on the recognition of DNA shape by transcription factors (TFs). TFs may also employ a direct readout mechanism that involves the reading of the base sequence in the DNA major groove at the binding site. TFs with winged helix-turn-helix (wHTH) motifs use an alpha helix to read the base sequence in the major groove while inserting a...
Fri, 01/27/2017 - 03:31
Abstract Shiga toxin producing Escherichia coli O157:H7 (STEC O157) is naturally found in the gastrointestinal tract of cattle and can cause severe disease in humans. There is limited understanding of the population dynamics and microevolution of STEC O157 at herd level. In this study, isolates from a closed beef herd of 23 cows were used to examine the population turnover in the herd. Of the...
Sat, 01/07/2017 - 03:30
Abstract Horizontal gene transfer can precipitate rapid evolutionary change. In 2010 the global pandemic of kiwifruit canker disease caused by Pseudomonas syringae pv. actinidiae (Psa) reached New Zealand. At the time of introduction, the single clone responsible for the outbreak was sensitive to copper, however, analysis of a sample of isolates taken in 2015 and 2016 showed that a quarter were...
Sat, 12/10/2016 - 18:00
SUMMARY Enterotoxigenic Escherichia coli produces a long type 4 pilus called Longus. The regulatory elements and the environmental signals controlling the expression of Longus-encoding genes are unknown. We identified two genes lngR and lngS in the Longus operon, whose predicted products share homology with transcriptional regulators. Isogenic lngR and lngS mutants were considerably affected in...
Thu, 11/24/2016 - 10:25
Abstract Campylobacter jejuni is a major cause of bacterial gastroenteritis worldwide, primarily associated with the consumption of contaminated poultry. C. jejuni lineages vary in host range and prevalence in human infection, suggesting differences in survival throughout the poultry processing chain. From 7,343 MLST-characterised isolates, we sequenced 600 C. jejuni and C. coli isolates from...
Mon, 11/21/2016 - 18:25
Summary Mucosa-associated microbial populations of the gastrointestinal tract are in intimate contact with the outer mucus layer. This proximity offers these populations a higher potential, than lumenal microbiota, in exerting effects on the host. Functional characteristics of the microbiota and influences of host- physiology shape the composition and activity of the mucosa-associated bacterial...
Mon, 11/21/2016 - 18:25
Summary Wide-spread abundance in soil and water, coupled with high toxicity have put arsenic at the top of the list of environmental contaminants. Early studies demonstrated that both concentration and the valence state of inorganic arsenic (arsenite, As(III) vs. arsenate As(V)) can be modulated by microbes. Using genetics, transcriptomic and proteomic techniques, microbe-arsenic detoxification,...
Mon, 11/21/2016 - 18:25
Coastal marine Vibrio cholerae populations usually exhibit high genetic diversity. To assess the genetic diversity of abundant V. cholerae non-O1/non-O139 populations in the Central European lake Neusiedler See we performed a phylogenetic analysis based on recA, toxR, gyrB and pyrH loci sequenced for 472 strains. The strains were isolated from three ecologically different habitats in a lake that...
Mon, 11/21/2016 - 18:15
Summary Water availability acts as the most-stringent constraint for life on Earth. Thus, understanding the water relations of microbial extremophiles is imperative to our ability to increase agricultural productivity (e.g., by enhancing the processing and turnover of dead organic matter in soils of arid regions); reduce human exposure to mycotoxins in buildings and our food-supply chain; prevent...
Mon, 10/03/2016 - 05:16
Abstract Pathogens embedded in biofilms are involved in many infections and are very difficult to treat with antibiotics because of higher resistance compared to planktonic cells. Therefore, new approaches for their control are urgently needed. One way to search for biofilm dispersing compounds is to look at defense strategies of organisms exposed to wet environments, which makes them prone to...
Wed, 08/03/2016 - 04:11
Abstract Toxic dinoflagellates pose serious threats to human health and to fisheries. The genus Gambierdiscus is significant in this respect because its members produce ciguatoxin that accumulates in predominantly tropical marine food webs and leads to ciguatera fish poisoning. Understanding the biology of toxic dinoflagellates is crucial to developing control strategies. To this end, we...
Mon, 06/27/2016 - 14:20
In this study, we aimed to analyze the global response to iron in the broad-range host pathogen Vibrio vulnificus under the hypothesis that iron is one of the main signals triggering survival mechanisms both inside and outside its hosts. To this end, we selected a strain from the main zoonotic clonal-complex, obtained a mutant in the ferric-uptakeregulator (Fur), and analyzed their...
Mon, 06/20/2016 - 11:50
Summary The opportunistic pathogen Pseudomonas aeruginosa controls the production of virulence factors by quorum sensing (QS). Besides cell density, QS in P. aeruginosa is co-regulated by metabolic influences, especially nutrient limitation. Previously, a co-culture model system was established consisting of P. aeruginosa and the chitinolytic bacterium Aeromonas hydrophila, in which parasitic...
Mon, 03/21/2016 - 11:36
Abstract Vibrio species naturally reside in the aquatic environment and a major metabolite in this habitat is the chitinous exoskeletons of crustacean zooplankton. In addition to serving as a nutrient, chitin-derived oligosaccharides also induce natural genetic competence in many Vibrio spp., a physiological state in which bacteria take up DNA from the extracellular environment and can integrate...
Tue, 03/08/2016 - 18:00
SUMMARY Talaromyces islandicus (“Penicillium islandicum”) is a widespread foodborne mold that produces numerous secondary metabolites, among them potent mycotoxins belonging to different chemical classes. A notable metabolite is the hepatotoxic and carcinogenic pentapeptide cyclochlorotine that contains the unusual amino acids β-phenylalanine, 2-aminobutyric acid and 3,4-dichloroproline. Although...
Tue, 02/23/2016 - 14:31
Abstract Fresh produce contaminated with human pathogens raises vital and ecological questions about bacterial survival strategies. Such occurrence was basil harboring Salmonella enterica serovar Senftenberg that caused an outbreak in 2007. This host was unanticipated due to its production of antibacterial substances, including linalool. We show that linalool perforates bacterial membranes,...
Tue, 02/23/2016 - 14:29
Summary Major concern in the Mixed Crop-Livestock (MCL) farms, in which livestock and vegetables grown closely in the same facility, is cross-contamination of zoonotic bacterial pathogens especially Salmonella. To investigate the distribution of Salmonella serovars in MCL and their products, a total of 1,287 pre-harvest samples from various farms and 1,377 post-harvest samples from retail...
Wed, 01/27/2016 - 03:41
Summary The potential negative impact for human health of veterinary use of antimicrobials in prophylaxis, metaphylaxis and growth promotion in animal husbandry was first established in the 1960s and 1970s. Determination of the molecular structure of antimicrobial resistance plasmids at that time explained the ability of antimicrobial resistance genes to disseminate among bacterial populations...
Fri, 01/15/2016 - 03:02
Abstract Microbial pollution of the marine environment through land-sea transfer of human and livestock pathogens is of concern. Salmonella was isolated from rectal swabs of free-ranging and stranded grey seal pups (21.1%; 37/175) and compared to strains from the same serovars isolated from human clinical cases, livestock, wild mammals and birds in Scotland, UK to characterise possible...
Wed, 12/02/2015 - 05:07
Summary Enteropathogenic Yersinia enterocolitica is able to grow within or outside the mammalian host. Previous transcriptomic studies have indicated that the regulator OmpR plays a role in the expression of hundreds of genes in enterobacteria. Here, we have examined the impact of OmpR on the production of Y. enterocolitica membrane proteins upon changes in temperature, osmolarity and pH....
Mon, 11/02/2015 - 02:47
Summary Enterotoxigenic Escherichia coli (ETEC) is a water and food borne pathogen that infects the small intestine of the human gut and causes diarrhea. ETEC adheres to the epithelium by means of colonization factors and secretes two enterotoxins, the heat labile toxin (LT) and/or the heat stable toxin (ST) that both de-regulate ion channels and cause secretory diarrhea. ETEC, as all E. coli, is...
Fri, 10/16/2015 - 05:11
Summary Campylobacter jejuni, the leading cause of human bacterial gastroenteritis, requires low environmental oxygen and high carbon dioxide for optimum growth, but the molecular basis for the carbon dioxide requirement is unclear. One factor may be inefficient conversion of gaseous CO2 to bicarbonate, the required substrate of various carboxylases. Two putative carbonic anhydrases (CA's) are...
Tue, 10/06/2015 - 09:53
Summary Bacteria employ bacteriocins for interference competition in microbial ecosystems. Colicin Ib (ColIb), a pore-forming bacteriocin, confers a significant fitness benefit to Salmonella enterica serovar Typhimurium (S. Tm) in competition against commensal E. coli in the gut. ColIb is released from S. Tm into the environment, where it kills susceptible competitors. However, colicin-specific...

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