Genus Vibrio Research Articles

Understanding the risks of co-exposures in a changing world: a case study of dual monitoring of the biotoxin domoic acid and Vibrio spp. in Pacific oyster.

Assessing the co-occurrence of multiple health risk factors in coastal ecosystems is challenging due to the complexity of multi-factor interactions and limited availability of simultaneously collected data. Understanding co-occurrence is particularly important for risk factors that may be associated with, or occur in similar environmental conditions. In marine ecosystems, the co-occurrence of harmful algal bloom toxins and bacterial pathogens within the genus Vibrio may impact both ecosystem and human health. This study examined the co-occurrence of Vibrio spp. and domoic acid (DA) produced by the harmful algae Pseudo-nitzschia by (1) analyzing existing California Department of Public Health monitoring data for V. parahaemolyticus and DA in oysters; and (2) conducting a 1-year seasonal monitoring of these risk factors across two Southern California embayments. Existing public health monitoring efforts in the state were robust for individual risk factors; however, it was difficult to evaluate the co-occurrence of these risk factors in oysters due to low number of co-monitoring instances between 2015 and 2020. Seasonal co-monitoring of DA and Vibrio spp. (V. vulnificus or V. parahaemolyticus) at two embayments revealed the co-occurrence of these health risk factors in 35% of sampled oysters in most seasons. Interestingly, both the overall detection frequency and co-occurrence of these risk factors were considerably less frequent in water samples. These findings may in part suggest the slow depuration of Vibrio spp. and DA in oysters as residual levels may be retained. This study expanded our understanding of the simultaneous presence of DA and Vibrio spp. in bivalves and demonstrates the feasibility of co-monitoring different risk factors from the same sample. Individual programs monitoring for different risk factors from the same sample matrix may consider combining efforts to reduce cost, streamline the process, and better understand the prevalence of co-occurring health risk factors.

Multidrug resistant Vibrio spp. identified from mussels farmed for human consumption in Central Italy.

This study investigated phenotypic and genotypic antimicrobial resistance profiles of Vibrio strains identified from Mytilus galloprovincialis farmed for human consumption in the Adriatic Sea Central Italy. A total of 475 mussels (M. galloprovincialis) were involved in the present study, and culture-dependent microbiological methods permitted to identify a total of 50 Vibrio strains that were tested for antibiotic susceptibility followed by the genetic determinant detections. Antibiograms showed resistance against ampicillin (36.0%), amoxicillin-clavulanic acid (30.0%), gentamycin (14.0%), and imipenem (18.0%). Biomolecular assays amplified a total of 264 antibiotic resistance genes harbored by both susceptible and resistant Vibrio species. Among resistance genes, aacC2 (62.0%) and aadA (58.0%) for aminoglycosides, blaTEM (54.0%) for beta-lactams, qnrS (24.0%) for quinolones, tetD (66.0%) for tetracyclines, and vanB (60.0%) for glycopeptides were mainly amplified by PCR assays. Vibrio genus is involved in the antibiotic resistance phenomenon diffusion in the aquatic environments, as demonstrated by the harboring of many genetic determinants representing a kind of genetic "dark world".

Phylogenomic analysis of the Ponticus clade: strains isolated from the spotted rose snapper (Lutjanus guttatus).

The family Vibrionaceae is classified into many clades based on their phylogenetic relationships. The Ponticus clade is one of its clades and consists of four species, Vibrio panuliri, V. ponticus, V. rhodolitus, and V. taketomensis. Two strains, CAIM 703 and CAIM 1902, were isolated from the diseased spotted rose snapper external lesion (Lutjanus guttatus), they were analyzed to determine their taxonomic position, a phylogenetic analysis was performed based on the 16S rRNA sequences proved that the two strains are members of the genus Vibrio and they belong to the Ponticus clade. Then, a phylogenomic analysis was performed with four type strains and four reference strains isolated from marine organisms and aquatic environments. Multilocus Sequence Analysis (MLSA) of 139 single-copy genes showed that CAIM 703 and CAIM 1902 belong to V. panuliri. The 16S rRNA sequence similarity value between CAIM 703 and CAIM 1902 was 99.61%. The Ponticus clade species showed Average Nucleotide Identity (ANI) values between 78 to 80% against the two strains for ANIb, except V. panuliri LBS2T (99% and 100% similarity). Finally, this analysis represents the first phylogenomic analysis of the Ponticus clade where V. panuliri strains are reported from Mexico.

Vibrio misgurnus sp. nov., a new pathogen of cultured loach (Misgurnus anguillicaudatus), closely related to Vibrio cholerae

An epidemic with petechial hemorrhages on the body surface recently occurred in the farmed loach (Misgurnus anguillicaudatus) in Sichuan province. Multiple antibiotic treatments were ineffective against this epidemic. This study aims to elucidate the cause of the disease. Two bacterial strains, GVCT and VCS were isolated from diseased loach. Experimental infections with these two isolates resulted in marked symptoms in the loach consistent with those observed in natural outbreaks. The taxonomic status was determined by phenotypic assay, chemotaxonomic and whole genome analysis. Strain GVCT exhibited unique phenotypic characteristics, including its β-glucosidase activity and inability to utilize casein and starch, which distinguished it from Vibrio cholerae ATCC14035T. Paired 16S rRNA gene sequence analysis confirmed that strains GVCT and VCS belong to the genus Vibrio. The primary fatty acids of strain GVCT are C16:0, summed Feature 3 (C16:1ω7c/C16:1ω6c), and summed Feature 8 (C18:1 ω6c/C18:1 ω7c), and the major respiratory quinone is Q-8. The predominant lipids were phosphatidylethanolamine (PE), phosphatidylglycerol (PG), aminophospholipids (APL) and an unidentified phosphoglycolipid designated PL1. Strains GVCT and VCS have genome sizes of 3.2 Mb and 3.3 Mb, as well as GC contents of 47.0 and 47.2 mol% respectively. Phylogenomic and whole-genome nucleotide sequence analyses further confirmed that these isolates represent a novel species of the genus Vibrio, for which the name Vibrio misgurnus sp. nov. is proposed, with strain GVCT as the type strain. Strain GVCT was found to be highly pathogenic to loach, causing high mortality and posing a threat to loach aquaculture, with a half-lethal dose (LD50) of strain GVCT for loach is 8.96 × 106 CFU/mL, and it was resistant to drugs such as enrofloxacin, doxycycline hydrochloride, flumequine, neomycin sulphate and florfenicol.

Alteration of shoaling behavior and dysbiosis in the gut of medaka (Oryzias latipes) exposed to 2-μm polystyrene microplastics

There is global concern that microplastics may harm aquatic life. Here, we examined the effects of fine polystyrene microplastics (PS-MPs, 2-μm diameter, 0.1 mg/L, 2.5 × 107 particles/L) on the behavior and the microbiome (linked to brain–gut interaction) of a fish model using medaka, Oryzias latipes. We found that shoaling behavior was reduced in PS-MP-exposed medaka compared with control fish during the exposure period, but it recovered during a depuration period. There was no difference in swimming speed between the PS-MP-exposed and control groups during the exposure period. Analysis of the dominant bacterial population (those comprising ≥1% of the total bacterial population) in the gut of fish showed that exposure to PS-MPs tended to increase the relative abundance of the phylum Fusobacteria and the genus Vibrio. Furthermore, structural-equation modeling of gut bacteria on the basis of machine-learning data estimated strong relationship involved in the reduction of the functional bacterial species of minority (<1% of the total bacterial population) such as the genera Muribaculum (an undefined role), Aquaspirillum (a candidate for nitrate metabolism and magnetotactics), and Clostridium and Phascolarctobacterium (potential producers of short-chain fatty acids, influencing behavior by affecting levels of neurotransmitters) as a group of gut bacteria in association with PS-MP exposure. Our results suggest that fish exposure to fine microplastics may cause dysbiosis and ultimately cause social behavior disorders linked to brain–gut interactions. This effect could be connected to reduction of fish fitness in the ecosystem and reduced fish survival.

Temporal dynamics of bacterial populations in recirculating aquaculture systems for sea urchin production

Introduction: Sea urchin aquaculture is a rising industry, and in consequence, there is a need to establish optimal culture parameters to ensure the health of the cultured animals.&#x0D; Objective: To evaluate the bacterial counts in the seawater of sea urchin (Arbacia dufresnii) aquaculture recirculating systems (RAS).&#x0D; Methods: The bacteriological water quality of two RAS containing sea urchins was determined. For approximately two months, weekly water samples were taken. The bacteriological quality was determined by counting total aerobic heterotrophic populations, lactic acid bacteria, enterobacterias and genus Vibrio. Physicochemical parameters were also measured.&#x0D; Results: There was no presence of disease or mortality. Enterobacteria and lactic acid bacteria were not detected from both RAS systems. The number of animals had an important effect on the observed difference in the count of total bacteria and Vibrio spp. In RAS 1 the maximum counts of total bacteria and Vibrio spp. were 2.8 x 105 ± 1.7 x 105 and 1.45 x 105 ± 3.6 x 104 UFC ml-1, respectively. In RAS 2 total bacteria and Vibrio spp. exhibited repetitive behavior over time influenced in part by water exchange and mainly by feeding. The results indicate that periodic water changes ensure a limited growth of bacterial strains as Vibrio and other bacteria.&#x0D; Conclusions: Our results suggests that the bacterial count levels recorded in this study can be used as a threshold or safety limit for Arbacia dufresnii aquaculture.

Phytochemical analysis and antibacterial activity of palm waste extract against Vibrio harveyi and Vibrio parahaemolyticus.

Vibrio harveyi and Vibrio parahaemolyticus are species of the Vibrio genus that often cause disease and mass mortality in crustaceans. If not handled quickly and appropriately, these diseases can cause considerable losses to farmers. Therefore, it is necessary to find a solution with safe and environmentally friendly disease prevention technology using natural ingredients, among others from plants, namely oil palm. Some parts of oil palm, namely leaves, fronds, fibres and oil palm pulp, which are palm waste, contain antibacterial compounds. This study aimed to assess the antibacterial activity of palm waste extracts, namely pulp, leaves, fronds and fibres using n-hexane, ethyl acetate, chloroform, ethanol and water maceration solvents against pathogenic bacteria V. harveyi and V. parahaemolyticus, and identify active compounds contained in palm waste. The results of the research are expected to produce innovative and sustainable solutions to control diseases in shrimp farming, contribute to the development of a sustainable fishing industry and open up the potential for utilizing palm waste as a value-added resource in the field of aquatic health. The results of observations on antibacterial activity tests and identifying the content of palm waste extract compounds were analysed descriptively displayed in the form of figures, tables and graphs. The results showed that palm waste extracts (pulp, leaves, fronds and fibres) with ethyl acetate and ethanol maceration solvents had very strong antibacterial potential, namely 20.14 ± 0.31 mm-25.52 ± 1.42 mm on V. harveyi bacteria and 20.41 ± 0.55 mm-25.00 ± 0.51 mm on V. parahaemolyticus bacteria. Palm extracts with n-hexane (>20 mm) and chloroform solvents generally have strong category antibacterial potential (10-20 mm), and palm extracts in water solvents have medium category potential (5-10 mm) against V. harveyi and V. parahemolyticus bacteria. The results of phytochemical tests on palm waste extracts with ethyl acetate and ethanol maceration solvents contain bioactive compounds of flavonoids, saponins, polyphenols and alkaloid tannins, steroids and triterpenoids. Palm extracts with n-hexane and chloroform solvents generally contain saponins, alkaloids, steroids and triterpenoids, while palm waste extracts with water solvents contain saponins.

Increased abundance of potentially pathogenic Vibrio and a marine heatwave co-occur with a Pacific Oyster summer mortality event

The Pacific Oyster (Crassostrea gigas) is an important aquaculture species, that has been globally affected by “summer mortality” outbreaks. The causes of summer mortality are often unclear, but several contributing factors have been implicated. To better understand the factors contributing to C. gigas summer mortality, we performed a 24 week experiment in tanks filled by a continuous flow of unfiltered surface seawater during a summer mortality high-risk period. Throughout this period, we measured a suite of environmental parameters, with weekly sampling to characterise the bacterial community composition, the abundance and diversity of the Vibrio genus, and the expression of oyster immune response genes. We observed three clear phases of oyster mortality: Phase 1 (day 0 to 75) was characterised by sporadic and low levels (mean < 1% per week) of oyster mortality; Phase 2 (day 82 to 119) involved constant levels of ongoing mortality (mean < 10% per week); and Phase 3 (day 125 to 161) involved a sharp increase in mortality (mean > 10% per week) reaching up to weekly mortality of 51%. The shift between phase 2 and 3 coincided with heavy rainfall and a marine heatwave (MHW) event at our study site, which lasted 13 days, when the average water temperature was elevated by 0.8 °C when compared to the weeks prior and following the MHW, and a maximum water temperature of 27.7 °C was reached. Oyster mortality was positively correlated with the occurrence of the MHW as well as bacterial and Vibrio abundance, and negatively correlated with seawater salinity that decreased from a salinity of 34.6 to 31.4 psu following rainfall events. In addition, the relative abundance of several Vibrio species, including V. campbellii, V. rotiferianus and V. owensii displayed positive correlations to oyster mortality. Shifts in the oyster-associated bacterial community and oyster immunity gene expression profiles occurred in parallel to increased mortality levels, with genes involved in the regulation of antimicrobial peptides (IkB1 and NF-kB p105) significantly over-expressed during high mortality. Overall, we observed a C. gigas mortality event that coincided with a marine heatwave, rainfall event and a shift in bacterial community composition. Our analyses provides further evidence for the putative role of Vibrio in summer mortality events.

Diversity of Culturable Bacteria from the Coral Reef Areas in the South China Sea and Their Agar-Degrading Abilities.

The South China Sea (SCS) is abundant in marine microbial resources with high primary productivity, which is crucial for sustaining the coral reef ecosystem and the carbon cycle. Currently, research on the diversity of culturable bacteria in the SCS is relatively extensive, yet the culturable bacteria in coral reefs has been poorly understood. In this study, we analyzed the bacterial community structure of seawater samples among Daya Bay (Fujian Province), Qionghai (Hainan Province), Xisha Islands, and the southern South China Sea based on culturable methods and detected their abilities for agar degradation. There were 441 bacterial strains, belonging to three phyla, five classes, 43 genera, and 101 species, which were isolated by marine agar 2216E (MA; Becton Dickinson). Strains within Gammaproteobacteria were the dominant group, accounting for 89.6% of the total bacterial isolates. To investigate vibrios, which usually correlated with coral health, 348 isolates were obtained from TCBS agar, and all isolates were identified into three phylum, three classes, 14 orders, 25 families, and 48 genera. Strains belonging to the genus Vibrio had the greatest number (294 strains), indicating the high selectivity of TCBS agar for vibrios. Furthermore, nineteen strains were identified as potentially novel species according to the low 16S rRNA gene similarity (<98.65%), and 28 strains (15 species) had agar-degrading ability. These results indicate a high diversity of culturable bacteria in the SCS and a huge possibility to find novel and agar-degrading species. Our study provides valuable microbial resources to maintain the stability of coral ecosystems and investigate their roles in the marine carbon cycle.

Genetic Insights into Biofilm Formation by a Pathogenic Strain of Vibrio harveyi.

The Vibrio genus includes bacteria widely distributed in aquatic habitats and the infections caused by these bacteria can affect a wide range of hosts. They are able to adhere to numerous surfaces, which can result in biofilm formation that helps maintain them in the environment. The involvement of the biofilm lifestyle in the virulence of Vibrio pathogens of aquatic organisms remains to be investigated. Vibrio harveyi ORM4 is a pathogen responsible for an outbreak in European abalone Haliotis tuberculata populations. In the present study, we used a dynamic biofilm culture technique coupled with laser scanning microscopy to characterize the biofilm formed by V. harveyi ORM4. We furthermore used RNA-seq analysis to examine the global changes in gene expression in biofilm cells compared to planktonic bacteria, and to identify biofilm- and virulence-related genes showing altered expression. A total of 1565 genes were differentially expressed, including genes associated with motility, polysaccharide synthesis, and quorum sensing. The up-regulation of 18 genes associated with the synthesis of the type III secretion system suggests that this virulence factor is induced in V. harveyi ORM4 biofilms, providing indirect evidence of a relationship between biofilm and virulence.

Segmental variations in intestinal microbiota composition and functional capacity along the digestive tract of Litopenaeus vannamei

Litopenaeus vannamei represents the most cultivated crustacean species, accounting for approximately 80% of global shrimp aquaculture output. The intestinal microbiota structure and functionality are known to critically influence L. vannamei growth. While previous investigations of shrimp gut microbes emphasized the whole intestine, limited research has examined the composition and functional differences of microbiota across specific intestinal sections in L. vannamei. In this study, healthy shrimp samples were collected and divided into four sections after removing the contents: S(stomach), H (from posterior stomach to the distal end of the hepatopancreas.), G (the section from hepatopancreas’s end to the sixth abdominal segment), and R(rectum). The microbial composition and function were analyzed across locations via 16 S rRNA high-throughput sequencing. The results revealed that significant α- and β-diversity distinctions existed between sections (p < 0.05). Microbial abundance and diversity were enriched within group G and H compared to group S and R. The result of PCoA analysis revealed similarities between group S, H, and G, while group R markedly differed (p < 0.05). Three dominant phyla were identified across sections - Firmicutes (enriched in group S and H), Bacteroidota (enriched in group G) and Proteobacteria (enriched in group R). At genus level, Bacillus, Flavobacterium, Vibrio, and Mycoplasmataceae predominated (>10%) across sections. The rectum pathways including carbon, nitrogen, sulfur metabolisms were significantly elevated. Quorum sensing and two-component systems were also overrepresented in rectum. One-way network analysis showed that the dominant microbiota of group S, H and G were Bacillus, Mycoplasmataceae, and Flavobacterium, which are promoters of beneficial bacteria in the gut, while the dominant flora of rectumthe most competitive genus of bacteria in the intestinal tract was Vibrio,and Pseudofulvibacter, Alcaligenaceae, and Pseudomonas represent potential probiotic genera that could be screened as antagonists against Vibrio in the shrimp gut. In summary, we hypothesize the stomach and H sections degraded organic matter, G section absorbed and digested macronutrients, and rectum section recycled materials and participated in circular metabolism. These segment-specific analyses provide novel perspectives into section-specific microbial interactions and functions along L. vannamei intestine.

Predominant heterotrophic diazotrophic bacteria are involved in Sargassum proliferation in the Great Atlantic Sargassum Belt.

Since 2011, the Caribbean coasts have been subject to episodic influxes of floating Sargassum seaweed of unprecedented magnitude originating from a new area "the Great Atlantic Sargassum Belt" (GASB), leading in episodic influxes and mass strandings of floating Sargassum. For the biofilm of both holopelagic and benthic Sargassum as well as in the surrounding waters, we characterized the main functional groups involved in the microbial nitrogen cycle. The abundance of genes representing nitrogen fixation (nifH), nitrification (amoA), and denitrification (nosZ) showed the predominance of diazotrophs, particularly within the GASB and the Sargasso Sea. In both location, the biofilm associated with holopelagic Sargassum harboured a more abundant proportion of diazotrophs than the surrounding water. The mean δ15N value of the GASB seaweed was very negative (-2.04‰), and lower than previously reported, reinforcing the hypothesis that the source of nitrogen comes from the nitrogen-fixing activity of diazotrophs within this new area of proliferation. Analysis of the diversity of diazotrophic communities revealed for the first time the predominance of heterotrophic diazotrophic bacteria belonging to the phylum Proteobacteria in holopelagic Sargassum biofilms. The nifH sequences belonging to Vibrio genus (Gammaproteobacteria) and Filomicrobium sp. (Alphaproteobacteria) were the most abundant and reached, respectively, up to 46.0% and 33.2% of the community. We highlighted the atmospheric origin of the nitrogen used during the growth of holopelagic Sargassum within the GASB and a contribution of heterotrophic nitrogen-fixing bacteria to a part of the Sargassum proliferation.

Effects of a phytobiotic-based additive on the growth, hepatopancreas health, intestinal microbiota, and Vibrio parahaemolyticus resistance of Pacific white shrimp, Litopenaeus vannamei.

Vibrio genus is a common pathogen in aquaculture and causes acute hepatopancreatic necrosis disease (AHPND) and massive mortality of shrimp. Many studies have suggested that a single functional ingredient such as plant extract or organic acid can reduce the dependence on antibiotics and promote the growth and immunity of aquatic animals. In this study, we evaluated the effects of a phytobiotic-based compound additive (Sanacore® GM, SNGM), which had a successful trajectory of commercial application in fish farming. However, its effects on the hepatopancreas health and intestinal microbiota of shrimp after Vibrio challenge have not been well evaluated. In the present study, Pacific white shrimp were fed diets with or without supplementation of SNGM, and the SNGM grades were 0-g/kg (CON), 3-g/kg (SNGM3), and 5-g/kg (SNGM5) diets. The feed trial lasted 60 days, after which a Vibrio parahaemolyticus challenge was performed. The results showed that compared to the CON group, both the SNGM3 and SNGM5 groups had a significantly higher weight gain and a lower feed conversion ratio as well as higher survival after Vibrio parahaemolyticus challenge. In the growth trial, the SNGM3 group had a significantly increased total protein, albumin concentration, and acid phosphatase activity in hemolymph compared to the CON group. In the challenge experiment, the SNGM3 and SNGM5 groups had increased albumin and glucose contents as well as the activities of phenoloxidase, lysozyme, alkaline phosphatase, and superoxide dismutase in hemolymph. Both the SNGM3 and SNGM5 groups had improved morphology of the hepatopancreas and intestine. The SNGM5 group had alleviated gut microbiota dysbiosis induced by Vibrio infection by increasing the potential probiotic bacterium abundance (Shewanella) and decreasing the potential pathogenic bacteria abundance (Vibrio, Photobacteriuma, Pseudoalteromonas, and Candidatus_Bacilloplasma). In conclusion, the dietary phytobiotic-based additive at 3-g/kg level increased the growth and Vibrio parahaemolyticus resistance of Pacific white shrimp by promoting immune-related enzyme activities and improving the morphological structure of the hepatopancreas and intestine and the intestinal microbiota composition.

Prospection of strains of Bacillus sporogenes in the digestive tract of native crustaceans and characterization of the probiotic potential.

The cultivation of marine shrimp is one of the fastest growing activities in the world. However, the emergence of diseases has resulted in a decrease in production and losses for the sector. Probiotics emerged as an option to the use of antibiotics to control these pathogens. The efficiency of applying this technology depends on the characteristics of the bacterial agents and their bioavailability in the shrimp intestine. The objective is to evaluate the viability and efficiency of bacteria isolated from the digestive tract of healthy crustaceans as probiotic agents in the cultivation of shrimp Litopenaeus vannamei. Eighteen strains of the genus Bacillus belonging to the following species were tested: Bacillus sp., B. cereus, B. thuringiensis, B. circulans, B. megaterium, B. subtilis and B. agaridevorans. Bacterial isolates were subjected to characterization as potential probiotics. The test results were considered satisfactory; thus, the tested strains have potential for use as probiotics in shrimp culture. Treatments that used of the genus Bacillus had reduced growth of the genus Vibrio after infection, both in the intestinal contents and in the intestine. With the results obtained, it can be suggested that further research be carried out on the probiotic potential of Bacillus sp.

Investigation of potentially pathogenic Vibrionaceae in Saint-Louis city, Senegal.

as cholera, due to toxigenic bacteria Vibrio cholera (serogroups O1 and O139), is a major public health threat in Africa, the aim of this work was to investigate potentially pathogenic Vibrionaceae bacteria firstly from human stool samples, and secondly from various environmental water points of Saint-Louis city in Senegal. a hospital-based study was conducted between 2013 and 2015. Stool samples were taken and cultured from daily incoming patients or hospitalized for acute diarrhea at Saint-Louis´ regional hospital. For environment, a monthly longitudinal sampling from January to October 2016 was carried out at 10 sites in the city. We used total DNA extracted from APW (alkaline peptone water) broth solutions and on suspect bacterial colonies to run PCR Multiplex targeting specific DNA fragments to detect Vibrio genus and specific species. In case of positivity, a simplex PCR was performed to test for cholera toxins Ctx, and V. parahaemolyticus TRH and TDH. for 43 patients screened, bacterial culture was positive in 6% of cases but no strain of V. cholerae or other Vibrio sp. was isolated. PCR on 90 APW solutions were positive for Vibrio sp.(n = 43), V. cholera(n = 27), V. mimicus(n = 16), V. parahaemolyticus(8), V. alginolyticus(n = 4), and V. vulnificus(n = 2). Unlike for those on suspected colonies which were positive for a majority of V. parahaemolyticus (n = 40) and V. cholerae non-O1 / O139 (n = 35). Six strains of V. parahaemolyticus carried TRH gene, 3 of which expressed simultaneously virulence TRH and TDH genes. For physicochemical parameters, all temperatures varied similarly according to a unimodal seasonality, as well as salinity. despite the presence of natural populations of Vibrionaceae, even toxigenic ones, was noted in water environment, along with favorable habitat conditions that could play a role in transmission of Vibriosis in the Saint Louis population, we did not isolate any of them from patients screened at the hospital.

Impact of epizootics on mussel farms: Insights into microbiota composition of Mytilus species

Outbreaks of marine mussel mortality on French farms could have different aetiologies. One of them implies Vibrio splendidus strains. Beyond the involvement of this pathogen, there is considerable evidence that diseases often result from interactions between several microbes and the host. In this study, we explored the bacterial communities associated with mussel species and the surrounding water collected from a mussel farm affected by mortalities. The microbiota of Mytilus edulis, Mytilus galloprovincialis and their hybrids displayed an abnormal abundance of Proteobacteria, in particular the genera Vibrio, Cobetia and Arcobacter. Despite the dysbiosis, the Mediterranean mussel showed a different microbiota profile with a higher richness and presence of the phylum Bacteroidetes. Bipartite network analyses at the level of bacteria families confirmed this finding and showed that the microbiomes of M. edulis and the hybrids tended to cluster together. In addition, injection of mussels with the virulent V. splendidus induced less mortality rate in M. galloprovincialis compared to the other Mytilus sp. suggesting a better resistance of the Mediterranean mussel to infection. Our findings point to a probable aetiology of pathobiome-mediated disease in mussels. To fully understand this phenomenon, more knowledge is needed on the roles of pathobiotic systems and their development during disease establishment.

Gut Bacteriomes and Ecological Niche Divergence: An Example of Two Cryptic Gastropod Species.

Symbiotic microorganisms may provide their hosts with abilities critical to their occupation of microhabitats. Gut (intestinal) bacterial communities aid animals to digest substrates that are either innutritious or toxic, as well as support their development and physiology. The role of microbial communities associated with sibling species in the hosts' adaptation remains largely unexplored. In this study, we examined the composition and plasticity of the bacteriomes in two sibling intertidal gastropod species, Littorina fabalis and L. obtusata, which are sympatric but differ in microhabitats. We applied 16S rRNA gene metabarcoding and shotgun sequencing to describe associated microbial communities and their spatial and temporal variation. A significant drop in the intestinal bacteriome diversity was revealed during the cold season, which may reflect temperature-related metabolic shifts and changes in snail behavior. Importantly, there were significant interspecies differences in the gut bacteriome composition in summer but not in autumn. The genera Vibrio, Aliivibrio, Moritella and Planktotalea were found to be predominantly associated with L. fabalis, while Granulosicoccus, Octadecabacter, Colwellia, Pseudomonas, Pseudoalteromonas and Maribacter were found to be mostly associated with L. obtusata. Based on these preferential associations, we analyzed the metabolic pathways' enrichment. We hypothesized that the L. obtusata gut bacteriome contributes to decomposing algae and detoxifying polyphenols produced by fucoids. Thus, differences in the sets of associated bacteria may equip their closely phylogenetically related hosts with a unique ability to occupy specific micro-niches.

Design of a multi-epitope vaccine (vme-VAC/MST-1) against cholera and vibriosis based on reverse vaccinology and immunoinformatics approaches

Vibriosis and cholera are serious diseases distributed worldwide and caused by six marine bacteria of the Vibrio genus. Thousands of deaths occur each year due to these illnesses, necessitating the development of new preventive measures. Presently, the existing cholera vaccine demonstrates an effectiveness of approximately 60%. Here we describe a new multi-epitope vaccine, ‘vme-VAC/MST-1’ based on vaccine targets identified by reverse vaccinology and epitopes predicted by immunoinformatics, two currently effective tools for predicting new vaccines for bacterial pathogens. The vaccine was designed to combat vibriosis and cholera by incorporating epitopes predicted for CTL, HTL, and B cells. These epitopes were identified from six vaccine targets revealed through subtractive genomics, combined with reverse vaccinology, and were further filtered using immunoinformatics approaches based on their predicted immunogenicity. To construct the vaccine, 28 epitopes (24 CTL/B and 4 HTL/B) were linked to the sequence of the cholera toxin B subunit adjuvant. In silico analyses indicate that the resulting immunogen is stable, soluble, non-toxic, and non-allergenic. Furthermore, it exhibits no homology to the host and demonstrates a strong capacity to elicit innate, B-cell, and T-cell immune responses. Our analysis suggests that it is likely to elicit immune reactions mediated through the TLR5 pathway, as evidenced by the molecular docking of the vaccine with the receptor, which revealed high affinity and a favorable reaction. Thus, vme-VAC/MST-1 is predicted to be a safe and effective solution against pathogenic Vibrio spp. However, further experimental analyses are required to measure the vaccine’s effects In vivo. Communicated by Ramaswamy H. Sarma

Isolation and characterization of bacteria from the gut of a mesopelagic copepod Cephalophanes reflugens (Copepoda: Calanoida)

Abstract The mesopelagic calanoid copepod Cephalophanes reflugens is characterized by its large eyes with semi-parabolic reflectors. It is hypothesized that the eyes aid in finding crustacean carcasses as food in poor deep-sea light and oligotrophic conditions. Here, the crustacean carcasses-associated luminous, chitin-degrading bacteria may play a vital role in detecting and digesting foods by the copepod. In this study, we collected adult female C. reflugens (n = 9) from the mesopelagic layers off southwestern Japan in the Pacific Ocean and obtained a total of 47 bacterial isolates from the gut contents. None of the isolates were luminescent, but almost half of the isolates were chitinolytic. Based on the 16S rRNA gene sequences, these chitinolytic bacteria were identified as members of the genus Vibrio, Photobacterium and Pseudoalteromonas. In culture experiments at 15°C, most of the chitinolytic isolates efficiently utilized colloidal chitin as the sole carbon source and degraded the carapace strip of shrimp (Litopenaeus vannamei). Some isolates showed these chitinoclastic activities even at low temperatures (&amp;lt;5°C), equivalent to that of the deep-sea waters. The present results imply that chitin-degrading bacteria significantly contribute to chitin digestion in the gut of C. reflugens, whereas the involvement of luminous bacteria in the feeding mechanism remains unidentified.

Whole genome sequencing of Vibrio harveyi from different sites in the Mediterranean Sea providing data on virulence and antimicrobial resistance genes

Vibriosis caused by Vibrio harveyi is an important bacterial infection in the Mediterranean farming of European seabass and gilthead sea bream. Genomic information about V. harveyi contributes to understanding its pathogenesis and virulence. Sixteen V. harveyi strains obtained from diseased seabass and sea bream from Croatia, France, Italy, Spain, Tunisia, and Turkey were sequenced using ONT MinION and Illumina HiSeq. The strains were sequenced, de novo assembled, and the genomes analysed for the presence of plasmids, virulence, and antibiotic resistance genes. Antibiotic resistance genes were compared with in vitro susceptibility testing using disc diffusion and microdilution methods. All studied strains had two circular chromosomes, and twelve strains had one to five circular plasmids. A total of 171 virulence genes were determined using the Virulence Factors of Bacterial Pathogens database (VFBD), 150 virulence genes were present on average in each genome and the distribution of virulence genes was similar across strains. Most of the reported virulence genes have been previously described in bacteria of the genus Vibrio, while genes sitA (4/16), sitB (3/16), sitC (4/16), and sitD (3/16) important for iron transport, and the ast gene (10/16) that encodes a heat-stable cytotoxic enterotoxin, were unique in our studied strains. Using the Comprehensive Antibiotic Resistance database (CARD), it was noted that all strains carried the CRP gene encoding resistance to macrolides, fluoroquinolone, and penams, but showed sensitivity to enrofloxacin and florfenicol using in vitro tests. The adeF gene coding for resistance to fluoroquinolones and tetracyclines was detected in lower percentage in thirteen strains was supported with detected sensitivity to florfenicol and oxytetracycline using in vitro tests. The E.coli parE gene was detected in eleven strains that showed sensitivity to florfenicol and oxytetracycline. The gene APH(3”)Ib responsible for resistance to aminoglycosides was present in one strain, though all strains showed susceptibility to gentamicin by in vitro testing. The Tet(D) gene coding for resistance to tetracyclines was found in a single strain showing reduced sensitivity to oxytetracycline. All tested strains were resistant to ampicillin by in vitro testing in line with previously described innate resistance. Phylogenetic analysis based on whole genome sequences showed a clear separation and clustering of the tested strains from the Mediterranean region. The new genomic data and knowledge provided in this study increase the understanding of the pathogenicity and antimicrobial resistance patterns of V. harveyi strains in the Mediterranean region, enabling a common regional approach to prevention and mitigation of the disease.