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In a global change scenario, ocean warming and pathogen infection can occur simultaneously in coastal areas, threatening marine species. Data are shown on the impact of temperature on early larvae of the Mediterranean mussel Mytilus galloprovincialis. Increasing temperatures (18-20-22 °C) altered larval phenotypes at 48 hpf and affected gene expression from eggs to 24 and 48 hpf, with shell biogenesis related genes among the most affected. The effects of temperature on larval susceptibility to infection were evaluated using Vibrio coralliilyticus, a coral pathogen increasingly associated with bivalve mortalities, whose ecology is affected by global warming. Malformations and mortalities at 48 hpf were observed at higher temperature and vibrio concentrations, with interactive effects. In non-lethal conditions, interactions on gene expression at 24 and 48 hpf were also detected. Although temperature is the main environmental driver affecting M. galloprovincialis early larvae, warming may increase the susceptibility to vibrio infection, with consequences on mussel populations., (Copyright © 2024 The Authors. Published by Elsevier Ltd.. All rights reserved.)

This study delves into the genomic features of 10 Vibrio strains collected from deep-sea hydrothermal vents in the Pacific Ocean, providing insights into their evolutionary history and ecological adaptations. Through sequencing and pan-genome analysis involving 141 Vibrio species, we found that deep-sea strains exhibit larger genomes with unique gene distributions, suggesting adaptation to the vent environment. The phylogenomic reconstruction of the investigated isolates revealed the presence of 2 main clades: The first is monophyletic, consisting exclusively of Vibrio alginolyticus, while the second forms a monophyletic clade comprising both Vibrio antiquarius and Vibrio diabolicus species, which were previously isolated from deep-sea vents. All strains carry virulence and antibiotic resistance genes related to those found in human pathogenic Vibrio species which may play a wider ecological role other than host infection in these environments. In addition, functional genomic analysis identified genes potentially related to deep-sea survival and stress response, alongside candidate genes encoding for novel antimicrobial agents. Ultimately, the pan-genome we generated represents a valuable resource for future studies investigating the taxonomy, evolution, and ecology of Vibrio species., (© The Author(s) 2024. Published by Oxford University Press on behalf of Society for Molecular Biology and Evolution.)

Vibrio aestuarianus is a bacterium related to mass mortality outbreaks of the Pacific oyster, Crassostrea gigas in Europe. In this study, the role of different planktonic substrates (phytoplankton cells, marine aggregates and chitin fragments) in mediating V. aestuarianus 02/041 infection of oysters was evaluated by controlled infection experiments. It was shown that phytoplankton cells and, to a greater extent, marine aggregates, significantly promote V. aestuarianus 02/041 intake by C. gigas maintained under stressful conditions in the laboratory. Such intake is associated with higher concentration of the pathogen in the bivalve hemolymph and compromised health status of infected oysters. In contrast, chitin particles do not play a significant role as transmission vector for V. aestuarianus 02/041 infecting its bivalve host. Interestingly, incorporation into marine aggregates foster extracellular proteases (ECPs) activity and a higher expression of bacterial virulence genes, that are potentially involved in bivalve infection. Results from this study contribute to elucidate transmission patterns of V. aestuarianus 02/041 to C. gigas that may be useful for the development of efficient measures to prevent and control oyster disease outbreaks., (© 2023 The Authors. Environmental Microbiology Reports published by Applied Microbiology International and John Wiley & Sons Ltd.)

Harmful marine bacteria, such as Vibrio or Aeromonas species, typically exist at low abundance in ocean environments but represent a reservoir from which epidemics can arise. Particularly, Vibrio strains and their associated infections are on the rise globally due to increasing sea surface temperature representing an emergent threat for human and animal health also being responsible for large economic losses in the aquaculture industry worldwide. New technological approaches are needed to improve strategies targeting these pathogens. This review discusses new approaches based on improved sampling strategies and novel analytical methods offering increased accuracy, high throughput, and informativeness to study and detect microbial pathogens in the marine environment. Detecting and characterizing ultra-low-abundance pathogenic strains can serve as a critical tool in risk management and outbreak prevention of diseases caused by emerging marine pathogens., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

Evolution of virulence traits from adaptation to environmental niches other than the host is probably a common feature of marine microbial pathogens, whose knowledge might be crucial to understand their emergence and pathogenetic potential. Here, we report genome sequence analysis of a novel marine bacterial species, Vibrio bathopelagicus sp. nov., isolated from warm bathypelagic waters (3309 m depth) of the Mediterranean Sea. Interestingly, V. bathopelagicus sp. nov. is closely related to coastal Vibrio strains pathogenic to marine bivalves. V. bathopelagicus sp. nov. genome encodes genes involved in environmental adaptation to the deep-sea but also in virulence, such as the R5.7 element, MARTX toxin cluster, Type VI secretion system and zinc-metalloprotease, previously associated with Vibrio infections in farmed oysters. The results of functional in vitro assays on immunocytes (haemocytes) of the Mediterranean mussel Mytilus galloprovincialis and the Pacific oyster Crassostrea gigas, and of the early larval development assay in Mytilus support strong toxicity of V. bathopelagicus sp. nov. towards bivalves. V. bathopelagicus sp. nov., isolated from a remote Mediterranean bathypelagic site, is an example of a planktonic marine bacterium with genotypic and phenotypic traits associated with animal pathogenicity, which might have played an evolutionary role in the origin of coastal marine pathogens., (© 2021 The Authors. Environmental Microbiology published by Society for Applied Microbiology and John Wiley & Sons Ltd.)

In the marine environment, bivalve mollusks constitute habitats for bacteria of the Vibrionaceae family. Vibrios belong to the microbiota of healthy oysters and mussels, which have the ability to concentrate bacteria in their tissues and body fluids, including the hemolymph. Remarkably, these important aquaculture species respond differently to infectious diseases. While oysters are the subject of recurrent mass mortalities at different life stages, mussels appear rather resistant to infections. Thus, Vibrio species are associated with the main diseases affecting the worldwide oyster production. Here, we review the current knowledge on Vibrio-bivalve interaction in oysters (Crassostrea sp.) and mussels (Mytilus sp.). We discuss the transient versus stable associations of vibrios with their bivalve hosts as well as technical issues limiting the monitoring of these bacteria in bivalve health and disease. Based on the current knowledge of oyster/mussel immunity and their interactions with Vibrio species pathogenic for oyster, we discuss how differences in immune effectors could contribute to the higher resistance of mussels to infections. Finally, we review the multiple strategies evolved by pathogenic vibrios to circumvent the potent immune defences of bivalves and how key virulence mechanisms could have been positively or negatively selected in the marine environment through interactions with predators., (© 2020 Society for Applied Microbiology and John Wiley & Sons Ltd.)

Ocean contamination by micro- and nanoplastics represents a potential threat to marine biota, from bacterial communities to higher organisms. In this work, the effect of in vivo exposure of Mytilus galloprovincialis to amino modified nanopolystyrene (PS-NH 2 ) (10 μg/L, 96 h) on hemolymph immune parameters and microbiota composition were investigated. Nanoplastics significantly affected immune parameters (decreased phagocytosis, increased ROS and lysozyme activity, inhibition of NO production). These changes were associated with a shift in hemolymph microbiota composition, with increase in some genera (Arcobacter-like, Psychrobium, Vibrio), and decreases in others (Shewanella, Mycoplasma). The results indicate that exposure to nanoplastics can impact on the microbiome of marine bivalves, and suggest that downregulation of immune defences induced by PS-NH 2 may favour potentially pathogenic bacteria. These data underline how exposure to nanoplastics may represent a potential threat to the complex interplay between innate immunity and host microbiota, thus affecting the homeostatic processes involved in maintenance of organism health., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Vibrio coralliilyticus has emerged as a coral pathogen of concern throughout the Indo-Pacific reef. The interest towards understanding its ecology and pathogenic potential has increased since V. coralliilyticus was shown to be strongly virulent also for other species; in particular, it represents a serious threat for bivalve aquaculture, being one of the most important emerging pathogen responsible for oyster larval mortalities worldwide. V. coralliilyticus has a tightly regulated temperature-dependent virulence and it has been related to mass mortalities events of benthic invertebrates also in the temperate northwestern Mediterranean Sea. However, no data are available on the effects of V. coralliilyticus in the mussel Mytilus galloprovincialis, the most abundant aquacultured species in this area. In this work, responses of M. galloprovincialis to challenge with V. coralliilyticus (ATCC BAA-450) were investigated. In vitro, short term responses of mussel hemocytes were evaluated in terms of lysosomal membrane stability, bactericidal activity, lysozyme release, ROS and NO production, and ultrastructural changes, evaluated by TEM. In vivo, hemolymph parameters were measured in mussels challenged with V. coralliilyticus at 24h p.i. Moreover, the effects of V. coralliilyticus on mussel early embryo development (at 48 hpf) were evaluated. The results show that both in vitro and in vivo, mussels were unable to activate immune response towards V. coralliilyticus, and that challenge mainly induced lysosomal stress in the hemocytes. Moreover, V. coralliilyticus showed a strong and concentration-dependent embryotoxicity. Overall, the results indicate that, although M. galloprovincialis is considered a resistant species to vibrio infections, the emerging pathogen V. coralliilyticus can represent a potential threat to mussel aquaculture., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

The increase in seawater temperature associated with global warming is a significant threat to coral health and is linked to increasing mass mortality events and Vibrio-related coral diseases. In the Mediterranean Sea, the endemic Cladocora caespitosa and the invasive species Oculina patagonica are the main scleractinian corals affected by mass mortalities. In this study, culturable Vibrio spp. assemblages associated with healthy and unhealthy colonies of these two shallow coral species were characterized to assess the presence of Vibrio pathogens in tissue necrosis. Vibrio communities associated with O. patagonica and C. caespitosa showed geographical differences, although these became more homogeneous in unhealthy specimens of both species. Furthermore, the number of recovered Vibrio specimens was more than five times higher in unhealthy than in healthy corals. Within these culturable vibrios, the known pathogens Vibrio mediterranei and Vibrio coralliilyticus were present in unhealthy colonies of both coral species in the two localities, suggesting that they could play a role in the health status of C. caespitosa and thus act as generalist pathogens in Mediterranean corals. Nonetheless, a clonal type of V. coralliilyticus detected in C. caespitosa was not associated with disease signs, suggesting that this species could encompass assemblages with different levels of virulence., (Copyright © 2017 The Author(s). Published by Elsevier GmbH.. All rights reserved.)

Autophagy is a highly conserved and regulated catabolic process involved in maintaining cell homeostasis in response to different stressors. The autophagic machinery is also used as an innate immune mechanism against microbial infection. In invertebrates, that lack acquired immunity, autophagy may thus play a key role in the protection against potential pathogens. In aquatic molluscs, evidence has been provided for induction of autophagy by starvation and different environmental stressors; however, no information is available on autophagic pathways in the immune cells, the hemocytes. In this work, the autophagic processes were investigated in the hemocytes of the marine bivalve, the mussel Mytilus galloprovincialis. The effects of classical inducers/inhibitors of mammalian autophagy were first tested. Rapamycin induced a decrease in lysosomal membrane stability-LMS that was prevented by the autophagy inhibitor Wortmannin. Increased MDC fluorescence and expression of LC3-II were also observed. Moreover, responses to in vitro challenge with the bivalve pathogen Vibrio tapetis were evaluated. Mussel hemocytes were unable to activate the immune response towards V. tapetis; however, bacterial challenge induced a moderate decrease in LMS, corresponding to lysosomal activation but no cytotoxicity; the effect was prevented by Wortmannin. TEM observations showed that V. tapetis resulted in rapid formation of autophagosomes and autolysosomes. Accordingly, increased LC3-II expression, decreased levels of phosphorylated mTor and of p62 were observed. The results represent the first evidence for autophagic processes in bivalve hemocytes in response to bacterial challenge, and underline the protective role of autophagy towards potential pathogenic vibrios., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

Climate change is having a dramatic impact on marine animal and plant communities but little is known of its influence on marine prokaryotes, which represent the largest living biomass in the world oceans and play a fundamental role in maintaining life on our planet. In this study, for the first time to our knowledge, experimental evidence is provided on the link between multidecadal climatic variability in the temperate North Atlantic and the presence and spread of an important group of marine prokaryotes, the vibrios, which are responsible for several infections in both humans and animals. Using archived formalin-preserved plankton samples collected by the Continuous Plankton Recorder survey over the past half-century (1958-2011), we assessed retrospectively the relative abundance of vibrios, including human pathogens, in nine areas of the North Atlantic and North Sea and showed correlation with climate and plankton changes. Generalized additive models revealed that long-term increase in Vibrio abundance is promoted by increasing sea surface temperatures (up to ∼1.5 °C over the past 54 y) and is positively correlated with the Northern Hemisphere Temperature (NHT) and Atlantic Multidecadal Oscillation (AMO) climatic indices (P < 0.001). Such increases are associated with an unprecedented occurrence of environmentally acquired Vibrio infections in the human population of Northern Europe and the Atlantic coast of the United States in recent years., Competing Interests: The authors declare no conflict of interest.

The interactions of Vibrio aestuarianus 01/032 with haemolymph of the bivalves Mytilus galloprovincialis and Crassostrea gigas were investigated to understand if haemolymph components (haemocytes and soluble factors) could be involved in the higher resistance to microbial infection shown by mussels in comparison with oysters. Although 01/032 bacteria adhered to haemocytes of both bivalves, they were sensitive to the bactericidal activity of whole haemolymph from mussel, but not from oyster; in addition, adhesion to mussel (but not oyster) haemocytes was affected by D-mannose. Mussel serum opsonins directed towards D-mannose-binding bacterial ligands were purified by affinity chromatography and were shown to mediate 01/032 interactions with M. galloprovincialis haemocytes. Nano-High Performance Liquid Chromatography-Electrospray Ionization-Tandem Mass Spectrometry (HPLC-ESI-MS/MS) analysis showed that the purified opsonin matched the protein precursor of Mytilus edulis extrapallial protein (EP). In the presence of M. galloprovincialis EP protein (MgEP), C. gigas haemocytes killed V. aestuarianus 01/032 almost as efficiently as mussel phagocytes. These findings suggest that the different sensitivity of 01/032 strain to the antibacterial activity of oyster and mussel haemolymph might partly depend on the fact that C. gigas serum lacks MgEP-like opsonins. These results represent the basis for understanding the different sensitivity to microbial infections shown by the two bivalve species., (© 2015 Society for Applied Microbiology and John Wiley & Sons Ltd.)

Vibrio-related infections are increasing worldwide both in humans and aquatic animals. Rise in global sea surface temperature (SST), which is approximately 1 °C higher now than 140 years ago and is one of the primary physical impacts of global warming, has been linked to such increases. In this chapter, major known effects of increasing SST on the biology and ecology of vibrios are described. They include the effects on bacterial growth rate, both in the field and in laboratory, culturability, expression of pathogenicity traits, and interactions with aquatic organisms and abiotic surfaces. Special emphasis is given to the effect of ocean warming on Vibrio interactions with zooplankters, which represent one of the most important aquatic reservoirs for these bacteria. The reported findings highlight the biocomplexity of the interactions between vibrios and their natural environment in a climate change scenario, posing the need for interdisciplinary studies to properly understand the connection between ocean warming and persistence and spread of vibrios in sea waters and the epidemiology of the diseases they cause.

The ecology of the oyster pathogens Vibrio splendidus and Vibrio aestuarianus in the brackish aquatic environment was extensively investigated in this study. By conducting laboratory experiments under natural setting conditions, it was shown that V. splendidus LGP32 strain generally exhibits longer persistence in both seawater and sediment than V. aestuarianus 01/32 strain. Both strains maintained viability and culturability for longer times in the sediment, suggesting that this compartment may represent a suitable niche for their persistence in the environment. In addition, both strains attached to chitin particles and copepods, the efficiency of attachment being higher in V. splendidus than in V. aestuarianus. Similarly, LGP32 strain showed a greater capability to form biofilm on poly-vinyl chloride (PVC) surfaces than 01/32 strain. LGP32 and 01/32 strains were also capable of entering a viable but non-culturable state after extended incubation at 5°C, a condition commonly found during cold season in the aquatic brackish environment. These results are consistent with field data collected during a 2-year sampling campaign in the northern Adriatic Sea and provide background information on the mechanisms promoting V. splendidus and V. aestuarianus persistence in coastal water, thus contributing to a better understanding of the epidemiology of the associated diseases., (© 2014 Society for Applied Microbiology and John Wiley & Sons Ltd.)

DNA- and RNA-based PCR and reverse-transcription real-time PCR assays were developed for diagnostic detection of the vcpA zinc-metalloprotease implicated in the virulence of the coral pathogen Vibrio coralliilyticus. Both PCR methods were highly specific for V. coralliilyticus and failed to amplify strains of closely-related Vibrio species. The assays correctly detected all globally occurring V. coralliilyticus isolates including a newly-described isolate [TAV24] infecting gorgonians in the Mediterranean Sea and highlighted those isolates that had been potentially misidentified, in particular V. tubiashii strains ATCC 19105 and RE22, historically described as important oyster pathogens. The real-time assay is sensitive, detecting 10 gene copies and the relationships between gene copy number and cycle threshold (C T ) were highly linear (R(2)≥ 99.7). The real-time assay was also not affected by interference from non-target DNA. These assays are useful for rapid detection of V. coralliilyticus and monitoring of virulence levels in environmental samples, allowing for implementation of timely management steps to limit and possibly prevent losses due to V. coralliilyticus infection, as well as furthering investigations of factors affecting pathogenesis of this important marine pathogen.

Marine bivalves can accumulate large numbers of bacteria, in particular Vibrio species, whose persistence in bivalve tissues largely depends on their sensitivity to the bactericidal activity of circulating hemocytes and hemolymph soluble factors. The interactions between vibrios and hemolymph have been investigated, in particular in bivalve species susceptible to infection by certain Vibrio spp. and strains. In this work, the effects of two bivalve pathogens, Vibrio splendidus LGP32 (V.s.) and Vibrio aestuarianus 01/032 (V.a.), isolated from oyster mortality outbreaks, on the hemocytes of Mytilus galloprovincialis were investigated. In vitro, V.s., but not V.a., induced a dramatic decrease in lysosomal membrane stability-LMS in the hemocytes; both vibrios induced a moderate lysozyme release, with V.s. > V.a.. The V.s.-induced decrease in LMS was mediated by activation of PI-3Kinase, as shown by use of different kinase inhibitors. TEM analysis showed rapid internalization of both vibrios; however, V.s. lead to cellular and lysosomal damage and was able to survive within the hemocytes, whereas significant killing of V.a. was observed. In vivo, in mussels challenged with either vibrio and sampled at 6, 24 and 96 h post-injection, transient decreases in hemocyte LMS and progressive increases in serum lysozyme activity were observed, with V.s. > V.a.. Moreover, whereas V.a. was efficiently cleared from hemolymph, V.s. showed significant growth, that was maximal at 24 h p.i. when lowest LMS values were recorded in the hemocytes. Both vibrios also induced significant decreases in LMS in the digestive gland, again with V.s. > V.a.. The results indicate distinct interactions between mussel hemocytes and the two vibrio strains tested. The effects of V.s. may be due to the capacity of this strain to interfere with the signaling pathways involved in hemocyte function, thus escaping the bactericidal activity of the host cell, as observed for certain mammalian pathogens. Although V.s. is considered not pathogenic to Mytilus, this vibrio strain can affect the lysosomal function at the cellular and tissue level, thus leading to stressful conditions., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

Vibrios are among the most common bacteria that inhabit surface waters throughout the world and are responsible for a number of severe infections both in humans and animals. Several reports recently showed that human Vibrio illnesses are increasing worldwide including fatal acute diarrheal diseases, such as cholera, gastroenteritis, wound infections, and septicemia. Many scientists believe this increase may be associated with global warming and rise in sea surface temperature (SST), although not enough evidence is available to support a causal link between emergence of Vibrio infections and climate warming. The effect of increased SST in promoting spread of vibrios in coastal and brackish waters is considered a causal factor explaining this trend. Field and laboratory studies carried out over the past 40 years supported this hypothesis, clearly showing temperature promotes Vibrio growth and persistence in the aquatic environment. Most recently, a long-term retrospective microbiological study carried out in the coastal waters of the southern North Sea provided the first experimental evidence for a positive and significant relationship between SST and Vibrio occurrence over a multidecadal time scale. As a future challenge, macroecological studies of the effects of ocean warming on Vibrio persistence and spread in the aquatic environment over large spatial and temporal scales would conclusively support evidence acquired to date combined with studies of the impact of global warming on epidemiologically relevant variables, such as host susceptibility and exposure. Assessing a causal link between ongoing climate change and enhanced growth and spread of vibrios and related illness is expected to improve forecast and mitigate future outbreaks associated with these pathogens.

The long-term effects of ocean warming on prokaryotic communities are unknown because of lack of historical data. We overcame this gap by applying a retrospective molecular analysis to the bacterial community on formalin-fixed samples from the historical Continuous Plankton Recorder archive, which is one of the longest and most geographically extensive collections of marine biological samples in the world. We showed that during the last half century, ubiquitous marine bacteria of the Vibrio genus, including Vibrio cholerae, increased in dominance within the plankton-associated bacterial community of the North Sea, where an unprecedented increase in bathing infections related to these bacteria was recently reported. Among environmental variables, increased sea surface temperature explained 45% of the variance in Vibrio data, supporting the view that ocean warming is favouring the spread of vibrios and may be the cause of the globally increasing trend in their associated diseases.

Mass mortality events of benthic invertebrates in the temperate north-western (NW) Mediterranean Sea have been observed in recent seasons. A 16 month in situ study in the Ligurian Sea (NW Mediterranean Sea) demonstrated that the occurrence of Paramuricea clavata mortality episodes were concomitant to a condition of prolonged high sea surface temperatures, low chlorophyll concentrations and the presence of culturable Vibrio spp. in seawater. The occurrence of Vibrio spp. at the seasonal scale was correlated with temperature; with few vibrios retrieved on specific media when the temperature dropped below 18 degrees C and a sharp increase of vibrios abundance (up to 3.4 x 10(4) MPN l(-1)) when the temperature was greater than or equal to 22 degrees C. Phylogenetic and phenotypic analysis of Vibrio isolates associated with healthy and diseased P. clavata colonies collected during a mortality episode showed that these bacteria were significantly more abundant in diseased than in healthy corals and were related to the V. harveyi, V. splendidus and V. coralliilyticus groups, the latter only identified in diseased organisms. Inoculation of bacterial isolates from these groups onto healthy P. clavata in aquaria caused disease signs and death in a range of Vibrio concentrations, temperature values and trophic conditions consistent with those recorded in the field. It is concluded that Vibrio infections may act as an additional triggering mechanism of mass mortality events in the coastal Mediterranean Sea and that their occurrence is climate-linked. Predicted global warming leading to long-lasting hot summer periods together with stratification resulting in energetic constraints represent a major threat to the survival of benthic invertebrates in the temperate NW Mediterranean Sea due to potential disease outbreak associated with Vibrio pathogens.

We carried out a 16-month in situ study to investigate the ecology of Vibrio spp. and pathogenic Vibrio species in coastal sediments of the Mediterranean Sea, employing multiple-regression analysis to reveal the major environmental factors controlling their occurrence in the benthic environment. In addition, association between vibrios and sediment-inhabiting meiofauna, which is a major component of benthic ecosystems, was investigated. Culturable and total Vibrio spp. estimates by most-probable-number technique coupled with standard polymerase chain reaction (PCR) and real-time PCR methods, respectively, were at least one order of magnitude higher in sediment than in seawater. In addition, potential human pathogenic species Vibrio cholerae, Vibrio vulnificus and Vibrio parahaemolyticus occurred in the sediment with V. parahaemolyticus being the most frequently found. In the pelagic environment, 60% of total variance in culturable Vibrio data was explained by sea surface temperature (40%), salinity (13%) and organic matter concentration (7%). In the benthic environment, sea surface temperature was the only factor that significantly affected culturable Vibrio occurrence although it explained only 25% of total variance, suggesting that additional unexplored factors may play a role as well. No correlation was found between culturable Vibrio spp. concentrations and the abundance of harpacticoid copepods in the sediment whilst a negative correlation was found between Vibrio spp. and nematode abundance which accounted for almost 90% of the total meiofaunal density. Taxonomic analysis revealed that selective bacterial feeders accounted for nearly 50% of the total nematode community and included genera such as Terschellingia, Molgolaimus and Halalaimus, suggesting that top-down control by nematode grazing may be an important factor affecting Vibrio occurrence in these sediments. It is concluded that the benthic marine environment may function as a reservoir of Vibrio spp. and potential pathogenic vibrios whose ecological features appeared substantially different from the ones recognised in the pelagic environment.

Aims: To investigate the role of surface membrane proteins (MP) to promote attachment to chitin particles and copepods of different environmental and clinical vibrios., Method and Results: The role of surface MP to promote attachment to chitin particles and the copepod Tigriopus fulvus was investigated in several environmental and clinical Vibrio strains by inhibition test methods. Attachment to both substrates was significantly inhibited by homologous MP treatment in all strains and percentages of inhibition were comparable with the ones observed with N-acetyl glucosamine (GlcNAc). Sarkosyl-insoluble MP extracted from tested strains were added to chitin particles either in the presence or in the absence of GlcNAc and the fraction bound to chitin in both conditions was visualized by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Chitin-binding proteins (CBP) defined as Sarkosyl-insoluble MP that bound chitin in the absence of GlcNAc but did not in the presence of the sugar were isolated in all strains., Conclusion: CBP are common in both environmental and clinical Vibrio strains and they have an important general role in mediating cell interactions with chitin-containing surfaces., Significant and Impact of the Study: The role of CBP should be taken into account when investigating environmental persistence of aquatic vibrios.