Characterization by numerical taxonomy and ribotyping of Vibrio splendidus biovar I and Vibrio scophthalmi strains associated with turbot cultures

Twelve Vibrio strains were examined phenotypically in 91 biochemical characters and genotypically by ribotyping. Ten were isolated from sea water and two from diseased turbot (Scophthalmus maximus). All isolates originated from one experimental system located in Ría de Vigo (Galicia, north-west Spain). Different type strains were used for comparative purposes. The taxonomic position was analysed with the NTSYST-pc and similarities among strains were calculated by the Simple Matching coefficient (SSM). rRNA gene restriction patterns were performed with the HindIII enzyme. The SSM coefficient separated the 12 Vibrio strains into two groups which included strains that showed a SSM coefficient quite similar to V. splendidus biovar 1 (ATCC 33125) and V. scophthalmi (CECT 4638). None of 91 phenotypical characters were specific in distinguishing both species. The ribotyping confirmed the taxonomic classification of strains. The pathogenicity of each strain was evaluated; 10 environmental strains were avirulent and two, isolated from diseased turbot, were virulent. Different biotypes and ribotypes were found among the avirulent isolates. This work showed ribotyping to be a valuable tool for identification and confirmed the necessity of extending the ribotype database within closely related Vibrio species in order to clarify the taxonomic position.

Analysis of 16S-23S rRNA intergenic spacer regions of Vibrio cholerae and Vibrio mimicus

Vibrio cholerae identification based on molecular sequence data has been hampered by a lack of sequence variation from the closely related Vibrio mimicus. The two species share many genes coding for proteins, such as ctxAB, and show almost identical 16S DNA coding for rRNA (rDNA) sequences. Primers targeting conserved sequences flanking the 3' end of the 16S and the 5' end of the 23S rDNAs were used to amplify the 16S-23S rRNA intergenic spacer regions of V. cholerae and V. mimicus. Two major (ca. 580 and 500 bp) and one minor (ca. 750 bp) amplicons were consistently generated for both species, and their sequences were determined. The largest fragment contains three tRNA genes (tDNAs) coding for tRNAGlu, tRNALys, and tRNAVal, which has not previously been found in bacteria examined to date. The 580-bp amplicon contained tDNAIle and tDNAAla, whereas the 500-bp fragment had single tDNA coding either tRNAGlu or tRNAAla. Little variation, i.e., 0 to 0.4%, was found among V. cholerae O1 classical, O1 El Tor, and O139 epidemic strains. Slightly more variation was found against the non-O1/non-O139 serotypes (ca. 1% difference) and V. mimicus (2 to 3% difference). A pair of oligonucleotide primers were designed, based on the region differentiating all of V. cholerae strains from V. mimicus. The PCR system developed was subsequently evaluated by using representatives of V. cholerae from environmental and clinical sources, and of other taxa, including V. mimicus. This study provides the first molecular tool for identifying the species V. cholerae.

Randomly amplified polymorphic DNA analysis of clinical and environmental isolates of Vibrio vulnificus and other vibrio species

Vibrio vulnificus is an estuarine bacterium that is capable of causing a rapidly fatal infection in humans. A randomly amplified polymorphic DNA (RAPD) PCR protocol was developed for use in detecting V. vulnificus, as well as other members of the genus Vibrio. The resulting RAPD profiles were analyzed by using RFLPScan software. This RAPD method clearly differentiated between members of the genus Vibrio and between isolates of V. vulnificus. Each V. vulnificus strain produced a unique band pattern, indicating that the members of this species are genetically quite heterogeneous. All of the vibrios were found to have amplification products whose sizes were within four common molecular weight ranges, while the V. vulnificus strains had an additional two molecular weight range bands in common. All of the V. vulnificus strains isolated from clinical specimens produced an additional band that was only occasionally found in environmental strains; this suggests that, as is the case with the Kanagawa hemolysin of Vibrio parahaemolyticus, the presence of this band may be correlated with the ability of a strain to produce an infection in humans. In addition, band pattern differences were observed between encapsulated and nonencapsulated isogenic morphotypes of the same strain of V. vulnificus.

Extended serotyping scheme for Vibrio anguillarum with the definition and characterization of seven provisional O-serogroups

The present paper summarizes the serotyping scheme of the fish pathogenic bacterium Vibrio anguillarum and defines seven additional O-serogroups. Strains, collected in our laboratories that were nontypable with antisera against the previously defined 16 O-serotypes, were used for generating new antisera and were characterized further by means of LPS profiles, Western blots, and serological reactions. On the basis of the results, it is suggested that the seven new O-serogroups are to be included in the existing serotyping system as serotypes O17-O23. However, the existence of further V. anguillarum strains that were not typable with any of the 23 O-antisera suggested the existence of additional O-serotypes within this species. The relevance of the description of additional O-serotypes for the species V. anguillarum is discussed.

Isolation of Vibrio vulnificus serovar E from aquatic habitats in Taiwan

The existence of strains of Vibrio vulnificus serovar E that are avirulent for eels is reported in this work. These isolates were recovered from water and oysters and differed from eel virulent strains in (i) fermentation and utilization of mannitol, (ii) ribotyping after HindIII digestion, and (iii) susceptibility to eel serum. Lipopolysaccharide of these strains lacked the highest molecular weight immunoreactive bands, which are probably involved in serum resistance.

Arbitrarily primed PCR to type Vibrio spp. pathogenic for shrimp

A molecular typing study on Vibrio strains implicated in shrimp disease outbreaks in New Caledonia and Japan was conducted by using AP-PCR (arbitrarily primed PCR). It allowed rapid identification of isolates at the genospecies level and studies of infraspecific population structures of epidemiological interest. Clusters identified within the species Vibrio penaeicida were related to their area of origin, allowing discrimination between Japanese and New Caledonian isolates, as well as between those from two different bays in New Caledonia separated by only 50 km. Other subclusters of New Caledonian V. penaeicida isolates could be identified, but it was not possible to link those differences to accurate epidemiological features. This contribution of AP-PCR to the study of vibriosis in penaeid shrimps demonstrates its high discriminating power and the relevance of the epidemiological information provided. This approach would contribute to better knowledge of the ecology of Vibrio spp. and their implication in shrimp disease in aquaculture.

Comparative study of biological properties and electrophoretic characteristics of lipopolysaccharide from eel-virulent and eel-A virulent Vibrio vulnificus strains

In Vibrio vulnificus, virulence for eels is associated with serovar E strains. In this study, we investigated some biological properties of purified lipopolysaccharides (LPSs) from serovar E and non-serovar E strains. Purified LPSs retained their O-polysaccharidic side chains and did not show any differences that could be related to host specificity, except for serological differences.

Clonality of Vibrio anguillarum strains isolated from fish from the Scandinavian countries, Sweden, Finland and Denmark

In order to investigate whether outbreaks of vibriosis in the Baltic region were caused by the spread of certain pathogenic clones, 291 Vibrio anguillarum isolates from Finland (n = 156), Sweden (n = 88) and Denmark (n = 47) were studied with respect to serogroup, ribotype, plasmid content, and biochemical phenotypes as expressed with the PhenePlate (PhP) typing system. For comparison, 54 V. anguillarum serogroup O1 from other countries worldwide were included. Most isolates from Finland, Sweden and Denmark belonged to serogroup O1 (255), followed by O2 (30). Four Finnish isolates cross-reacted strongly with antisera against two new serogroups VaNT2 and VaNT4, whereas two strains were non-typeable. The serogroup O1 isolates displayed ten different ribotype patterns, whereas the other strains were considerably more diverse with respect to ribotypes. Most of the O1 isolates carried the 67 kb virulence plasmid and a group of Finnish isolates, in addition, carried an 86 kb plasmid. Additional plasmids with molecular weights of 63, 76, 135 or 260-290 kb were found in single O1 isolates. With few exceptions, strains of serogroup O2 either had no plasmids or carried one or two small plasmids. PhenePlate typing revealed considerable diversity within the species, serogroup O1 being the most homogeneous. A few PhP types were dominant, whereas other types were observed only in one to four isolates. The prevalence of the different types changed significantly from one year to another but in Finland, one clonal lineage became increasingly important from 1992 (20% of isolates) to 1996 (80%). Remaining clones were mostly restricted to specific geographic areas. By cluster analysis, it was demonstrated that most of the isolates from Finland, Sweden and Denmark belonged to two clusters, and most of the strains from Southern Europe fell into two other, distinct clusters. Most isolates from the UK, North America, Chile and Tasmania grouped together in a distinct cluster. For the typing of V. anguillarum, O-serotyping should be the primary method. For isolates belonging to serogroups other than O1, plasmid profiling in combination with ribotyping gives a very good discrimination between strains, whereas for serogroup O1, another method is required. It is concluded that PhP typing is a tool that provides a good discrimination between O1 isolates.

Low incidence of Vibrio vulnificus among Vibrio isolates from sea water and shellfish of the western Mediterranean coast

A specific search for Vibrio vulnificus in natural marine samples from the Spanish Mediterranean Sea was carried out by nested PCR and cultural approaches using thiosulphate-citrate-bile salts-sucrose agar (TCBS) and cellobiose-polymixin B-colistin agar (CPC), incubated at 40 degrees C, as selective media. Presumptive colonies were identified by PCR using specific primers against 23S rRNA sequences. This species was isolated from sea water and edible bivalves, mainly after preenrichment in alkaline peptone water (APW) at 40 degrees C followed by CPC agar. None of the V. vulnificus isolates identified corresponded to serovar E. Dominant Vibrio species on directly inoculated TCBS plates incubated at 25 degrees C were V. splendidus below 20 degrees C and V. harveyi and V. mediterranei above that temperature. Low percentages of several pathogenic vibrios were recorded but V. vulnificus was never recovered at this incubation temperature. The incidence of this species in the samples studied was lower than that described for other geographical areas, probably due to the high salinity values of the Mediterranean Sea.

Vibrio anguillarum resistance to rainbow trout (Oncorhynchus mykiss) serum: role of O-antigen structure of lipopolysaccharide

The sensitivity of Vibrio anguillarum to the bactericidal effect of rainbow trout serum was investigated with different strains of serogroups O1 and O2a, which are the most frequently found serogroups in clinical outbreaks of vibriosis. All of the V. anguillarum strains were able to activate complement in rainbow trout serum, but smooth strains of V. anguillarum serogroup O1 were resistant to complement-mediated killing in the absence of specific antibodies. In the case of V. anguillarum serogroup O2a strains, 80% of the analyzed strains were resistant to rainbow trout serum even when specific antibodies were present. Analysis of the lipopolysaccharide structures of the tested V. anguillarum strains showed a positive correlation between the O-antigen size of the lipopolysaccharide and resistance to serum killing. The classical complement pathway was responsible for the antibody-dependent serum killing of susceptible V. anguillarum strains. When serum-resistant V. anguillarum serogroup O2a strains were grown in glucose-enriched Lennox L broth, they produced lipopolysaccharide molecules with fewer high-molecular-weight O-antigen units than did strains grown in broth without the addition of glucose. Strains grown in glucose-enriched medium became sensitive to rainbow trout serum killing, indicating that the high-molecular-weight O-antigen side chains prevented the activated complement from damaging the bacterium.

Vibrios associated with mortality in cultured plaice Pleuronectes platessa fry

Fifty two bacterial strains, identified as Vibrio spp., were isolated from diseased plaice fry. The most numerous group comprised V. anguillarum (26/52), of which 3 isolates belonged to serogroup O2a, 16 corresponded to serogroup O18, and 7 isolates were non-typeable. All serogroup O18 isolates had identical ribotype patterns. Fourteen isolates were identified as V. splendidus biotype I (n = 11) or V. splendidus-like (n = 3). Seven isolates were V. fluvialis, representing the first isolation of this species in Denmark and the first description of V. fluvialis associated with diseased fish. All V. fluvialis isolates had identical ribotype patterns, indicating the presence of a single clone. The last 5 isolates belonged to 2 different, unidentified Vibrio species (n = 2 and 3, respectively). Although all isolates were recovered from diseased plaice fry, their exact role as pathogens for the fry is as yet uncertain. Selected isolates were tested for virulence to salmon and turbot. When injected into juvenile salmonid fish, the recorded LD50 values were higher than 10(6), indicating that their virulence was relatively low. However, virulence seemed to deteriorate upon subculturing, and therefore, the strains may have been more virulent upon primary isolation from the plaice fry.

Reassessment of the taxonomic position of Vibrio iliopiscarius (Onarheim et al. 1994) and proposal for Photobacterium iliopiscarium comb. nov

The phylogenetic position of Vibrio iliopiscarius was inferred by the maximum-likelihood, maximum-parsimony and neighbour-joining methods on the basis of almost complete 16S rRNA gene sequences. The results showed that this species falls into the same cluster as Photobacterium species and is clearly distinct from other Vibrio species. Its nearest phylogenetic neighbour is Photobacterium phosphoreum. From these results, it is concluded that V. iliopiscarius should be reclassified as Photobacterium iliopiscarium comb. nov., the type strain of which is PS1T (= ATCC 51760T).

Heterogeneity among isolates of Vibrio vulnificus recovered from eels (Anguilla anguilla) in Denmark

The findings of this study demonstrate that Vibrio vulnificus isolates recovered from diseased eels in Denmark are heterogeneous as shown by O serovars, capsule types, ribotyping, phage typing, and plasmid profiling. The study includes 85 V. vulnificus isolates isolated from the gills, intestinal contents, mucus, spleen, and kidneys of eels during five disease outbreaks on two Danish eel farms from 1995 to 1997, along with a collection of 12 V. vulnificus reference strains. The results showed that more than one serovar may be capable of causing disease in eels and that these isolates are genetically heterogenous as shown by ribotyping. Ribotyping also showed that the same isolates may persist in an eel farm and cause recurrent outbreaks. Phage typing did not correlate with ribotyping or serotyping. However, we observed that 26 of 28 isolates, which were not susceptible to any of the phages, showed the same ribotype, O serovar, and capsule type. This suggests that these isolates may possess features that make them resistant to lysis by the phages used in this study. Ninety-three of 97 isolates harbored between one and three high-molecular-weight plasmids which previously had been suggested to be associated with eel virulence. The subdivision of V. vulnificus into two biotypes based on the indole reaction can no longer be supported, since 82 of 97 isolates in this study were indole positive, and a subdivision into serovars appears to be more correct.

Assignment of Vibrio sp. strain ABE-1 to Colwellia maris sp. nov., a new psychrophilic bacterium

A psychrophilic bacterium, previously described as Vibrio sp. strain ABE-1T, has been reassigned by phenotypic characterization, chemotaxonomic analysis and 16S rRNA phylogenetic analysis. The organism was curved rods and it could reduce nitrate to nitrite and hydrolyse gelatin and DNA, but not chitin. NaCl was required for growth. This strain was susceptible to the vibriostatic compound O/129. The major isoprenoid quinone was ubiquinone-8 and the DNA G + C content was 39.4 mol%. The whole-cell fatty acids comprised saturated and monounsaturated fatty acids with 10-18 C atoms; saturated and monounsaturated C16 fatty acids were predominant. Strain ABE-1T contained the unique trans-unsaturated fatty acid, 9-trans-hexadecenoic acid. Although strain ABE-1T has been identified as a Vibrio species, the strain did not ferment glucose. Phylogenetic analysis based on 16S rRNA sequencing indicated that strain ABE-1T was more closely related to Colwellia species than to Vibrio species. However, strain ABE-1T differed from other reported Colwellia species in terms of phylogenetic position, some phenotypic characteristics, chemotaxonomic analysis and relatedness by DNA-DNA hybridization. Accordingly, the name Colwellia maris is proposed. The type strain is ABE-1T (= JCM 10085T).

Direct identification of Vibrio vulnificus in clinical specimens by nested PCR

This study was performed to establish optimal nested PCR conditions and a high-yield DNA extraction method for the direct identification of Vibrio vulnificus in clinical specimens. We designed two sets of primers targeting the V. vulnificus hemolysin/cytolysin gene. The target of the first primer set (P1-P2; sense, 5'-GAC-TAT-CGC-ATC-AAC-AAC-CG-3', and antisense, 5'-AGG-TAG-CGA-GTA-TTA-CTG-CC-3', respectively) is a 704-bp DNA fragment. The second set (P3-P4; sense, 5'-GCT-ATT-TCA-CCG-CCG-CTC-AC-3', and antisense, 5'-CCG-CAG-AGC-CGT-AAA-CCG-AA-3', respectively) amplifies an internal 222-bp DNA fragment. We developed a direct DNA extraction method that involved boiling the specimen pellet in a 1 mM EDTA-0.5% Triton X-100 solution. The new DNA extraction method was more sensitive and reproducible than other conventional methods. The DNA extraction method guaranteed sensitivity as well, even when V. vulnificus cells were mixed with other bacteria such as Escherichia coli or Staphylococcus aureus. The nested PCR method could detect as little as 1 fg of chromosomal DNA and single CFU of V. vulnificus. We applied the nested PCR protocol to a total of 39 serum specimens and bulla aspirates from septicemic patients. Seventeen (94.4%) of the 18 V. vulnificus culture-positive specimens were positive by the nested PCR. Eight (42.1%) of the 19 culture-negative samples gave positive nested PCR results.

Genetic relatedness among environmental, clinical, and diseased-eel Vibrio vulnificus isolates from different geographic regions by ribotyping and randomly amplified polymorphic DNA PCR

Genetic relationships among 132 strains of Vibrio vulnificus (clinical, environmental, and diseased-eel isolates from different geographic origins, as well as seawater and shellfish isolates from the western Mediterranean coast, including reference strains) were analyzed by random amplified polymorphic DNA (RAPD) PCR. Results were validated by ribotyping. For ribotyping, DNAs were digested with KpnI and hybridized with an oligonucleotide probe complementary to a highly conserved sequence in the 23S rRNA gene. Random amplification of DNA was performed with M13 and T3 universal primers. The comparison between ribotyping and RAPD PCR revealed an overall agreement regarding the high level of homogeneity of diseased-eel isolates in contrast to the genetic heterogeneity of Mediterranean isolates. The latter suggests the existence of autochthonous clones present in Mediterranean coastal waters. Both techniques have revealed a genetic proximity among Spanish fish farm isolates and a close relationship between four Spanish eel farm isolates and some Mediterranean isolates. Whereas the differentiation within diseased-eel isolates was only possible by ribotyping, RAPD PCR was able to differentiate phenotypically atypical isolates of V. vulnificus. On the basis of our results, RAPD PCR is proposed as a better technique than ribotyping for rapid typing in the routine analysis of new V. vulnificus isolates.

A proposal to transfer Vibrio marinus (Russell 1891) to a new genus Moritella gen. nov. as Moritella marina comb. nov

The taxonomic positions of Vibrio marinus and 11 related natural isolates were examined. Their phylogenetic positions on the basis of almost complete 16S rRNA sequences were determined by maximum likelihood, maximum parsimony and neighbor-joining analyses. V. marinus and the 11 isolates fell into a single cluster that was clearly distinct from other genera. There is now strong evidence that V. marinus should be reclassified as Moritella marina gen. nov., comb. nov.

Randomly amplified polymorphic DNA analysis of starved and viable but nonculturable Vibrio vulnificus cells

Vibrio vulnificus is an estuarine bacterium capable of causing a rapidly fatal infection in humans. Because of the low nutrient levels and temperature fluctuations found in the organism's natural habitat, the starvation state and viable but nonculturable (VBNC) state are of particular interest. A randomly amplified polymorphic DNA (RAPD) PCR protocol was developed previously for the detection of V. vulnificus strains grown in rich media and has been applied to starved and VBNC cells of V. vulnificus in the present study. As cells were subjected to starvation in artificial seawater, changes in the RAPD profile were detected as early as 15 min into the starvation period. Most noticeable was a uniform loss of RAPD amplification products. By 4 h of starvation, the cells were undetectable by the RAPD method. Cells that had been starved for up to 1 year again became detectable by the RAPD method when nutrients were added to the starvation microcosm. The same loss of signal, but at a lower rate, was also seen as cells entered the VBNC state. VBNC cells were resuscitated by a temperature upshift and were once again detectable by the RAPD method. The addition of chloramphenicol prevented the RAPD signal from being lost in both the starvation and VBNC states. This suggests that DNA binding proteins produced during starvation and entrance into the VBNC state may be responsible for the inability of the RAPD method to amplify V. vulnificus DNA in these states.

Characterization of Vibrio vulnificus isolated from cockles (Anadara granosa): antimicrobial resistance, plasmid profiles and random amplification of polymorphic DNA analysis

Antibiotic susceptibility, plasmid profiles and random amplification of polymorphic DNA (RAPD) were used to study strains of Vibrio vulnificus isolated from cockles (Anadara granosa). Thirty-six isolates were analyzed. The prevalent biotypes were 1 (72.2% of the isolates) and 2 (27.8%). Among these, 21 strains of biotype 1 and two strains of biotype 2 contained plasmid DNA bands ranging in size from 1.4 to 9.7 MDa. Thirty-one (83.3%) were found to be resistant to one or more of the antimicrobial agents tested, however no specific correlation between antimicrobial resistance patterns and a single biotype was found. In addition, no particular plasmid profile was predictive of a particular pattern of antibiotic susceptibility. Two primers produced polymorphisms in all strains tested, producing bands ranging from 0.25 to 2.7 kb, indicating a high variability among both biotype 1 and biotype 2 of the V. vulnificus strains investigated. RAPD identity across biotypes was also observed among Vibrio vulnificus strains.

An epimerase gene essential for capsule synthesis in Vibrio vulnificus

The extracellular capsule polysaccharide (CPS) of Vibrio vulnificus is a primary virulence factor which allows survival of the bacteria in the human host. To study the genes involved in expression of the capsule, we generated mutants that lost the ability to produce CPS following the insertion of a minitransposon into the genome of an encapsulated, clinical strain of V. vulnificus. A genomic region, from one nonencapsulated mutant, containing the transposon and flanking V. vulnificus DNA was cloned, and a probe complementary to the chromosomal DNA immediately adjacent to the transposon was used to locate this fragment in the genome of the encapsulated parent strain. The fragment, which contained a putative capsule gene, was cloned and, when supplied in trans, complemented the mutation in the nonencapsulated mutant to restore capsule production. In addition, virulence studies, using the 50% lethal dose assay, showed that the restoration of capsule production also restored the virulence of the organism. Sequence analysis of the gene disrupted by the transposon revealed that it matched a nucleotide-sugar epimerase of Vibrio cholerae O139, with 75 and 85% identities at the nucleotide and amino acid levels, respectively. In addition, computer analysis recognized epimerases of various organisms as highly similar to the putative epimerase of V. vulnificus. Finally, a combination of PCR amplification and Southern blotting showed that this epimerase is common to at least 10 strains of V. vulnificus that each express a serologically distinct CPS. Our results indicate that the epimerase gene is essential for capsule expression in V. vulnificus.

Differentiation of marine luminous bacteria using commercial identification plates

Differentiation of marine luminous bacteria using Biology GN plate combined with API 20e or the BBL Crystal ID plate inoculated with cell suspensions in artificial seawater was accomplished by comparison to type species using cluster analysis. Inoculum density affected the results from Biolog GN plates, but had less of an effect on the reactions obtained from API 20e strip or BBL Crystal ID plate. In a few cases, combination of the Biolog GN traits along with either the API 20e or Crystal ID traits was necessary to differentiate some marine luminous bacteria.

Microbiological monitoring of Castellammare Gulf (TP) waters for their suitability in marine aquaculture

A three year investigation into the microbiological conditions of the waters of the Gulf of Castellammare (TP) was carried out in order to evaluate the possible utilization of this area as an aquaculture site. Analysis of a total of 168 samples was aimed at estimating the quantitative distribution of total and fecal coliforms, enterococci and halophilic vibrios. The qualitative distribution of Vibrio species was also studied with particular reference to potentially pathogenic species. Coliforms showed the highest densities (10(2)-10(3) CFU/100 ml) in November 1993 at the coastal stations and mostly negative values during the subsequent samplings; in contrast, halophilic vibrios prevailed in the warm months. V. alginolyticus and V. fluvialis prevailed respectively among the Vibrio population grown at 35 and 24 degrees C, grouped in 13 and in 4 clusters at similarity levels of 81-96%. Quantitative data demonstrate the presence of low levels of microbial contamination, which suggests the general suitability of the area for fish farming.

Structural characterization of the lipopolysaccharide O-antigen and capsular polysaccharide of Vibrio ordalii serotype O:2

Structures of the capsular and O-chain polysaccharides of Vibrio ordalii serotype O:2, the causative agent of vibriosis in salmonid fish, were determined by high-field NMR techniques, mass spectrometric methods and partial hydrolysis. Both polymers were shown to be composed of linear tetrasaccharide repeating units, having the structure: carbohydrate sequence [see text].

Vibrio pectenicida sp. nov., a pathogen of scallop (Pecten maximus) larvae

Five strains were isolated from moribund scallop (Pecten maximus) larvae over 5 years (1990-1995) during outbreaks of disease in a hatchery (Argenton, Brittany, France). Their pathogenic activity on scallop larvae was previously demonstrated by experimental exposure. The phenotypic and genotypic features of the strains were identical. The G + C content of the strains was in the range 39-41 mol%. DNA-DNA hybridization showed a minimum of 73% intragroup relatedness. Phylogenetic analysis of small-subunit rRNA sequences confirmed that these strains should be affiliated within the family Vibrionaceae and that they are closely related to Vibrio tapetis and Vibrio splendidus. Phenotypic and genotypic analyses revealed that the isolates were distinct from these two vibrios and so constitute a new species in the genus Vibrio. They utilized only a limited number of organic substrates as sole carbon sources, including betaine and rhamnose, but did not utilize glucose and fructose. In addition, their responses were negative for indole, acetoin, decarboxylase and dihydrolase production. The name Vibrio pectenicida is proposed for the new species; strain A365 is the type strain (= CIP 105190T).

Vibrio halioticoli sp. nov., a non-motile alginolytic marine bacterium isolated from the gut of the abalone Haliotis discus hannai

Six alginolytic, facultatively anaerobic, non-motile marine bacteria were isolated from the gut of abalone Haliotis discus hannai. DNA-DNA hybridization data showed that the six strains constituted a single genospecies. Phylogenetic analyses of 16S rDNA sequences indicated that the isolates should be assigned to the genus Vibrio. The phenotypic features of the isolates were closely related to Vibrio fischeri and Vibrio pelagius biovar I, but 13 traits (motility, luminescence, alginase production, lipase production, lysine decarboxylase, indole production, growth in 1 and 6% NaCl and assimilation of five carbon compounds) distinguished these strains from V. fischeri, and 17 traits (motility, growth at 37 degrees C, lipase production, indole production, growth in 1 and 6% NaCl, acid from sucrose and D-sorbitol, and assimilation of nine carbon compounds) distinguished these strains from V. pelagius. The G + C content of the isolates was 41.6-43.1 mol%. According to DNA-DNA hybridization data and 16S rDNA phylogenetic analyses, it was concluded that the six isolates constitute a new species different from any other Vibrio species. The name Vibrio halioticoli sp. nov. (type strain IAM 14596T) is proposed. A set of phenotypic features which enables differentiation of the new species from other species of the Vibrionaceae family is described.