Prevalence, Antibiotics Resistance and Plasmid Profiling of Vibrio spp. Isolated from Cultured Shrimp in Peninsular Malaysia

Vibrio is the most common bacterium associated with diseases in crustaceans. Outbreaks of vibriosis pose a serious threat to shrimp production. Therefore, antibiotics are commonly used as preventative and therapeutic measures. Unfortunately, improper use of antibiotics leads to antibiotic resistance. Nevertheless, information on the occurrence of Vibrio spp. and antibiotic use in shrimp, particularly in Malaysia, is minimal. This study aimed to provide information on the occurrence of Vibrio spp., its status of antibiotic resistance and the plasmid profiles of Vibrio spp. isolated from cultured shrimp in Peninsular Malaysia. Shrimp were sampled from seven farms that were located in different geographical regions of Peninsular Malaysia. According to the observations, 85% of the shrimp were healthy, whereas 15% were unhealthy. Subsequently, 225 presumptive Vibrio isolates were subjected to biochemical tests and molecular detection using the pyrH gene. The isolates were also tested for antibiotic susceptibility against 16 antibiotics and were subjected to plasmid profiling. Eventually, 13 different Vibrio spp. were successfully isolated and characterized using the pyrH gene. They were the following: V. parahaemolyticus (55%), V. communis (9%), V. campbellii (8%), V. owensii (7%), V. rotiferianus (5%), Vibrio spp. (4%), V. alginolyticus (3%), V. brasiliensis (2%), V. natriegens (2%), V. xuii (1%), V. harveyi (1%), V. hepatarius (0.4%) and P. damselae (3%). Antibiotic susceptibility profiles revealed that all isolates were resistant to penicillin G (100%), but susceptible to norfloxacin (96%). Furthermore, 16% of the isolates revealed MAR of less than 0.2, while 84% were greater than 0.2. A total of 125 isolates harbored plasmids with molecular weights between 1.0 and above 10 kb, detected among the resistant isolates. The resistant isolates were mediated by both chromosomal and plasmid factors. These findings support the use of surveillance data on the emerging patterns of antimicrobial-resistance and plasmid profiles of Vibrio spp. in shrimp farms. The findings from this study can be used to develop a better disease management strategy for shrimp farming.

Cnidarian Immunity and the Repertoire of Defense Mechanisms in Anthozoans

Anthozoa is the most specious class of the phylum Cnidaria that is phylogenetically basal within the Metazoa. It is an interesting group for studying the evolution of mutualisms and immunity, for despite their morphological simplicity, Anthozoans are unexpectedly immunologically complex, with large genomes and gene families similar to those of the Bilateria. Evidence indicates that the Anthozoan innate immune system is not only involved in the disruption of harmful microorganisms, but is also crucial in structuring tissue-associated microbial communities that are essential components of the cnidarian holobiont and useful to the animal's health for several functions including metabolism, immune defense, development, and behavior. Here, we report on the current state of the art of Anthozoan immunity. Like other invertebrates, Anthozoans possess immune mechanisms based on self/non-self-recognition. Although lacking adaptive immunity, they use a diverse repertoire of immune receptor signaling pathways (PRRs) to recognize a broad array of conserved microorganism-associated molecular patterns (MAMP). The intracellular signaling cascades lead to gene transcription up to endpoints of release of molecules that kill the pathogens, defend the self by maintaining homeostasis, and modulate the wound repair process. The cells play a fundamental role in immunity, as they display phagocytic activities and secrete mucus, which acts as a physicochemical barrier preventing or slowing down the proliferation of potential invaders. Finally, we describe the current state of knowledge of some immune effectors in Anthozoan species, including the potential role of toxins and the inflammatory response in the Mediterranean Anthozoan Anemonia viridis following injection of various foreign particles differing in type and dimensions, including pathogenetic bacteria.

Prevalence, antimicrobial susceptibility and plasmid profiling of Vibrio spp. isolated from cultured groupers in Peninsular Malaysia

BACKGROUND

Numerous prevalence studies of Vibrio spp. infection in fish have been extensively reported worldwide, including Malaysia. Unfortunately, information on the prevalence of Vibrio spp. in groupers (Epinephelus spp.) is limited. In this study, groupers obtained from nine farms located at different geographical regions in Malaysia were sampled for the presence of pathogenic Vibrio spp. and their susceptibility profiles against seven antibiotics.

RESULTS

Out of 270 grouper samples, 195 (72%) were detected with the presence of Vibrio spp. Vibrio communis showed highest prevalence in grouper (28%), followed by V. parahaemolyticus (25%), V. alginolyticus (19%), V. vulnificus (14%), V. rotiferianus (3%), Vibrio sp. (3%), V. campbellii (2%), V. mytili (2%), V. furnissii (2%), V. harveyi (1%), V. tubiashii (1%), V. fluvialis (0.3%) and V. diabolicus (0.3%). Assessment on the antibiotic susceptibility profiles of the Vibrio spp. revealed that majority of the isolates were susceptible to tetracycline, streptomycin, erythromycin and bacitracin, but resistance to ampicillin, penicillin G and vancomycin. The mean MAR index of the Vibrio isolates was 0.51, with 85% of the isolates showed MAR index value of higher than 0.2. Results indicate that the Vibrio spp. were continuously exposed to antibiotics. Furthermore, the plasmid profiles of Vibrio spp. showed that 38.7% of the isolates harbored plasmid with molecular weight of more than 10 kb, while 61.3% were without plasmid. During curing process, Vibrio spp. lost their plasmid, but remained resistant to ampicillin, penicillin G, bacitracin and vancomycin while a few isolates remained resistant to erythromycin, streptomycin and tetracycline. The results suggested that the resistance to antibiotics in isolated Vibrio spp. might be due to chromosomal and plasmid borne.

CONCLUSIONS

This study demonstrates the prevalence of Vibrio spp. in groupers and the distribution of multidrug resistance strains that could be of concern to the farmers in Malaysia. In addition, data from this study can be further used in fish disease management plan.

Cnidarian Interaction with Microbial Communities: From Aid to Animal's Health to Rejection Responses

The phylum Cnidaria is an ancient branch in the tree of metazoans. Several species exert a remarkable longevity, suggesting the existence of a developed and consistent defense mechanism of the innate immunity capable to overcome the potential repeated exposure to microbial pathogenic agents. Increasing evidence indicates that the innate immune system in Cnidarians is not only involved in the disruption of harmful microorganisms, but also is crucial in structuring tissue-associated microbial communities that are essential components of the Cnidarian holobiont and useful to the animal's health for several functions, including metabolism, immune defense, development, and behavior. Sometimes, the shifts in the normal microbiota may be used as "early" bio-indicators of both environmental changes and/or animal disease. Here the Cnidarians relationships with microbial communities and the potential biotechnological applications are summarized and discussed.

Alcanivorax dieselolei, an alkane-degrading bacterium associated with the mucus of the zoanthid Palythoa caribaeorum (Cnidaria, Anthozoa)

Analyses of 16S rDNA genes were used to identify the microbiota isolated from the mucus of the zoanthid Palythoa caribaeorum at Porto de Galinhas on the coast of Pernambuco State, Brazil. This study is important as the first report of this association, because of the potential biotechnological applications of the bacterium Alcanivorax dieselolei, and as evidence for the presence of a hydrocarbon degrading bacterium in a reef ecosystem such as Porto de Galinhas.

Characterization of Bacterial Communities Associated with the Tyrian Purple Producing Gland in a Marine Gastropod

Dicathais orbita is a marine mollusc recognised for the production of anticancer compounds that are precursors to Tyrian purple. This study aimed to assess the diversity and identity of bacteria associated with the Tyrian purple producing hypobranchial gland, in comparison with foot tissue, using a high-throughput sequencing approach. Taxonomic and phylogenetic analysis of variable region V1-V3 of 16S rRNA bacterial gene amplicons in QIIME and MEGAN were carried out. This analysis revealed a highly diverse bacterial assemblage associated with the hypobranchial gland and foot tissues of D. orbita. The dominant bacterial phylum in the 16S rRNA bacterial profiling data set was Proteobacteria followed by Bacteroidetes, Tenericutes and Spirochaetes. In comparison to the foot, the hypobranchial gland had significantly lower bacterial diversity and a different community composition, based on taxonomic assignment at the genus level. A higher abundance of indole producing Vibrio spp. and the presence of bacteria with brominating capabilities in the hypobranchial gland suggest bacteria have a potential role in biosynthesis of Tyrian purple in D. orbita.

Unique and conserved genome regions in Vibrio harveyi and related species in comparison with the shrimp pathogen Vibrio harveyi CAIM 1792

Vibrio harveyi CAIM 1792 is a marine bacterial strain that causes mortality in farmed shrimp in north-west Mexico, and the identification of virulence genes in this strain is important for understanding its pathogenicity. The aim of this work was to compare the V. harveyi CAIM 1792 genome with related genome sequences to determine their phylogenic relationship and explore unique regions in silico that differentiate this strain from other V. harveyi strains. Twenty-one newly sequenced genomes were compared in silico against the CAIM 1792 genome at nucleotidic and predicted proteome levels. The proteome of CAIM 1792 had higher similarity to those of other V. harveyi strains (78%) than to those of the other closely related species Vibrio owensii (67%), Vibrio rotiferianus (63%) and Vibrio campbellii (59%). Pan-genome ORFans trees showed the best fit with the accepted phylogeny based on DNA-DNA hybridization and multi-locus sequence analysis of 11 concatenated housekeeping genes. SNP analysis clustered 34/38 genomes within their accepted species. The pangenomic and SNP trees showed that V. harveyi is the most conserved of the four species studied and V. campbellii may be divided into at least three subspecies, supported by intergenomic distance analysis. blastp atlases were created to identify unique regions among the genomes most related to V. harveyi CAIM 1792; these regions included genes encoding glycosyltransferases, specific type restriction modification systems and a transcriptional regulator, LysR, reported to be involved in virulence, metabolism, quorum sensing and motility.

Contrasting inter- and intraspecies recombination patterns in the "Harveyi clade" vibrio collected over large spatial and temporal scales

Recombination plays an important role in the divergence of bacteria, but the frequency of interspecies and intraspecies recombination events remains poorly understood. We investigated recombination events that occurred within core genomes of 35 Vibrio strains (family Vibrionaceae, Gammaproteobacteria), from six closely related species in the so-called “Harveyi clade.” The strains were selected from a collection of strains isolated in the last 90 years, from various environments worldwide. We found a close relationship between the number of interspecies recombination events within core genomes of the 35 strains and the overall genomic identity, as inferred from calculations of the average nucleotide identity. The relationship between the overall nucleotide identity and the number of detected interspecies recombination events was comparable when analyzing strains isolated over 80 years apart, from different hemispheres, or from different ecologies, as well as in strains isolated from the same geographic location within a short time frame. We further applied the same method of detecting recombination events to analyze 11 strains of Vibrio campbellii, and identified disproportionally high number of intraspecies recombination events within the core genomes of some, but not all, strains. The high number of recombination events was detected between V. campbellii strains that have significant temporal (over 18 years) and geographical (over 10,000 km) differences in their origins of isolation. Results of this study reveal a remarkable stability of Harveyi clade species, and give clues about the origins and persistence of species in the clade.

Characterization of vibrios diversity in the mucus of the polychaete Myxicola infundibulum (Annellida, Polichaeta)

Vibrios are among the most abundant culturable microbes in aquatic environments. They can be either free-living in the water column or associated with several marine organisms as mutualists, saprophytes, or parasites. In the present study we analysed vibrios abundance and diversity in the mucus of the polychaete Myxicola infundibulum, complementing culture-based with molecular methods. Vibrios reached 4.6 × 10(3) CFU mL(-1) thus representing a conspicuous component of the heterotrophic culturable bacteria. In addition, luminous vibrios accounted for about 60% of the total culturable vibrios in the mucus. The isolates were assigned to: Vibrio gigantis, Vibrio fischeri, Vibrio jasicida, Vibrio crassostreae, Vibrio kanaloae, and Vibrio xuii. Two Vibrio isolates (MI-13 and MI-15) may belong to a new species. We also tested the ability of the Vibrio isolates to grow on M. infundibulum mucus as the sole carbon source. All strains showed appreciable growth in the presence of mucus, leading us to conclude that this matrix, which is abundant and covers the animal entirely, may represent a microcosm and a food source for some bacteria, playing a crucial role in the structuring of a mucus-associated beneficial microbial community. Moreover, the trophic relationship between vibrios and M. infundibulum mucus could be enhanced by the protection that mucus offers to vibrios. The results of this study represent a contribution to the growing evidence for complex and dynamic invertebrate-microbe associations present in nature and highlight the importance of exploring relationships that Vibrio species establish with marine invertebrates.

Culturable heterotrophic bacteria associated with healthy and bleached scleractinian Madracis decactis and the fireworm Hermodice carunculata from the remote St. Peter and St. Paul Archipelago, Brazil

We report on the first characterization of the culturable heterotrophic bacteria of the scleractinian Madracis decactis. In addition, we characterized the culturable bacteria associated with the fireworm Hermodice carunculata, observed predating partially bleached coral colonies. Our study was carried out in the remote St. Peter and St. Paul Archipelago (SPSPA), Mid-Atlantic Ridge, Brazil. We constituted a 403 isolates collection and subsequently characterized it by means of pyrH and 16S rRNA partial sequences. We identified Photobacterium, Bacillus, and Vibrio species as members of the culturable microbiota of healthy M. decactis. V. campbellii, V. harveyi, V. communis, and V. maritimus were the most commonly found Vibrio species in healthy corals, representing more than 60 % of all vibrio isolates. Most of the vibrios isolated from the fireworm's tissues (n = 143; >90 %) were identified as V. shiloi. However, we did not recover V. shiloi from bleached M. decactis. Instead, we isolated V. communis, a novel Photobacterium species, Bacillus, Kocuria, and Pseudovibrio, suggesting a possible role of other facultative anaerobic bacteria and/or environmental features (such as water quality) in the onset of bleaching in SPSPA's M. decactis.

Taxonomic revision of Harveyi clade bacteria (family Vibrionaceae) based on analysis of whole genome sequences

Use of inadequate methods for classification of bacteria in the so-called Harveyi clade (family Vibrionaceae, Gammaproteobacteria) has led to incorrect assignment of strains and proliferation of synonymous species. In order to resolve taxonomic ambiguities within the Harveyi clade and to test usefulness of whole genome sequence data for classification of Vibrionaceae, draft genome sequences of 12 strains were determined and analysed. The sequencing included type strains of seven species: Vibrio sagamiensis NBRC 104589T, Vibrio azureus NBRC 104587T, Vibrio harveyi NBRC 15634T, Vibrio rotiferianus LMG 21460T, Vibrio campbellii NBRC 15631T, Vibrio jasicida LMG 25398T, and Vibrio owensii LMG 25443T. Draft genome sequences of strain LMG 25430, previously designated the type strain of [Vibrio communis], and two strains (MWB 21 and 090810c) from the ‘beijerinckii’ lineage were also determined. Whole genomes of two additional strains (ATCC 25919 and 200612B) that previously could not be assigned to any Harveyi clade species were also sequenced. Analysis of the genome sequence data revealed a clear case of synonymy between V. owensii and [V. communis], confirming an earlier proposal to synonymize both species. Both strains from the ‘beijerinckii’ lineage were classified as V. jasicida, while the strains ATCC 25919 and 200612B were classified as V. owensii and V. campbellii, respectively. We also found that two strains, AND4 and Ex25, are closely related to Harveyi clade bacteria, but could not be assigned to any species of the family Vibrionaceae. The use of whole genome sequence data for the taxonomic classification of the Harveyi clade bacteria and other members of the family Vibrionaceae is also discussed.

Virulence Changes to Harveyi Clade Bacteria Infected with Bacteriophage from Vibrio owensii

Vibrio owensii is one of the most virulent vibrios known being able to kill crustacean larvae at 10(2) CFU ml(-1). This study describes virulence changes to naïve strains of Vibrio harveyi and Vibrio campbellii when infected with the bacteriophage VOB from a closely related species V. owensii 47666-1. The bacteriophage from V. owensii was induced into lytic phase by using mitomycin C at 100 ng ml(-1). One strain of V. harveyi and two strains of V. campbellii from 29 tested containing no prophage were susceptible to lysogenic conversion with VOB. Virulence changes induced in Harveyi clade bacteria included the up-regulation of protein secretion, statistically significant increased haemolysin and chitinase production and increased mortality to nauplii of Penaeus monodon. No change in siderophore production was observed. Bacteriophage VOB is likely to be responsible for some of the virulence factors expressed by V. owensii. As this bacteriophage is able to infect strains of V. harveyi and V. campbellii this phage may contribute to increased virulence of other vibrios in aquaculture and in the natural environment.

Partial characterization of an exopolysaccharide secreted by a marine bacterium, Vibrio neocaledonicus sp. nov., from New Caledonia

AIMS

Exopolysaccharides (EPS) are industrially valuable molecules with numerous useful properties. This study describes the techniques used for the identification of a novel Vibrio bacterium and preliminary characterization of its EPS.

METHODS AND RESULTS

Bioprospection in marine intertidal areas of New Caledonia followed by screening for EPS producing brought to selection of the isolate NC470. Phylogenetic analysis (biochemical tests, gene sequencing and DNA-DNA relatedness) permitted to identify NC470 as a new member of the Vibrio genus. The EPS was produced in batch fermentation, purified using the ultrafiltration process and analysed by colorimetry, Fourier Transform Infrared spectroscopy, gas chromatography, Nuclear Magnetic Resonance and HPLC-size exclusion chromatography. This EPS exhibits a high N-acetyl-hexosamines and uronic acid content with a low amount of neutral sugar. The molecular mass was 672 × 10(3)  Da. These data are relevant for possible technological exploitation.

CONCLUSIONS

We propose the name Vibrio neocaledonicus sp. nov for this isolate NC470, producing an EPS with an unusual sugar composition. Comparison with other known polymers permitted to select applications for this polymer.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study contributes to evaluate the marine biodiversity of New Caledonia. It also highlights the biotechnological potential of New Caledonia marine bacteria.

Genetic and phylogenetic evidence for horizontal gene transfer among ecologically disparate groups of marine Vibrio

Vibrio represents a diverse bacterial genus found in different niches of the marine environment, including numerous genera of marine sponges (phylum Porifera), inhabiting different depths and regions of benthic seas, that are potentially important in driving adaptive change among Vibrio spp. Using 16S rRNA gene sequencing, a previous study showed that sponge-derived (SD) vibrios clustered with their mainstream counterparts present in shallow, coastal ecosystems, suggesting a genetic relatedness between these populations. Sequences from the topA, ftsZ, mreB, rpoD, rctB and toxR genes were used to investigate the degree of relatedness existing between these two separate populations by examining their phylogenetic and genetic disparity. Phylogenies were constructed from the concatenated sequences of the six housekeeping genes using maximum-parsimony, maximum-likelihood and neighbour-joining algorithms. Genetic recombination was evaluated using the incongruence length difference test, Split decomposition and measuring overall compatibility of sites. This combined technical approach provided evidence that SD Vibrio strains are largely genetically homologous to their shallow-water counterparts. Moreover, the analyses conducted support the existence of extensive horizontal gene transfer between these two groups, supporting the idea of a single panmictic population structure among vibrios from two seemingly distinct, marine environments.

Vibrio owensii induces the tissue loss disease Montipora white syndrome in the Hawaiian reef coral Montipora capitata

Incidences of coral disease in the Indo-Pacific are increasing at an alarming rate. In particular, Montipora white syndrome, a tissue-loss disease found on corals throughout the Hawaiian archipelago, has the potential to degrade Hawaii’s reefs. To identify the etiologic agent of Montipora white syndrome, bacteria were isolated from a diseased fragment of Montipora capitata and used in a screen for virulent strains. A single isolate, designated strain OCN002, recreated disease signs in 53% of coral fragments in laboratory infection trials when added to a final concentration of 10⁷ cells/ml of seawater. In addition to displaying similar signs of disease, diseased coral fragments from the field and those from infection trials both had a dramatic increase in the abundance of associated culturable bacteria, with those of the genus Vibiro well represented. Bacteria isolated from diseased fragments used in infection trails were shown to be descendants of the original OCN002 inocula based on both the presence of a plasmid introduced to genetically tag the strain and the sequence of a region of the OCN002 genome. In contrast, OCN002 was not re-isolated from fragments that were exposed to the strain but did not develop tissue loss. Sequencing of the rrsH gene, metabolic characterization, as well as multilocus sequence analysis indicated that OCN002 is a strain of the recently described species Vibrio owensii. This investigation of Montipora white syndrome recognizes V. owensii OCN002 as the first bacterial coral pathogen identified from Hawaii’s reefs and expands the range of bacteria known to cause disease in corals.

Vibrio jasicida sp. nov., a member of the Harveyi clade, isolated from marine animals (packhorse lobster, abalone and Atlantic salmon)

Six isolates of a facultatively anaerobic bacterium were recovered in culture from marine invertebrates and vertebrates, including packhorse lobster (Jasus verreauxi), abalone (Haliotis sp.) and Atlantic salmon (Salmo salar), between 1994 and 2002. The bacteria were Gram-negative, rod-shaped and motile by means of more than one polar flagellum, oxidase-positive, catalase-positive and able to grow in the presence of 0.5–8.0 % NaCl (optimum 3.0–6.0 %) and at 10–37 °C (optimum 25–30 °C). On the basis of 16S rRNA gene sequence analysis and multilocus sequence analysis (MLSA) using five loci (2443 bp; gyrB, pyrH, ftsZ, mreB and gapA), the closest phylogenetic neighbours of strain TCFB 0772T were the type strains of Vibrio communis (99.8 and 94.6 % similarity, respectively), Vibrio owensii (99.8 and 94.1 %), Vibrio natriegens (99.4 and 88.8 %), Vibrio parahaemolyticus (99.4 and 90.3 %), Vibrio rotiferianus (99.2 and 94.4 %), Vibrio alginolyticus (99.1 and 89.3 %) and Vibrio campbellii (99.1 and 92.3 %). DNA–DNA hybridization confirmed that the six isolates constitute a unique taxon that is distinct from other known species of Vibrio . In addition, this taxon can be readily differentiated phenotypically from other Vibrio species. The six isolates therefore represent a novel species, for which the name Vibrio jasicida sp. nov. is proposed; the novel species is represented by the type strain TCFB 0772T ( = JCM 16453T  = LMG 25398T) (DNA G+C content 45.9 mol%) and reference strains TCFB 1977 ( = JCM 16454) and TCFB 1000 ( = JCM 16455).

Vibrio inhibens sp. nov., a novel bacterium with inhibitory activity against Vibrio species

Strain BFLP-10(T), isolated from faeces of wild long-snouted seahorses (Hippocampus guttulatus), is a Gram-negative, motile and facultatively anaerobic rod. This bacterium produces inhibitory activity against Vibrio species. Phylogenetic analysis based on 16S rRNA gene sequences showed that strain BFLP-10(T) was a member of the genus Vibrio and was most closely related to Vibrio owensii (99%), Vibrio communis (98.9%), Vibrio sagamiensis (98.9%) and Vibrio rotiferianus (98.4%). However, multilocus sequence analysis using gyrB, pyrH, recA and topA genes revealed low levels of sequence similarity (<91.2%) with these closely related species. In addition, strain BFLP-10(T) could be readily differentiated from other closely related species by several phenotypic properties and fatty acid profiles. The G+C content of the DNA was 45.6 mol%. On the basis of phenotypic, chemotaxonomic and phylogenetic data, strain BFLP-10(T) represents a novel species within the genus Vibrio, for which the name Vibrio inhibens sp. nov. is proposed. The type strain is BFLP-10(T) (=CECT 7692(T)=DSM 23440(T)).

Genetic and phylogenetic evidence for misidentification of Vibrio species within the Harveyi clade

AIM

  This report describes the use of a six-gene multi-locus sequence analysis (MLSA) to correctly identify Vibrio strains of the Harveyi clade.

METHODS AND RESULTS

  Vibrio isolates were characterized using a six housekeeping gene MLSA. The study provided evidence supporting: (i) a substantial number of reference strains maintained within commercial culture collections are misidentified taxonomically at the species level; (ii) two V. alginolyticus subclades retain species-level divergence; and (iii) V. communis and V. owensii likely are the same species.

CONCLUSION

  A significant number (n = 10) of Harveyi clade Vibrio strains have been inaccurately identified, including evidence that V. communis and V. owensii strains, two recently discovered species assigned to the Harveyi clade, comprise a single species.

SIGNIFICANCE AND IMPACT OF THE STUDY

  As Harveyi clade vibrios have an enormous impact on human and aquatic animal health, it is of paramount importance to identify members of the Harveyi clade correctly.

Vibrio variabilis sp. nov. and Vibrio maritimus sp. nov., isolated from Palythoa caribaeorum

Two novel vibrio isolates (R-40492T and R-40493T) originating from the zoanthid Palythoa caribaeorum in Brazil in 2005 were taxonomically characterized by means of a polyphasic approach comprising multilocus sequence analysis (MLSA), DNA–DNA hybridization (DDH), ΔT m analysis and phenotypic characterization. Phylogenetic analysis based on 16S rRNA gene sequences showed that R-40492T and R-40493T fell within the genus Vibrio and were most closely related to each other with 99 % similarity; similarities of these two novel isolates towards Vibrio neptunius LMG 20536T, Vibrio coralliilyticus LMG 20984T, Vibrio nigripulchritudo LMG 3896T, Vibrio sinaloensis LMG 25238T and Vibrio brasiliensis LMG 20546T varied between 97.1 and 98.5 %. DDH experiments showed that the two isolates had less than 15 % relatedness to the phylogenetically most closely related Vibrio species. R-40492T and R-40493T had 55–57 % relatedness to each other. The ΔTm between R-40492T and R-40493T was 6.12 °C. In addition, MLSA of concatenated sequences (16S rRNA, ftsZ, gyrB, recA, rpoA, topA, pyrH and mreB; 6035 bp in length) showed that the two novel isolates formed a separate branch with less than 92 % concatenated gene sequence similarity towards known species of vibrios. Two novel species are proposed to accommodate these novel isolates, namely Vibrio variabilis sp. nov. (type strain, R-40492T = LMG 25438T = CAIM 1454T) and Vibrio maritimus sp. nov. (type strain, R-40493T = LMG 25439T = CAIM 1455T).

Multilocus sequence analysis provides basis for fast and reliable identification of Vibrio harveyi-related species and reveals previous misidentification of important marine pathogens

Vibrio harveyi and related bacteria are important pathogens responsible for severe economic losses in the aquaculture industry worldwide. Phenotypic tests and 16S rRNA gene analysis fail to discriminate species within the V. harveyi group because these are phenotypically and genetically nearly identical. This study used multilocus sequence analysis to identify 36 V. harveyi-like isolates obtained from a wide range of sources in Australia and to re-evaluate the identity of important pathogens. Phylogenies inferred from the 16S rRNA gene and five concatenated protein-coding genes (rpoA-pyrH-topA-ftsZ-mreB) revealed four well-supported clusters identified as V. harveyi, V. campbellii, V. rotiferianus and V. owensii. Results revealed that important V. campbellii and V. owensii prawn pathogens were previously misidentified as V. harveyi and also that the recently described V. communis sp. nov. is likely a junior synonym of V. owensii. Although the MLSA topologies corroborated the 16S rRNA gene phylogeny, the latter was less informative than each of the protein-coding genes taken singularly or the concatenated dataset. A two-locus phylogeny based on topA-mreB concatenated sequences was consistent with the five-locus MLSA phylogeny. Global Bayesian phylogenies inferred from topA-mreB suggested that this gene combination provides a practical yet still accurate approach for routine identification of V. harveyi-related species.

Vibrio xiamenensis sp. nov., a cellulase-producing bacterium isolated from mangrove soil

A taxonomic study was carried out on a cellulase-producing bacterium, strain G21(T), isolated from mangrove soil in Xiamen, Fujian province, China. Cells were Gram-negative, slightly curved rods, motile with a single polar flagellum. The strain grew at 15-40 °C and in 0.5-10% (w/v) NaCl. Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain G21(T) belonged to the genus Vibrio and formed a clade with Vibrio furnissii ATCC 350116(T) (97.4% sequence similarity), V. fluvialis LMG 7894(T) (97.1%) and V. ponticus CECT 5869(T) (96.1%). However, multilocus sequence analysis (using rpoA, recA, mreB, gapA, gyrB and pyrH sequences) and DNA-DNA hybridization experiments indicated that the strain was distinct from the closest related Vibrio species. Additionally, strain G21(T) could be differentiated from them phenotypically by the ability to grow in 10% NaCl but not on TCBS plates, its enzyme activity spectrum, citrate utilization, oxidization of various carbon sources, hydrolysis of several substrates and its cellular fatty acid profile. The G+C content of the genomic DNA was 46.0 mol%. The major cellular fatty acids were summed feature 3 (C(16:1)ω7c and/or iso-C(15:0) 2-OH), C(16:0) and C(18:1)ω7c. The major polar lipids were phosphatidylethanolamine and phosphatidylglycerol, with trace amounts of diphosphatidylglycerol. The predominant quinones were Q-8 and Q-7. Based on phylogenetic, phenotypic and chemotaxonomic characteristics and DNA-DNA hybridization analysis, it is concluded that strain G21(T) represents a novel species of the genus Vibrio, for which the name Vibrio xiamenensis sp. nov. is proposed. The type strain is G21(T) ( = DSM 22851(T)  = CGMCC 1.10228(T)).

Vibrio caribbeanicus sp. nov., isolated from the marine sponge Scleritoderma cyanea

A Gram-negative, oxidase-positive, catalase-negative, facultatively anaerobic, motile, curved rod-shaped bacterium, strain N384(T), was isolated from a marine sponge (Scleritoderma cyanea; phylum Porifera) collected from a depth of 795 feet (242 m) off the west coast of Curaçao. On the basis of 16S rRNA gene sequencing, strain N384(T) was shown to belong to the genus Vibrio, most closely related to Vibrio brasiliensis LMG 20546(T) (98.8% similarity), Vibrio nigripulchritudo ATCC 27043(T) (98.5%), Vibrio tubiashii ATCC 19109(T) (98.6%) and V. sinaloensis DSM 21326(T) (98.2%). The DNA G+C content of strain N384(T) was 41.6 mol%. An analysis of concatenated sequences of five genes (gyrB, rpoA, pyrH, mreB and ftsZ; 4068 bp) demonstrated a clear separation between strain N384(T) and its closest neighbours and clustered strain N384(T) into the 'Orientalis' clade of vibrios. Phenotypically, the novel species belonged to the arginine dihydrolase-positive, lysine decarboxylase- and ornithine decarboxylase-negative (A+/L-/O-) cluster. The novel species was also differentiated on the basis of fatty acid composition, specifically that the proportions of iso-C(13:0), iso-C(15:0), C(15:0), iso-C(16:0), C(16:0), iso-C(17:0), C(17:1)ω8c and C(17:0) were significantly different from those found in V. brasiliensis and V. sinaloensis. The results of DNA-DNA hybridization, average nucleotide identity and physiological and biochemical tests further allowed differentiation of this strain from other described species of the genus Vibrio. Collectively, these findings confirm that strain N384(T) represents a novel Vibrio species, for which the name Vibrio caribbeanicus sp. nov. is proposed, with the type strain N384(T) ( = ATCC BAA-2122(T) = DSM 23640(T)).