Frequent nonhomologous replacement of replicative helicase loaders by viruses in Vibrionaceae.

Several microbial genomes lack textbook-defined essential genes. If an essential gene is absent from a genome, then an evolutionarily independent gene of unknown function complements its function. Here, we identified frequent nonhomologous replacement of an essential component of DNA replication initiation, a replicative helicase loader gene, in Vibrionaceae. Our analysis of Vibrionaceae genomes revealed two genes with unknown function, named vdhL1 and vdhL2, that were substantially enriched in genomes without the known helicase-loader genes. These genes showed no sequence similarities to genes with known function but encoded proteins structurally similar with a viral helicase loader. Analyses of genomic syntenies and coevolution with helicase genes suggested that vdhL1/2 encodes a helicase loader. The in vitro assay showed that Vibrio harveyi VdhL1 and Vibrio ezurae VdhL2 promote the helicase activity of DnaB. Furthermore, molecular phylogenetics suggested that vdhL1/2 were derived from phages and replaced an intrinsic helicase loader gene of Vibrionaceae over 20 times. This high replacement frequency implies the host's advantage in acquiring a viral helicase loader gene.

Identification of promoter activity in gene-less cassettes from Vibrionaceae superintegrons.

Integrons are genetic platforms that acquire new genes encoded in integron cassettes (ICs), building arrays of adaptive functions. ICs generally encode promoterless genes, whose expression relies on the platform-associated Pc promoter, with the cassette array functioning as an operon-like structure regulated by the distance to the Pc. This is relevant in large sedentary chromosomal integrons (SCIs) carrying hundreds of ICs, like those in Vibrio species. We selected 29 gene-less cassettes in four Vibrio SCIs, and explored whether their function could be related to the transcription regulation of adjacent ICs. We show that most gene-less cassettes have promoter activity on the sense strand, enhancing the expression of downstream cassettes. Additionally, we identified the transcription start sites of gene-less ICs through 5'-RACE. Accordingly, we found that most of the superintegron in Vibrio cholerae is not silent. These promoter cassettes can trigger the expression of a silent dfrB9 cassette downstream, increasing trimethoprim resistance >512-fold in V. cholerae and Escherichia coli. Furthermore, one cassette with an antisense promoter can reduce trimethoprim resistance when cloned downstream. Our findings highlight the regulatory role of gene-less cassettes in the expression of adjacent cassettes, emphasizing their significance in SCIs and their clinical importance if captured by mobile integrons.

Dynamics of efflux pumps in antimicrobial resistance, persistence, and community living of Vibrionaceae.

The marine bacteria of the Vibrionaceae family are significant from the point of view of their role in the marine geochemical cycle, as well as symbionts and opportunistic pathogens of aquatic animals and humans. The well-known pathogens of this group, Vibrio cholerae, V. parahaemolyticus, and V. vulnificus, are responsible for significant morbidity and mortality associated with a range of infections from gastroenteritis to bacteremia acquired through the consumption of raw or undercooked seafood and exposure to seawater containing these pathogens. Although generally regarded as susceptible to commonly employed antibiotics, the antimicrobial resistance of Vibrio spp. has been on the rise in the last two decades, which has raised concern about future infections by these bacteria becoming increasingly challenging to treat. Diverse mechanisms of antimicrobial resistance have been discovered in pathogenic vibrios, the most important being the membrane efflux pumps, which contribute to antimicrobial resistance and their virulence, environmental fitness, and persistence through biofilm formation and quorum sensing. In this review, we discuss the evolution of antimicrobial resistance in pathogenic vibrios and some of the well-characterized efflux pumps' contributions to the physiology of antimicrobial resistance, host and environment survival, and their pathogenicity.

Elevated estuary water temperature drives fish gut dysbiosis and increased loads of pathogenic vibrionaceae.

Marine water temperatures are increasing globally, with eastern Australian estuaries warming faster than predicted. There is growing evidence that this rapid warming of coastal waters is increasing the abundance and virulence of pathogenic members of the Vibrionaceae, posing a significant health risk to both humans and aquatic organisms. Fish disease, notably outbreaks of emerging pathogens in response to environmental perturbations such as heatwaves, have been recognised in aquaculture settings. Considerably less is known about how rising sea surface temperatures will impact the microbiology of wild fish populations, particularly those within estuarine systems that are more vulnerable to warming. We used a combination of Vibrio-specific quantitative PCR and amplicon sequencing of the 16S rRNA and hsp60 genes to examine seawater and fish (Pelates sexlineatus) gut microbial communities across a quasi-natural experimental system, where thermal pollution from coal-fired power stations creates a temperature gradient of up to 6 °C, compatible with future predicted temperature increases. At the warmest site, fish hindgut microbial communities were in a state of dysbiosis characterised by shifts in beta diversity and a proliferation (71.5% relative abundance) of the potential fish pathogen Photobacterium damselae subsp. damselae. Comparable patterns were not identified in the surrounding seawater, indicating opportunistic proliferation within estuarine fish guts under thermal stress. A subsequent evaluation of predicted future warming-related risk due to pathogenic Vibrionaceae in temperate estuarine fish demonstrated that warming is likely to drive opportunistic pathogen increases in the upper latitudinal range of this estuarine fish, potentially impacting adaptations to future warming. These findings represent a breakthrough in our understanding of the dynamics of emerging pathogens in populations of wild aquatic organisms within environments likely to experience rapid warming under future climate change.

Improving environmental monitoring of Vibrionaceae in coastal ecosystems through 16S rRNA gene amplicon sequencing.

The Vibrionaceae family groups genetically and metabolically diverse bacteria thriving in all marine environments. Despite often representing a minor fraction of bacterial assemblages, members of this family can exploit a wide variety of nutritional sources, which makes them important players in biogeochemical dynamics. Furthermore, several Vibrionaceae species are well-known pathogens, posing a threat to human and animal health. Here, we applied the phylogenetic placement coupled with a consensus-based approach using 16S rRNA gene amplicon sequencing, aiming to reach a reliable and fine-level Vibrionaceae characterization and identify the dynamics of blooming, ecologically important, and potentially pathogenic species in different sites of the northern Adriatic Sea. Water samples were collected monthly at a Long-Term Ecological Research network site from 2018 to 2021, and in spring and summer of 2019 and 2020 at two sites affected by depurated sewage discharge. The 41 identified Vibrionaceae species represented generally below 1% of the sampled communities; blooms (up to ~ 11%) mainly formed by Vibrio chagasii and Vibrio owensii occurred in summer, linked to increasing temperature and particulate matter concentration. Pathogenic species such as Vibrio anguilllarum, Vibrio tapetis, and Photobacterium damselae were found in low abundance. Depuration plant samples were characterized by a lower abundance and diversity of Vibrionaceae species compared to seawater, highlighting that Vibrionaceae dynamics at sea are unlikely to be related to wastewater inputs. Our work represents a further step to improve the molecular approach based on short reads, toward a shared, updated, and curated phylogeny of the Vibrionaceae family.

The pan-genome of Splendidus clade species in the family Vibrionaceae: Insights into evolution, adaptation, and pathogenicity.

The Splendidus clade is the largest clade in Vibrionaceae, and its members are often related to mortality of marine animals with huge economic losses. The molecular bases of their pathogenicity and virulence, however, remain largely unknown. In particular, the complete genome sequences of the Splendidus clade species are rarely registered, which is one of the obstacles to predict core and/or unique genes responsible for their adaptation and pathogenicity, and to perform a fine scale meta-transcriptome during bacterial infection to their hosts. In this study, we obtained the complete genomes of all type strains in the Splendidus clade and revealed that (1) different genome sizes (4.4-5.9 Mb) with V. lentus the biggest and most of them had several big plasmids, likely because of the different features on mobilome elements; (2) the Splendidus clade consists of 19 species except V. cortegadensis, and 3 sub-clades (SC) were defined with the 15 most closely related members as SC1; (3) different carbohydrate degradation preferences may be the result of environmental adaptation; and (4) a broad prediction of virulence factors (VFs) revealed core and species unique VF genes.

Identification of Key Functions Required for Production and Utilization of the Siderophore Piscibactin Encoded by the High-Pathogenicity Island irp-HPI in Vibrionaceae.

Piscibactin is a widespread siderophore system present in many different bacteria, especially within the Vibrionaceae family. Previous works showed that most functions required for biosynthesis and transport of this siderophore are encoded by the high-pathogenicity island irp-HPI. In the present work, using Vibrio anguillarum as a model, we could identify additional key functions encoded by irp-HPI that are necessary for piscibactin production and transport and that have remained unknown. Allelic exchange mutagenesis, combined with cross-feeding bioassays and LC-MS analysis, were used to demonstrate that Irp4 protein is an essential component for piscibactin synthesis since it is the thioesterase required for nascent piscibactin be released from the NRPS Irp1. We also show that Irp8 is a MFS-type protein essential for piscibactin secretion. In addition, after passage through the outer membrane transporter FrpA, the completion of ferri-piscibactin internalization through the inner membrane would be achieved by the ABC-type transporter FrpBC. The expression of this transporter is coordinated with the expression of FrpA and with the genes encoding biosynthetic functions. Since piscibactin is a major virulence factor of some pathogenic vibrios, the elements of biosynthesis and transport described here could be additional interesting targets for the design of novel antimicrobials against these bacterial pathogens.

Vibrio Clade 3.0: New Vibrionaceae Evolutionary Units Using Genome-Based Approach.

Currently, over 190 species in family Vibrionaceae, including not-yet-cultured taxa, have been described and classified into over nine genera, in which the number of species has doubled compared to the previous vibrio evolutionary update (Vibrio Clade 2.0) (Sawabe et al. 2014). In this study, "Vibrio Clade 3.0," the second update of the molecular phylogenetic analysis was performed based on nucleotide sequences of eight housekeeping genes (8-HKGs) retrieved from genome sequences, including 22 newly determined genomes. A total of 51 distinct clades were observed, of which 21 clades are newly described. We further evaluated the delineation powers of the clade classification based on nucleotide sequences of 34 single-copy genes and 11 ribosomal protein genes (11-RPGs) retrieved from core-genome sequences; however, the delineation power of 8-HKGs is still high and that gene set can be reliably used for the classification and identification of Vibrionaceae. Furthermore, the 11-RPGs set proved to be useful in identifying uncultured species among metagenome-assembled genome (MAG) and/or single-cell genome-assembled genome (SAG) pools. This study expands the awareness of the diversity and evolutionary history of the family Vibrionaceae and accelerates the taxonomic applications in classifying as not-yet-cultured taxa among MAGs and SAGs.

Combining Ancestral Reconstruction with Folding-Landscape Simulations to Engineer Heterologous Protein Expression.

Obligate symbionts typically exhibit high evolutionary rates. Consequently, their proteins may differ considerably from their modern and ancestral homologs in terms of both sequence and properties, thus providing excellent models to study protein evolution. Also, obligate symbionts are challenging to culture in the lab and proteins from uncultured organisms must be produced in heterologous hosts using recombinant DNA technology. Obligate symbionts thus replicate a fundamental scenario of metagenomics studies aimed at the functional characterization and biotechnological exploitation of proteins from the bacteria in soil. Here, we use the thioredoxin from Candidatus Photodesmus katoptron, an uncultured symbiont of flashlight fish, to explore evolutionary and engineering aspects of protein folding in heterologous hosts. The symbiont protein is a standard thioredoxin in terms of 3D-structure, stability and redox activity. However, its folding outside the original host is severely impaired, as shown by a very slow refolding in vitro and an inefficient expression in E. coli that leads mostly to insoluble protein. By contrast, resurrected Precambrian thioredoxins express efficiently in E. coli, plausibly reflecting an ancient adaptation to unassisted folding. We have used a statistical-mechanical model of the folding landscape to guide back-to-ancestor engineering of the symbiont protein. Remarkably, we find that the efficiency of heterologous expression correlates with the in vitro (i.e., unassisted) folding rate and that the ancestral expression efficiency can be achieved with only 1-2 back-to-ancestor replacements. These results demonstrate a minimal-perturbation, sequence-engineering approach to rescue inefficient heterologous expression which may potentially be useful in metagenomics efforts targeting recent adaptations.

Veronia nyctiphanis gen. nov., sp. nov., Isolated from the Stomach of the Euphausiid Nyctiphanes simplex (Hansen, 1911) in the Gulf of California, and Reclassification of Enterovibrio pacificus as Veronia pacifica comb. nov.

The bacterial strain 42Xb2 T was isolated from a female adult krill Nyctiphanes simplex infected with the apostome parasitoid ciliate Pseudocollinia brintoni in January 2007 in the Gulf of California. The strain has the morphological, phenotypic, and molecular characteristics of the bacteria of the family Vibrionaceae. The 16S rRNA gene sequence has a similarity of 97.7% with Enterovibrio pacificus SW014 T and 96.1% similarity with Enterovibrio norvegicus LMG 19839 T. A phylogenomic and a multilocus sequence analyses placed this strain close to the genera Enterovibrio, Grimontia, and Salinivibrio, but clearly forming a separate branch from these bacterial genera. Genomic analyses presented further support this result. A novel genus Veronia gen. nov. and a species Veronia nyctiphanis sp. nov. is here described with CAIM 600 T (= DSM 24592 T = CECT 7578 T) as the type strain. Morphological, physiological, and genetic evidence presented here support the unification of Enterovibrio pacificus and Veronia nyctiphanis in the new genus Veronia. Enterovibrio pacificus is reclassified as Veronia pacifica. V. pacifica is assigned as the type species of the new genus Veronia.Genome Sequencing Data The GenBank/EMBL/DDBJ accession numbers for the genome sequence of Veronia nyctiphanis CAIM 600 T is PEIB01 and of Enterovibrio pacificus CAIM 1920 T is LYBM01. The 16S rRNA gene sequence of V. nyctiphanis CAIM 600 T is JX129353.

LuxT controls specific quorum-sensing-regulated behaviors in Vibrionaceae spp. via repression of qrr1, encoding a small regulatory RNA.

Quorum sensing (QS) is a process of chemical communication bacteria use to transition between individual and collective behaviors. QS depends on the production, release, and synchronous response to signaling molecules called autoinducers (AIs). The marine bacterium Vibrio harveyi monitors AIs using a signal transduction pathway that relies on five small regulatory RNAs (called Qrr1-5) that post-transcriptionally control target genes. Curiously, the small RNAs largely function redundantly making it difficult to understand the necessity for five of them. Here, we identify LuxT as a transcriptional repressor of qrr1. LuxT does not regulate qrr2-5, demonstrating that qrr genes can be independently controlled to drive unique downstream QS gene expression patterns. LuxT reinforces its control over the same genes it regulates indirectly via repression of qrr1, through a second transcriptional control mechanism. Genes dually regulated by LuxT specify public goods including an aerolysin-type pore-forming toxin. Phylogenetic analyses reveal that LuxT is conserved among Vibrionaceae and sequence comparisons predict that LuxT represses qrr1 in additional species. The present findings reveal that the QS regulatory RNAs can carry out both shared and unique functions to endow bacteria with plasticity in their output behaviors.

Vibrionaceae core, shell and cloud genes are non-randomly distributed on Chr 1: An hypothesis that links the genomic location of genes with their intracellular placement.

BACKGROUND: The genome of Vibrionaceae bacteria, which consists of two circular chromosomes, is replicated in a highly ordered fashion. In fast-growing bacteria, multifork replication results in higher gene copy numbers and increased expression of genes located close to the origin of replication of Chr 1 (ori1). This is believed to be a growth optimization strategy to satisfy the high demand of essential growth factors during fast growth. The relationship between ori1-proximate growth-related genes and gene expression during fast growth has been investigated by many researchers. However, it remains unclear which other gene categories that are present close to ori1 and if expression of all ori1-proximate genes is increased during fast growth, or if expression is selectively elevated for certain gene categories. RESULTS: We calculated the pangenome of all complete genomes from the Vibrionaceae family and mapped the four pangene categories, core, softcore, shell and cloud, to their chromosomal positions. This revealed that core and softcore genes were found heavily biased towards ori1, while shell genes were overrepresented at the opposite part of Chr 1 (i.e., close to ter1). RNA-seq of Aliivibrio salmonicida and Vibrio natriegens showed global gene expression patterns that consistently correlated with chromosomal distance to ori1. Despite a biased gene distribution pattern, all pangene categories contributed to a skewed expression pattern at fast-growing conditions, whereas at slow-growing conditions, softcore, shell and cloud genes were responsible for elevated expression. CONCLUSION: The pangene categories were non-randomly organized on Chr 1, with an overrepresentation of core and softcore genes around ori1, and overrepresentation of shell and cloud genes around ter1. Furthermore, we mapped our gene distribution data on to the intracellular positioning of chromatin described for V. cholerae, and found that core/softcore and shell/cloud genes appear enriched at two spatially separated intracellular regions. Based on these observations, we hypothesize that there is a link between the genomic location of genes and their cellular placement.

Genome Mining Reveals the Biosynthetic Pathways of Polyhydroxyalkanoate and Ectoines of the Halophilic Strain Salinivibrio proteolyticus M318 Isolated from Fermented Shrimp Paste.

Salinivibrio proteolyticus M318, a halophilic bacterium isolated from fermented shrimp paste, is able to produce polyhydroxyalkanoate (PHA) from different carbon sources. In this study, we report the whole-genome sequence of strain M138, which comprises 2 separated chromosomes and 2 plasmids, and the complete genome contains 3,605,935 bp with an average GC content of 49.9%. The genome of strain M318 contains 3341 genes, 98 tRNA genes, and 28 rRNA genes. The 16S rRNA gene sequence and average nucleotide identity analysis associated with morphological and biochemical tests showed that this strain has high homology to the reference strain Salinivibrio proteolyticus DSM 8285. The genes encoding key enzymes for PHA and ectoine synthesis were identified from the bacterial genome. In addition, the TeaABC transporter responsible for ectoine uptake from the environment and the operon doeABXCD responsible for the degradation of ectoine were also detected. Strain M318 was able to produce poly(3-hydroxybutyrate) [P(3HB)] from different carbon sources such as glycerol, maltose, glucose, fructose, and starch. The ability to produce ectoines at different NaCl concentrations was investigated. High ectoine content of 26.2% of cell dry weight was obtained by this strain at 18% NaCl. This report provides genetic information regarding adaptive mechanisms of strain M318 to stress conditions, as well as new knowledge to facilitate the application of this strain as a bacterial cell factory for the production of PHA and ectoine.

Sequence analysis of nonulosonic acid biosynthetic gene clusters in Vibrionaceae and Moritella viscosa.

Nonulosonic acid (NulO) biosynthesis in bacteria is directed by nab gene clusters that can lead to neuraminic, legionaminic or pseudaminic acids. Analysis of the gene content from a set mainly composed of Aliivibrio salmonicida and Moritella viscosa strains reveals the existence of several unique nab clusters, for which the NulO products were predicted. This prediction method can be used to guide tandem mass spectrometry studies in order to verify the products of previously undescribed nab clusters and identify new members of the NulOs family.

Population genomics of Vibrionaceae isolated from an endangered oasis reveals local adaptation after an environmental perturbation.

BACKGROUND: In bacteria, pan-genomes are the result of an evolutionary "tug of war" between selection and horizontal gene transfer (HGT). High rates of HGT increase the genetic pool and the effective population size (Ne), resulting in open pan-genomes. In contrast, selective pressures can lead to local adaptation by purging the variation introduced by HGT and mutation, resulting in closed pan-genomes and clonal lineages. In this study, we explored both hypotheses, elucidating the pan-genome of Vibrionaceae isolates after a perturbation event in the endangered oasis of Cuatro Ciénegas Basin (CCB), Mexico, and looking for signals of adaptation to the environments in their genomes. RESULTS: We obtained 42 genomes of Vibrionaceae distributed in six lineages, two of them did not showed any close reference strain in databases. Five of the lineages showed closed pan-genomes and were associated to either water or sediment environment; their high Ne estimates suggest that these lineages are not from a recent origin. The only clade with an open pan-genome was found in both environments and was formed by ten genetic groups with low Ne, suggesting a recent origin. The recombination and mutation estimators (r/m) ranged from 0.005 to 2.725, which are similar to oceanic Vibrionaceae estimations. However, we identified 367 gene families with signals of positive selection, most of them found in the core genome; suggesting that despite recombination, natural selection moves the Vibrionaceae CCB lineages to local adaptation, purging the genomes and keeping closed pan-genome patterns. Moreover, we identify 598 SNPs associated with an unstructured environment; some of the genes associated with these SNPs were related to sodium transport. CONCLUSIONS: Different lines of evidence suggest that the sampled Vibrionaceae, are part of the rare biosphere usually living under famine conditions. Two of these lineages were reported for the first time. Most Vibrionaceae lineages of CCB are adapted to their micro-habitats rather than to the sampled environments. This pattern of adaptation is concordant with the association of closed pan-genomes and local adaptation.

The roles of histidine and tyrosine residues in the active site of collagenase in Grimontia hollisae.

Collagenase from the Grimontia hollisae strain 1706B (Ghcol) is a zinc metalloproteinase with the zinc-binding motif H492EXXH496. It exhibits higher collagen-degrading activity than the collagenase from Clostridium histolyticum, which is widely used in industry. We previously examined the pH and temperature dependencies of Ghcol activity; Glu493 was thought to contribute acidic pKa (pKe1), while no residue was assigned to contribute alkaline pKa (pKe2). In this study, we introduced nine single mutations at the His or Tyr residues in and near the active site. Our results showed that H412A, H485A, Y497A, H578A and H737A retained the activities to hydrolyze collagen and gelatin, while H426A, H492A, H496A and Y568A lacked them. Purification of active variants H412A, H485A, H578A and H737A, along with inactive variants H492A and H496A, were successful. H412A preferred (7-methoxycoumarin-4-yl)acetyl-L-Lys-L-Pro-L-Leu-Gly-L-Leu-[N3-(2,4-dinitrophenyl)-L-2,3-diaminopropionyl]-L-Ala-L-Arg-NH2 to collagen, while H485A preferred collagen to the peptide, suggesting that His412 and His485 are important for substrate specificity. Purification of the active variant Y497A and inactive variants H426A and Y568A were unsuccessful, suggesting that these three residues were important for stability. Based on the reported crystal structure of clostridial collagenase, Tyr568 of Ghcol is suggested to be involved in catalysis and may be the ionizable residue for pKe2.

Heterologous expression of a cryptic gene cluster from Grimontia marina affords a novel tricyclic peptide grimoviridin.

Microviridins are a class of ribosomally synthesized and post-translationally modified peptides (RiPPs) that have been isolated from a wide variety of cyanobacterial strains. There are similar gene clusters of RiPPs distributed in the genomes of bacteria belonging to the phyla Proteobacteria and Bacteroidetes. A cryptic gene cluster for the production of microviridin-type peptide was found in the genome of the marine γ-Proteobacterium Grimontia marina. Heterologous production of new microviridin-type peptide named grimoviridin was accomplished in Escherichia coli using the biosynthetic gene cluster of G. marina. The structure of grimoviridin was determined by analysis of MS and NMR data. Grimoviridin contained one isopeptide and two ester bonds, which had exactly the same bridging pattern as other microviridin-type peptides. The absolute stereochemistries of constituent amino acids were determined to be all L-forms by modified Marfey's method. Grimoviridin showed potent inhibitory activity against trypsin with an IC50 value of 238 nM. This is the first report of heterologous production of microviridin-type peptide using a biosynthetic gene cluster from a Proteobacterium. Key points • Heterologous production afforded new microviridin-type peptide named grimoviridin. • This is the first report of microviridin-type peptide from proteobacterial origin. • Grimoviridin showed potent inhibitory activity against trypsin.

Recombinant collagenase from Grimontia hollisae as a tissue dissociation enzyme for isolating primary cells.

Collagenase products are crucial to isolate primary cells in basic research and clinical therapies, where their stability in collagenolytic activity is required. However, currently standard collagenase products from Clostridium histolyticum lack such stability. Previously, we produced a recombinant 74-kDa collagenase from Grimontia hollisae, which spontaneously became truncated to ~60 kDa and possessed no stability. In this study, to generate G. hollisae collagenase useful as a collagenase product, we designed recombinant 62-kDa collagenase consisting only of the catalytic domain, which exhibits high production efficiency. We demonstrated that this recombinant collagenase is stable and active under physiological conditions. Moreover, it possesses higher specific activity against collagen and cleaves a wider variety of collagens than a standard collagenase product from C. histolyticum. Furthermore, it dissociated murine pancreata by digesting the collagens within the pancreata in a dose-dependent manner, and this dissociation facilitated isolation of pancreatic islets with masses and numbers comparable to those isolated using the standard collagenase from C. histolyticum. Implantation of these isolated islets into five diabetic mice led to normalisation of the blood glucose concentrations of all the recipients. These findings suggest that recombinant 62-kDa collagenase from G. hollisae can be used as a collagenase product to isolate primary cells.

Complete Genome Sequence of Strain YCSC6, a Marine Bacterium Isolated from Saturated Saltpan with Activity Against Uronema marinum.

Salinivibrio proteolyticus strain YCSC6 was isolated from a saturated saltpan and demonstrated to have strong insecticidal activity against turbot's pathogenic ciliate-Uronema marinum. In this study, we sequenced its complete genome. Results showed that it consists of two circular chromosomes: 2.49 Mbps and 0.74 Mbps, respectively. It encodes 3429 protein-coding sequences. Biosynthetic gene clusters predicted to synthesize bacteriocins and antimicrobial peptides were discovered, which might be the key factors to lyse and kill U. marinum. The complete genome sequence of strain YCSC6 provides insights into the fundamental genetic potential for elucidating its insecticidal mechanism against U. marinum.

Enterovibrio baiacu sp. nov.

We report here the novel species to encompass the isolate A649T (=CBAS 716T = CBRVS P1061T) obtained from viscera of the healthy pufferfish Sphoeroides spengleri (Family Tetraodontidae). Genomic taxonomy analysis demonstrates that the novel strain A649T had < 95% average amino acid identity/average nucleotide identity (AAI/ANI) and < 70% similarity of genome-to-genome distance (GGDH) towards its closest neighbors which places A649T into a new Enterovibrio species (Enterovibrio baiacu sp nov.). In silico phenotyping disclosed several features that may be used to differentiate related Enterovibrio species. The nearly complete genome assembly of strain A649T consisted of 5.4 Mbp and 4826 coding genes.