Vibrio harveyi Exhibits the Growth Advantage in Stationary Phase Phenotype during Long-Term Incubation.

The bioluminescent marine bacterium Vibrio harveyi can exist within a host, acting as a mutualist or a parasitic microbe, and as planktonic cells in open seawater. This study demonstrates the ability of V. harveyi populations to survive and adapt under nutrient stress conditions in the laboratory, starting in an initially rich medium. V. harveyi populations remain viable into long-term stationary phase, for at least 1 month, without the addition of nutrients. To determine whether these communities are dynamic, populations were sampled after 10, 20, and 30 days of incubation and examined for their competitive ability when cocultured with an unaged, parental population. While populations incubated for 10 or 20 days showed some fitness advantage over parental populations, only after 30 days of incubation did all populations examined outcompete parental populations in coculture, fully expressing the growth advantage in stationary phase (GASP) phenotype. The ability to express GASP, in the absence of additional nutrients after inoculation, verifies the dynamism of long-term stationary-phase V. harveyi populations, implies the ability to generate genetic diversity, and demonstrates the plasticity of the V. harveyi genome, allowing for rapid adaptation for survival in changing culture environments. Despite the dynamism, the adaptation to the changing culture environment occurs less rapidly than in Escherichia coli, possibly due to Vibrio harveyi's lower mutation frequency. IMPORTANCE Vibrio harveyi populations exist in many different niches within the ocean environment, as free-living cells, symbionts with particular squid and fish species, and parasites to other marine organisms. It is important to understand V. harveyi's ability to survive and evolve within each of these niches. This study focuses on V. harveyi's lifestyle outside the host environment, demonstrating this microbe's ability to survive long-term culturing after inoculation in an initially rich medium and revealing increased competitive fitness correlated with incubation time when aged V. harveyi populations are cocultured with unaged, parental cultures. Thus, this study highlights the development of the growth advantage in stationary phase (GASP) phenotype in V. harveyi populations suggesting a dynamic population with fluctuating genotype frequencies throughout long-term, host-independent incubation.

ToxR modulates biofilm formation in fish pathogen Vibrio harveyi.

Vibrio harveyi is a common aquaculture pathogen causing diseases in a variety of aquatic animals. toxR, a conserved virulence-associated gene in vibrios, is identified in V. harveyi 345, a pathogenic strain isolated from diseased fish. In this study, to gain insight into function of ToxR in V. harveyi, an in-frame deletion of the toxR gene was constructed to reveal the role of ToxR in the physiology and virulence of V. harveyi. The statistical analysis showed no significant differences in the growth ability, motility, extracellular protease secretion, antibiotic susceptibility, virulence by intraperitoneal injection and the ability of V. harveyi to colonize the spleen and liver tissues of the pearl gentian grouper between the wild-type (WT) and the toxR mutant. However, the deletion of toxR increased the biofilm formation. The structure of the V. harveyi biofilm was further analysed by using scanning electron microscopy (SEM) and confocal laser scanning microscopy, and the results showed that deletion of toxR increased the number and density of V. harveyi biofilm. Since biofilm production is flagella, exopolysaccharide (EPS) and lipopolysaccharide dependent, 16 of V. harveyi biofilm-related genes were selected for further analysis. Based on quantitative real-time reverse transcription-PCR, the expression levels of these genes, including genes flrB, motY and mshA, flaE, flrA and gmhD, were significantly up-regulated in the ΔtoxR+ strain as compared with the WT+ and C-ΔtoxR strains during the early and mid-exponential, while epsG, flaA, flaE, flgD, flgE, flrB, flrC, lpxB, motY, mshA and scrG genes were inhibited because of deletion of the toxR gene in the stationary growth phase. Our results indicate that ToxR plays an important role in controlling the biofilm in V. harveyi.

Non-O1/non-O139 vibrios - occurrence not only in Europe in recent years.

Non-O1/non-O139 vibrios refer to all vibrios except toxin producing Vibrio cholerae serogroups O1 and O139. The prevalence of illness caused by non-O1/non-O139 vibrios steadily increases all over the world in the last 20 years, which is very probably related to global warming. These infections are reported year-round from tropical and subtropical climate zones, but they were also detected in the mild climate zone of the United States of America and Europe. In mild climate, they have markedly seasonal occurrence, typically peaking in May to October. A human can be infected after ingestion of contaminated food, especially seafood and fish, or water or while bathing. In Europe, non-O1/non-O139 vibrios were detected in the Baltic Sea, North Sea and Mediterranean Sea but also in ponds and rivers. Depending on the pathogen entry route, the clinical manifestation may appear as gastroenteritis, otitis, wound infection or severe up to fatal illness, predominantly in immunocompromised patients. There is no specific prevention. Non-specific prevention includes good personal and food handling hygiene practices and avoiding contact of unhealed wounds with sea or surface swimming water. Given the severity and increasing frequency of infections caused by non-O1/non-O139 vibrios, they should be considered in differential diagnosis of gastrointestinal and wound infections, especially in patients with a history of consumption of fish and seafood or with a history of contact of unhealed wounds with sea or other open swimming water.

Identification and functional analysis of the perforin-1 like gene in disease resistance in half smooth tongue sole (Cynoglossus semilaevis).

The pore-forming protein perforin is one of the effectors of cell-mediated killing via the granule exocytosis pathway. In this study, a genome-wide association study was conducted in Vibrio harveyi disease-resistant and disease-susceptible families of half smooth tongue sole (Cynoglossus semilaevis) to determine the genes accounting for host resistance, and a perforin homologue was identified, designated perforin-1 like (CsPRF1l). The full-length cDNA of CsPRF1l is 1835 bp, and encodes 514 amino acids. The CsPRF1l gene consists of 10 exons and 9 introns, spanning approximately 7 kb. The amino acid sequence of CsPRF1l shows 60.35, 54.03, 41.92, and 34.17% identities to Morone saxatilis PRF1l, Oryzias melastigma PRF1l, Danio rerio PRF1.5 and Homo sapiens PRF, respectively. Sequence analysis revealed the presence of membrane attack complex/perforin (MACPF) and C2 domains in CsPRF1l. Quantitative real-time PCR showed that CsPRF1l presented a higher intestinal expression level in disease-resistant families than in susceptible families. Tissue expression pattern analysis showed that CsPRF1l is present in most of the tested tissues and highly expressed in the intestine, brain, stomach and gills. After challenge with V. harveyi, CsPRF1l mRNA was markedly upregulated in the liver, spleen, kidney, intestine, gills and skin. In addition, the recombinant CsPRF1l protein exhibited obvious antimicrobial activity against V. harveyi in vitro and in a zebrafish model. Collectively, these data indicate that CsPRF1l modulates host immune defense against V. harveyi invasion and provide clues about the efficacy of rCsPRF1l in fish that will give rise to useful therapeutic applications for V. harveyi infection in C. semilaevis.

High-cell-density fed-batch cultivations of Vibrio natriegens.

OBJECTIVES: With generation times of less than 10 min under optimal conditions, the halophilic Vibrio natriegens is the fastest growing non-pathogenic bacterium isolated so far. The availability of the full genome and genetic engineering tools and its ability to utilize a wide range of carbon sources make V. natriegens an attractive host for biotechnological production processes. However, high-cell-density cultivations, which are desired at industrial-scale have not been described so far. RESULTS: In this study we report fed-batch cultivations of V. natriegens in deep-well plates and lab-scale bioreactor cultivations at different temperatures in mineral salt medium (MSM). Upon switching from exponential glucose to constant glucose-feeding cell death was induced. Initial NaCl concentrations of 15-18 g L-1 and a temperature reduction from 37 to 30 °C had a positive effect on cell growth. The maximal growth rate in MSM with glucose was 1.36 h-1 with a specific oxygen uptake rate of 22 mmol gCDW-1 h-1. High biomass yields of up to 55 g L-1 after only 12 h were reached. CONCLUSIONS: The shown fed-batch strategies demonstrate the potential of V. natriegens as a strong producer in industrial biotechnology.

Potential application values of a marine red yeast, Rhodosporidiums sphaerocarpum YLY01, in aquaculture and tail water treatment assessed by the removal of ammonia nitrogen, the inhibition to Vibrio spp., and nutrient composition.

In recent years, marine red yeasts have been increasingly used as feed diets for larviculture of aquatic animals mainly due to their rich nutrition and immunopotentiation, however little attention is given to their other probiotic profits. In this study, a marine red yeast strain YLY01 was isolated and purified from farming water and it was identified as a member of Rhodosporidiums sphaerocarpum by the phylogeny based on 18S rDNA sequence. The strain YLY01 could effectively remove ammonia nitrogen from an initial 9.8 mg/L to 1.3 mg/L in 48 h when supplemented with slight yeast extract and glucose in water samples and the removal rate of ammonia nitrogen was up to 86%. Shrimps (Litopenaeus vannamei) in experimental group incubated with the yeast YLY01 exhibited a higher survival rate than those in blank control group and positive control group challenged by Vibrio harveyi, and it manifested that the strain has high biosecurity to at least shrimps. The strain YLY01 could inhibit the growth of Vibrio cells when a small quantity of carbon source was added into farming water. In addition, a nutrition composition assay showed the contents of protein, fatty acids, and total carotenoids of the yeast YLY01 were 30.3%, 3.2%, and 1.2 mg/g of dry cell weight, respectively. All these results indicated that the marine red yeast YLY01 has a great potential to be used as a versatile probiotic in aquaculture and to be developed as a microbial agent for high-ammonia tail water treatment.

Long noncoding RNA IRL regulates NF-κB-mediated immune responses through suppression of miR-27c-3p-dependent IRAK4 downregulation in teleost fish.

Growing pieces of evidence show that the long noncoding RNAs (lncRNAs) as new regulators participate in the regulation of various physiological and pathological processes. The study of lncRNA in lower invertebrates is still unclear compared with that in mammals. Here, we identified a novel lncRNA, termed IRAK4-related lncRNA (IRL), as a key regulator for innate immunity in teleost fish. We find that miR-27c-3p inhibits IRAK4 expression and thus weakens the NF-κB-mediated signaling pathway. Furthermore, the Gram-negative bacterium Vibrio anguillarum and lipopolysaccharide significantly upregulated host lncRNA IRL expression. Results indicate that IRL functions as a competing endogenous RNA for miR-27c-3p to regulate protein abundance of IRAK4; thus, invading microorganisms are eliminated and immune responses are promoted. Our study also demonstrates the regulation mechanism that lncRNA IRL can competitively adsorb miRNA to regulate the miR-27c-3p/IRAK4 axis that is widespread in teleost fish.

Vibrio tetraodonis sp. nov.: genomic insights on the secondary metabolites repertoire.

Description of a Gram-negative, motile, circular-shaped bacterial strain, designated A511T obtained from the skin of the pufferfish Sphoeroides spengleri (Family Tetraodontidae), collected in Arraial do Cabo, Brazil. Optimum growth occurs at 20-28 °C in the presence of 3% NaCl. The genome sequence of the novel isolate consisted of 4.36 Mb, 3,976 coding genes and G + C content of 42.5%. Genomic taxonomy analyses based on average amino acid (AAI), genome-to-genome-distance (GGDH) and phylogenetic reconstruction placed A511T (= CBAS 712T = CAIM 1939T) into a new species of the genus Vibrio (Vibrio tetraodonis sp. nov.). The genome of the novel species contains eight genes clusters (~ 183.9 Kbp in total) coding for different types of bioactive compounds that hint to several possible ecological roles in the pufferfish host.

Fungal volatiles mediate cheese rind microbiome assembly.

In vitro studies in plant, soil, and human systems have shown that microbial volatiles can mediate microbe-microbe or microbe-host interactions. These previous studies have often used artificially high concentrations of volatiles compared to in situ systems and have not demonstrated the roles volatiles play in mediating community-level dynamics. We used the notoriously volatile cheese rind microbiome to identify bacteria responsive to volatiles produced by five widespread cheese fungi. Vibrio casei had the strongest growth stimulation when exposed to all fungi. In multispecies community experiments, fungal volatiles caused a shift to a Vibrio-dominated community, potentially explaining the widespread occurrence of Vibrio in surface-ripened cheeses. RNA sequencing identified activation of the glyoxylate shunt as a possible mechanism underlying volatile-mediated growth promotion and community assembly. Our study demonstrates how airborne chemicals could be used to control the composition of microbiomes and illustrates how volatiles may impact the development of cheese rinds.

Gene identification and functional analysis of peptidoglycan recognition protein from the spotted sea bass (Lateolabrax maculatus).

Peptidoglycan recognition proteins (PGRPs), which are structurally conserved innate immune molecules in invertebrate and vertebrate animals, play the important roles in regulation of innate immune responses. In this paper, three PGRP genes of spotted sea bass, Lateolabrax maculatus, were cloned, designated as Ssb-PGRP2, Ssb-PGRP-L2 and Ssb-PGRP-SC2, respectively. Sequence analysis showed that the deduced amino acid sequences of Ssb-PGRP2, Ssb-PGRP-L2 and Ssb-PGRP-SC2 proteins contained respectively 468, 482 and 167 amino acid residues, and had the typical structural features of PGRPs, i.e. conserved PGRP domain and Zn2+ binding domain including four specific amino acid residues which were required for amidase activity. q-PCR analysis of total mRNA showed that the mRNA expression of three PGRP genes were detected in all the examined tissues and the expression patterns of Ssb-PGRP2, Ssb-PGRP-L2 and Ssb-PGRP-SC2 were different. After injected with LPS, Poly (I:C) and Edwardsiella tarda, there was a clear time-dependent expression pattern for each of the three PGRP genes in head kidney, spleen, intestine and gill of the spotted sea bass. In our study, three recombinant proteins corresponding to the three members of the peptidoglycan recognition protein family were expressed and purified. Moreover, all of the three recombinant PGRP proteins significantly inhibited bacterial survival and growth, and expressed bactericidal effects on Vibrio harveyi, Staphylococcus aureus and Edwardsiella tarda. In particular, it was firstly verified that their antimicrobial activity presented the superimposed effect. Overall, these findings indicated that three PGRP genes of spotted sea bass were at least involved in host defense against bacterial infections.

Depuration processes affect the Vibrio community in the microbiota of the Manila clam, Ruditapes philippinarum.

As filter-feeders, bivalve molluscs accumulate Vibrio into edible tissues. Consequently, an accurate assessment of depuration procedures and the characterization of the persistent Vibrio community in depurated shellfish represent a key issue to guarantee food safety in shellfish products. The present study investigated changes in the natural Vibrio community composition of the Ruditapes philippinarum microbiota with specific focus on human pathogenic species. For this purpose, the study proposed a MLSA-NGS approach (rRNA 16S, recA and pyrH) for the detection and identification of Vibrio species. Clam microbiota were analysed before and after depuration procedures performed in four depuration plants, using culture-dependent and independent approaches. Microbiological counts and NGS data revealed differences in terms of both contamination load and Vibrio community between depuration plants. The novel MLSA-NGS approach allowed for a clear definition of the Vibrio species specific to each depuration plant. Specifically, depurated clam microbiota showed presence of human pathogenic species. Ozone treatments and the density of clams in the depuration tank probably influenced the level of contamination and the Vibrio community composition. The composition of Vibrio community specific to each plant should be carefully evaluated during the risk assessment to guarantee a food-safe shellfish-product for the consumer.

Design and Reconstruction of Regulatory Parts for Fast-frowing Vibrio natriegens Synthetic Biology.

The fast-growing Vibrio natriegens is an attractive robust chassis for diverse synthetic biology applications. However, V. natriegens lacks the suitable constitutive regulatory parts for precisely tuning the gene expression and, thus, recapitulating physiologically relevant changes in gene expression levels. In this study, we designed, constructed, and screened the synthetic regulatory parts by varying the promoter region and ribosome binding site element for V. natriegens with different transcriptional or translational strengths, respectively. The fluorescence intensities of the cells with different synthetic regulatory parts could distribute evenly over a wide range of 5 orders of magnitude. The selected synthetic regulatory parts had good stability in both nutrient-rich and minimal media. The precise combinatorial modulation of galP (GalP = galactose permease) and glk (Glk = glucokinase) from Escherichia coli by using three synthetic regulatory parts with different strengths was confirmed in a phosphoenolpyruvate:carbohydrate phosphotransferase system with inactive V. natriegens strain to alter the glucose transport. This work provides the simple, efficient, and standardized constitutive regulatory parts for V. natriegens synthetic biology.

Metal sensing-carbon dots loaded TiO2-nanocomposite for photocatalytic bacterial deactivation and application in aquaculture.

Nowadays, bioactive nanomaterials have been attracted the researcher's enthusiasm in various fields. Herein, Diplocyclos palmatus leaf extract-derived green-fluorescence carbon dots (DP-CDs) were prepared using the hydrothermal method. Due to the strong fluorescence stability, the prepared DP-CDs were coated on filter-paper to make a fluorometric sensor-strip for Fe3+ detection. After, a bandgap-narrowed DP-CDs/TiO2 nanocomposite (DCTN) was prepared using the methanolic extract of D. palmatus. The prepared DCTN exhibited improved photocatalytic bacterial deactivation under sunlight irradiation. The DCTN-photocatalysis slaughtered V. harveyi cells by the production of reactive oxygen species, which prompting oxidative stress, damaging the cell membrane and cellular constituents. These results suggest the plausible mode of bactericidal action of DCTN-photocatalysis under sunlight. Further, the DCTN has shown potent anti-biofilm activity against V. harveyi, and thereby, DCTN extended the survival of V. harveyi-infected shrimps during the in vivo trial with Litopenaeus vannamei. Notably, this is the first report for the disinfection of V. harveyi-mediated acute-hepatopancreatic necrosis disease (AHPND) using nanocomposite. The reduced internal-colonization of V. harveyi on the hepatopancreas as well as the rescue action of the pathognomonic effect in the experimental animals demonstrated the anti-infection potential of DCTN against V. harveyi-mediated AHPND in aquaculture.

Vibrio natriegens: an ultrafast-growing marine bacterium as emerging synthetic biology chassis.

The marine bacterium Vibrio natriegens is the fastest-growing non-pathogenic bacterium known to date and is gaining more and more attention as an alternative chassis organism to Escherichia coli. A recent wave of synthetic biology efforts has focused on the establishment of molecular biology tools in this fascinating organism, now enabling exciting applications - from speeding up our everyday laboratory routines to increasing the pace of biotechnological production cycles. In this review, we seek to give a broad overview on the literature on V. natriegens, spanning all the way from its initial isolation to its latest applications. We discuss its natural ecological niche and interactions with other organisms, unveil some of its extraordinary traits, review its genomic organization and give insight into its diverse metabolism - key physiological insights required to further develop this organism into a synthetic biology chassis. By providing a comprehensive overview on the established genetic tools, methods and applications we highlight the current possibilities of this organism, but also identify some of the gaps that could drive future lines of research, hopefully stimulating the growth of the V. natriegens research community.

External pH modulation during the growth of Vibrio tapetis, the aetiological agent of brown ring disease.

AIMS: Brown ring disease (BRD) is an infection of the Manila clam Ruditapes philippinarum due to the pathogen Vibrio tapetis. During BRD, clams are facing immunodepression and shell biomineralization alteration. In this paper, we studied the role of pH on the growth of the pathogen and formulated hypothesis on the establishment of BRD by V. tapetis. METHODS AND RESULTS: In this study, we monitored the evolution of pH during the growth of V. tapetis in a range of pH and temperatures. We also measured the pH of Manila clam haemolymph and extrapallial fluids (EPFs) during infection by V. tapetis. We highlighted that V. tapetis modulates the external pH during its growth, to a value of 7·70. During the development of BRD, V. tapetis also influences EPFs and haemolymph pH in vitro in the first hours of exposure and in vivo after 3 days of infection. CONCLUSIONS: Our experiments have shown a close interaction between V. tapetis CECT4600, a pathogen of Manila clam that induces BRD, and the pH of different compartments of the animals during infection. These results indicate that the bacterium, through a direct mechanism or as a consequence of physiological changes encountered in the animal during infection, is able to interfere with the pH of Manila clam fluids. This pH modification might promote the infection process or at least create an imbalance within the animal that would favour its persistence. This last hypothesis should be tested in future experiment. SIGNIFICANCE AND IMPACT OF THE STUDY: This study is the first observation of pH modifications in the context of BRD and might orient future research on the fine mechanisms of pH modulation associated with BRD.

Unraveling the anti-biofilm potential of green algal sulfated polysaccharides against Salmonella enterica and Vibrio harveyi.

One of the main reasons for the bacterial resistance to antibiotics is caused by biofilm formation of microbial pathogens during bacterial infections. Salmonella enterica and Vibrio harveyi are known to form biofilms and represent a major health concern worldwide, causing human infections responsible for morbidity and mortality. The current study aims to investigate the effect of purified sulfated polysaccharides (SPs) from Chlamydomonas reinhardtii (Cr) on planktonic and biofilm growth of these bacteria. The effect of Cr-SPs on bacterial planktonic growth was assessed by using the agar well diffusion method, which showed clear zones ranging from 13 to 26 mm in diameter from 0.5 to 8 mg/mL of Cr-SPs against both the bacteria. Time-kill activity and reduction in clonogenic propagation further help to understand the anti-microbial potential of Cr-SPs. The minimum inhibitory concentration of Cr-SPs against S. enterica and V. harveyi was as low as 440 µg/mL and 490 µg/mL respectively. Cr-SPs inhibited bacterial cell attachment up to 34.65-100% at 0.5-8 mg/mL in S. enterica and V. harveyi respectively. Cr-SPs also showed 2-fold decrease in the cell surface hydrophobicity, indicating their potential to prevent bacterial adherence. Interestingly, Cr-SPs efficiently eradicated the preformed biofilms. Increased reduction in total extracellular polysaccharide (EPS) and extracellular DNA (eDNA) content in a dose-dependent manner demonstrates Cr-SPs ability to interact and destroy the bacterial EPS layer. SEM analysis showed that Cr-SPs effectively distorted preformed biofilms and also induced morphological changes. Furthermore, Cr-SPs also showed anti-quorum-sensing potential by reducing bacterial urease and protease activities. These results indicate the potential of Cr-SPs as an anti-biofilm agent and will help to develop them as alternative therapeutics against biofilm-forming bacterial infections. KEY POINTS: • Cr-SPs not only inhibited biofilm formation but also eradicated preformed biofilms. • Cr-SPs altered bacterial cell surface hydrophobicity preventing biofilm formation. • Cr-SPs efficiently degraded eDNA of the EPS layer disrupting mature biofilms. • Cr-SPs reduced activity of quorum-sensing-mediated enzymes like protease and urease.

Vibrio communities along a salinity gradient within a marine saltern hypersaline environment (Saline di Tarquinia, Italy).

Vibrio species are ubiquitous in a number of different aquatic environments and promptly adapting to environmental changes due to high genome plasticity. The presence of these bacteria in marine salterns, in relation to a salinity gradient has been not investigated yet. Moreover, it is not clear if these hypersaline environments could represent a reservoir for Vibrio spp. This work investigated, through a metagenetic approach, the distribution of Vibrio (over 2 years) in different ponds along the salinity gradient within the 'Saline di Tarquinia' salterns, considering also the adjacent coastal waters and an isolated brine storage basin (BSB). Vibrio occurrence was higher in the sea than in the ponds and BSB, where it usually represented a rare taxon (abundance <1%). In the sea, it showed abundances in-between 1%-2.6% in 8 months out of 24. Four OTUs were assigned to the Vibrio genus; except for one that was more abundant in BSB, the others were much higher in the sea. Redundancy analysis (RDA) suggested a different distribution of the OTUs in relation to water temperature and salinity. Vibrio was found, even with low abundances, at the highest salinities also, suggesting the salterns as a possible reservoir for the bacterium.

NAG-thiazoline is a potent inhibitor of the Vibrio campbellii GH20 ß-N-Acetylglucosaminidase.

Vibrio spp. play a vital role in the recycling of chitin in oceans, but several Vibrio strains are highly infectious to aquatic animals and humans. These bacteria require chitin for growth; thus, potent inhibitors of chitin-degrading enzymes could serve as candidate drugs against Vibrio infections. This study examined NAG-thiazoline (NGT)-mediated inhibition of a recombinantly expressed GH20 ß-N-acetylglucosaminidase, namely VhGlcNAcase from Vibrio campbellii (formerly V. harveyi) ATCC BAA-1116. NGT strongly inhibited VhGlcNAcase with an IC50 of 11.9 ± 1.0 µm and Ki 62 ± 3 µm, respectively. NGT was also found to completely inhibit the growth of V. campbellii strain 650 with an minimal inhibitory concentration value of 0.5 µm. ITC data analysis showed direct binding of NGT to VhGlcNAcase with a Kd of 32 ± 1.2 µm. The observed ΔG°binding of -7.56 kcal·mol-1 is the result of a large negative enthalpy change and a small positive entropic compensation, suggesting that NGT binding is enthalpy-driven. The structural complex shows that NGT fully occupies the substrate-binding pocket of VhGlcNAcase and makes an exclusive hydrogen bond network, as well as hydrophobic interactions with the conserved residues around the -1 subsite. Our results strongly suggest that NGT could serve as an excellent scaffold for further development of antimicrobial agents against Vibrio infections. DATABASE: Structural data are available in PDB database under the accession number 6K35.

Indole contributes to tetracycline resistance via the outer membrane protein OmpN in Vibrio splendidus.

As an interspecies and interkingdom signaling molecule, indole has recently received attention for its diverse effects on the physiology of both bacteria and hosts. In this study, indole increased the tetracycline resistance of Vibrio splendidus. The minimal inhibitory concentration of tetracycline was 10 µg/mL, and the OD600 of V. splendidus decreased by 94.5% in the presence of 20 µg/mL tetracycline; however, the OD600 of V. splendidus with a mixture of 20 µg/mL tetracycline and 125 µM indole was 10- or 4.5-fold higher than that with only 20 µg/mL tetracycline at different time points. The percentage of cells resistant to 10 µg/mL tetracycline was 600-fold higher in the culture with an OD600 of approximately 2.0 (higher level of indole) than that in the culture with an OD600 of 0.5, which also meant that the level of indole was correlated to the tetracycline resistance of V. splendidus. Furthermore, one differentially expressed protein, which was identified as the outer membrane porin OmpN using SDS-PAGE combined with MALDI-TOF/TOF MS, was upregulated. Consequently, the expression of the ompN gene in the presence of either tetracycline or indole and simultaneously in the presence of indole and tetracycline was upregulated by 1.8-, 2.54-, and 6.01-fold, respectively, compared to the control samples. The combined results demonstrated that indole enhanced the tetracycline resistance of V. splendidus, and this resistance was probably due to upregulation of the outer membrane porin OmpN.

Next-Generation Microbial Workhorses: Comparative Genomic Analysis of Fast-Growing Vibrio Strains Reveals Their Biotechnological Potential.

Vibrio is a recognized fast-growing bacterial genus, which is considered to be attractive for the development of next-generation biotechnological workhorses. Here, three Vibrio strains FA1, FA2, and FA3, capable of growing rapidly in cost-effective media, are isolated and systematically evaluated. Genome sequencing and comparative genomic analyses are performed to reveal the underlying genetic differences between the strains and estimate their biotechnological potential. Studies of their phylogenetic tree, colinear visualization, and orthology uncover some difference in the gene content related to cell growth of the four Vibrio strains FA1, FA2, FA3, and ATCC 14048, which may explain growth superiority of the isolated strains. It is noted that there are more copies of several genes related to the DNA replication in the FA2 genome than in the other compared Vibrio strains. Furthermore, the genes responsible for amino synthesis are found, such as asD, within strains FA1 and FA2. Gene cluster cadABC, which relates to cell adaptation at acidic pH, only exists in strains FA1, FA2, and FA3. Finally, the wide spectra of substrates and genetic operability of these three isolated Vibrio strains are initially verified. This study provides excellent candidates for the development of next-generation fast-growing microbial workhorses, which may be very useful in synthetic biology.