Authors: William A Norfolk, Charlyn Shue, W Matthew Henderson...

Transmission of occurs opportunistically through direct seawater exposure and is a function of its abundance in the environment. Like other spp., are considered conditionally rare taxa in marine waters, with populations capable of forming large, short-lived blooms under specific environmental conditions, which remain poorly defined. Prior research has established the importance of temperature and salinity as the major determinants of geographical and temporal range. However, bloom formation can be strongly influenced by other factors that may be more episodic and localized, such as changes in iron availability. Here we confirm the broad temperature and salinity tolerance of and demonstrate the importance of iron supplementation as a key factor for growth in the absence of thermal or osmotic stress. The results of this research highlight the importance of episodic iron input as a crucial metric to consider for the assessment of risk.

Topics: Vibrio alginolyticus; Iron

PubMed: 37966200
DOI: 10.1128/spectrum.02680-23

Authors: Zhenzhou Huang, Yanjun Li, Keyi Yu...

, an emergent species of genus, exists in aquatic and marine environments. It has undergone genetic diversification, but its detailed genomic diversity is still unclear. Here, we performed a multi-dimensional comparative genomic analysis to explore the population phylogeny, virulence-related genes and potential drug resistance genes of 184 isolates. Although genetic diversity is complex, we analysed the population structure using three sub-datasets, including the subdivision for three lineages into sublineages and the distribution of strains in the marine ecological niche. Accessory genes, most of which reclassified genomes as different but with relatively close affinities, were nonuniformly distributed among these isolates. We demonstrated that the spread of some post-evolutionary isolates (mainly L3 strains isolated from Chinese territorial seas) was likely to be closely related to human activities, whereas other more ancestral strains (strains in the L1 and L2) tended to be locally endemic and formed clonal complex groups. In terms of pathogenicity, the potential virulence factors were mainly associated with toxin, adherence, motility, chemotaxis, and the type III secretion system (T3SS). We also found five types of antibacterial drug resistance genes. The prevalence of β-lactam resistance genes was 100%, which indicated that there may be a potential risk of natural resistance to β-lactam drugs. Our study reveals insights into genomic characteristics, evolution and potential virulence-associated gene profiles of .

Topics: Vibrio alginolyticus; Genome, Bacterial; Phylogeny; Virulence Factors; Evolution, Molecular; Virulence; Vibrio Infections; Genetic Variation; Humans; Anti-Bacterial Agents; Drug Resistance, Bacterial; Animals

PubMed: 38687697
DOI: 10.1080/22221751.2024.2350164

Authors: Qingfang Hao, Yue Bai, Haolong Zhou...

Bacteriophages, or phages, can be used as natural biological control agents to eliminate pathogenic bacteria during aquatic product cultivation. Samples were collected from seafood aquaculture water and aquaculture environmental sewage, and phage VA5 was isolated using the double-layer agar plate method, with as the host bacteria. The purified phage strain was subjected to genome sequencing analysis and morphological observation. The optimal multiplicity of infection (MOI), the one-step growth curve, temperature stability, and pH stability were analyzed. Phage VA5 was observed to have a long tail. Whole-genome sequencing revealed that the genome was circular dsDNA, with 35,866 bp length and 46% G+C content. The optimal MOI was 1, the incubation period was 20 min, the outbreak period was 30 min, and the cleavage amount was 92.26 PFU/cell. The phage showed good activity at -20 °C, 70 °C, and pH 2-10. Moreover, the phage VA5 exhibited significant inhibitory effects on -infected shrimp culture. The isolated phage VA5 has a wide range of host bacteria and is a good candidate for biological control of pathogenic bacteria.

PubMed: 38137966
DOI: 10.3390/microorganisms11122822

Comparative Study

Authors: Fan Mao, Kunna Liu, Nai-Kei Wong...

species are ubiquitously distributed in marine environments, with important implications for emerging infectious diseases. However, relatively little is known about defensive strategies deployed by hosts against pathogens of distinct virulence traits. Being an ecologically relevant host, the oyster can serve as an excellent model for elucidating mechanisms underlying host- interactions. We generated a mutant strain ( ) with attenuated virulence by knocking out the encoding gene, a core component of type III secretion system (T3SS), which led to starkly reduced apoptotic rates in hemocyte hosts compared to the control. In comparative proteomics, it was revealed that distinct immune responses arose upon encounter with strains of different virulence. Quite strikingly, the peroxisomal and apoptotic pathways are activated by infection, whereas phagocytosis and cell adhesion were enhanced in infection. Results for functional studies further show that strain stimulated respiratory bursts to produce excess superoxide (O2) and hydrogen peroxide (HO) in oysters, which induced apoptosis regulated by p53 target protein (p53tp). Simultaneously, a drop in sGC content balanced off cGMP accumulation in hemocytes and repressed the occurrence of apoptosis to a certain extent during infection. We have thus provided the first direct evidence for a mechanistic link between virulence of spp. and its immunomodulation effects on apoptosis in the oyster. Collectively, we conclude that adaptive responses in host defenses are partially determined by pathogen virulence, in order to safeguard efficiency and timeliness in bacterial clearance.

Topics: Animals; Apoptosis; Bacterial Proteins; Crassostrea; Cyclic GMP; Gene Knockout Techniques; Hemocytes; Host-Pathogen Interactions; Hydrogen Peroxide; Sequence Deletion; Superoxides; Type III Secretion Systems; Vibrio alginolyticus; Virulence

PubMed: 34621277
DOI: 10.3389/fimmu.2021.746017

Authors: Jingyun Fu, Ying Li, Lihong Zhao...

Phage therapy was taken as an alternative strategy to antibiotics in shrimp farming for the control of species of and which cause substantial mortality and significant economic losses. In this study, a new phage vB_ValM_PVA8 (PVA8), which could efficiently infect pathogenic isolates of and , was isolated from sewage water and characterized by microbiological and genomic analyses. The phage was characterized to be a member of the family with elongated head and contractile tail by transmission electron microscopy. Genome sequencing showed that PVA8 had a 246,348-bp double-stranded DNA genome with a G + C content of 42.6%. It harbored totally 388 putative open reading frames (ORFs), among them 92 (23.71%) assigned to functional genes. Up to 27 transfer RNA (tRNA) genes were found in the genome, and the genes for virulence, antibiotic resistance, and lysogeny were not detected. NCBI genomic blasting results and the phylogenetic analysis based on the sequences of the large terminase subunits and the DNA polymerase indicated that PVA8 shared considerable similarity with phage V09 and bacteriophage KVP40. The phage had a latent period of 20 min and a burst size of 309 PFUs/infected cell with the host , and it was stable over a broad pH range (4.0-11.0) and a wide temperature span (-80°C to 60°C), respectively, which may benefit its feasibility for phage therapy. In addition, it had the minimum multiplicity of infection (MOI) of 0.0000001, which revealed its strong multiplication capacity. The shrimp cultivation lab trials demonstrated that PVA8 could be applied in treating pathogenic infection disease of shrimp with a survival rate of 88.89% comparing to that of 34.43% in the infected group, and the pond application trails confirmed that the implementation of PVA8 could rapidly yet effectively reduce the level of the . Taken together, PVA8 may be potential to be explored as a promising biological agent for control in aquaculture farming industry.

PubMed: 37250064
DOI: 10.3389/fmicb.2023.1105924

Authors: Jingyun Fu, Ying Li, Lihong Zhao...

Vibrio alginolyticus is one of the major pathogens causing vibriosis to a variety of aquatic animals as well as bringing about severe food safety concerns. Nowadays, phage therapy has received increasing attention as an alternative to the antibiotics that have being limited for use in aquaculture industries. In this work, a potent bacteriophage, vB_ValM_PVA23 (PVA23), which efficiently infects pathogenic strains of V. alginolyticus, was isolated from sewage water and characterized by microbiological and genomic analyses. Based on the transmission electronic observation, the phage was characterized to be the Myoviridae family. It has a latent period of 10 min and a burst size of 203 PFUs/infected bacterium, and was stable over a broad pH range (5.0−11.0) and a wide temperature span (−80 °C to 60 °C), respectively. Genome sequencing results show that PVA23 has a 246,962-bp double-stranded DNA with a G + C content of 41.25%. The lab and plant shrimp farming trials demonstrated that phage preparation derived from PVA23 out-performed the chemical disinfectant iodine treatment in the prevention of V. alginolyticus propagation, and the phage application could rapidly yet significantly reduce the level of V. alginolyticus in the pond within 12 h, with negligible rebound observed. These results suggests that phage PVA23 has the potential to be used as an anti-V. alginolyticus agent in aquaculture industries.

Topics: Animals; Bacteriophages; Vibrio alginolyticus; Genomics; Myoviridae; Vibrio Infections; Genome, Viral

PubMed: 36680175
DOI: 10.3390/v15010135

Authors: Uun Yanuhar, Hendra Nurcahyo, Luluk Widiyanti...

BACKGROUND AND AIM

The need for fish seeds resistant to bacterial and viral infections has encouraged studies on the molecular pathogenesis mechanism of bacteria, such as and , regarding the receptor organs, protein adhesion mechanisms, and antibody responses of the humpback grouper. This study aims to confirm the characteristics of the specific proteins expressed in the receptor organ of the humpback grouper () using the expression of and bacteria.

MATERIALS AND METHODS

The study was conducted by isolating crude protein and whole cells from both the bacteria. In addition, serum and organ tissue were also isolated from fish samples. Then, hemagglutination and dot blot tests with polyacrylamide gel electrophoresis analysis were performed to determine the highest expression of receptor from the whole bacterial cells and crude protein from both healthy and infected ( and ) fishes. Scanning electron microscope results showed that and could express bundle-forming pili, which is involved in bacterial autoaggregation and the mediation of the initial attachment of bacteria to their host cells.

RESULTS

These results indicated that all the specific receptors for protein in fish organs recognized vibriosis antigens. The specificity test showed that the brain, eye, and kidney organs' receptors provided a quality and quantity level of responses at 22.63, 53.95, and 43.15 kDa, respectively. The polyclonal anti- immunoglobulin M (IgM) antibodies were more cross-reactive than the anti- IgM. Hence, this shows that bacteria are more pathogenic than .

CONCLUSION

In the future, the molecular characteristics of and antigens and the specific receptor organ proteins in the humpback grouper can be developed as the basis for constructing molecular peptide-based vaccine materials.

PubMed: 35765493
DOI: 10.14202/vetworld.2022.1269-1282

Authors: Bing Liu, Jianxiang Fang, Huizhen Chen...

is a widely distributed marine bacterium that is a threat to the aquaculture industry as well as human health. Evidence has revealed critical roles for small RNAs (sRNAs) in bacterial physiology and cellular processes by modulating gene expression post-transcriptionally. GcvB is one of the most conserved sRNAs that is regarded as the master regulator of amino acid uptake and metabolism in a wide range of Gram-negative bacteria. However, little information about GcvB-mediated regulation in is available. Here we first characterized GcvB in ZJ-T and determined its regulon by integrated transcriptome and quantitative proteome analysis. Transcriptome analysis revealed 40 genes differentially expressed (DEGs) between wild-type ZJ-T and mutant ZJ-T-Δ, while proteome analysis identified 50 differentially expressed proteins (DEPs) between them, but only 4 of them displayed transcriptional differences, indicating that most DEPs are the result of post-transcriptional regulation of . Among the differently expressed proteins, 21 are supposed to be involved in amino acid biosynthesis and transport, and 11 are associated with type three secretion system (T3SS), suggesting that GcvB may play a role in the virulence besides amino acid metabolism. RNA-EMSA showed that Hfq binds to GcvB, which promotes its stability.

Topics: Amino Acids; Bacterial Proteins; Gene Expression Regulation, Bacterial; Proteome; Proteomics; Regulon; Transcriptome; Vibrio alginolyticus

PubMed: 36012664
DOI: 10.3390/ijms23169399

Authors: Ke Zhou, Ke-Yong Tian, Xin-Qin Liu...

, a Gram-negative rod bacterium found in marine environments, is known to cause opportunistic infections in humans, including ear infections, which can be difficult to diagnose. We investigated the microbiological and otopathogenic characteristics of a strain isolated from an ear exudate specimen obtained from a patient with chronic otitis externa to provide a basis for the future diagnosis of -associated infections. The identification of was accomplished using a combination of matrix-assisted laser desorption/ionization-time-of-flight mass spectrometry (MALDI-TOF MS), classical biochemical identification methods, and the use of -selective media and advanced molecular identification methodologies. Antimicrobial susceptibility testing revealed that the strain was resistant to ampicillin and sensitive to β-lactam, aminoglycosides, fluoroquinolones, and sulfonamide antibiotics. The potential otopathogenic effects of were determined through the performance of cell viability, cell apoptosis, and cell death assays in tympanic membrane (TM) keratinocytes and HEI-OC1 cells treated with -conditioned medium using cell-counting kit (CCK)-8 assay, a wound-healing migration assay, Annexin V/propidium iodide (PI) flow cytometric analysis, and terminal deoxynucleotidyl transferase deoxyuridine triphosphate (dUTP) nick-end labeling (TUNEL staining). The results indicated that the identified strain exerts cytotoxic effects on keratinocytes and HEI-OC1 cells by inhibiting cell proliferation and migration and inducing apoptosis and cell death. To evaluate the ototoxicity of , the cell density and morphological integrity of hair cells (HCs) and spiral ganglion neurons (SGNs) were analyzed after exposing cochlear organotypic explants to the bacterial supernatant, which revealed the pre-dominant susceptibility and vulnerability of HCs and SGNs in the basal cochlear region to the ototoxic insults exerted by . Our investigation highlights the challenges associated with the identification and characteristic analysis of the strain isolated in this case and ultimately aims to increase the understanding and awareness of clinicians and microbiologists for the improved diagnosis of -associated ear infections and the recognition of its potential otopathogenic and ototoxic effects.

PubMed: 34975783
DOI: 10.3389/fmicb.2021.750642

Authors: Bing Liu, Qian Gao, Xin Zhang...

, like other species, is a widely distributed marine bacterium that is able to outcompete other species in variable niches where diverse organic matters are supplied. However, it remains unclear how these cells sense and adjust metabolic flux in response to the changing environment. CsrA is a conserved RNA-binding protein that modulates critical cellular processes such as growth ability, central metabolism, virulence, and the stress response in -proteobacteria. Here, we first characterize the homolog in . The results show that CsrA activates swarming but not swimming motility, possibly by enhancing the expression of lateral flagellar associated genes. It is also revealed that CsrA modulates the carbon and nitrogen metabolism of , as evidenced by a change in the growth kinetics of various carbon and nitrogen sources when CsrA is altered. Quantitative RT-PCR shows that the transcripts of the genes encoding key enzymes involved in the TCA cycle and amino acid metabolism change significantly, which is probably due to the variation in mRNA stability given by CsrA binding. This may suggest that CsrA plays an important role in sensing and responding to environmental changes.

PubMed: 34835507
DOI: 10.3390/microorganisms9112383