| Vibrio alginolyticus,a kind of gram-negative bacillus,is an important opportunist pathogen for marine organisms,and associated with the epidemic of many marine cultured animals,including fish,shellfish,shrimp and coral reefs.V.alginolyticus is also a highly pathogenic bacterium for people who are in contact with seafood easily,which may cause otitis and wound infections.In recent years,V.alginolyticus has been frequently approved to be the cause of disease on marine cultured fish in China and resulted in considerable losses.Bacterial adhesion to fish tissue surfaces is an important step in the initial stage of infection.Intestine and injured skin are considered to be the portals of entry for Vibrio species into fish.Mucous layer can be found covering intestine and skin of fish.The bacterial linkage to the mucus is an essential requirement for the infection by different pathogenic bacteria,and thus,the capability of adhesion to mucus is considered to be a crucial bacterial virulence factor.The bacterial adhesion was influenced remarkably by bacterial factors,adhesion substrate and environmental factors.The bacterial adhesion is speculated to be regulated by genes.Although several genes were proved associated with the bacterial adhesion,the gene regulation mechanism of bacterial adhesion is still practically unknown.Although the global genome of V.alginolyticus have been sequenced and resequenced in recently years,the transcriptome of it is still unclear.In this study,several adhesion tender strains of V.alginolyticus was obtained by cultured under stress conditions,and the transcriptome of adhesion tender strains as well as the normal strain of V.alginolyticus was sequenced and analysed for a better understanding about the genic regulation of adhesion of V.alginolyticus.After various inducement and adherence screening,four stress induced strains named 1A,3A,4A and 6A,including wild type 10 A was selected for trancriptome analysis,which resulted 3,962,3,924,3,978,3,987 and 3,994 CDSs,respectively.Through DEGs enrichment analysis in GO,COG and KEGG pathway,we found that 1A strain owned the most DEGs,followed by 6A,then 3A and finally 4A,which showed amazingly consistent with the adhesion phenotype of these strains and also revealed that strains with sharply declined adhesion capacity tended to own more DEGs.We statistically analysed the enrichment of sundry pathways containing DEGs and observed that ABC pathway,which contained some genes involving oligopeptide,amino acid,arginine/ ornithine,glycine betaine/proline,tungstate,nitrate/nitrite and vitamin B12 transportation was significantly enriched.We also viewed DEGs enrichment level from ABC system among four under-treatment strains,which showed the same trend as mentioned above.To further understand how these transporting gene affected the four strains' adherence,we analysed their down-regulated fold change with obtained adhesion ability with control group and screened a few genes which showed better correlation of coefficient or bigger absolute value of gradient,such as oppF,livH,livM,livK,aotJ,aotM,proX,proV1,proW2,nrtA,nrtC and tupB.Most of them seemed to negatively regulated adhesion,but oppF,aotJ,proW2 and proX exhibited positive regulation.We also found that livH,livM,livG,nrtA and nrtC were extremely down regulated with about 13 fold change in 3A.Interestingly,all liv and nrt genes presented negative role.Over all,this research firstly sequenced the transcriptome of V.alginolyticus.By environment-impacted factors inducement,adhesion screening and seeking for mostly related genes,several subfamily genes from ABC system were associated to adhesion phenotype and identified a proportion of adhesion-related genes. |
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