Expression pattern of the ST heat-stable enterotoxin gene cassettes in Vibrios superintegrons

BACKGROUNDVibrio mimicus has been associated with a cholera-like diarrhea and other gastroenteritis due to the presence of virulence factors such as the heat-stable ST enterotoxin. In spite of its relevant role in Vibrio pathogenesis, there is still a lack of information concerning ST expression dynamics and associated genomic context. OBJECTIVEthis study aimed to determine the prevalence, genomic context, and expression of the st gene found in V. cholerae and V. mimicus strains. METHODSgenome sequencing, in silico analyses of st promoter region and genomic context, and relative quantification pf st expression by real time RT-PCR were applied. FINDINGSThe st gene was found within the SI of both Vibrio species, presenting variations in their amino acid sequences. The in silico analysis of the st 5UTR identified different promoter versions among them. Significant differences were observed in the st expression level, which varied from 10X to 640X-fold, correlating with the differences found in the promoter versions. MAIN CONCLUSIONSTherefore, the present study highlighted the link between the ST toxin gene and the superintegron, not only for V. cholerae, but also for V. mimicus. The differential st expression revealed that it is detrimental to the cognate promoter version, which would impact the toxin production and strain virulence.