Proteins involved in difference of sorbitol fermentation rates of the toxigenic and nontoxigenic Vibrio cholerae El Tor strains revealed by comparative proteome analysis

We found the production of formate and lactic acid in the sorbitol fermentation medium of the nontoxigenic strain was earlier than of the toxigenic strain. We compared the protein expression profiles of the toxigenic strain N16961 and nontoxigenic strain JS32 cultured in sorbitol fermentation medium, by using fructose fermentation medium as the control. Seventy-three differential protein spots were found and further identified by MALDI-MS. The difference of product of fructose-specific IIA/FPR component gene and mannitol-1-P dehydrogenase, may be involved in the difference of sorbitol transportation and dehydrogenation in the sorbitol fast- and slow-fermenting strains. The difference of the relative transcription levels of pyruvate formate-lyase to pyruvate dehydrogenase between the toxigenic and nontoxigenic strains may be also responsible for the time and ability difference of formate production between these strains.Multiple factors involved in different metabolism steps may affect the sorbitol fermentation in the toxigenic and nontoxigenic strains of V. cholerae El Tor.Vibrio cholerae is the causative agent of the diarrheal disease cholera. Out of the 200 serogroups of V. cholerae, only two biotypes of serogroup O1 (classical and El Tor) and serogroup O139 cause severe diarrhea and epidemic cholera [1], although not all strains in these two serogroups are pathogenic. Toxigenic and nontoxigenic V. cholerae strains are genetically diverse. The toxigenic strains form a genetically homogenous group, while nontoxigenic strains are heterogeneous and may have diverse origins [2-4]. The nontoxigenic strains, which are usually isolated from environmental sources such as sewage, oysters, and brackish water, do not carry cholera toxin (CT) and other major virulence genes necessary for human pathogenesis [5].V. cholerae is capable of metabolizing many types of carbohydrates. Previously, we found that not only is D-sorbitol metabolized by V. cholerae, but it is also fermente