Elucidation of the role of the minC gene in filament formation by Listeria monocytogenes under stress conditions

Abstract

The study was conducted to understand structural changes in cell morphology of stress tolerant Listeria monocytogenes strains after exposure to the different food related stresses and to investigate the involvement of the minC gene in filament formation under stress as a putative mechanism. Morphological changes in L. monocytogenes were studied under the stresses of high salt concentration (12.5 percent), extreme pH (4.5 and 9.0) and low temperature (4 degrees C). The structural changes were recorded employing light and electron microscopy. The expression of the minC gene under stress was studied by qPCR. Long filament formations were observed under salt stress, while, no structural changes could be observed for isolates grown in extreme pH and low temperature stresses. Scanning electron microscopic studies showed 3-10 times elongation of cells under stress which got reverted to normal size after removal of stress. Interestingly, it was noted that with the increase in stress, rod shaped cells became elongated. Six to 11 fold expression of the minC gene was observed under high salt stress. The results suggested that the filament formation could be one of the mechanisms by bacteria to tolerate high salt stress. It also supported the hypothesis that the minC gene over-expression could be the factor behind filamentous morphology.