Effect of Heavy Metals Stresses on Growth, Surface Structure and Biochemical Features of Listeria monocytogenes PTCC 1297: An in Vitro Study

Although many food-borne pathogens may generally cause illness, Listeria monocytogenes is an opportunistic organism that causes harm to individuals who are particularly vulnerable to disease. Unlike organic pollutants, heavy metals do not decay and thus pose a different kind of challenge for remediation. Microbial bioremediation is an efficient strategy due to its low cost and efficient targeting of heavy metals. The aim of this work was evaluate the growth, surface structure and biochemical features of L. monocytogenes PTCC 1297 endured to toxic heavy metals for humans. The effects of various concentrations of mercury (II) bromide (HgBr2), lead (II) oxide (PbO), and cadmium sulfate (CdSO4) (0.1% - 0.5% wt/vol) were evaluated. All stresses were applied to exponential phase cells whereas non-stressed exponential phase cells served as a control and the cells were allowed to grow for 24 hours. For evaluating the growth of L. monocytogenes PTCC 1297 after the inoculation procedure and exposure of cells to selected stresses, the colony count method was used. Scanning Electron Microscopy (SEM) was used to visualize the surface structure of bacteria. The amount of HgBr2 (0.1% wt/vol) and CdSO4 (0.2% wt/vol) were considered as lethal doses for L. monocytogenes PTCC 1297 (Serotype 4a). Different concentrations of PbO could not kill bacteria yet decreased their growth. The bacteria showed different morphologic and biochemical characteristics under each stressor. It can be concluded that L. monocytogenes PTCC 1297 can be resistant to lead