Abstract

The sensitivity of pure cultures of Staphylococcus epidermidis and Klebsiella pneumoniae towards arsenic was studied with particular reference to biochemical changes induced by the heavy metal in these organisms. Arsenic strongly inhibited the growth and viability of both the organisms. Addition of arsenic prolonged the lag phase and this was found to be the concentration dependent phenomenon. The Minimum inhibitory concentration (MIC) determined was 200 ppm and 20 ppm in S. epidermidis and K. pneumoniae respectively that inhibited growth, synthesis of protein, DNA, RNA completely and activity of dehydrogenases of the TCA cycle. In S. epidermidis and K. pneumoniae, cell wall, membrane and cytoplasm 24.5%, 32.5%, 43% and 20%, 35%, 45% arsenic respectively got incorporated. As the activity of dehydrogenases was inhibited by arsenic, cells were incapable of oxidizing substrate. It resulted in limited supply of energy rich compounds such as ATP that affected the synthesis of macromolecules. Ultimately multiplication and growth of the organism got ceased.

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