Mutation of Bacterial Cells by Controlled Desiccation

Abstract

PREVIOUS work has established reasonably well that the reorientation or removal of water molecules bound to macromolecules may result in the loss of viability and infectivity of bacterial cells and virus particles¹. During the above studies when auxotrophic cells were held at certain levels of relative humidity (RH), prototrophic mutants were found, apparently produced as a direct result of desiccation. Later the mutation of bacterial cells by ultra-violet light was found to be more easily achieved if the cells were partially desiccated at 40 per cent RH (ref. 2), indicating that bound water molecules played some part in the mechanisms responsible for mutation. Cells or virus particles held at RH levels between 80 and 30 per cent contain from 35 g water/100 g of cell solids (35 per cent water) to 3 per cent water¹. Because 30–40 g water/100 g of solid is just sufficient to hydrate fully protein RNA and DNA, desiccation below 80 per cent RH affects only the quantity of bound water in the cell. The apparent mutation of cells from desiccation suggested that water molecules were, in part, responsible for maintaining the biological integrity of DNA, and therefore further studies were warranted. It is the purpose of this paper to present the results of preliminary investigations.