The Inheritance of Environmentally Induced Characters in Bacteria

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Abstract
Single-cell cultures of Salmonella pullorum, Eberthella typhosa, and S. schotmulleri were able to adapt themselves to concs. of NaCl, HgCl2, and CuSO4 considerably higher than those required to inhibit growth of nonadapted strains. The resistant strains were specific in their ability to overcome the growth-inhibiting properties of each chemical. Single cell cultures of resistant strains retained their resistance for long periods of time and through numerous transfers. Their permanency and specificity suggest a change in hereditary constitution; thus are probably mutations. Populations of the bacteria studied contain a few individuals which possess the ability to withstand the action of the chemicals employed without previous contact with the chemical. In view of the hereditary nature of the changes and their specificity it seems logical to classify them as mutations. Furthermore, the fact that these resistant forms are found in small numbers in normal populations lends further support to this idea. It may be concluded that the adaptation of strains of bacteria to certain adverse environmental conditions probably consists of selecting from the population mutants which possess this resistant character, thus giving rise to a strain composed entirely of resistant individuals.