Bacterial Transformation: I. Opaque and Translucent Variants of a Strain of Bacillus Dysenteriae (Gay-Harris Group)

Abstract

A strain of B. dysenteriae isolated at Alexandria in 1928 from a case of acute bacillary dysentery revealed on agar two distinct types of colony: One, opaque by transmitted light, showed faint green-golden red fluorescence by refracted artificial light; the other, clear or semitranslucent, showed no fluorescence. The original isolation was made by the transfer of a nonlactosefermenting colony from Endo's medium to a tube of MacConkey's lactose-bile salt-neutral red-peptone water medium, for the control of purity and, after thirty-six hours' incubation, without any sign of fermentation, the spreading on agar of a small loopful with a view to development of single colonies. On preparing pure line strains by transfer of single colonies, the two types of colony were found to give identical biochemical reactions, and cross-agglutination with specific serums further confirmed their identity. It thus became evident that here was an instance of bacterial variation within the species. This micro-organism, which is of fairly frequent occurrence in dysentery stools in Egypt,1 is a gram-negative, nonmotile bacillus, which grows well on ordinary mediums, does not frequent lactose, produces indol and ferments?with production of acid only?dextrose, maltose, saccharose, mannite, dulcite and dextrin, the latter but feebly and nonprogressively. In a Durham culture tube containing 1 per cent dextrin in peptone water, with neutral red as indicator and a pK value of 8, a