Bacterial Variation, with Special Reference to Pleomorphism and Filtrability

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Abstract
In Bacillus megatherium cultures which had undergone partial autolysis, many of the cells appeared like flattened sausage skins. This appearance was particularly striking in cells which had folded over on themselves, all that was left of the original being the cell envelope. The morphology of B. megatherium cells is strongly influenced by environment. Differences in composition of medium, temp. and length of incubation were accompanied by wide differences in cell morphology, varying from the usual rod type to extremely long filaments, true branching forms, boat-, spade- and long and short club-shaped cells. Some of these forms were accompanied by amorphous and granular debris. These variants need not indicate or represent orderly stages in a complicated life cycle. The main emphasis here was placed on repeated attempts to demonstrate filterability with 1 strain of B. megatherium, 2 of Brucella abortus, and 4 of Br. melitensis. Chamberland L2, L3 and L5, and Berkefeld N candles were used. Some 180 filtrates were prepared from cultures of various ages, and studied in different media and under widely different conditions. The washing forward process of Hauderoy was followed in part of the work. Considerable effort was made also to demonstrate the "G" colonies of Hadley. Finally, numerous sewage filtration exps. were carried out; all the exps. were carefully controlled. The authors were unable to demonstrate so-called phases in a definite life cycle, or any stages in which the organisms employed were filterable.