Variations Within a Bacterial Species—I Morphologic Variations

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Abstract
Summary In discussing variability in bacteria attention is called to the fact that conditions which made for so-called normal growth often preclude the possibility of obtaining other structures which may develop in the same species under more natural conditions. It is pointed out that variations may occur not only because of different phases in a life cycle, each with its own set of forms and functions, but also because of racial or clonal differences within a species. While using a flagella stain on a peritrichous, spore-forming organism, originally isolated from a mosaic infected Irish potato tuber, numerous stained particles were observed, and here pictured, in young and old cultures. These particles frequently possessed flagella. Similar particles were found within the confines of regular rods, often with flagella subtended or oriented toward such particles. They vary greatly in size and shape, the tiniest approaching the size of the particles constituting the “contagium vivum fluidum” of tobacco mosaic. Similar particles, but not as abundant, have been observed in B. typhi, B. vulgatus, B. mesentericus, B. subtilis, and Proteus vulgaris. Attempts are made to compare these to gonidia, buds, and reproductive granules described by Löhnis and others. Three different lines of evidence are detailed for determining the viability of the particles, including direct microscopic observation of growth or reproduction, ultra-filtration experiments, and pure culture isolations of particles. It is concluded that the evidence for viability is uncertain, the ultra-filtration work favoring the theory that the particles are alive while the other lines of evidence are mostly negative. The writer is inclined to the belief that the particles represent a disintegration process in the course of ordinary autolytic changes. Various types of spirals are described and figured, some being observable in unstained preparations that are taken to be abnormal flagella. A description of giant, mycelioid cells is given and the bodies compared with those previously described in a large number of bacteria.

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