Form and internal structure of cellular aggregations in early Escherichia coli microcultures.

Abstract

SUMMARY: A critical examination of results obtained with several microculture techniques showed that considerable variations may occur in the formation of cell aggregations, localized in definite zones in the preparation. The cellular aggregation studied in the greatest detail was the clonal microcolony. Time-lapse photomicrography of developing Escherichia coli microcolonies revealed that the arrangement of organisms follows an orderly pattern in both the smooth and rough phases. The genealogical history of the microcolony showed that cells are grouped by genealogical origin. The microcolonial configuration in both smooth and rough phases, at room temperature and 87°, consisted of closely packed arrays of organisms. At these temperatures, palisading appeared to be the primary movement through which the structure of the microcolonies was established. The usual palisading movement was of the sliding type, although buckling palisades were occasionally found in rough-phase cultures. At 44°, the microcolonial configuration in both smooth and rough phases did not invariably evolve through palisading. In these aberrant cases, the organisms appeared simply to push each other about, so that the final appearance was that of a loosely packed collection of organisms presenting as an irregular reticulum. Nevertheless, genealogical distribution remained orderly.