MORPHOLOGICAL-CHANGES IN GROWTH PHENOMENA OF BACTERIAL COLONY PATTERNS

We have investigated the morphological change in colonies of bacteria called Bacillus subtilis. Patterns of colonies grown on the surface of thin agar plates were found to change drastically through the variation of environmental conditions; concentrations of nutrient C(n) and agar C(a) in the agar medium. They were classified into five types; DLA-like, Eden-like, DBM-like, intermediate and homogeneously spreading. The active movement of individual bacterial cells was seen in expanding periphery of a colony at intermediate and low C(a) (soft agar medium). Such bacterial cell movements are found to induce the shift from DLA- and Eden-like patterns to those found for softer agar medium. Physical implication of the pattern changes is discussed.