Bacterial Growth in Stressed Environments

In the late 1980s, Fujikawa and Matsushita studied colonies of the bacteria Bacillus subtilis 168 (B 168), common in food, under stressed consitions causing the colonies to adopt a fractal form.

Experimental parameters include
    the hardness of the agar on which the bacteria grow and
    the nutrient concentration.
Friendly conditions, soft agar and abundant nutrients, result in compact growth with smooth boundaries.
In more unfriendly conditions, the bacteria can grow in patterns (on the left) resembling DLA clusters (on the right).
A straightforward explanation is that growth is limited by the presence of nutrients, in turn limited by (slow) diffusion from the perimeter of the Petri dish, where the bacteria have not yet grown.
Nutrient diffusing inward is more likely to be absorbed by the outer-most branches of the bacteria colony, so there is a shielding effect like that of DLA.
But is this right? Several groups are studying this problem.

Return to bacteria growth in stressed environments.