[Variability of Bacillus thuringiensis under various growth conditions]

When a lysogenic culture of Bacillus thuringiensis subsp. galleriae 69-6 was grown under the batch conditions, 93-99% of cells in the population produced R-form colonies and ca. 1% yielded S-form colonies. The amount of spore-forming cells was 99% in R-variants and 8% in S-variants. The quantity of S-variants rose abruptly to 99% when the culture was grown under the chemostat conditions. The number of S-variants increased with the rate and the duration of growth. The process was influenced by growth-limiting factors. Temperate phage variants capable of host culture lysis on solid media (i.e. h-mutants) were not found under the conditions of batch cultivation. However, such phage particles (h-mutants) appeared under the conditions of chemostat. The titre of these phage particles reached 10(8), 10(7) and 10(4) particles per 1 ml at limitation with yeast extract, glucose and phosphorus, respectively. Under the conditions of chemostat, the particles behaved as temperate ones and their growth was not found. Irrespective of the limitation, the phage titre did not correlate with the ratio of R and S-forms in the population. When the growth was limited with phosphorus, the quantity of S-forms increased abruptly while the spontaneous induction of the phage was inhibited. The quantity of cells capable of spore formation decreased in the cultures isolated from the chemostat and grown on MPA: 69-80% of the cells in R-forms and merely 8% in S-forms.