Colonial heterogeneity of Thiobacillus versutus

In acetate-limited chemostat cultures started with single-colony cultures of Thiobacillus versutus, a mutant appeared after approximately 85 volume changes. The inhomogeneity of the culture was detected by the development of two different types of colonies on agar plates. When a pure culture of the mutant was grown in a chemostat, parent colonies appeared after almost the same period of time. Electron micrographs of the mutant grown on butyrate showed the presence of fibrils surrounding the cells. The cells of the parent strain were bald when grown under the same conditions. The growth kinetics of the parent and the mutant were investigated in batch cultures with a variety of substrates and were found to be identical. Major differences between the two strains were observed during growth on mannitol; the mutant attained a lower yield and excreted large amounts of extracellular polysaccharides.