Peculiarities in the chromosomal DNA structure in Acidianus brierleyi and Ferriplasma acidophilum grown under varied conditions

Distinctions in the structure of the chromosomal DNAs from two strains of t he thermophilic archaebacterium Acidianus brierleyi (DSM 1651 and str6kar) and from a mesophilic strain Ferriplasma acidophilum "y" were revealed by p ulsed-held gel electrophoresis. The chromosomal DNA structure of the microo rganisms studied remained stable regardless of the energy source used (Fe2, S-0, FeS2), the pH value of growth medium (varied from 2.2 to 0.7), or th e concentration of zinc ions (elevated up to 70 g/l). Cultures grown on dif ferent energy substrates somewhat differed in their maximum growth rates in the exponential phase and in biomass yields. The maximum biomass yield was provided by the oxidation of elemental sulfur. Experimental lowering of th e pH values or elevation of zinc ion concentration in the medium resulted i n a decrease of the growth rate and biomass yield. The mechanisms regulatin g the activity of substrate oxidation and the factors essential for genetic stability and evolution of characters are discussed.