Ring-forming, oligotrophic Microcyclus organisms in the water and mud of Lake Balaton.

Seventeen oligotrophic Microcyclus strains were isolated from water- and mud-samples obtained in the region of the Keszthely-Bay (Lake Balaton, Hungary) using different synthetic media with 1% Na2S2O3. Fifteen strains occurred in samples collected in the winter period. For numerical analysis, all isolates were compared with four authentic strains of recognized Microcyclus spp. on the basis of 88 selected tests. They proved to be typical members of the species Microcyclus aquaticus (Orskov), considerably differing at the same time from Microcyclus major, with the exception of a single, presumably extreme variant.