[Phenotypic features of Ferroplasma acidiphilum strains Yt and Y-2].

Earlier, we described a new family of mesophilic, strictly autotrophic Fe(2+)-oxidizing archaebacteria, Ferroplasmaceae, which belongs to the order Thermoplasmales and includes the genus Ferroplasma and species F. acidiphilum (strain YT) [1]. The present work is concerned with a comparative study of phenotypic characteristics of the type strain YT and a new strain, F. acidiphilum Y-2, isolated from dense pulps produced during oxidation of arsenogold concentrates from the Bakyrchikskoe (Kazakhstan) and Olimpiadinskoe (Krasnoyarsk Krai) ore deposits, respectively. The G + C content of DNA from strains YT and Y-2 comprised 35.1 and 35.2 mol%, respectively; the level of DNA-DNA homology between the strains was 84%. Restriction profiles of chromosomal DNA from both strains exhibited a similarity coefficient of 0.87. Genotypic characteristics of these strains indicate their affiliation to the same species. The cells of both strains are polymorphic and lack cell walls. Strains of F. acidiphilum oxidized ferrous oxide and pyrite as the sole source of energy and fixed carbon dioxide as the sole carbon source. Strains required yeast extract as a growth factor. Optimum pH for cell growth ranged from 1.7 to 1.8; the temperature optima for the growth of strains YT and Y-2 were 34-36 and 40-42 degrees C, respectively. Comparative analysis of total lipids revealed their close similarity in the strains; two glycophospholipids comprised 90% of total lipids: lipid I, beta-D-glucopyranosylcaldarchaetidylglycerol (about 55%), and lipid II, trihexosylcaldarchaetidylglycerol (26%), whose isopranyl chains contained no cyclopentane rings. The carbohydrate fraction of lipid I hydrolysate contained only D-glucose, whereas hydrolysate of lipid II contained both D-glucose and D-galactose in a molar ratio of 2:1. Thus, it was established that the intraspecific phylogenetic divergence within F. acidiphilum is manifested in two the strains by different temperature optima against the background of similarity in other phenotypic properties.