SECONDARY ANAEROBES IN HALOALKALIPHILIC COMMUNITIES IN LAKES OF TUVA

A study of secondary anaerobes of microbial communities in athalassic environments with pH 8-10, 1-20% salinity, and different hydrochemical compositions (nine lakes in Tuva) revealed the predominance of methyl otrophic methanogens and hydrogen- and lactate-utilizing sulfate reduc ers under extreme conditions. Neither methanogenesis on hydrogen or ac etate nor aceticlastic sulfidogenesis were observed. Lithotrophic acet ogenesis was observed under various conditions with maximum activity a t pH 8 and 5% salinity. A major sink of H-2 was shown to be provided b y lithotrophic sulfate reducers able to grow at pH as high as 10 and 1 5% salinity; at higher salinity, sulfidogenesis was noted only on lact ate. Some secondary anaerobes were found to develop under extreme cond itions not previously known to allow their growth. The general distrib ution of secondary anaerobes on the pH-salinity matrix is presented.