Anaerobic Microbial Communities in High Sodium Environment
George ZAVARZIN*, and Tatjana ZHILINA
Institute of Microbiology, Prospect 60-let Octiabria, 7/2, 117811 Moscow, Russia
There are two types of high sodium environments: those caused by evaporation of marine water and caused by evaporation of carbonate bearing water in the inner parts of continents. The general idea was to find relict microbial communities in this extreme environment (1). Anaerobic communities, from high sodium environment, except for phototrophic ones escaped studies. Previously we analysed trophic relationships in halophilic community caused by the decomposition of osmoregulating compounds - disaccharides, heterosides, betaine - by specific microorganisms. Food web included members of the Order Haloanaerobiales such as new species of Halobacteroides, Haloanaerobiurn, homoacetogenic Acetohalobium and methylotrophic methanogen Methanohalobium interlinked in their trophic relations (2).
Anaerobic microbial community from soda depositing Lake Magadi, Kenya (3), and lakes south of Baikal in cryoarid zone (4) with pH 10 were studied with idea to find representatives of the key functional groups in decomposition pathway beginning from the terminal steps forming H2-sink. As in salinas only methylotrophic pathway of methanogenesis by alkaliphilic Methanosalsus zhilinaeae (5) was found. The main H2-sink is represented by sulfidogenesis with new obligately alkaliphilic lithotrophic Desulfonatronovibrio hydrogenovorans (6) which utilizes only H2 or formate and being ubiqitous for equatorial and cryoarid zones (7). In addition alkaliphilic Desulfonatronum lacustre (8) utilizing ethanol as well as H2 was isolated from high pH - low salinity lake in Tuva. Alkaliphilic counterpart to homoacetic Acetohalobium was represented by Natroniella acetigena (9), a new member of Haloanarobiales. Production of H2 was performed by new species of alkaliphilic dissipotrophic fermentative Spirochaeta alcalica, S. africana, S. asiatica (10). Peptolytic pathway was performed by the new members of low G+C clostridial branch, capable to utilize few amino acids.
Halophilic and alkaliphilic anaerobic communities are trophically organized along the same general lines but functional groups are represented by differing organisms. Anaerobic inhabitants of alkaline lakes differ phylogenetically from their neutrophilic and halophilic counterparts at least on the species-generic level. There are two lines of fitness to environment, one is by the cell adaptability, the other for extreme enviromnents is on the community level with different species performing
