Synthesis of osmoprotectants by halophilic and alkaliphilic methanotrophs

The H-1-NMR analysis of methanol extracts of halophilic and halotolerant al kaliphilic methanotrophs isolated from the soda lakes of Southern Transbaik al and Tuva showed that bacterial cells grown at an optimum salinity accumu lated mainly sucrose and 5-oxo-1-proline, whereas cells adapted to 0.5-1.0 M NaCl additionally synthesized ectoine. A more detailed study showed that nitrogen deficiency in the growth medium of Methylobacter alcaliphilus 20Z decreased the synthesis of nitrogen-containing osmoprotectants, ectoine and 5-oxo1-proline. M. alcaliphilus 20Z cells exhibited activities of UDP-gluc ose pyrophosphorylase and sucrose-phosphate synthase involved in sucrose sy nthesis. Glutamine synthetase in vitro did not require NH4+ ions, which imp lies that this enzyme is involved in 5-oxo-1-proline synthesis. Cells grown at high salinity exhibited elevated levels of aspartate kinase, aspartate- semialdehyde dehydrogenase, and ectoine synthase. This suggests that ectoin e is synthesized via aspartate and aspartate-semialdehyde, i.e., via the ro ute earlier established for extremely halophilic bacteria.