[The biology and osmoadaptation of haloalkaliphilic methanotrophs]

Abstract

There is increasing evidence for the presence and activity of methanotrophic bacteria in saline and alkaline aquatic environments located in different ecogeographical regions. Alkalitolerant halophilic and alkaliphilic halotolerant methanotrophs of type I were found to be able to utilize methane and methanol, to oxidize ammonium ions, and to transform various organic compounds in a wide range of water salinities (up to 12% NaCl) and pH values (from 5 to 11). The ecophysiological importance of methanotrophs in microbial communities inhabiting saline and alkaline aquatic environments is due to their involvement in the global cycles of methane and major bioelements (C, N, and S). Specific cyto- and biochemical properties of haloalkaliphilic methanotrophs--the synthesis of osmoprotectants (ectoine, 5-hydroxyproline, and sucrose), the accumulation of potassium ions, the formation of glycoprotein S layers on the outer surface of their cell walls, and the modification of the chemical composition of their membranes--allow them to adapt to highly saline and alkaline habitats. Due to their specific properties, haloalkaliphilic methanotrophs may become of use in modern biotechnology.