Organic compounds lacking carbon-carbon bonds - usually single carbon (C1) compounds - are commonly found in the environment and include methane, methanol, methylated amines, halogenated methanes, and methyl sulfonates. These molecules are of particular environmental relevance, as some of them (methane, methyl sulfonates) directly contribute to the greenhouse effect, while others (methanol, methylated amines) serve as substrates for methanogenesis. Methane and formaldehyde (CH2O) in particular are found in important quantities on Earth as well as in interstellar space, and may have represented key organic compounds in the prebiotic and early cellular evolution of our planet. Investigations of microbial metabolism of C1 compounds under various types of extreme environmental conditions are thus highly relevant for our understanding of both the carbon biogeochemical cycle and the evolution of life.
Methylomicrobium alcaliphilum 20Z is a halotolerant alkaliphilic methanotroph, able to grow by using methane as the sole carbon and energy source under conditions of high salinity (up to 10% NaCl) and extremely alkaline pH values (pH>9). Indeed, Methylomicrobium-like strains are widely distributed in highly saline and alkaline basins such as soda lakes, where they play a key role in the mitigation of methane emissions. In addition to its environmental significance, M. alcaliphilum 20Z also has great potential for biotechnological applications, due to several exceptional physiological characteristics including high resistance to extreme conditions, high affinity for methane (Ks 0.9-2 µM), and high rate of methane oxidation (up to 200 mU). Its simple cultivation requirements and its activity under a wide range of experimental conditions of pH, salinity and temperature make it one of the most robust methanotrophic cultures suitable for industrial use known so far.