Genome Analysis and Reconstruction of Metabolic Pathways of Amino Acid and Betaine Degradation in the Haloalkaliphilic Bacterium Anoxynatronum sibiricum

The genome of the haloalkaliphilic anaerobe Anoxynatronum sibiricum Z-7981^T, isolated previously from the soda Lake Nizhnee Beloe (Republic of Buryatia, Russia), was analyzed. The microorganism was shown to be capable of utilizing betaine as an electron acceptor in the Stickland reaction. Supplementing the medium with betaine had a stimulating effect on the growth of A. sibiricum on those amino acids that could be utilized individually. Furthermore, it enabled the strain to utilize several additional amino acids that could not support its growth in the absence of the acceptor. Based on the genomic characteristics and experimental growth data, metabolic schemes are proposed to describe amino acid degradation in the presence and absence of betaine. The schemes for threonine, glutamate, and lysine utilization together with betaine have been compiled for the first time. For all amino acids used, the qualitative and quantitative composition of metabolic products was determined and the stoichiometric substrate/product ratios were obtained. Balance equations were derived for all identified variants of the Stickland reaction, including those not previously described in the literature.