Features of Betaine Reduction by Haloalkaliphilic Bacteria Alkaliphilus peptidifermentans during Growth on Amino Acids and Ethanolamine

The ability of the haloalkaliphilic anaerobic bacterium Alkaliphilus peptidifermentans Z-7036 to utilize betaine in oxidation-reduction reactions as an electron acceptor was studied. During growth on serine/threonine, a previously unknown molar stoichiometric ratio with betaine of 1 : 2 was revealed. To explain this phenomenon, a pathway for the degradation of these amino acids was proposed and the sites of conjugation with the betaine reductase complex were determined. The activities of key enzymes of threonine and serine metabolism were measured. The Stickland reaction with betaine for proline and ornithine was demonstrated for the first time and a rationale for its implementation was proposed. Biochemical mechanisms were revealed that make it possible to reduce betaine during growth on ethanolamine. Based on the genome annotation, schemes of metabolic pathways for the degradation of threonine, serine, proline, glutamate, arginine, ornithine and ethanolamine were constructed. For all used substrates, the exchange products were determined and stoichiometric ratios with betaine and products were obtained.