Gas chromatographic study of exopolysaccharides composition and their role in the protection against oxidative stress in microaerophilic bacterium " Thioflexothrix psekupsii" D3 gge. noo., sp. noo
The aim of this work was to study the composition of exopolysaccharides at the new representative of colorless sulfur bacteria «T. psekupsii», and to proof their participation in the antioxidant protection. The composition of «T. psekupsii» exopolysaccharides was analyzed by GLC. It was established that the main component of «T. psekupsii» EPS was galactose and firmly bound to the cell wall EPS fraction was presented by high molecular galactose homopolymer. Chromatographic data were confirmed by genome sequencie, which revealed the presence of genes that determine the enzymes involved into the synthesis of galactose and galactan: galE, encoding UDP-glucose 4-epimerase (EC 5.1.3.2), glF, encoding UDP-galactopyranose mutase (EC 5.4.99.9). EPS concentration was determined by the phenol method at different oxygen concentrations to prove its role in the antioxidant protection. The correlation between O<sub>2</sub> concentration in the cultural medium and EPS concentration was revealed. With the decreasing of O<sub>2</sub> concentration the concentration of EPS decreases too. It is shown that «T. psekupsii» spends ten times more carbon for EPS synthesis than for protein synthesis, which indicates the importance of EPS for this bacterium. These data demonstrate that «T. psekupsii» EPS are presented by the galactose polymer, which is involved into the cell protecting from the damaging effects of oxygen.