[Oxidation-reduction and production of molecular hydrogen by Escherichia coli in the hyperosmotic medium]

It was shown that Escherichia coli is able to grow in anaerobic conditions in hyperosmotic media containing 0.5 M sodium chloride or equivalent amount of sucrose. However, in the presence of 0.5 M NaCl, bacterial growth rate and the intensity of oxidation-reduction processes decrease, and the production of molecular hydrogen is absent. Growth rate in the presence of 0.5 M NaCl is four times lower than that in the presence of sucrose. Under hyperosmotic stress by 0.5 M NaCl but not by equivalent amount of sucrose, the uptake of K+ with a high rate is observed. Proline is able to increase the growth rate and the intensity of oxidation-reduction processes and to restore the production of molecular hydrogen as well as to induce the uptake of K+ with a high rate under a hyperosmotic stress. Such effects are observed at pH 7.5 and are absent at pH 5.5. Proline also increases cell size independently of medium pH. It is likely that the effect of proline on oxidation-reduction processes and production of H2 is mediated through the accumulation of K+ in bacteria.