Description and physiological characterization of a coryneform hydrogen bacterium, strain 14 g

Summary

A new hydrogen bacterium has been isolated by enrichment culture on hydrogen, carbon dioxide, and oxygen. It is a strictly aerobic, Gram-positive, immotile rod. Irregular cell shapes, the snapping type of cell division and the partial fragmentation of the rods into coccoid cells in older heterotrophic cultures indicate that strain 14 g is a coryneform bacterium.

Strain 14 g grows well in a mineral salts medium under a gas atmosphere of 80% hydrogen, 10% carbon dioxide and 10% oxygen. With increasing oxygen partial pressures, the growth rate decreases. While growth is good or excellent on organic acids, carbohydrates are utilized not at all.

Autotrophically grown cells are able to oxidize organic substrates after a relatively short lag-phase. Growth is retarded when hydrogen is present in the gas atmosphere. Citrate utilization is even inhibited by hydrogen.

In gluconate grown cells gluconokinase, the enzymes of the Entner-Doudoroff system and a NAD-dependent 6-phosphogluconate dehydrogenase are present. All enzymes are inducible.

The uptake rate of the oxygen-hydrogen mixture by resting cells is very high and amounts to 2500 μl gas/mg protein·h. Carbon dioxide does not stimulate the oxyhydrogen-reaction. The hydrogenase activity of intact cells measured with methylene blue as a hydrogen acceptor is limited by the penetration of methylene blue into the cell. In cell-free extracts the hydrogen uptake rate amounts to 2260 μl H₂/mg protein·h with methylene blue as H-acceptor. The hydrogenase of strain 14 g is a strictly inducible enzyme. It is completely part culate and does not reduce pyridime nucleotides.