Effect of pyruvate on the metabolic regulation of nitrogenase activity in Rhodospirillum rubrum in darkness

Abstract

Rhodospirillum rubrum, a photosynthetic diazotroph, is able to regulate nitrogenase activity in response to environmental factors such as ammonium ions or darkness, the so-called switch-off effect. This is due to reversible modification of the Fe-protein, one of the two components of nitrogenase. The signal transduction pathway(s) in this regulatory mechanism is not fully understood, especially not in response to darkness. We have previously shown that the switch-off response and metabolic state differ between cells grown with dinitrogen or glutamate as the nitrogen source, although both represent poor nitrogen sources. In this study we show that pyruvate affects the response to darkness in cultures grown with glutamate as nitrogen source, leading to a response similar to that in cultures grown with dinitrogen. The effects are related to P II protein uridylylation and glutamine synthetase activity. We also show that pyruvate induces de novo protein synthesis and that inhibition of pyruvate formate-lyase leads to loss of nitrogenase activity in the dark.

Plankton Diversity In The Labuhanbatu Bilar River

“…So that the role of soil microbes such as N-fixing bacteria is expected to help supply N in the soil through fixing and fixing nitrogen. Nitrogen must be fixed by groups of prokaryotes that produce complex enzymes, namely nitrogenases that can reduce dinitrogen from the atmosphere to ammonium (Selao, 2010). Saraswati (2008) added that there are groups of symbiotic and nonsymbiotic N-fixing bacteria, and to enrich this group of bacteria, it is necessary to add organic matter to the soil.…”

New Approach for the Construction and Calibration of Gas-Tight Setups for Biohydrogen Production at the Small Laboratory Scale

“…Here, we demonstrate our method by analysing the gas utilisation and production of the purple photosynthetic bacterium, R. rubrum, under semi-aerobic (O2-limited growth, see below for a more detailed discussion of the relevant physiology), "dark photosynthetic" growth conditions. In R. rubrum (as for other photosynthetic organisms, H2 is released when "photosynthetic" anaerobic metabolism produces an excess amount of reducing equivalents, which is the case when fructose or pyruvate are one of the carbon substrates [18,20]. We have shown previously that under conditions of semi-aerobic growth (pO2 < 0.3% [18,21]) in a special culture medium, M2SF medium, that R. rubrum will maximally express photosynthetic genes that are normally produced under anaerobic photosynthetic conditions [15].…”

“…The result is a noticeable trough in the A882/A660 profile, which indicates the transition to semiaerobic growth. Under normal M2SF growth conditions, the H2-producing nitrogenase is completely repressed by the high levels of ammonia in the medium [23,24]), so that H2 can only be produced by the action of the formate-hydrogen lyase [20,25,26], or the reversible hydrogenases [23,27], both of which are reversibly inhibited by O2.…”