Relation between pH, Hydrogenase and Nitrogenase Activity, NH+4 Concentration and Hydrogen Production in Cultures of Rhodobacter Sulfidophilus

Abstract

Rhodobacter sulJidophilus, a sulphide-tolerant, salt-tolerant member of the Rhodospirillaceae, was shown to produce molecular hydrogen on a mineral medium with lactate as electron donor and glutamate as nitrogen source. A maximum production of about 1.1 mmol H2 (mmol added lactate):' was found at pH 6-75. The in vivo activity of hydrogenase and nitrogenase showed that hydrogenase activity (and thus the H2 recycling system) was greatest at pH 6.5 and 6-75 and thus, at least partially, was responsible for the lack of Hz production below 6.75, but that nitrogenase activity was greatest at between pH 6.5 and 7.0, and decreased to zero at pH 8.0, resulting'in reduced H2 production at pH 7.5 and none at pH 8-0. When sufficient NH,+ had accumulated in the culture, nitrogenase activity remained below the maximum value and no H2 production occurred.

Culture conditions affecting H2 production by phototrophic bacterium Rhodobacter sphaeroides KD131

“…Koku et al [15] presented that the optimum pH level for nitrogenase of the photosynthetic bacteria ranged from 7.1 to 7.3. However, similar to our results, alkaline pH over 8 was reported to inhibit the nitrogenase activity during photo-H 2 production [28,29].…”

The Hyb Hydrogenase Permits Hydrogen-Dependent Respiratory Growth of Salmonella enterica Serovar Typhimurium

“…The H 2 uptake hydrogenase activity of the WT and ALZ42 strains was assayed in whole cells by following the reduction of methylene blue spectrophotometrically by a method modified from Stults et al and Peng et al (34, 35). Cells were grown with 20% H 2 in CR-Hyd medium (without glucose and supplemented with 0.5% sodium fumarate and 5 µM NiCl 2 ) to mid-exponential phase ( A 600 = 0.4).…”

Mixed culture hydrogenotrophic nitrate reduction in drinking water

“…Hydrogen metabolism is widely distributed among various well-described physiological groups of bacteria, such as the methanogenic and acetogenic bacteria [49], the phototrophic bacteria [38,48], the sulfate-reducers [69,70], the organotrophic fermentative bacteria [15,28], or the N2-fixing bacteria [50]. Hydrogen is also reported to be a driving mechanism for the microbial degradation of micropollutants, such as atrazine, in soils and drinking water [67].…”