Response of a strict anaerobe to oxygen: survival strategies in Desulfovibrio gigas

Abstract

The biochemical response to oxygen of the strictly anaerobic sulfate-reducing bacterium Desulfovibrio gigas was studied with the goal of elucidating survival strategies in oxic environments. Cultures of D. gigas on medium containing lactate and sulfate were exposed to oxygen (concentration 5-120 mM). Growth was fully inhibited by oxygen, but the cultures resumed growth as soon as they were shifted back to anoxic conditions. Following 24 h exposure to oxygen the growth rate was as high as 70 % of the growth rates observed before oxygenation. Catalase levels and activity were enhanced by exposure to oxygen whereas superoxide-scavenging and glutathione reductase activities were not affected. The general pattern of cellular proteins as analysed by two-dimensional electrophoresis was altered in the presence of oxygen, the levels of approximately 12 % of the detected proteins being markedly increased. Among the induced proteins, a homologue of a 60 kDa eukaryotic heat-shock protein (Hsp60) was identified by immunoassay analysis. In the absence of external substrates, the steady-state levels of nucleoside triphosphates detected by in vivo 31 P-NMR under saturating concentrations of oxygen were 20 % higher than under anoxic conditions. The higher energy levels developed under oxygen correlated with a lower rate of substrate (glycogen) mobilization, but no experimental evidence for a contribution from oxidative phosphorylation was found. The hypothesis that oxygen interferes with ATP dissipation processes is discussed.

Oxygen reduction in the strict anaerobe Desulfovibrio vulgaris Hildenborough: characterization of two membrane-bound oxygen reductases

“…SRB might have developed adaptation strategies to protect them against oxygen, including oxygen removal. The ability to reduce oxygen is widespread among SRB (Dannenberg et al, 1992;Fareleira et al, 2003;Fournier et al, 2006;Fröhlich et al, 1999;Kjeldsen et al, 2005;Kuhnigk et al, 1996;Mukhopadhyay et al, 2007;Sass et al, 2002;Sigalevich & Cohen, 2000). However, oxygen reduction by SRB seems to be a protective mechanism against the harmful effects of oxygen rather than an energycoupled conservation mechanism to allow growth.…”

Crystal structure of the electron transfer complex rubredoxin–rubredoxin reductase of Pseudomonas aeruginosa

“…A central iron, coordinated by four cysteines, constitutes the redox-active site alternating between ϩ2 and ϩ3 oxidation states. Rdxs are crucial for oxidative stress responses in anaerobic organisms by rapidly transferring metabolic reducing equivalents to superoxide reductases or rubredoxin:oxygen oxidoreductases to reduce oxygen or reactive oxygen species (11,12). The link to general metabolism is provided by NAD(P)H and NAD(P)H:RdxRs (11,13,14).…”

Microbial community functional structure in response to micro-aerobic conditions in sulfate-reducing sulfur-producing bioreactor

“…However, a growing number of studies have demonstrated that some SRB can tolerate a certain degree of DO (Abdollahi and Wimpenny, 1990;Cypionka et al, 1985;Fareleira et al, 2003;Mogensen et al, 2005). Consistently, no significant differences in the abundance of dsrA/B genes were observed between S1, S2 and S3, indicating that low levels of DO had less effect on SRB in the bioreactor.…”