Membrane-bound oxygen reductases of the anaerobic sulfate-reducing Desulfovibrio vulgaris Hildenborough: roles in oxygen defence and electron link with periplasmic hydrogen oxidation

Abstract

Cytoplasmic membranes of the strictly anaerobic sulfate-reducing bacterium Desulfovibrio vulgaris Hildenborough contain two terminal oxygen reductases, a bd quinol oxidase and a cc(b/ o)o 3 cytochrome oxidase (Cox). Viability assays pointed out that single Dbd, Dcox and double DbdDcox deletion mutant strains were more sensitive to oxygen exposure than the WT strain, showing the involvement of these oxygen reductases in the detoxification of oxygen. The Dcox strain was slightly more sensitive than the Dbd strain, pointing to the importance of the cc(b/o)o 3 cytochrome oxidase in oxygen protection. Decreased O 2 reduction rates were measured in mutant cells and membranes using lactate, NADH, ubiquinol and menadiol as substrates. The affinity for oxygen measured with the bd quinol oxidase (K m , 300 nM) was higher than that of the cc(b/o)o 3 cytochrome oxidase (K m , 620 nM). The total membrane activity of the bd quinol oxidase was higher than that of the cytochrome oxidase activity in line with the higher expression of the bd oxidase genes. In addition, analysis of the DbdDcox mutant strain indicated the presence of at least one O 2 -scavenging membrane-bound system able to reduce O 2 with menaquinol as electron donor with an O 2 affinity that was two orders of magnitude lower than that of the bd quinol oxidase. The lower O 2 reductase activity in mutant cells with hydrogen as electron donor and the use of specific inhibitors indicated an electron transfer link between periplasmic H 2 oxidation and membrane-bound oxygen reduction via the menaquinol pool. This linkage is crucial in defence of the strictly anaerobic bacterium Desulfovibrio against oxygen stress.

Cytochrome bd from Escherichia coli catalyzes peroxynitrite decomposition

“…The rationale for the latter observation could be that, based on the available literature, beyond its role in cell bioenergetics, cytochrome bd seems to accomplish several important physiological functions that enable bacterial survival in different ecological niches and, importantly, resistance to the hostile conditions created by the immune system in response to microbial infections (reviewed in [14,41,42]). In agreement with this hypothesis, there is growing evidence in the literature pointing to a protective role of cytochrome bd against a number of stressors, including H 2 O 2 [23,[42][43][44][45][46][47][48][49][50][51][52], NO• [41,[53][54][55][56][57][58], CO [59], nitrite [60,61] and excess O 2 itself [62]. Intriguingly, all these species are implicated in the host immune response against microbial infections.…”

A Post-Genomic View of the Ecophysiology, Catabolism and Biotechnological Relevance of Sulphate-Reducing Prokaryotes

“…In fact, oxygen consumption with membranes of D. vulgaris was observed after the addition of reduced cytochrome c 553 (Lamrabet et al, 2011;Lobo et al, 2008). Additionally, a Δcox deletion mutant was affected in the cytochrome c 553 oxidase activity while a Δbd strain was not (Ramel et al, 2013). The later strain was affected in oxidase activity with quinol-like substrates.…”

“…The later strain was affected in oxidase activity with quinol-like substrates. The involvement of the two oxygen reductases in oxygen detoxification was revealed by the lower viability of the Δbd, Δcox and ΔbdΔcox deletion strains, with the Δcox strain being the most sensitive one (Ramel et al, 2013).…”

Respiratory Pathways Reconstructed by Multi-Omics Analysis in Melioribacter roseus, Residing in a Deep Thermal Aquifer of the West-Siberian Megabasin

“…The homolog of the cc(o/b)o 3 cytochrome oxidase of M. roseus has been comprehensively characterized only in D. vulgaris , in which the involvement of this enzyme in oxygen reduction coupled to proton motive force generation was demonstrated. However, no growth stimulation by oxygen was observed for this organism, and transcriptomic data only suggested a detoxifying role of this enzyme in the metabolism of the strict anaerobe, D. vulgaris (Lamrabet et al, 2011; Ramel et al, 2013). In general, our proteomic analysis revealed induction of the cc(o/b)o 3 cytochrome oxidase (MROS_0035-0038) during aerobic growth of M. roseus in comparison to fermentative growth, while the differences in expression of the cbb 3 cytochrome oxidase proteins (MROS_1513-1515) and the bd -type oxidase (MROS_0842-0843) were not reliably detected.…”

“…Sequence analysis of the catalytic subunits MROS_0038 and MROS_1513 (CoxI and CcoNO, respectively) and the analysis of the genomic context of their genes (Podosokorskaya et al, 2013; Karnachuk et al, 2015) revealed that CoxI is highly similar (66% amino acid sequence identity at 97% query coverage) to the atypical heme-copper cc(o/b)o 3 cytochrome oxidase with an unusual heme content, which was recently described in a strict anaerobe Desulfovibrio vulgaris Hildenborough as a proton-translocating enzyme involved in oxygen detoxification (Ramel et al, 2013). The CcoNO of M. roseus was proposed to be a typical cbb 3 -type oxidoreductase with homologs in various Bacteroidetes, mainly aerobic ones (Podosokorskaya et al, 2013; Karnachuk et al, 2015).…”