The O₂-independent pathway of ubiquinone biosynthesis is essential for denitrification inPseudomonas aeruginosa

Abstract

<jats:title>ABSTRACT</jats:title><jats:p>Many proteobacteria, such as <jats:italic>Escherichia coli</jats:italic>, contain two main types of quinones, benzoquinones represented by ubiquinone (UQ) and naphthoquinones such as menaquinone (MK) and dimethyl-menaquinone (DMK). MK and DMK function predominantly in anaerobic respiratory chains, whereas UQ is the major electron carrier used for reduction of dioxygen. However, this division of labor is probably not so stric. Indeed, a pathway that produces UQ under anaerobic conditions in an UbiU-, UbiV- and UbiT-dependent manner has been recently discovered in <jats:italic>E. coli</jats:italic> while its physiological relevance is not yet understood because of the presence of MK and DMK in this bacterium. In the present study, we established that UQ<jats:sub>9</jats:sub> is the single quinone of <jats:italic>P. aeruginosa</jats:italic> and that is required for growth under anaerobic respiration (denitrification). We demonstrated that ORFs <jats:italic>PA3911, PA3912</jats:italic> and <jats:italic>PA3913</jats:italic>, which are homologues to the <jats:italic>E. coli ubiT, ubiV</jats:italic> and <jats:italic>ubiU</jats:italic> genes, respectively, were essential for UQ<jats:sub>9</jats:sub> biosynthesis and thus for denitrification in <jats:italic>P. aeruginosa</jats:italic>. These three genes were hereafter called <jats:italic>ubiT<jats:sub>Pa</jats:sub>, ubiV<jats:sub>Pa</jats:sub></jats:italic> and <jats:italic>ubiU<jats:sub>Pa</jats:sub></jats:italic>. We showed that UbiV<jats:sub>Pa</jats:sub> accommodates a [4Fe-4S] cluster. Moreover, we demonstrated that UbiU<jats:sub>Pa</jats:sub> and UbiT<jats:sub>Pa</jats:sub> were able to bind UQ and that the isoprenoid tail of UQ was the structural determinant for the recognition by these Ubi proteins. Since the denitrification metabolism of <jats:italic>P. aeruginosa</jats:italic> is believed to be important for pathogenicity in cystic fibrosis patients, our results highlight the O<jats:sub>2</jats:sub>-independent UQ biosynthesis pathway as a new possible target to develop innovative antibiotics.</jats:p>

Genome-scale modeling ofPseudomonas aeruginosaPA14 unveils its broad metabolic capabilities and role of metabolism in drug potentiation

“…For this analysis, the reactions pertaining to ubiquinone-8 (UQ8) were shut down, and the flux-sum was computed for UQ9, and was divided by the computed growth rate. The model was clearly able to predict that the UQ9 production is higher in anaerobic condition than in aerobic condition which has been experimentally demonstrated (Figure 3) [34].…”

“…Likewise, the model is able to simulate growth under multiple environmental conditions, which reflects the metabolic diversity of the strain. Guided by the model simulations, we were able to predict that anaerobic biosynthesis of ubiquinone-9 is required for the growth of PA14, and a recent study [34] corroborated this hypothesis. Finally, the model was able to recapitulate the potentiation of an antibiotic by metabolite supplementation [36].…”

“…Since no alternative pathway could be identified in P. aeruginosa by literature search or annotation-based methods, this metabolite was removed, and the biomass reaction was adjusted. For UQ9, a recent study [34] has demonstrated that UQ9 can be produced anaerobically by an alternate pathway within the aerobic UQ9 biosynthesis chain. In this pathway, the biosynthetic proteins are shared except for the proteins that catalyze the three reactions associated with oxidation of intermediate metabolites.…”

Revisiting the intrageneric structure of the genusPseudomonaswith complete whole genome sequence information: Insights into Diversity and Host-related Genetic Determinants

“…Thus, by analyzing functional homogeneity of core genes in this study, we could detect multiple genes that show diversified functions while still keeping a relatively conserved structure across different genomes. Among these proteins, 4-hydroxybenzoate synthetase, Molybdopterin-guanine dinucleotide biosynthesis protein A, D-hexose-6-phosphate mutarotase and sulfur transfer complex TusBCD TusB component are involved in resource usage with broad substrate specificity (63)(64)(65), and Flagellar hook-length control protein FliK is implicated in regulating bacterial motility (66,67). These functions typically play an important role in environmental adaptation of the bacteria.…”

The Biosynthetic Pathway of Ubiquinone Contributes to Pathogenicity of Francisella novicida

“…UQ is the major electron carrier used for the reduction of dioxygen by various cytochrome oxidases, whereas MK and DMK function predominantly in anaerobic respiratory chains (9). However, as demonstrated recently in Pseudomonas aeruginosa, UQ can also be produced and used as a main respiratory quinone under anaerobic conditions (10). Besides its role in bioenergetics, UQ was also reported to be involved in gene regulation, oxidative stress, virulence and resistance to antibiotics (11,12).…”