The Group B Streptococcus NADH oxidase Nox-2 is involved in fatty acid biosynthesis during aerobic growth and contributes to virulence.
Numerous Streptococcaceae produce an H2O-forming NADH oxidase, Nox-2, which has been generally implicated in aerobic survival. We examined the roles of Nox-2 in Group B Streptococcus (GBS), a leading agent of neonatal infections. While nox2 inactivation caused an aerobic growth arrest, no improvement was seen by addition of antioxidants to cultures, suggesting that this defect was not due to accumulation of toxic oxygen species. Using several approaches, we show that the observed inability of the nox2 mutant to grow aerobically is mainly due to an underlying defect in fatty acid (FA) biosynthesis: (i) the nox2 aerobic growth defect is fully and rapidly complemented by adding oleic acid to culture medium, and (ii) direct assimilation of this unsaturated FA in both wild type (WT) and nox2 GBS membranes is demonstrated and correlated with mutant growth rescue. We propose that NAD+ depletion in the nox2 mutant results in reduced acetyl-CoA production, which perturbs FA biosynthesis and hence blocks growth in aerobiosis. The nox2 aerobic growth defect was also complemented when GBS respiration metabolism was activated by exogenous haem and menaquinone. The membrane NADH oxidase activity generated by the functional respiratory chain thus compensates the cytoplasmic NADH oxidase deficiency. The nox2 mutant was attenuated for virulence, as assessed in lung, intraperitoneal and intravenous murine infection models. As the nox2 defect seems only to affect aerobic growth of GBS, its reduced virulence supports the suggestion that aerobic conditions and NADH oxidase activities are relevant to the GBS infection process.
Yamamoto
Yuji
Y
Unité Bactéries Lactiques et Pathogènes Opportunistes, Institut National de la Recherche Agronomique, Bâtiment 222, 78352 Jouy en Josas, France.
Pargade
Vincent
V
Lamberet
Gilles
G
Gaudu
Philippe
P
Thomas
Fabrice
F
Texereau
Joelle
J
Gruss
Alexandra
A
Trieu-Cuot
Patrick
P
Poyart
Claire
C
D000085:Acetates / Q000494:pharmacology; D000220:Adaptation, Biological; D000693:Anaerobiosis / Q000502:physiology*; D000818:Animals; D000975:Antioxidants / Q000494:pharmacology; D001426:Bacterial Proteins / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D049109:Cell Proliferation; D004789:Enzyme Activation; D005227:Fatty Acids / Q000096:biosynthesis* / Q000737:chemistry / Q000494:pharmacology; D009154:Mutation; D009247:NADH, NADPH Oxidoreductases / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D019301:Oleic Acid / Q000494:pharmacology; D011136:Polysorbates / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D013292:Streptococcus agalactiae / Q000472:pathogenicity* / Q000502:physiology*; D014774:Virulence / Q000502:physiology
D000085:Acetates; D000975:Antioxidants; D001426:Bacterial Proteins; D005227:Fatty Acids; D011136:Polysorbates; D019301:Oleic Acid; D009247:NADH, NADPH Oxidoreductases; C121789:Nox-2 protein, bacteria