Suppression of Escherichia coli formate hydrogenlyase activity by trimethylamine N-oxide is due to drainage of the inducer formate.
The effect of the addition of trimethylamine N-oxide (TMAO) in the growth medium on Escherichia coli anaerobic fermentative and respiratory pathways was examined. Formate dehydrogenase H (FDH-H) activity was totally repressed by the addition of 40 mM TMAO, whereas the overall hydrogenase (HYD) activity was reduced by 25%. Accordingly, expression of lacZ operon fusions with the fdhF and hycB structural genes specifying FDH-H and HYD3 was reduced sevenfold and eightfold, respectively, leading to suppression of an active formate hydrogenlyase system. In contrast, global respiratory formate-dependent phenazine methosulphate reductase (FDH-PMS) activity, which consists of both the major anaerobic FDH-N enzyme and the aerobic FDH-Z isoenzyme, was increased approximately twofold. This was corroborated by a 2.5-fold stimulation of the sole fdoG-uidA transcriptional fusion which reflects the synthesis of the respiratory aerobic FDH-Z enzyme. In fdhD, fdhE or torA mutants lacking either FDH-PMS activity or TMAO reductase (TOR) activity, the formate hydrogenlyase pathway was no longer inhibited by TMAO. In addition, introduction of 30 mM formate in the growth medium was found to relieve the repressive effect of TMAO in the wild-type strain. When TMAO was added as terminal electron acceptor a significant enhancement of anaerobic growth was observed with the wild-type strain and the fdoG mutant. It was associated with the concomitant suppression of the formate hydrogenlyase enzymes. This was in contrast to the fdnG and torA mutants whose growth pattern and fermentative enzymes remained unaffected. Taken together, these results strongly suggest that formate-dependent reduction of TMAO via FDH-N and TOR reduces the amount of formate available for induction of the formate hydrogenlyase pathway.
Abaibou
Hafid
H
Laboratoire de Génétique Moléculaire des Micro-organismes et des Interactions Cellulaires CNRS UMR 5577, Institut National des Sciences Appliquées, 20 avenue A. Einstein, 69621 Villeurbanne Cedex, France.
Giordano
Gérard
G
Laboratoire de Chimie Bactérienne, CNRS UPR 9043, 31 chemin Joseph Aiguier, 13402 Marseille Cedex 20, France.
Mandrand-Berthelot
Marie-Andrée
MA
Laboratoire de Génétique Moléculaire des Micro-organismes et des Interactions Cellulaires CNRS UMR 5577, Institut National des Sciences Appliquées, 20 avenue A. Einstein, 69621 Villeurbanne Cedex, France.
D000693:Anaerobiosis; D004579:Electron Transport; D004794:Enzyme Repression; D004926:Escherichia coli / Q000187:drug effects / Q000235:genetics*; D005560:Formate Dehydrogenases / Q000235:genetics* / Q000378:metabolism; D005561:Formates / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D006864:Hydrogenase / Q000235:genetics*; D008744:Methylamines / Q000494:pharmacology*; D008773:Methylphenazonium Methosulfate / Q000378:metabolism; D009097:Multienzyme Complexes / Q000235:genetics*; D009154:Mutation; D016877:Oxidants / Q000494:pharmacology*; D010089:Oxidoreductases, N-Demethylating / Q000235:genetics / Q000378:metabolism
D005561:Formates; D008744:Methylamines; D009097:Multienzyme Complexes; D016877:Oxidants; C030544:formic acid; D008773:Methylphenazonium Methosulfate; D006864:Hydrogenase; D005560:Formate Dehydrogenases; C054017:formate hydrogenlyase; D010089:Oxidoreductases, N-Demethylating; C023186:trimethylamine dehydrogenase; C005855:trimethyloxamine