Pseudomonas aeruginosa has been reported to degrade C1 and inorganic nitrogen compounds through multiple metabolic pathways. This study aims to shed light on the uncharted CH 4 and NH 4 oxidation pathways in P. aeruginosa strain AAK/M5 for utilization of C1 and N1 compounds in syntrophic nitrifying denitrifying medium. Around 9% and 11% higher NH 4 + –N and NO 3 – –N removal respectively was observed in presence of CH 4 as carbon source. Similarly, CH 4 removal was 3.6-fold higher in the set supplemented with NO 3 – -N as nitrogen source than the set with NH 4 + -N. Intermediates of methane oxidation viz., CH 3 OH, HCOOH, and that of nitrate reduction viz., NO 2 – –N were also detected. Induction of methane/ammonia monooxygenase in presence of CuSO 4 revealed highest NH 4 + –N removal (84.89 mg/L) and CH 4 removal (30%) at 10 µM CuSO 4 . Degradation kinetics using high density resting bacterial cells in phosphate buffer resulted in µ max (min − 1 ) of 0.0018, 0.0049, 0.0034, 0.0038, and 0.0012, for NH 4 + –N, NH 2 + –N, NO 3 – –N, NO 2 – –N and CH 3 OH respectively. Additionally, affirmation of CH 4 /NH 3 oxidizing enzyme was done via in silico analysis which revealed the presence of two enzymes sharing 38.3% and 31.4% homology with ammonia monooxygenase subunit C and soluble methane monooxygenase subunit C, respectively. Furthermore, a quinoprotein methanol dehydrogenase was detected in the genome. The results thus suggested the CH 4 metabolizing capacity of P. aeruginosa AAK/M5 in presence of ammonical/nitrate nitrogen by virtue of key enzymes sharing homology with ammonia monooxygenase and soluble methane monooxygenase.
Singh et al. (Thu,) studied this question.