Carbaryl as a carbon and nitrogen source: An inducible methylamine metabolic pathway at the biochemical and molecular levels in Pseudomonas sp. strain C5pp

Abstract

Carbaryl is the most widely used carbamate family pesticide, and its persistent nature causes it to pollute both soil and water ecosystems. Microbes maintain the Earth's biogeochemical cycles by metabolizing various compounds present in the matter, including xenobiotics, as a sole source of carbon, nitrogen, and energy. Soil isolate Pseudomonas sp. strain C5pp metabolizes carbaryl efficiently as the carbon source. Periplasmic carbaryl hydrolase catalyzes the conversion of carbaryl to 1-naphthol and methylamine. 1-Naphthol was further used as a carbon source via gentisate, whereas the metabolic fate of methylamine is not known. Here, we demonstrate that strain C5pp showed efficient growth on carbaryl when supplied as a carbon and nitrogen source, suggesting that the methylamine generated was used as the nitrogen source. Genes involved in the methylamine metabolism were annotated and characterized at the biochemical and molecular level. Transcriptional and enzyme activity studies corroborate that the γ-glutamylmethylamide/Nmethylglutamate (GMA/NMG) pathway is involved in the metabolism of carbaryl and methylamine as a nitrogen source. Compared to carbaryl, methylamine was found to be an effective inducer for the metabolic and transporter genes. Strain C5pp also harbored genes involved in sarcosine metabolism that were cotranscribed and induced by sarcosine. The presence of inducible pathways for metabolism of carbaryl as a nitrogen and carbon source helps in complete and efficient mineralization of carbaryl by strain C5pp, thereby maintaining the biogeochemical cycles.