A novel denitrifying bacterial isolate that degrades trimethylamine both aerobically and anaerobically via two different pathways

The aerobic and anaerobic degradation of trimethylamine by a newly isolated denitrifying bacterium from an enrichment culture with trimethylamine inoc ulated with activated sludge was studied. Based on 16S rDNA analysis, this strain was identified as a Paracoccus sp. The isolate, strain T231, aerobic ally degraded trimethylamine, dimethylamine and methylamine and released a stoichiometric amount of ammonium ion into the culture fluid as a metabolic product, indicating that these methylated amines were completely degraded to formaldehyde and ammonia. The strain degraded trimethylamine also under denitrifying conditions and consumed a stoichiometric amount of nitrate, de monstrating that complete degradation of trimethylamine was coupled with ni trate reduction. Cell-free extract prepared from cells grown aerobically on trimethylamine exhibited activities of trimethylamine mono-oxygenase, trim ethylamine N-oxide demethylase, dimethylamine mono-oxygenase, and methylami ne mono-oxygenase. Cell-free extract from cells grown anaerobically on trim ethylamine and nitrate exhibited activities of trimethylamine dehydrogenase and dimethylamine dehydrogenase. These results indicate that strain T231 h ad two different pathways for aerobic and anaerobic degradation of trimethy lamine. This is a new feature for trimethylamine metabolism in denitrifying bacteria.