Isolation, characterization, and metabolic diversity of denitrifying bacteria capable of degrading trimethylamine

Abstract

Denitrifying bacteria capable of degrading trimethylamine, a hazardous environmental pollutant, were isolated from six different environmental sites by selective enrichment procedures. The isolates were putatively divided into four groups on the basis of similarity of their 16S rDNA sequences. Although all isolates were members of the a-subclass of Proteobacteria, they exhibited diverse characteristics in terms of taxonomic and physiological properties. Some strains included in the same group showed different characteristics, which are dependent on their habitats and environmental conditions. The diversity of these isolates indicates that various denitrifying bacteria in different categories that are distributed into various environmental sites play an important role in removing trimethylamine under denitrifying conditions. One of the isolated denitrifying bacterium, strain T231, capable of degrading trimethylamine was identified. Strain T231 was a Gram-negative, coccoid, non-motile, and non-spore forming organism. The G + C content of DNA was 68 mol%. Its major cellular fatty acids were a straight-chain unsaturated acid, Cl g:1, and hydroxy acids, 3-OH C10:0 and 3-OH C14:o. The main quinone was ubiqunone Q-10. The 16S rDNA sequences indicated that strain T231 belongs to the a-subclass of Proteobacteria, and it is the closest to Paracoccus aminovorans with 98% similarity. Strain T231 had the ability to utilize trimethylamine, dimethylamine and methylamine as a sole carbon and energy source under aerobic and denitrifying conditions. The aerobic and anaerobic degradation of trimethylamine by strain T231 was studied. The isolate aerobically 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 consum...