Anaerobic mineralization of quaternary carbon atoms: isolation of denitrifying bacteria on dimethylmalonate.

The microbial capacity to degrade simple organic compounds with quaternary carbon atoms was demonstrated by enrichment and isolation of five denitrifying strains on dimethylmalonate as the sole electron donor and carbon source. Quantitative growth experiments showed a complete mineralization of dimethylmalonate. According to phylogenetic analysis of the complete 16S rRNA genes, two strains isolated from activated sewage sludge were related to the genus Paracoccus within the alpha-Proteobacteria (98.0 and 98.2% 16S rRNA gene similarity to Paracoccus denitrificans(T)), and three strains isolated from freshwater ditches were affiliated with the beta-Proteobacteria (97.4 and 98.3% 16S rRNA gene similarity to Herbaspirillum seropedicae(T) and Acidovorax facilis(T), respectively). Most-probable-number determinations for denitrifying populations in sewage sludge yielded 4.6 x 10(4) dimethylmalonate-utilizing cells ml(-1), representing up to 0.4% of the total culturable nitrate-reducing population.