Distribution of the Microbial Community Structure in Sulfur-Based Autotrophic Denitrification Columns

Abstract

Substrate-dependent evolution of a bacterial community capable of transforming nitrate was examined in sulfur-based autotrophic denitrification columns. The 16S rRNA genes and denaturing gradient gel electrophoresis (DGGE) analysis revealed that the initial bacterial consortium was well adapted to column operation time and distribution of nitrate concentration. In the lower part of a 200-day operated column where nitrate was introduced, a bacterial strain designated OTU DE-1 was abundant, occupying 92% of the community. The species was identified as Thiobacillus denitrificans with a similarity of 97% by BLAST search. A heterotroph designated as OTU DE-2 showing a similarity of 94% to Cenibacterium arsenoxidans was then enriched in the middle part of the column occupying 82% of the community, indicating the presence of organic electron donors. Interestingly, OTU DE-5 with a similarity of 98% to Chlorobium limicola, which is commonly present in hydrogen sulfide-rich environments, was found in the upper part of the column where sulfate level was high with little nitrate. The microbial community was consistent with observed concentrations of nitrate, nitrite, and sulfate with column height and operation time.