Bacterial Diversity in Biological Filtration Plant for the Removal of Iron and Manganese from Groundwater

Bacterial diversity of the microbial consortia in a biological filtration plant for the elimination of iron (Fe) and manganese (Mn) from groundwater in Joyo City, Kyoto, Japan, was studied. PCR-based denaturing gradient gel electrophoresis (DGGE) analysis of bacterial 16S ribosomal RNA (rRNA) genes represented at least 15 signals, and nucleotide sequences of the dominant fragments showed similarities to Gallionella and Nitrospira. Phylogenetic analysis using the obtained nucleotide sequences of the 16S rRNA gene clone library showed the presence of the bacteria related to Hyphomicrobium, Gallionella, and Sideroxydans, which are supposed to be involved in Fe and Mn removal. In contrast, no 16S rRNA gene clone affiliated with the genus Leptothrix, which have been regarded as a major Fe- and Mn-oxidizer in biological filtration system, was observed. Though a large number of 16S rRNA gene clones closely related to Nitrospira was obtained, no clone showed high sequence similarity to known ammonium oxidizing bacteria (AOB). However, PCR-amplification of the ammonia monooxigenase gene (amoA) of AOB and ammonia oxidizing archaea (AOA) indicated the presence of both AOB and AOA in this biological filtration plant.