Genomic and ecophysiological differentiation of two Candidatus Accumulibacter clades.

摘要

This study addressed genomic and ecophysicological differences between Candidatus Accumulibacter phosphatis Clade IA and Clade IIA. Accumulibacter is a model organism for a wastewater treatment process known as enhanced biological phosphorus removal (EBPR).;We explored the dynamics of the entire bacterial community at a full-scale EBPR plant over a two year period through regular sampling and automated ribosomal intergenic spacer analysis (ARISA). We determined that the community changed significantly over a year, but that communities had similar composition within seasons across the two years. Surprisingly, Clade IA and IIA ARISA fragments were present for nearly every sample during the two-year study.;We studied the abilities of Clade IA and IIA populations to couple nitrate reduction with phosphorus uptake using batch-test reactors enriched in each clades separately. It was revealed that Clade IA was able to couple these processes; Clade IIA could not.;We examined kinetic differences between these two clades and determined that Clade IA had faster acetate uptake and phosphorus release and uptake kinetics than Clade IIA, but that the two clades had statistically indistinguishable PHA synthesis and degradation rates.;Several large scaffolds for Clade IA were assembled from metagenomic sequence. Comparative genomics revealed that the same EBPR genes were present in both Clade IA and IIA, but the clades only shared roughly half of their genes at a nucleotide sequence identity averaging 78%. Interestingly, Clade IA lacked most of the genes required for carbon and nitrogen fixation that were present in Glade IIA. Glade IA contained fewer CRISPR loci than Glade IIA, implying that it is more susceptible to phage predation.;The results from this study clearly suggest that these two Accumulibacter clades have significant metabolic and genomic differences, providing evidence that the two clades occupy different niches in the activated sludge microbial community.