Environmental distribution and population biology of Candidatus Accumulibacter, a primary agent of biological phosphorus removal.

Members of the uncultured bacterial genus Candidatus Accumulibacter are capable of intracellular accumulation of inorganic phosphate in activated sludge wastewater treatment plants (WWTPs) performing enhanced biological phosphorus removal, but were also recently shown to inhabit freshwater and estuarine sediments. Additionally, metagenomic sequencing of two bioreactor cultures enriched in Candidatus Accumulibacter, but housed on separate continents, revealed the potential for global dispersal of particular Candidatus Accumulibacter strains, which we hypothesize is facilitated by the ability of Candidatus Accumulibacter to persist in environmental habitats. In the current study, we used sequencing of a phylogenetic marker, the ppk1 gene, to characterize Candidatus Accumulibacter populations in diverse environments, at varying distances from WWTPs. We discovered several new lineages of Candidatus Accumulibacter which had not previously been detected in WWTPs, and also uncovered new diversity and structure within previously detected lineages. Habitat characteristics were found to be a key determinant of Candidatus Accumulibacter lineage distribution while, as predicted, geographic distance played little role in limiting dispersal on a regional scale. However, on a local scale, enrichment of particular Candidatus Accumulibacter lineages in WWTP appeared to impact local environmental populations. These results provide evidence of ecological differences among Candidatus Accumulibacter lineages.

Metagenomic and functional analysis of hindgut microbiota of a wood-feeding higher termite.

From the standpoints of both basic research and biotechnology, there is considerable interest in reaching a clearer understanding of the diversity of biological mechanisms employed during lignocellulose degradation. Globally, termites are an extremely successful group of wood-degrading organisms and are therefore important both for their roles in carbon turnover in the environment and as potential sources of biochemical catalysts for efforts aimed at converting wood into biofuels. Only recently have data supported any direct role for the symbiotic bacteria in the gut of the termite in cellulose and xylan hydrolysis. Here we use a metagenomic analysis of the bacterial community resident in the hindgut paunch of a wood-feeding 'higher' Nasutitermes species (which do not contain cellulose-fermenting protozoa) to show the presence of a large, diverse set of bacterial genes for cellulose and xylan hydrolysis. Many of these genes were expressed in vivo or had cellulase activity in vitro, and further analyses implicate spirochete and fibrobacter species in gut lignocellulose degradation. New insights into other important symbiotic functions including H2 metabolism, CO2-reductive acetogenesis and N2 fixation are also provided by this first system-wide gene analysis of a microbial community specialized towards plant lignocellulose degradation. Our results underscore how complex even a 1-microl environment can be.