“ Candidatus Accumulibacter” Population Structure in Enhanced Biological Phosphorus Removal Sludges as Revealed by Polyphosphate Kinase Genes

Abstract

We investigated the fine-scale population structure of the "Candidatus Accumulibacter" lineage in enhanced biological phosphorus removal (EBPR) systems using the polyphosphate kinase 1 gene (ppk1) as a genetic marker. We retrieved fragments of "Candidatus Accumulibacter" 16S rRNA and ppk1 genes from one laboratory-scale and several full-scale EBPR systems. Phylogenies reconstructed using 16S rRNA genes and ppk1 were largely congruent, with ppk1 granting higher phylogenetic resolution and clearer tree topology and thus serving as a better genetic marker than 16S rRNA for revealing population structure within the "Candidatus Accumulibacter" lineage. Sequences from at least five clades of "Candidatus Accumulibacter" were recovered by ppk1-targeted PCR, and subsequently, specific primer sets were designed to target the ppk1 gene for each clade. Quantitative real-time PCR (qPCR) assays using "Candidatus Accumulibacter"-specific 16S rRNA and "Candidatus Accumulibacter" clade-specific ppk1 primers were developed and conducted on three laboratoryscale and nine full-scale EBPR samples and two full-scale non-EBPR samples to determine the abundance of the total "Candidatus Accumulibacter" lineage and the relative distributions and abundances of the five "Candidatus Accumulibacter" clades. The qPCR-based estimation of the total "Candidatus Accumulibacter" fraction as a proportion of the bacterial community as measured using 16S rRNA genes was not significantly different from the estimation measured using ppk1, demonstrating the power of ppk1 as a genetic marker for detection of all currently defined "Candidatus Accumulibacter" clades. The relative distributions of "Candidatus Accumulibacter" clades varied among different EBPR systems and also temporally within a system. Our results suggest that the "Candidatus Accumulibacter" lineage is more diverse than previously realized and that different clades within the lineage are ecologically distinct.

Endophytic Microbiota Associated with the Root Tips and Leaves of Baccharis dracunculifolia

“…Members of this genus are widely known to accumulate polyphosphate and remove enhanced biological phosphorus in activated sludge of wastewater treatment plants. Candidatus Accumulibacter has also been reported as an endophyte in roots of Typha angustifolia [ 54,55 ]. Gammaproteobacteria class predominated in the healthy leaf sample especially the genus Providencia.…”

From macro to lab-scale: Changes in bacterial community led to deterioration of EBPR in lab reactor

“…Numerous studies by Flowers et al [52], He et al [15,53] and Oehmen et al [30,31,33] have found that lower COD/P ratios of 10-15 should be used for successful enrichment (>80% of all bacteria) of Accumulibacter in lab-scale reactors. However, there are some contradicting studies which indicate that low C/P ratios are not sufficient for outcompeting GAOs nor achieving low phosphorus effluent even in lab-scale optimal conditions.…”

“…Well-defined operational conditions reduce the number of ecological niches available to bacteria. He et al [15] investigated two lab-scale SBRs fed with acetate and nine full-scale EBPR plants. The SBRs were inoculated with sludge originated from the full-scale plants.…”

“…In the majority of lab-scale experiments, SBRs with 6 h cycles were used to enrich either PAOs or GAOs [2,11,12,15,27,28,[30][31][32][33]49,53].…”

“…The most well-known PAO is Candidatus Accumulibacter phosphatis in the Betaproteobacteria subclass 2 closely related to Rhodocyclus (hereafter referred to as Accumulibacter or R-PAO), consisting of two distinct types that each include a few subclades [15,16]. Members of the actinobacterial genus Tetrasphaera were shown to actively participate in EBPR and often are even more abundant in fullscale wastewater treatment plants (WWTPs) than Accumulibacter [17][18][19].…”