Community structures and population dynamics of “Candidatus Accumulibacter” in activated sludges of wastewater treatment plants using ppk1 as phylogenetic marker

Candidatus Accumulibacter has been identified as dominant polyphosphate-accumulating organisms（PAOs） in enhanced biological phosphorus（P） removal（EBPR） from wastewater.This study revealed the relevance of community structure, abundance and seasonal population dynamics of Candidatus Accumulibacter to process operation of wastewater treatment plants（WWTPs） in China using ppk1 gene as phylogenetic marker. All sludge samples had properties of denitrifying P removal using nitrate as an electron acceptor.Accumulibacter abundance in the anaerobic-anoxic-oxic（A^2O） process was the highest（26%of total bacteria）, and higher in winter than in summer with a better EBPR performance.Type-II was the dominant Accumulibacter in all processes, and type-I accounted for a small proportion of total Accumulibacter. The abundance of Clade-IIC as the most dominant clade reached 2.59 × 10~9 cells/g MLSS and accounted for 87.3% of total Accumulibacter. Clade IIC mainly contributed to denitrifying P removal. Clades IIA, IIC and IID were found in all processes, while clade-IIF was only found in oxidation ditch process through phylogenetic analysis. High proportion of clade IID to total Accumulibacter led to poor performance of aerobic P-uptake in inverted A^2O process. Therefore, Accumulibacter clades in WWTPs were diverse, and EBPR performance was closely related to the clade-level community structures and abundances of Accumulibacter.

Integrated genomics provides insights into the evolution of the polyphosphate accumulation trait of Ca.Accumulibacter

Candidatus Accumulibacter,a prominent polyphosphate-accumulating organism(PAO)in wastewater treatment,plays a crucial role in enhanced biological phosphorus removal(EBPR).The genetic underpinnings of its polyphosphate accumulation capabilities,however,remain largely unknown.Here,we conducted a comprehensive genomic analysis of Ca.Accumulibacter-PAOs and their relatives within the Rhodocyclaceae family,identifying 124 core genes acquired via horizontal gene transfer(HGT)at its least common ancestor.Metatranscriptomic analysis of an enrichment culture of Ca.Accumulibacter revealed active transcription of 44 of these genes during an EBPR cycle,notably including the polyphosphate kinase 2(PPK2)gene instead of the commonly recognized polyphosphate kinase 1(PPK1)gene.Intriguingly,the phosphate regulon(Pho)genes showed minimal transcriptions,pointing to a distinctive fact of Pho dysregulation,where PhoU,the phosphate signaling complex protein,was not regulating the high-affinity phosphate transport(Pst)system,resulting in continuous phosphate uptake.To prevent phosphate toxicity,Ca.Accumulibacter utilized the laterally acquired PPK2 to condense phosphate into polyphosphate,resulting in the polyphosphate-accumulating feature.This study provides novel insights into the evolutionary emergence of the polyphosphate-accumulating trait in Ca.Accumulibacter,offering potential advancements in understanding the PAO phenotype in the EBPR process.

广州中心城区污水厂聚磷菌丰度差异及影响因素

为研究华南地区采用传统厌氧/缺氧/好氧(AAO)工艺和膜生物反应器(MBR)工艺(典型工艺为厌氧/缺氧/好氧/缺氧/膜池)的城市污水净化厂的生物除磷效能差异及其关键影响因素,采用16S rRNA基因扩增子测序技术对13座污水净化厂的24条生产线中聚磷菌Candidatus Accumulibacter及Tetrasphaera的相对丰度进行检测。结果表明,采用AAO和MBR工艺的污水厂中两种聚磷菌的丰度差异显著,AAO工艺中Candidatus Accumulibacter的平均相对丰度为MBR工艺的3倍;采用MBR工艺的污水厂中均未检测到Tetrasphaera。对水质参数、运行条件、除磷效能、工艺模式及聚磷菌菌群结构进行典型对应分析(CCA),结果显示,除进水碳磷比、厌氧池水力停留时间外,硝化液回流模式是导致聚磷菌丰度差异的重要因素。