Welles L, Lopez-Vazquez C M, Hooijmans C M, van Loosdrecht M C M, Brdjanovic D
Department of Environmental Engineering and Water Technology, UNESCO-IHE Institute for Water Education, Westvest 7, 2611AX, Delft, The Netherlands.
Department of Biotechnology, Delft University of Technology, Van der Maasweg 9, 2629 HZ, Delft, The Netherlands.
AMB Express. 2016 Dec;6(1):44. doi: 10.1186/s13568-016-0214-z. Epub 2016 Jul 4.
P-limitation in enhanced biological phosphorus removal (EBPR) systems fed with acetate, has generally been considered as a condition leading to enrichment of organisms of the genotype' Candidatus Competibacter phosphatis' expressing the glycogen-accumulating organisms (GAO) phenotype. Recent studies have demonstrated in short-term experiments that organisms of the genotype 'Candidatus Accumulibacter phosphatis' clade I and II, known to express the polyphosphate-accumulating organisms (PAO) phenotype can switch to the GAO phenotype when poly-P is absent, but are performing the HAc-uptake at lower kinetic rates, where clade I showed the lowest rates. The objective of this study was to verify whether organisms of the genotype 'Candidatus Accumulibacter phosphatis' can also be enriched under P-limiting conditions while expressing a GAO phenotype and more specifically to see which specific clade prevails. A sequencing batch reactor was inoculated with activated sludge to enrich an EBPR culture for a cultivation period of 128 days (16 times the solids retention time) under P-limiting conditions. A mixed culture was obtained comprising of 49 % 'Candidatus Accumulibacter phosphatis' clade II and 46 % 'Candidatus Competibacter phosphatis'. The culture performed a full GAO metabolism for anaerobic HAc-uptake, but was still able to switch to a PAO metabolism, taking up excessive amounts of phosphate during the aerobic phase when it became available in the influent. These findings show that P-limitation, often used as strategy for enrichment of 'Candidatus Competibacter phosphatis', does not always lead to enrichment of only 'Candidatus Competibacter phosphatis'. Furthermore, it demonstrates that 'Candidatus Accumulibacter phosphatis' are able to proliferate in activated sludge systems for periods of up to 128 days or longer when the influent phosphate concentrations are just enough for assimilation purposes and no poly-P is formed. The 'Candidatus Accumulibacter phosphatis' retain the ability to switch to the PAO phenotype, taking up phosphate from the influent as soon as it becomes available.
在以乙酸盐为进料的强化生物除磷（EBPR）系统中，磷限制通常被认为是一种导致表达糖原积累生物体（GAO）表型的“聚磷菌（Candidatus Competibacter phosphatis）”基因型生物体富集的条件。最近的研究在短期实验中表明，已知表达聚磷积累生物体（PAO）表型的“聚磷菌（Candidatus Accumulibacter phosphatis）”进化枝I和II的生物体在缺乏多聚磷酸盐时可转变为GAO表型，但它们以较低的动力学速率摄取乙酸，其中进化枝I的速率最低。本研究的目的是验证“聚磷菌（Candidatus Accumulibacter phosphatis）”基因型的生物体在表达GAO表型的同时是否也能在磷限制条件下富集，更具体地说，是要看哪种特定的进化枝占优势。一个序批式反应器接种了活性污泥，以便在磷限制条件下培养128天（固体停留时间的16倍）来富集EBPR培养物。获得了一种混合培养物，其中包含49%的“聚磷菌（Candidatus Accumulibacter phosphatis）”进化枝II和46%的“聚磷菌（Candidatus Competibacter phosphatis）”。该培养物对厌氧乙酸摄取进行了完全的GAO代谢，但仍能够转变为PAO代谢，在进水有过量磷酸盐时，在好氧阶段摄取过量的磷酸盐。这些发现表明，经常用作富集“聚磷菌（Candidatus Competibacter phosphatis）”策略的磷限制并不总是仅导致“聚磷菌（Candidatus Competibacter phosphatis）”的富集。此外，这表明当进水磷酸盐浓度仅足以用于同化目的且不形成多聚磷酸盐时，“聚磷菌（Candidatus Accumulibacter phosphatis）”能够在活性污泥系统中增殖长达128天或更长时间。“聚磷菌（Candidatus Accumulibacter phosphatis）”保留了转变为PAO表型的能力，一旦进水有磷酸盐，就会摄取磷酸盐。
