Kolakovic Srdana, Freitas Elisabete B, Reis Maria A M, Carvalho Gilda, Oehmen Adrian
UCIBIO, REQUIMTE, Department of Chemistry, Faculdade de Ciencias e Tecnologia, Universidade Nova de Lisboa, 2829-516 Caparica, Portugal.
UCIBIO, REQUIMTE, Department of Chemistry, Faculdade de Ciencias e Tecnologia, Universidade Nova de Lisboa, 2829-516 Caparica, Portugal; Advanced Water Management Centre (AWMC), The University of Queensland, St Lucia, Queensland, 4072, Australia.
Water Res. 2021 Jul 1;199:117210. doi: 10.1016/j.watres.2021.117210. Epub 2021 May 5.
Accumulibacter is a well-known group of organisms, typically considered to be polyphosphate accumulating organisms (PAOs), but potentially capable of glycogen accumulating organism (GAO) metabolism under limiting influent phosphate levels. Metabolic features of Accumulibacter are typically linked to its phylogenetic identity at the Type or clade level, though it is unclear the extent to which Accumulibacter diversity can correlate with its capacity to perform P removal. This paper investigates the fine-scale diversity of Accumulibacter and its link with enhanced biological phosphorus removal (EBPR) performance under various operating conditions, to understand the conditions and community structure leading to successful and unsuccessful EBPR operation. For this purpose, the organic carbon feeding rate and total organic carbon concentration were varied during three distinct operational periods, where influent phosphate was never limiting. Accumulibacter was always the dominant microbial group (>80% of all bacteria according to quantitative fluorescence in situ hybridisation - FISH) and low levels of Competibacter and other GAOs were consistently observed (<15% of all bacteria). Steady state was achieved in each of the three periods, with average phosphorus removal levels of 36%, 99% and >99%, respectively. Experimentally determined stoichiometric activity supported the expression of a mixed PAO/GAO metabolism in the first steady state period and the typical PAO metabolism in the other two steady state periods. FISH quantification and amplicon sequencing of the polyphosphate kinase (ppk1) functional gene indicated that Accumulibacter clade IIC was selected in the first steady state period, which shifted to clade IA after decreasing the carbon feeding rate in steady state period 2, and finally shifted back to clade IIC in the third steady state period. Fine-resolution Ppk-based phylogenetic analysis revealed three different clusters within Accumulibacter clade IIC, where clusters IICii and IICiii were linked to poor EBPR performance in period 1, and cluster IICi was linked to good EBPR performance in period 3. This study shows that the deterioration of EBPR processes through GAO activity at non-limiting P concentrations can be linked to organisms that are typically classified as PAOs, not only to known GAOs such as Competibacter. Intra-clade phylogenetic diversity within Accumulibacter showed that some clusters actually behave similarly to GAOs even without influent phosphate limitation. This study highlights the need to closely re-examine traditional interpretations regarding the link between the microbial community composition and identity with the performance and metabolism of EBPR systems.
聚磷菌属是一类知名的微生物群体，通常被认为是聚磷积累微生物（PAO），但在进水磷酸盐水平受限的情况下，可能具备糖原积累微生物（GAO）的代谢能力。聚磷菌属的代谢特征通常与其在类型或进化枝水平上的系统发育身份相关，不过目前尚不清楚聚磷菌属的多样性与其除磷能力之间的关联程度。本文研究了聚磷菌属的精细尺度多样性及其在各种运行条件下与强化生物除磷（EBPR）性能的联系，以了解导致EBPR运行成功和失败的条件及群落结构。为此，在三个不同的运行阶段改变了有机碳投加速率和总有机碳浓度，在此期间进水磷酸盐从未成为限制因素。聚磷菌属始终是主要的微生物群体（根据定量荧光原位杂交 - FISH技术，占所有细菌的80%以上），并且始终观察到低水平的竞争杆菌属和其他GAO（占所有细菌的15%以下）。在这三个阶段均实现了稳态，平均除磷水平分别为36%、99%和>99%。实验测定的化学计量活性支持在第一个稳态阶段存在混合PAO/GAO代谢，而在另外两个稳态阶段存在典型的PAO代谢。对聚磷酸激酶（ppk1）功能基因进行FISH定量和扩增子测序表明，在第一个稳态阶段选择了聚磷菌属IIC进化枝，在稳态阶段2降低碳投加速率后转变为IA进化枝，最终在第三个稳态阶段又变回IIC进化枝。基于Ppk的精细分辨率系统发育分析揭示了聚磷菌属IIC进化枝内的三个不同簇，其中簇IICii和IICiii与阶段1中较差的EBPR性能相关，而簇IICi与阶段3中良好的EBPR性能相关。这项研究表明，在非限制磷浓度下通过GAO活性导致的EBPR过程恶化可能与通常被归类为PAO的微生物有关，而不仅仅是与诸如竞争杆菌属等已知GAO有关。聚磷菌属内进化枝内的系统发育多样性表明，即使在没有进水磷酸盐限制的情况下，一些簇的行为实际上与GAO相似。这项研究强调需要密切重新审视关于微生物群落组成和身份与EBPR系统性能和代谢之间联系的传统解释。
