Community Assembly and Ecology of Activated Sludge under Photosynthetic Feast–Famine Conditions

Here, we demonstrate that photosynthetic
oxygen production under
light–dark and feast–famine cycles with no mechanical
aeration and negligible oxygen diffusion is able to maintain phosphorus
cycling activity associated with the enrichment of polyphosphate accumulating
organisms (PAOs). We investigate the ecology of this novel system
by conducting a time series analysis of prokaryotic and eukaryotic
biodiversity using the V3–V4 and V4 regions of the 16S and
18S rRNA gene sequences, respectively. In the Eukaryotic community,
the initial dominant alga observed was Desmodesmus. During operation, the algal community became a more diverse consortium
of Desmodesmus, Parachlorella, Characiopodium, and Bacillariophytina.
In the Prokaryotic community, there was an initial enrichment of the
PAO Candidatus Accumulibacter phosphatis (Accumulibacter)
Acc-SG2, and the dominant ammonia-oxidizing organism was Nitrosomonas
oligotropha; however, these populations decreased in relative
abundance, becoming dominated by Accumulibacter Acc-SG3 and Nitrosomonas ureae. Furthermore, functional guilds that
were not abundant initially became enriched including the putative Cyanobacterial PAOs Obscuribacterales and Leptolyngbya and the H2-oxidizing denitrifying
autotroph Sulfuritalea. After a month of operation,
the most-abundant prokaryote belonged to an uncharacterized clade
of Chlorobi classified as Chlorobiales;SJA-28 Clade III, the first reported enrichment of this lineage.
This experiment represents the first investigation into the ecological
interactions and community assembly during photosynthetic feast–famine
conditions. Our findings suggest that photosynthesis may provide sufficient
oxygen to drive polyphosphate cycling.

本研究证实，在无机械曝气、氧气扩散可忽略的明暗循环与饱食-饥饿循环条件下，光合产氧过程能够维持与聚磷微生物（polyphosphate accumulating organisms, PAOs）富集相关的磷循环活性。
我们分别采用16S rRNA基因V3-V4区与18S rRNA基因V4区的测序数据，对原核生物与真核生物的生物多样性开展时间序列分析，以此探究该新型系统的生态学特征。
真核生物群落中，初始优势藻类为栅藻属（Desmodesmus）；运行过程中，藻类群落逐渐演变为包含栅藻属、拟小球藻属（Parachlorella）、柱囊藻属（Characiopodium）以及硅藻门（Bacillariophytina）的多样化共生群落。
原核生物群落中，初始富集的聚磷微生物为候选聚磷杆菌（Candidatus Accumulibacter phosphatis, Accumulibacter）Acc-SG2，优势氨氧化微生物为寡养亚硝化单胞菌（Nitrosomonas oligotropha）；但上述类群的相对丰度逐渐降低，群落转而被Accumulibacter Acc-SG3与脲基亚硝化单胞菌（Nitrosomonas ureae）主导。
此外，初始丰度较低的功能类群也逐渐得到富集，包括推测的蓝细菌源聚磷微生物暗杆菌目（Obscuribacterales）、细鞘丝藻属（Leptolyngbya），以及氢氧化反硝化自养菌硫小菌属（Sulfuritalea）。
运行一个月后，丰度最高的原核生物属于一类未被表征的绿菌门（Chlorobi）演化支，归类为绿菌目（Chlorobiales）SJA-28 演化支III，这是该谱系首次被报道实现富集。
本实验首次针对光合饱食-饥饿循环条件下的生态互作与群落构建过程开展研究，结果表明光合作用可产生充足氧气以驱动聚磷循环。