Tetrasphaera聚磷菌研究进展及其除磷能力辨析

Research advances of Tetrasphaera as polyphosphate accumulating organisms and analysis on their P-removal potential

强化生物除磷(EBPR)工艺在污水脱氮除磷中扮演着重要角色,其机理研究与工程应用也较为成熟.长期以来,Accumulibacter菌属(A菌)作为EBPR工艺最主要的聚磷菌(PAOs)已被广泛接受.同时,具有聚磷能力的Tetrasphaera菌属(T菌)亦被发现,且在某些特定环境下其丰度甚至远高于A菌,进而引发业内一定的关注.本文通过对T菌发现、研究过程的梳理,总结了关于T菌丰度、代谢途径及影响其活性的因素等方面的研究成果.与A菌不同,T菌代谢途径具有多样性,可依赖发酵代谢进行细胞维持和增殖,其发酵产物甚至可以供给A菌利用.T菌可利用大分子有机物(如葡萄糖、氨基酸等)和VFAs(亲和性较低)进行厌氧释磷,继而完成好氧、甚至缺氧吸磷过程.T菌主要菌株(T.elongata)因缺少合成PHA相关酶基因而不能以PHA作为内聚产物在厌氧环境下储能;糖原和游离氨基酸被检测到可作为T菌的能源/碳源内聚物,但亦有结果相左的研究.借助于拉曼光谱技术,一些污水处理厂中T菌与A菌被证实对磷去除的贡献大小相当.总之,目前对T菌的研究还十分有限,现有研究仍不足以证明它们在EBPR中可稳定发挥除磷贡献.今后应在T菌不同代谢途径控制因素及所需环境条件方面进行深入研究,以确认T菌可否持续、稳定地实现除磷作用.

Enhanced biological phosphorus removal(EBPR)plays a key role in biological nutrient removal(BNR),which has been well studied and widely applied in practical wastewater treatment.It has long been widely accepted that Accumulibacter is the major group of polyphosphate⁃accumulating organisms(PAOs)in EBPR.Meanwhile,a group of bacteria named Tetrasphaera with polyphosphate accumulating capability have been also observed in a larger abundance than Accumulibacter in some wastewater treatment plants(WWTPs),which thus arouse some research interests in them.Herein,the abundances,metabolic pathways,and influencing factors of Tetrasphaera are summarized here by summarizing the research advances of Tetrasphaera.Unlike Accumulibacter,Tetrasphaera have various metabolic pathways,and can rely on fermentation metabolisms for cell maintenance and growth,in which fermentation products can be even utilized by Accumulibacter.In terms of P⁃removal,Tetrasphaera can utilize macromolecular organic substances(such as glucose,amino acids,etc.)and VFAs(Accumulibacter has a low affinity to these macromolecular substances)to fulfill phosphate release anaerobically,and then phosphate uptake under aerobic and/or anoxic conditions.Moreover,the dominating isolate of Tetrasphaera(T.elongata)cannot synthesize PHA as intracellular storage compounds to provide carbon and energy sources for aerobic/anoxic phosphate uptake due to lack of genes for relevant enzymes for PHA synthesis.By contrast,glycogen and free amino acids are likely to be the energy/carbon source polymers for P⁃removal metabolisms,which still remains unclear.With the help of Raman Micro⁃Spectroscopy,contribution of Tetrasphaera to P⁃removal in some WWTPs are comparable to Accumulibater.So far,limited research and information about Tetrasphaera are far away to verify Tetrasphaera exerting reliable P⁃removal in full⁃scale WWTPs.Thus,these knowledge gaps need further research on influencing factors and environmental conditions regulating reliable and consistent P⁃removal metabolisms of Tetrasphaera for an exact conclusion.