Stroot P G, Oerther D B
Dept. of Civil & Environmental Engineering, University of Cincinnati, Cincinnati, OH 45221, USA.
Water Sci Technol. 2003;47(11):241-50.
Conventional activated sludge systems require bacteria to grow to avoid washout through decay and routine solids wasting. Recently we developed a procedure targeting precursor 16S ribosomal RNA to measure the in situ growth activity of phylogenetically defined microbial populations, and this procedure was used to study the growth of bacteria in activated sludge systems. The current study significantly expands this previous work by quantifying levels of precursor 16S ribosomal RNA within individual cells of pure cultures of bacteria exposed to various culture conditions. Initially, three ranges (Type I, Type II, and Type III) of precursor 16S ribosomal RNA levels were defined by whole cell fluorescence in situ hybridization of a pure culture of Acinetobacter calcoaceticusT prepared in three culture conditions. Low levels of precursor 16S ribosomal RNA (Type I) corresponded to a stationary phase culture prepared overnight in Luria-Bertani medium. Intermediate levels of precursor 16S ribosomal RNA (Type II) corresponded to a culture transferred into fresh Luria-Bertani medium, and high levels of precursor 16S ribosomal RNA (Type III) corresponded to a culture treated with the growth inhibiting antibiotic chloramphenicol. Subsequently, the abundance of individual cells of each Type were measured in four different pure cultures after exposure to 0.45-microm filtered primary effluent collected from four different conventional activated sludge treatment plants in Cincinnati, OH, USA. Individual cells of each Type were observed in the culture of A. calcoaceticusT exposed to each of the four primary effluents. Only Type I cells were observed in cultures of A. johnsoniiT, A. johnsonii strain 210a, and Escherichia coliT exposed to each of the four primary effluents. These results suggest that the growth of A. calcoaceticusT was inhibited by an unidentified component of filtered primary effluent present in each of the four wastewaters; whereas the growth of A. johnsoniiT, A. johnsonii strain 210a, and E. coliT were not inhibited. These results have significance for understanding the growth of phylogenetically defined microbial populations within activated sludge treatment systems. If the pattern of elevated p16S rRNA levels observed in A. calcoaceticusT is prevalent in many microbial populations in activated sludge systems, this may have implications for preventing washout of critical microbial populations that may be experiencing growth inhibition.
传统活性污泥系统需要细菌生长，以避免因衰减和常规固体废弃物排放而被冲出系统。最近，我们开发了一种针对前体16S核糖体RNA的程序，用于测量系统发育定义的微生物种群的原位生长活性，并将该程序用于研究活性污泥系统中细菌的生长。当前的研究通过量化暴露于各种培养条件下的细菌纯培养物单个细胞内前体16S核糖体RNA的水平，显著扩展了之前的这项工作。最初，通过在三种培养条件下制备的乙酸钙不动杆菌T纯培养物的全细胞荧光原位杂交，定义了前体16S核糖体RNA水平的三个范围（I型、II型和III型）。低水平的前体16S核糖体RNA（I型）对应于在Luria-Bertani培养基中过夜制备的稳定期培养物。中等水平的前体16S核糖体RNA（II型）对应于转移到新鲜Luria-Bertani培养基中的培养物，高水平的前体16S核糖体RNA（III型）对应于用生长抑制抗生素氯霉素处理的培养物。随后，在暴露于从美国俄亥俄州辛辛那提市四个不同的传统活性污泥处理厂收集的0.45微米过滤后的原污水后，在四种不同的纯培养物中测量了每种类型的单个细胞的丰度。在暴露于四种原污水中的每一种的乙酸钙不动杆菌T培养物中都观察到了每种类型的单个细胞。在暴露于四种原污水中的每一种的约翰逊不动杆菌T、约翰逊不动杆菌菌株210a和大肠杆菌T培养物中，只观察到了I型细胞。这些结果表明，乙酸钙不动杆菌T的生长受到了四种废水中每一种所含过滤后原污水中一种未鉴定成分的抑制；而约翰逊不动杆菌T、约翰逊不动杆菌菌株210a和大肠杆菌T的生长未受到抑制。这些结果对于理解活性污泥处理系统中系统发育定义的微生物种群的生长具有重要意义。如果在乙酸钙不动杆菌T中观察到的p16S rRNA水平升高的模式在活性污泥系统中的许多微生物种群中普遍存在，这可能对防止可能正在经历生长抑制的关键微生物种群被冲出系统具有影响。
