Temperature Variations Shape Niche Occupation of <i>Nitrotoga</i>-like Bacteria in Activated Sludge
Yanchen Liu, Siqi Li, Gaofeng Ni, Haoran Duan, Xia Huang, Zhiguo Yuan, Min Zheng
Abstract
Oxidation of nitrite to nitrate is an essential process in wastewater treatment systems. Previous culturing studies have revealed that a new nitrite-oxidizing Candidatus Nitrotoga genus is particularly adaptive in cold habitats. This study provides the first observation of the influence of temperature on the competition and adaptation behavior of Nitrotoga-like bacteria in activated sludge nitrifying communities. With Nitrotoga-dominated sludge as the inoculum, two laboratory nitrifying reactors were fed with real domestic wastewater and operated at reduced temperatures from 14 to 4 °C and increased temperatures from 22 to 34 °C. Within 180 days of operation, activated sludge samples were regularly collected for 16S rRNA gene-based quantitative polymerase chain reaction, Illumina, and third-generation PacBio sequencing analyses. The results demonstrated that temperature is a deciding factor affecting niche occupation of Nitrotoga-like bacteria. However, the classification of the species-level community showed that Candidatus Nitrotoga fabula-like populations remain less competitive at low temperatures, whereas two Nitrospira species belonging to sublineage I are adaptive over a wide temperature range of 4–34 °C. In addition, a temperature coefficient (θ) for the Nitrotoga-containing activated sludge was estimated to be 1.042 between 4 and 22 °C.