Nitrotoga” is a NOB of high environmental relevance, but physiological data exist for only a few representatives. Initially, it was detected in specialized niches of low temperature and low nitrite concentrations, but later on, its ubiquitous distribution revealed its critical role for N removal in engineered systems like WWTPs. In this study, we analyzed the competition between
in bioreactors and identified conditions where the
was almost replaced by
sp. BS. We show that the pH value is an important factor that regulates the composition of the nitrite-oxidizing enrichment with a dominance of
sp. BS versus
at a neutral pH of 7.4 in combination with a temperature of 17°C. The physiological diversity of novel
cultures improves our knowledge about niche differentiation of NOB with regard to functional nitrification under suboptimal conditions.