Nitrospira
-like bacteria are among the most diverse and widespread nitrifiers in natural ecosystems and the dominant nitrite oxidizers in wastewater treatment plants (WWTPs). The recent discovery of comammox-like
Nitrospira
strains, capable of complete oxidation of ammonia to nitrate, raises new questions about specific traits responsible for the functional versatility and adaptation of this genus to a variety of environments. The availability of new
Nitrospira
genome sequences from both nitrite-oxidizing and comammox bacteria offers a way to analyze traits in different
Nitrospira
functional groups. Our comparative genomics analysis provided new insights into the adaptation of
Nitrospira
strains to specific lifestyles and environmental niches.