Genome sequence of “Nitrosospira lacus” APG3, a psychrotolerant ammonia-oxidizing bacterium isolated from sandy lake sediment. Nitrosospira lacus isolate:APG3

“Nitrosospira lacus” APG3 is an obligate chemolithotrophic ammonia-oxidizing bacterium (AOB) that was isolated from sandy freshwater lake sediment in Seattle, Washington. APG3 belongs to Nitrosospira Cluster 0, which contains no representative species. The closest relative to APG3, determined via the draft genome, is Nitrosospira multiformis with a 98.6% similarity in the 16S rRNA gene sequence. Differences in genome were found between the two species. Physiological studies demonstrate APG3 is psychrotolerant, able to use urea as an energy source and sensitive to high ammonia concentrations. A single copy of the ammonia-monooxygenase operon was found in the genome lacking a singleton amo C gene; to our knowledge this is the first case in an AOB genome. The further genome analysis may shed light on the gene diversity, global genome rearrangement and early evolution of betaproteobacterial AOB.