Complete genome sequence of Nitrosomonas sp. Is79, an ammonia oxidizing bacterium adapted to low ammonium concentrations

Abstract

Nitrosomonas sp. Is79 is a chemolithoautotrophic ammonia-oxidizing bacterium that belongs to the family Nitrosomonadaceae within the phylum Proteobacteria. Ammonia oxidation is the first step of nitrification, an important process in the global nitrogen cycle ultimately resulting in the production of nitrate. Nitrosomonas sp. Is79 is an ammonia oxidizer of high interest because it is adapted to low ammonium and can be found in freshwater environments around the world. The 3,783,444-bp chromosome with a total of 3,553 protein coding genes and 44 RNA genes was sequenced by the DOE-Joint Genome Institute Program CSP 2006.

Keywords: Ammonia oxidation; Ammonia-oxidizing bacteria; Nitrosomonas; freshwater; nitrification; nitrogen cycle; oligotrophic.

Figure 1

Phylogenetic tree showing the position of Nitrosomonas sp. Is79 relative to the other described strains within the family. Nitrosomonas sp. AL212 is not a formally described strain, but was included because the whole genome of this strain became recently available [12]. The tree was constructed from 1,272 aligned characters of the 16S rRNA gene sequence under the maximum likelihood criterion and rooted in accordance with a current taxonomy using the software package MEGA [35]. Numbers adjacent to the branches are support values from 1,000 ML bootstrap replicates (left) and from 1,000 maximum parsimony bootstrap replicates (right) if larger than 60% [35]. Strains with whole genome sequencing projects registered in GOLD [36] are shown in red and the published in red-bold: Nitrosomonas europaea (AL954747), Nitrosomonas eutropha (CP000450), Nitrosospira multiformis (CP000103), Nitrosomonas sp. AL212 (CP002552) and Nitrosomonas sp. Is79 (CP02876).

Figure 2

Graphical map of the genome. From the outside to the center: Genes on forward strand and Genes on reverse strand (color by COG categories), RNA genes (tRNAs green, rRNAs red, other RNAs black), GC content, GC skew.

Figure 3

Organization of the amo gene clusters in the genome of Nitrosomonas sp. Is79.

Figure 4

Phylogenetic tree of betaproteobacterial ammonia oxidizers inferred using the Maximum Likelihood criterion using the software package MEGA [35] based on the protein sequence of the large subunit of the RuBisCO (cbbL). The alignment was inferred by ClustalW software [35]. Numbers adjacent to the branches are support values from 1,000 ML bootstrap replicates if higher than 60% [35].