title: The impact of genome analyses on our understanding of ammonia-oxidizing bacteria.
abstract: The availability of whole-genome sequences for ammonia-oxidizing bacteria (AOB) has led to dramatic increases in our understanding of these environmentally important microorganisms. Their genomes are smaller than many other members of the proteobacteria and may indicate genome reductions consistent with their limited lifestyle. The genomes have a surprising level of gene repetition including genes for ammonia catabolism, iron acquisition, and insertion sequences. The gene profiles reveal limited genes for catabolism and transport of complex organic compounds, but complete pathways for some other compounds. This led to the observation of chemolithoheterotrophic growth of Nitrosomonas europaea. Genes for sucrose synthesis/degradation were identified. The core metabolic module of aerobic ammonia oxidation, the extraction of electrons from hydroxylamine to generate proton-motive force and reductant, has evolutionary roots in the denitrification inventory of anaerobic sulfur-dependent bacteria. The extension by ammonia monooxygenase provides a mechanism to feed this module using ammonia and O(2).
authors.affiliation: Department of Botany and Plant Pathology, Oregon State University, Corvallis, Oregon 97331, USA. arpd@science.oregonstate.edu
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Arp
authors.forename: Patrick S G
authors.initials: PS
authors.lastname: Chain
authors.forename: Martin G
authors.initials: MG
authors.lastname: Klotz
mesh_terms: D000641:Ammonia / Q000378:metabolism*; D001419:Bacteria / Q000235:genetics / Q000378:metabolism*; D005075:Biological Evolution; D004463:Ecology; D016680:Genome, Bacterial; D009566:Nitrates / Q000378:metabolism; D010084:Oxidation-Reduction; D013395:Sucrose / Q000378:metabolism
chemical_list: D009566:Nitrates; D013395:Sucrose; D000641:Ammonia