This project will provide genome sequence information for two oligotrophic ammonia-oxidizing bacteria that mediate the first step in the process of nitrification, Nitrosomonas oligotropha and Isolate IS-79. These bacteria belong to a cluster of the Nitrosomonas with higher substrate affinity (low Km), lower growth rates, and increased sensitivity to high ammonia concentrations compared to N. europaea and N. eutropha, which have already been sequenced. Comparison of the genomes of N. oligotropha and Isolate IS-79 to the genomes of the relatively closely related but physiologically distinct Nitrosomonas species offers an opportunity to identify the genetic basis of the important physiological adaptation for growth in low-nutrient environments. This group of ammonia-oxidizing bacteria are important in freshwater environments and implicated as the mediators of nitrification problems in
drinking water distribution systems. Moreover, the ammonia-oxidizing bacteria are generally considered a keystone group for ecosystem function and as a model for the application of molecular techniques to the environment.
There is continued interest in the ecophysiology and molecular ecology of nitrification among varied research communities. Researchers that work on biogeochemical nutrient cycling, global change, and large-scale microbial ecology projects are interested in nitrification and the relationship between taxonomy and ecophysiology. In fact, the kinetic parameters used in textbooks for modeling nitrification processes in the environment are more closely represented by those found in the N. oligotropha-related bacteria than those in N. europaea. Wastewater systems managers have an applied interest in the physiology and genetics of this group of ammonia-oxidizing bacteria, because it appears to be widely distributed in treatment systems. Other researchers use bacterial genomic sequences to gain insights into particular metabolic or physiological processes, systems, protein complexes, molecular phylogenies, or other questions for which genomics can be applied. The addition of these two organisms to the already sequenced ammonia-oxidizing bacteria will make this functional group a model for comparative and evolutionary genomics with strong links to ecophysiology.
CSP project participants: Jeanette M. Norton (Utah State Univ.), Daniel J. Arp (Oregon State Univ.), Annette Bollmann (Northeastern Univ.), Martin G. Klotz (Univ. of Louisville), Hendrikus J. Laanbroek (Univ. of Utrecht), Lisa Y. Stein (UC Riverside), and Yuichi Suwa (Natl. Inst. of Advanced Industrial Science and Technology, Japan).