The long term objectives of this research are to examine at the molecular level the regulation of nitrogen utilization by the gram negative soil microorganism Rhizobium fredii. This group of bacteria is recently (1982) discovered and although preliminary data has been obtained, complete characterization of their biochemistry has not been undertaken. For these studies the histidine utilization (hut) genes of R. fredii, strain USDA 191, will be used as a model system to understand how it can utilize poor nitrogen sources.
The specific aims of this proposal are to: 1. Determine the number and the activity of the R. fredii hut enzymes. 2. Construct a genomic cosmid library of R. fredii, strain USDA 191, and isolate the clones containing the hut genes. 3. Begin a detailed characterization of this hut DNA, by construction of a restriction endonuclease map and sub-cloning the DNA into appropriate DNA sequencing vectors. This project should successfully integrate biochemical and DNA/molecular approaches to characterize this system and provide future opportunities for detailed investigations into gene regulation.
