This research will further characterize essential genes that are required for bacterial nucleoid partitioning. Partitioning defective mutants within the S. typhimurium temperature sensitive lethal collection have been identified, and preliminary data documents the "Par" phenotype. Genetic data show's that most of these new par mutations lie in genes other than parA-through-parF, the known Par genes. Experiments are genetically and molecularly characterizing, these new par genes. The genes will be mapped, complementing clones will be isolated, and to the extent necessary to provide new information, the genes sequenced. Interactions between the Par proteins will be sought by suppressor analysis. %%% Faithful partitioning ensures that bacteria contain single copies of their genes. The process works without microtubules or any apparent analog, suggesting that an entirely novel mechanism accomplishes faithful bacterial DNA segregation. As such, this process may provide new targets for antibacterial drug design. The comparison of prokaryotic, eukaryotic and archebacterial DNA partitioning, will suggest whether these fundamental processes arose after the separation of the primary kingdoms.