As the genomes of bacteria are explored in greater detail, it has become obvious that most genes are present at a single position on the chromosome. The most obvious exceptions to this observation are the genes that encode for ribosomal RNAs, for which there are as many as 15 copies. This work will represent the first comprehensive effort to explain the puzzling occurrence of multiple ribosomal RNA genes in bacteria. Preliminary results suggest that the number of rRNA genes reflects the ecological strategies of diverse bacteria: those possessing multiple copies may exhibit increasing competitive fitness when nutrient availability fluctuates, while those possessing few copies may be more efficient at growth under constant, low-nutrient conditions. The PIs will examine the possibility that the number of ribosomal RNA genes in a bacterial genome represents one trait among a group of interdependent traits that influence the distribution of bacterial populations in nature. The principles derived from this research should be applicable to understanding the distribution of bacteria that play crucial roles in the global cycling of elements as well as bacteria used in bioremediation or those that have symbiotic relationships with plants or animals.
