Genetic Diversity of Bacteria Along a Stream Continuum

Adaptation is a fundamental concept in ecology and evolution. Determining whether organisms are adapted requires genetic analysis of the organism. We characterized the genetic structure of isolates of two species of aquatic bacteria (Pseudomonas cepacia and P. pickettii) using starch gel electrophoresis to determine the relationship between genetic diversity and stream location. Genetic diversity in these species of bacteria did not change longitudinally. However, each location in the stream had genetically unique bacteria. Genetic distance among isolates was found to be related to geographical distance, i.e., isolates farther apart in the stream were more genetically dissimilar. The results suggest localized adaptation. Soil forms of P. cepacia collected from the same catchment were very different genetically from the aquatic forms of the same species. Analyzing patterns of allozymes may be of value in determining the source of bacteria in aquatic ecosystems.