GENETIC-STRUCTURE OF A LOTIC POPULATION OF BURKHOLDERIA (PSEUDOMONAS)CEPACIA

The genetic structure of a population of Burkholderia (Pseudomonas) ce pacia isolated from a southeastern blackwater stream was investigated by using multilocus enzyme electrophoresis to examine the allelic vari ation in eight structural gene loci. Overall, 213 isolates were collec ted at transect points along the stream continuum, from both the sedim ents along the bank and the water column. Multilocus enzyme electropho resis analysis revealed 164 distinct electrophoretic types, and the me an genetic diversity of the entire population was 0.574, Genetic diver sity values did not vary spatially along the stream continuum. From a canonical discriminant analysis, Mahalonobis distances (measurements o f genetic similarity between populations) revealed significant differe nces among the subpopulations at the sediment sampling points, suggest ing bacterial adaptation to a heterogeneous (or patchy) microgeographi cal environment. Multilocus linkage disequilibrium analysis of the iso lates revealed only limited association between alleles, suggesting fr equent recombination, relative to binary fission, in this population. Furthermore, the dendrogram created from the data of this study and th e allele mismatch distribution are typical of a population characteriz ed by extensive genetic mixing. We suggest that B. cepacia be added to the growing list of bacteria that are not obligatorily clonal.