Clonal population structure of Pseudomonas stutzeri, a species with exceptional genetic diversity

Genetic diversity and genetic relationships among 42 Pseudomonas stutzeri s trains belonging to several genomovars and isolated from different sources were investigated in an examination of 20 metabolic enzymes by multilocus e nzyme electrophoresis analysis. Forty-two distinct allele profiles were ide ntified, indicating that all multilocus genotypes were represented by a sin gle strain. All 20 loci were exceptionally polymorphic, with an average of 15.9 alleles per locus. To the best of our knowledge, this P. stutzeri samp le exhibited the highest mean genetic diversity (H = 0.876) found to date i n all bacterial species studied by multilocus enzyme electrophoresis. A hig h frequency of occurrence of null alleles was identified. The index of asso ciation (I-A) for the P. stutzeri strains analyzed was 1.10. The I-A values were always significantly different from zero for all subgroups studied, i ncluding clinical and environmental isolates and strains classified as geno movar 1. These results suggest that the population structure of P. stutzeri is strongly clonal, indicating that there is no significant level of assor tative recombination that might destroy linkage disequilibrium.