Prevalence of monochloroacetate degrading genotypes among soil isolates of Pseudomonas sp

This study reports the isolation of Pseudomonas sp. strains with monochloroacetate (MCA) degradation function, from uncontaminated soil, and the use of Southern blot hybridization technique to detect MCA degrading catabolic genes and their divergence. Based on their capacity to remove Cl- from MCA in a minimal medium containing 185 ppm Cl-, the strains were classified into three groups: poor degraders (Cl- release between 0-15 ppm), medium degraders (Cl- release between 16-30 ppm), and high degraders (Cl- release between 31-45 ppm). We have applied a gene probe assay for determining the diversity of MCA degradative genotypes of 61 strains. Two different gene probes, dehCI and dehCII were used in Southern blot hybridization assays. Majority of the DNA samples that produced signals on the membrane blots (18 out of 24) hybridized with only dehCI DNA probe, while 6 strains hybridized with only dehCII probe. On the other hand, 37 isolates did not hybridize to either of the gene probes used. The results indicated the high specificity of the DNA hybridization method and the divergence of metabolic functions and/or genotypes among the native MCA-degrading Pseudomonas sp. populations in the soil.