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Physical comparison of parathion hydrolase plasmids from Pseudomonas diminuta and Flavobacterium sp

W W Mulbry1, P C Kearney, J O Nelson

  • 1Pesticide Degradation Laboratory, U.S. Department of Agriculture, Beltsville, Maryland 20705.

Plasmid
|September 1, 1987
PubMed

Insights

Two bacterial plasmids, pPDL2 and pCMS1, share homologous organophosphate degradation (opd) genes within a conserved 5.1 kb region. This finding highlights genetic similarity in pesticide-degrading enzymes between Flavobacterium and Pseudomonas species.

Area of Science:

  • Molecular Biology
  • Environmental Microbiology
  • Biochemistry

Background:

  • Parathion hydrolase enzymes are crucial for the degradation of organophosphate pesticides.
  • Two plasmids, pPDL2 (Flavobacterium sp.) and pCMS1 (Pseudomonas diminuta), encode homologous parathion hydrolase genes (opd).
  • Previous studies confirmed gene homology via DNA-DNA hybridization and restriction mapping.

Purpose of the Study:

  • To precisely delineate the region of homology encoding parathion hydrolase genes between pPDL2 and pCMS1.
  • To investigate the extent of conserved DNA sequences surrounding the opd genes on both plasmids.

Main Methods:

  • Restriction mapping of pPDL2 (39-kb) and pCMS1 (70-kb) plasmids.
  • DNA hybridization experiments using PstI restriction fragments of pCMS1 as probes against Flavobacterium plasmid DNA.
  • Comparative analysis of restriction patterns to identify homologous regions.

Main Results:

  • The parathion hydrolase (opd) genes reside within a highly conserved region of approximately 5.1 kb on both plasmids.
  • This conserved region encompasses approximately 2.6 kb upstream and 1.7 kb downstream of the opd genes.
  • No significant DNA homology was detected between the two plasmids outside this specific 5.1 kb region.

Conclusions:

  • The parathion hydrolase genes (opd) are located in a conserved genetic locus shared by Flavobacterium and Pseudomonas.
  • This conserved region likely plays a critical role in the maintenance and expression of the organophosphate degradation genes.
  • The findings provide a detailed understanding of the genetic basis for parathion hydrolase in these bacterial species.

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