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Plasmid Involvement in Parathion Hydrolysis by Pseudomonas diminuta
C M Serdar1, D T Gibson, D M Munnecke
1Center for Applied Microbiology, Department of Microbiology, The University of Texas at Austin, Austin, Texas 78712 and Department of Botany and Microbiology, University of Oklahoma, Norman, Oklahoma 73019.
Pseudomonas diminuta hydrolyzes the pesticide parathion using parathion hydrolase. Loss of this enzyme activity in derivatives was linked to a missing plasmid (pCS1).
Area of Science:
- Microbiology
- Environmental Science
- Biochemistry
Background:
- Parathion is an organophosphate pesticide that poses environmental risks.
- Microbial degradation offers a potential strategy for parathion remediation.
- Pseudomonas diminuta is a bacterium with potential bioremediation capabilities.
Purpose of the Study:
- To investigate the ability of Pseudomonas diminuta to hydrolyze parathion.
- To identify the genetic basis for parathion hydrolase activity in this organism.
Main Methods:
- Culturing Pseudomonas diminuta and measuring parathion hydrolase activity.
- Inducing genetic changes using mitomycin C to generate hydrolase-negative mutants.
- Analyzing mutant strains for the presence of plasmids using electron microscopy.
Main Results:
- Pseudomonas diminuta exhibited significant parathion hydrolase activity (3,400 U/L).
- Mitomycin C treatment resulted in a high frequency of hydrolase-negative derivatives (9-12%).
- These derivatives lacked a specific plasmid (pCS1) with an estimated molecular mass of 44 x 10 daltons.
Conclusions:
- Parathion hydrolysis by Pseudomonas diminuta is mediated by an enzyme, parathion hydrolase.
- A plasmid, designated pCS1, appears essential for the expression of parathion hydrolase activity.
- This finding suggests a genetic basis for pesticide degradation in Pseudomonas diminuta, potentially involving plasmid-encoded genes.
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