Possible involvement of plasmids in degradation of malathion and chlorpyriphos by Micrococcus sp

Area of Science:

• Microbiology
• Environmental Science
• Biochemistry

Background:

• Micrococcus sp. strains M-36 and AG-43 possess plasmids.
• These strains exhibit the ability to degrade the organophosphate pesticides malathion and chlorpyriphos.
• Plasmid-borne genes are often involved in microbial degradation of xenobiotics.

Purpose of the Study:

• To investigate the role of plasmids in the degradation of malathion and chlorpyriphos by Micrococcus sp.
• To determine if plasmid loss affects the pesticide degradation capabilities of these strains.

Main Methods:

• Culturing Micrococcus sp. strains M-36 and AG-43.
• Treating strains with acridine orange and sodium dodecyl sulfate to eliminate plasmids, creating derivatives SDS-36 and AO-43.
• Assessing the ability of parent and derivative strains to use malathion and chlorpyriphos as sole carbon sources for growth.
• Utilizing agarose gel electrophoresis to confirm the presence or absence of plasmids in parent and derivative strains.
• Testing nalidixic acid resistance in M-36 and its plasmid-cured derivative.

Main Results:

• Micrococcus sp. strains M-36 and AG-43, harboring plasmids, could degrade malathion and chlorpyriphos.
• Plasmid-cured derivatives (SDS-36 and AO-43) lost the ability to utilize these pesticides for growth.
• Agarose gel electrophoresis confirmed plasmid presence in M-36 and AG-43, and absence in SDS-36 and AO-43.
• Nalidixic acid resistance in M-36 was lost concurrently with plasmid elimination.

Conclusions:

• Plasmids likely play a crucial role in the degradation of malathion and chlorpyriphos by Micrococcus sp. strains M-36 and AG-43.
• The observed loss of pesticide degradation and antibiotic resistance upon plasmid elimination strongly suggests plasmid involvement.