Inactivation and mutagenesis by phototoxins usingEscherichia coli strains differing in sensitivity to near- and...

Area of Science:

• Microbiology
• Photochemistry
• Genetics

Background:

• Phototoxins are compounds activated by light, with potential applications in pest control.
• Understanding their mechanisms of action is crucial for developing targeted applications.
• Escherichia coli serves as a model organism for studying DNA damage and repair mechanisms.

Purpose of the Study:

• To elucidate the inactivation mechanisms and mutagenicity of various plant phototoxins in Escherichia coli.
• To differentiate between DNA adduct formation, photodynamic action, and membrane damage.
• To establish a rapid screening assay for plant phototoxin properties.

Main Methods:

• Utilized four strains of Escherichia coli with defined genetic backgrounds for UV sensitivity.
• Exposed bacteria to near-UV (NUV) light in the presence of different phototoxins (psoralen, angelicin, xanthotoxin, xanthotoxol, alpha-terthienyl).
• Assessed inactivation kinetics and measured mutagenicity using a histidine independence assay.

Main Results:

• Psoralen and angelicin primarily cause DNA adducts, while xanthotoxin involves DNA adducts and oxygen-dependent photodynamic action.
• Alpha-terthienyl induces membrane damage independent of bacterial UV-repair genes.
• Psoralen and xanthotoxin were mutagenic; angelicin was less so; xanthotoxol and alpha-terthienyl were not mutagenic under NUV.
• Imperatorin and berberine showed no phototoxicity or mutagenicity.

Conclusions:

• Plant phototoxins exhibit diverse mechanisms of action against bacteria, including DNA damage and membrane disruption.
• The developed assay effectively screens phototoxins for their mode of action and mutagenicity.
• This research aids in identifying plant-derived compounds with potential insecticidal properties.