Bacteria affect Caenorhabditis elegans responses to MeHg toxicity

Area of Science:

• Environmental Toxicology
• Molecular Biology
• Genetics

Background:

• Methylmercury (MeHg) is a potent neurotoxin that bioaccumulates in food webs.
• Caenorhabditis elegans (C. elegans) is a valuable model organism for studying MeHg toxicity and genetic influences.
• Bacterial food sources can influence C. elegans biology, including chemical metabolism.

Purpose of the Study:

• To investigate how different types of bacterial food modify methylmercury (MeHg) toxicity in C. elegans.
• To understand the impact of food availability and bacterial status (live vs. dead) on MeHg-induced toxicity.
• To explore the role of the FOXO transcription factor DAF-16 in mediating these effects.

Main Methods:

• Utilized wild-type and transgenic C. elegans strains.
• Exposed worms to varying concentrations of MeHg under different feeding conditions (live bacteria, dead bacteria, fasted).
• Assessed MeHg toxicity, oxidative stress, developmental delay, and DAF-16 localization.

Main Results:

• Bacterial food significantly reduced chronic MeHg toxicity in C. elegans in a dose- and live-status-dependent manner.
• Fasted worms exhibited the highest MeHg-induced death rate, followed by those fed dehydrated dead bacteria, dead bacteria, and live bacteria.
• Dehydrated dead bacteria food attenuated MeHg-induced oxidative stress and developmental delay, and altered DAF-16 localization.
• DAF-16 nuclear localization shifted from the intestine to muscle in fed worms, independent of MeHg treatment.

Conclusions:

• Bacterial food source is a critical factor influencing toxicological outcomes in C. elegans chronic exposure studies.
• The composition and status of bacterial food can modulate the response to environmental toxins like MeHg.
• DAF-16's role in response to MeHg is influenced by diet, highlighting the complex interplay between nutrition and toxicology.