Food size and cGMP affects feeding behaviour in Pristionchus pacificus

Background

Animals evolved different locomotory behaviors in order to find food in their environment. I studied the food seeking locomotion and pharyngeal pumping of nematodes Pristionchus pacificus on various food sources.

Methods

For this study I used P. pacificus PS312, and the mutants Ppa-egl-4, which is a null mutation in the cGMP dependent protein kinase, and Ppa-obi-1, which is an oriental beetle pheromone insensitive mutant, and the double mutant Ppa-egl-4;obi-1. I tested these strains on plates containing no food and on E.coli OP50, HB101, Caulobacter crescentus (NA1000) and Bacillus subtilis. I analyzed locomotory behavior using an automated tracking system, and I obtained pharyngeal pumping data by visually counting with a microscope at 80X magnification.

Results

I observed that locomotion of the strains differed on plates with no food and plates with food. On plates with no food, P. pacificus PS312 displayed a higher reversal rate compared to the Ppa-obi-1 strain. The double mutant egl-;obi-1 displayed similar locomotion patterns to Ppa-obi-1 on HB101. Furthermore, when I compared PS312 pharyngeal pumping rates on and off food on two different size bacteria E. coli and C. crescentus, results showed a significant increased rate on PS312 on C. crescentus, which was the smaller bacteria.

Conclusion

My results indicated that Ppa-obi-1 may act in either a parallel pathway, or upstream of Ppa-egl-4. PS312 raised on C. crescentus (NA1000) for 3 generations retained memory of the food experience regardless of whether they were removed from food or placed back on NA1000 as food. Increasing bacterial size using mutant C. crescentus strains seem to further decrease pumping rates off food. My data suggest strong roles for food sizes and cGMP sensing proteins in maintaining feeding patterns in P. pacificus.