Nematodes, the earth’s profuse metazoa are found ubiquitously in nature. In order to survive in diverse environments, nematodes have evolved distinct feeding strategies and they can use different food sources.
More...Nematodes, the earth’s profuse metazoa are found ubiquitously in nature. In order to survive in diverse environments, nematodes have evolved distinct feeding strategies and they can use different food sources. While some nematodes are specialists, including parasites of plants and animals, others are omnivorous feeders, which can live on a diet of bacteria, protozoans, fungi or yeast. The diplogastrid model nematode Pristionchus pacificus is one such omnivorous feeder that also shows a mouth dimorphism governing microbial vs. predatory feeding. In the wild, P. pacificus is often found in a necromenic association with beetles and is known to be able to feed on a variety of microbes as well as on nematode prey. However, in laboratory studies, used Escherichia coli OP50 has been used as standard food source, similar to studies in Caenorhabditis elegans. Here, we investigate Pristionchus-fungi interactions under laboratory conditions. After screening different yeast strains, P. pacificus was found to reproduce on Cryptococcus albidus and Cryptococcus curvatus. We describe life history traits of P. pacificus on both yeast strains, including developmental timing, survival and brood size, all of which indicate that Cryptococcus represent a suitable food source for P. pacificus. P. pacificus gene expression profiles revealed activation of genes encoding enzymes of protein, sugar and fatty acid metabolism and support that general housekeeping functions can still be maintained on yeast diet. In addition, we observed a significant down regulation of genes involved in pathogenicity and xenobiosis in worms growing on yeasts as opposed to E. coli OP50. Thus, our study suggests Cryptococcus yeasts to represent a suitable alternative food source for P. pacificus nematodes.
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