A generalist microbial predator shows innate attraction to more profitable prey, but does not learn from experience

How do generalists adjust to variation in prey abundance and profitability and seek out their preferred prey? We investigated this question in the soil protist Dictyostelium discoideum , a generalist predator of many species of bacteria. Despite their generalist diet, amoebas proliferate more quickly on some bacteria than on others. We tested amoeba chemoattraction towards 23 bacterial species and found that they are generally more attracted to the more profitable prey bacteria. Naïve amoebas were also preferentially more attracted to an edible mutant rather than the inedible wild type of a soil Pseudomonas isolate. These results suggest that D. discoideum amoebas have an innate prey preference that is adaptive. We also tested how experience with different prey bacteria affects chemoattraction in amoebas. Given the huge number of bacterial species in soil, learning from experience should be advantageous. However, we found no evidence that experience with prey bacteria affects preference. Our results suggest that generalist amoebas are innately attracted to the more profitable prey bacteria and this innate attraction cannot be overridden by recent experience.