Preconditioning With Natural Microbiota Strain MYb71 Influences Behavior.

In comparison with the standard monoxenic maintenance in the laboratory, rearing the nematode on its natural microbiota improves its fitness and immunity against pathogens. Although is known to exhibit choice behavior and pathogen avoidance behavior, little is known about whether actively chooses its (beneficial) microbiota and whether the microbiota influences worm behavior. We examined eleven natural isolates in a multiple-choice experiment for their choice behavior toward four natural microbiota bacteria and found that microbiota choice varied among isolates. The natural isolate MY2079 changed its choice behavior toward microbiota isolate MYb71 in both multiple-choice and binary-choice experiments, in particular on proliferating bacteria: MYb71 was chosen less than other microbiota bacteria or OP50, but only after preconditioning with MYb71. Examining escape behavior and worm fitness on MYb71, we ruled out pathogenicity of MYb71 and consequently learned pathogen avoidance behavior as the main driver of the behavioral change toward MYb71. The change in behavior of MY2079 toward microbiota bacterium MYb71 demonstrates how the microbiota influences the worm's choice. These results might give a baseline for future research on host-microbiota interaction in the model.