Prey particle surface property mediates differential selection by the ubiquitous appendicularian Oikopleura dioica

Cell surface properties can strongly mediate microbial interactions with predators in soil and host-pathogen systems. Yet, the role of microbial surface properties in avoiding or enhancing predation in the ocean is less well known. Appendicularians are globally abundant marine suspension feeders that capture marine microorganisms in a complex mucous filtration system. We used artificial microspheres to test whether the surface properties of prey particles influenced selection by the appendicularian, Oikopleura dioica. We used a range of microsphere sizes (0.5, 1, 2, and 3 μm), concentrations (~ 10³–10⁶ particles mL⁻¹), and two charges (amine-modified, more positive vs. carboxylate-modified, more negative) to represent open-ocean microbial communities. We found that appendicularians selected between the particles of different charge. More negatively charged particles were enriched in the gut by up to 3.8-fold, while more positive particles were enriched in the mucous filters by up to 4.7-fold, leading to different particle fates. These results expand understanding of the mechanisms by which filter-feeders select between prey and reveal a mechanism by which marine bacteria could rapidly alter their susceptibility to predation, either through adaption or acclimation.