Department Plankton and Microbial Ecology, Leibniz Institute of Freshwater Ecology and Inland Fisheries (IGB), 16775 Stechlin, Germany.
Graduate School of Life Sciences, Tohoku University, 6-3, Aoba, Sendai 980-8578, Japan.
Int J Mol Sci. 2022 Sep 3;23(17):10082. doi: 10.3390/ijms231710082.
Protist grazing pressure plays a major role in controlling aquatic bacterial populations, affecting energy flow through the microbial loop and biogeochemical cycles. Predator-escape mechanisms might play a crucial role in energy flow through the microbial loop, but are yet understudied. For example, some bacteria can use planktonic as well as surface-associated habitats, providing a potential escape mechanism to habitat-specific grazers. We investigated the escape response of the marine bacterium in the presence of either planktonic (nanoflagellate: ) or surface-associated (amoeba: ) protist predators, following population dynamics over time. In the presence of , cell density increased in the water, but decreased on solid surfaces, indicating an escape response towards the planktonic habitat. In contrast, the planktonic predator induced bacterial escape to the surface habitat. While cell numbers dropped substantially after a sharp initial increase, exhibited a slow, but constant growth throughout the entire experiment. In the presence of , rapidly formed cell clumps in the water habitat, which likely prevented consumption of the planktonic by the flagellate, resulting in a strong decline in the predator population. Our results indicate an active escape of via phenotypic plasticity (i.e., behavioral and morphological changes) against predator ingestion. This study highlights the potentially important role of behavioral escape mechanisms for community composition and energy flow in pelagic environments, especially with globally rising particle loads in aquatic systems through human activities and extreme weather events.
原生动物的摄食压力在控制水生细菌种群方面起着重要作用，影响着微生物环和生物地球化学循环中的能量流动。逃避捕食者的机制可能在微生物环中的能量流动中起着至关重要的作用，但目前研究还不够充分。例如，一些细菌可以利用浮游生物和附着在表面的栖息地，为特定栖息地的食草动物提供潜在的逃避机制。我们研究了海洋细菌在浮游生物（纳米鞭毛虫：）或附着在表面的（变形虫：）原生动物捕食者存在的情况下，随着时间的推移，其种群动态的逃避反应。在存在的情况下，细胞密度在水中增加，但在固体表面减少，表明向浮游生物栖息地的逃避反应。相比之下，浮游生物捕食者 诱导细菌逃避到表面栖息地。虽然 细胞数量在急剧增加后大幅下降，但 在整个实验过程中缓慢但持续增长。在存在的情况下， 在水栖息地迅速形成细胞团块，这可能阻止了鞭毛虫对浮游 的消耗，导致捕食者种群数量急剧下降。我们的研究结果表明，通过表型可塑性（即行为和形态变化）， 积极逃避捕食者的摄食。本研究强调了行为逃避机制在浮游环境中的群落组成和能量流动中可能具有重要作用，特别是在人类活动和极端天气事件导致水生系统中全球颗粒负荷增加的情况下。
