Predators and nutrient availability favor protozoa-resisting bacteria in aquatic systems

The long co-existence of bacteria and protozoa has led to the development of bacterial protozoa resistance strategies, which are suggested to serve as drivers for the evolution of pathogenic bacteria. However, the ecological mechanisms underpinning selection for protozoa-resistance in aquatic bacteria are poorly known. To assess the role of nutrient availability and predation-pressure on selection for protozoa-resisting bacteria (PRB), an enrichment-dilution experiment was designed using laboratory microcosms containing natural lake water. PRB was monitored by screening 16S rRNA amplicon sequence data for reads assigned to bacteria that previously has been shown to resist degradation by amoebae. To estimate the effects of the microbial food web dynamics (microscopy of; heterotrophic bacteria, phytoplankton, protozoa and rotifers) and physicochemical variables on the PRB abundance in the study system, a joint species distribution modelling approach was used.

细菌与原生生物（protozoa）的长期共存，促使细菌演化出原生生物抗性策略，该策略被认为是致病菌演化的核心驱动因素之一。然而，当前学界对水生细菌中驱动原生生物抗性演化的生态机制仍知之甚少。为探究养分有效性与捕食压力对原生生物抗性细菌（protozoa-resisting bacteria, PRB）演化选择的调控作用，本研究利用含有天然湖水的实验室微宇宙（microcosms）体系设计了富集-稀释实验。本研究通过筛查16S rRNA扩增子测序数据中匹配此前已被证实可抵御变形虫（amoebae）降解的细菌的序列读段，对PRB进行监测。为解析研究体系内微生物食物网动态（涵盖异养细菌、浮游植物、原生生物与轮虫的显微观测）及理化变量对PRB丰度的影响，本研究采用了联合物种分布建模（joint species distribution modelling）方法。