Comparing phenotypic plasticity in bacterial prey traits and ecological consequences by using specialist vs. generalist strains and organic aggregates as model systems

细菌细胞大小、微集落形成和附着在颗粒/聚集体表面的变化可以被视为水生细菌对抗原生动物放牧和环境条件变化的关键特征，例如营养物质和有机物的可用性。因此，具有低表型可塑性（非可塑性，自由或表面附着）的专家可以与具有高表型可塑性（可塑性，在自由和表面附着生命阶段之间切换）的通才区分开来。性状可塑性可以是诱导的（表型可塑性，通才）或遗传的（快速进化，专才）。从理论上讲，具有低表型可塑性（自由或依附）的专才的变化导致明显的捕食者-猎物周期，而具有高表型可塑性的通才抑制这些振荡，从而稳定系统。模型预测，多面手会受到环境参数波动（如生态系统扰动）的青睐，但它们的稳定效应会导致对专才的偏爱。然而，在实验分析捕食者-猎物相互作用和动态时，细菌生活方式的这种差异并没有被考虑在内。我们的建议解决了DynaTrait的核心问题，即在捕食者/猎物水平上存在的性状变异通过何种机制影响营养水平上的动态，然后反馈给性状变异的维持。我们将结合实验和建模企业来研究快速进化和表型可塑性的反掠食性防御对趋化动物捕食-猎物动态的影响。我们不再只使用一个具有高表型可塑性的捕食者，而是使用两个具有窄可塑性的捕食者（一个捕食自由细菌，另一个捕食表面附着的细菌）。我们的工作集中在不同的细菌生活方式和因此的生理特征的专业和通才猎物细菌。我们认为多面手的猎物抑制了捕食者的捕食周期，从而稳定了系统。稳定的环境条件会导致非可塑性特色型猎物（小性状范围）的优势，而变化的环境会导致可塑性通才型猎物（高性状范围）的优势。因此，表型可塑性猎物决定了两种不同专业捕食者的共存，而专业细菌与通用细菌比例的变化影响了有机物循环效率和生态系统功能。趋化实验和建模企业之间的紧密联系使我们能够阐明微生物之间相互作用的生态和进化模式。在第二步中，我们的目标是将这些模式与系统中的有机物循环联系起来。因此，我们将使用基于性状的方法来更好地定义微生物水平上的表型可塑性在多大程度上反馈给生物多样性和生态系统功能。

Changes in bacterial cell size, microcolony formation and attachment to particle/aggregate surfaces can be regarded as key traits of aquatic bacteria to counteract protozoan grazing and changes in environmental conditions, e.g. the availability of nutrients and organic matter. Thereby, specialist with a low phenotypic plasticity (non-plastic, either free or surface attached) can be distinguished from generalists with a high phenotypic plasticity (plastic, switching between free and surface-attached life stages). Trait plasticity can be induced (phenotypic plasticity; generalists) or inherited (rapid evolution; specialists). Theoretically changes of specialists with a low phenotypic plasticity (either free or attached) lead to pronounced predator-prey cycles, whereas generalists with a high phenotypic plasticity dampens these oscillations and hence stabilize the system. Models predict that generalists are favored by fluctuations in environmental parameters, e.g. ecosystem disturbances, but that their stabilizing effect leads to a preference of specialists. Yet, such differences in bacterial lifestyle have not been taken into account when experimentally analyzing predator-prey interactions and dynamics. Our proposal addresses the core question of DynaTrait, i.e. by which mechanisms the existing trait variation at the prey/predator levels influences the dynamics at both trophic levels, which then feeds back on the maintenance of trait variation. We will combine experimental and modelling enterprises to examine the (combined) effects of rapid evolution and phenotypic plasticity of antipredatory defense on predator-prey dynamics in chemostats. Instead of using only one predator with high phenotypic plasticity, we will use 2 predators with a narrow plasticity (a predator grazing free bacteria and a second predator feeding on surface-attached bacteria).Our work focus on the different bacterial lifestyles and hence physiological traits of specialist and generalist prey bacteria. We propose that generalist prey dampens predator prey cycles and thus stabilize the system. Stable environmental conditions should lead to dominance of non-plastic specialist prey (small trait range), whereas changing environments should favor plastic generalist prey (high trait range). Phenotypically plastic prey thus determines coexistence of 2 different specialist predators and changes in specialist to generalist bacteria ratio affect organic matter cycling efficiency and ecosystem functioning. The tight inter-linkage of chemostat experiments and modeling enterprises allows us to elucidating ecological and evolutionary patterns for generalization of interactions between microorganisms. In a second step we aim to link these patterns to organic matter cycling in the system. Thus we will use the trait based approach to better define to which extent phenotypic plasticity on the microorganism level feeds back to biodiversity and ecosystem function.