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、微菌落形成和附着在颗粒/聚集体表面的变化可被视为水生细菌对抗原生动物捕食和环境条件变化(如养分和有机物的可用性)的关键特征。因此，表型可塑性低的专家(非塑料、自由或表面附着的)可以与表型可塑性高的通才(塑料，在自由和表面附着的生命阶段之间切换)区分开来。性状可塑性可以诱导(表型可塑性；多面手)或遗传(快速进化；专家)。从理论上讲，表型可塑性低的专家(无论是自由的还是附属的)的变化会导致明显的捕食者-猎物循环，而表型可塑性高的多面手会抑制这些振荡，从而稳定系统。模型预测，环境参数的波动对多面手有利，例如生态系统扰动，但它们的稳定作用导致专家的偏好。然而，在实验分析捕食者-猎物的相互作用和动力学时，细菌生活方式的这种差异并未被考虑在内。我们的建议解决了DyaTrait的核心问题，即猎物/捕食者水平上现有的特征变异通过什么机制影响两个营养水平的动态，然后反馈到特征变异的维持上。我们将结合实验和模型企业来检验快速进化和反捕食防御的表型可塑性对化学恒化器中捕食者-猎物动态的(综合)影响。我们将不再只使用一种表型可塑性高的捕食者，而是使用两种可塑性很小的捕食者(一种捕食者捕食自由细菌，另一种捕食者以表面附着的细菌为食)。我们的工作重点是不同的细菌生活方式，从而研究专业和通用捕食性细菌的生理特征。我们提出了通用型食饵抑制捕食者食饵循环，从而使系统稳定。稳定的环境条件应该导致非塑料专业猎物(小特征范围)的优势，而变化的环境应该有利于塑料多面手猎物(高特征范围)。因此，表型塑料猎物决定了两种不同的专业捕食者的共存，专业与通用细菌比例的变化影响了有机质循环的效率和生态系统的功能。恒化器实验和模型企业之间的紧密联系使我们能够阐明生态和进化模式，以概括微生物之间的相互作用。在第二步中，我们的目标是将这些模式与系统中的有机物质循环联系起来。因此，我们将使用基于特征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.