Ralph M. Parsons Laboratory, Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA.
Microbiol Mol Biol Rev. 2012 Dec;76(4):792-812. doi: 10.1128/MMBR.00029-12.
Intuitively, it may seem that from the perspective of an individual bacterium the ocean is a vast, dilute, and largely homogeneous environment. Microbial oceanographers have typically considered the ocean from this point of view. In reality, marine bacteria inhabit a chemical seascape that is highly heterogeneous down to the microscale, owing to ubiquitous nutrient patches, plumes, and gradients. Exudation and excretion of dissolved matter by larger organisms, lysis events, particles, animal surfaces, and fluxes from the sediment-water interface all contribute to create strong and pervasive heterogeneity, where chemotaxis may provide a significant fitness advantage to bacteria. The dynamic nature of the ocean imposes strong selective pressures on bacterial foraging strategies, and many marine bacteria indeed display adaptations that characterize their chemotactic motility as "high performance" compared to that of enteric model organisms. Fast swimming speeds, strongly directional responses, and effective turning and steering strategies ensure that marine bacteria can successfully use chemotaxis to very rapidly respond to chemical gradients in the ocean. These fast responses are advantageous in a broad range of ecological processes, including attaching to particles, exploiting particle plumes, retaining position close to phytoplankton cells, colonizing host animals, and hovering at a preferred height above the sediment-water interface. At larger scales, these responses can impact ocean biogeochemistry by increasing the rates of chemical transformation, influencing the flux of sinking material, and potentially altering the balance of biomass incorporation versus respiration. This review highlights the physical and ecological processes underpinning bacterial motility and chemotaxis in the ocean, describes the current state of knowledge of chemotaxis in marine bacteria, and summarizes our understanding of how these microscale dynamics scale up to affect ecosystem-scale processes in the sea.
从单个细菌的角度来看，海洋似乎是一个广阔、稀释且在很大程度上均匀的环境。海洋微生物学家通常从这个角度来考虑海洋。实际上，由于普遍存在的营养斑、羽流和梯度，海洋细菌栖息在一个高度异质的化学环境中，这种异质性在微观尺度上也很明显。较大生物体的溶解物质渗出和排泄、裂解事件、颗粒、动物表面以及从水-沉积物界面的通量，所有这些都有助于形成强烈而普遍的异质性，其中趋化作用可能为细菌提供显著的适应优势。海洋的动态性质对细菌觅食策略施加了强烈的选择压力，许多海洋细菌确实表现出适应能力，使其趋化运动特征与肠道模型生物相比表现出“高性能”。快速游动速度、强烈的定向反应以及有效的转弯和转向策略确保了海洋细菌能够成功地利用趋化作用，对海洋中的化学梯度做出非常快速的反应。这些快速反应在广泛的生态过程中具有优势，包括附着在颗粒上、利用颗粒羽流、保持靠近浮游植物细胞的位置、在宿主动物上定殖以及在靠近水-沉积物界面的偏好高度盘旋。在较大的尺度上，这些反应可以通过增加化学转化的速度、影响下沉物质的通量以及潜在改变生物量纳入与呼吸之间的平衡来影响海洋生物地球化学。本综述强调了海洋中细菌运动和趋化作用的物理和生态过程，描述了海洋细菌趋化作用的当前知识状况，并总结了我们对这些微观动态如何影响海洋生态系统过程的理解。
