Département des Sciences Biologiques, Groupe de Recherche Interuniversitaire en Limnologie, Université du Québec à Montréal Montréal, QC, Canada ; Département de Biologie, Centre d'Études Nordiques, Unité Mixte Internationale Takuvik, Institut de Biologie Intégrative et des Systèmes, Université Laval QC, Canada.
Front Microbiol. 2013 May 9;4:112. doi: 10.3389/fmicb.2013.00112. eCollection 2013.
Metabolic plasticity and functional redundancy are fundamental properties of microbial communities, which shape their response to environmental forcing, and also mediate the relationship between community composition and function. Yet, the actual quantification of these emergent community properties has been elusive, and we thus do not know how they vary across bacterial communities, and their relationship to environmental gradients and to each other. Here we present an experimental framework that allows us to simultaneously quantify metabolic plasticity and functional redundancy in freshwater bacterioplankton communities, and to explore connections that may exists between them. We define metabolic plasticity as the rate of change in single-cell properties (cell wall integrity, cell size, single-cell activity) relative to changes in community composition. Likewise, we define functional redundancy as the rate of change in carbon substrate uptake capacities relative to changes in community composition. We assessed these two key community attributes in transplant experiments where bacterioplankton from various aquatic habitats within the same watershed were transplanted from their original water to waters from other systems that differ in their main resources. Our results show that metabolic plasticity is an intrinsic property of bacterial communities, whereas the expression of functional redundancy appears to be more dependent on environmental factors. Furthermore, there was an overall strong positive relationship between the level of functional redundancy and of metabolic plasticity, suggesting no trade-offs between these community attributes but rather a possible co-selection. The apparent continuum in the expression of both functional redundancy and plasticity among bacterial communities and the link between them, in turn suggest that the link between community diversity and function may also vary along a continuum, from being very tight, to being weak, or absent.
代谢可塑性和功能冗余是微生物群落的基本特性，它们决定了群落对环境胁迫的响应，也调节了群落组成与功能之间的关系。然而，这些新兴群落特性的实际量化一直难以实现，因此我们不清楚它们在细菌群落中是如何变化的，以及它们与环境梯度和彼此之间的关系。在这里，我们提出了一个实验框架，使我们能够同时量化淡水浮游细菌群落的代谢可塑性和功能冗余，并探索它们之间可能存在的联系。我们将代谢可塑性定义为单细胞特性（细胞壁完整性、细胞大小、单细胞活性）相对于群落组成变化的变化率。同样，我们将功能冗余定义为碳底物摄取能力相对于群落组成变化的变化率。我们在移植实验中评估了这两个关键的群落属性，在这些实验中，来自同一流域不同水生栖息地的浮游细菌从其原始水被移植到来自其他系统的水，这些水在其主要资源方面有所不同。我们的结果表明，代谢可塑性是细菌群落的固有特性，而功能冗余的表达似乎更依赖于环境因素。此外，功能冗余和代谢可塑性的水平之间存在总体上强烈的正相关关系，这表明这两个群落属性之间没有权衡，而是可能存在共同选择。细菌群落中功能冗余和可塑性表达之间的明显连续性，以及它们之间的联系，反过来表明，群落多样性和功能之间的联系也可能沿着一个连续体变化，从非常紧密到微弱或不存在。
