Department of Biology, Indiana University, Bloomington, Indiana, USA.
Department of Biology, Indiana University, Bloomington, Indiana, USA
Microbiol Mol Biol Rev. 2021 Jan 13;85(1). doi: 10.1128/MMBR.00135-20. Print 2021 Feb 17.
The transfer of nutrients between cells, or cross-feeding, is a ubiquitous feature of microbial communities with emergent properties that influence our health and orchestrate global biogeochemical cycles. Cross-feeding inevitably involves the externalization of molecules. Some of these molecules directly serve as cross-fed nutrients, while others can facilitate cross-feeding. Altogether, externalized molecules that promote cross-feeding are diverse in structure, ranging from small molecules to macromolecules. The functions of these molecules are equally diverse, encompassing waste products, enzymes, toxins, signaling molecules, biofilm components, and nutrients of high value to most microbes, including the producer cell. As diverse as the externalized and transferred molecules are the cross-feeding relationships that can be derived from them. Many cross-feeding relationships can be summarized as cooperative but are also subject to exploitation. Even those relationships that appear to be cooperative exhibit some level of competition between partners. In this review, we summarize the major types of actively secreted, passively excreted, and directly transferred molecules that either form the basis of cross-feeding relationships or facilitate them. Drawing on examples from both natural and synthetic communities, we explore how the interplay between microbial physiology, environmental parameters, and the diverse functional attributes of extracellular molecules can influence cross-feeding dynamics. Though microbial cross-feeding interactions represent a burgeoning field of interest, we may have only begun to scratch the surface.
细胞间的营养物质转移，即交叉喂养，是微生物群落的普遍特征，具有涌现性质，影响着我们的健康，并协调着全球生物地球化学循环。交叉喂养不可避免地涉及到分子的外化。这些分子中的一些直接作为交叉喂养的营养物质，而另一些则可以促进交叉喂养。总的来说，促进交叉喂养的外化分子在结构上是多种多样的，从小分子到大分子都有。这些分子的功能同样多种多样，包括废物、酶、毒素、信号分子、生物膜成分以及对大多数微生物（包括产生细胞）有高价值的营养物质。外化和转移的分子种类繁多，由此衍生出的交叉喂养关系也多种多样。许多交叉喂养关系可以概括为合作关系，但也容易受到剥削。即使那些看起来是合作关系的关系，在合作伙伴之间也存在一定程度的竞争。在这篇综述中，我们总结了主要类型的主动分泌、被动排泄和直接转移的分子，它们要么构成交叉喂养关系的基础，要么促进交叉喂养关系。我们通过来自自然和合成群落的例子，探讨了微生物生理学、环境参数以及细胞外分子的多样化功能属性之间的相互作用如何影响交叉喂养动力学。尽管微生物的交叉喂养相互作用是一个新兴的研究领域，但我们可能才刚刚开始触及表面。
