Nutritional interdependencies Bacteria and archaea show a wide range of nutritional specialism. Not every organism can synthesize essential components and may need to trade for them. Taking as an example a diverse and interesting family of enzyme cofactors—the cobalt-containing cobamides, which include vitamin B12—Sokolovskaya et al. reviewed the interdependencies among microorganisms for this suite of nutrients. Cobamides are required for many processes, from catabolism of carbon sources to nucleotide biosynthesis, and are needed by a majority of microbes, from those in the gut to those in the oceans. Availability of cobamides is patchy and habitat specific, and nonspecific scavenging may not be adequate to obtain a specific cobamide structure required by an organism. Therefore, a variety of mutualisms have evolved to deliver and import specific structural variants of cobamides between organisms or among consortia of eukaryotes and prokaryotes by an equal variety of subtle and distinct mechanisms. Science, this issue p. 48 BACKGROUND Nearly every plant, animal, and environment on earth is host to a diverse community of microorganisms that influence each other and their environment. Microorganisms within communities interact on a molecular level by competing for resources or sharing valuable nutrients (such as cobamides, which we highlight in this Review). Such molecular interactions influence the physiology of individual microorganisms as well as the overall function of communities. Therefore, studying how microbes interact with each other is essential for understanding, and potentially interfering with, microbial processes that influence human and environmental health. Cobamides are structurally diverse, cobalt-containing cofactors, the most familiar of which is vitamin B12 (also known as cobalamin). Since the initial discovery of vitamin B12 as the treatment for the disease pernicious anemia in 1948, microbiologists have identified more than a dozen cobamides—B12 and analogs—that are produced exclusively by bacteria and archaea. Although vitamin B12 is most widely appreciated for its role in human health, B12 and other cobamides also play important roles in the context of microbial communities. Microbes use cobamides as catalysts for chemical reactions involved in amino acid synthesis, carbon metabolism, and many other functions. Importantly, microorganisms in all domains of life need cobamides, but most depend on surrounding species to produce this nutrient, which results in a network of cobamide-dependent interactions. A nuance of these interactions, derived from the structural diversity of cobamides, is that organisms are selective toward particular cobamides, and different species have distinct cobamide preferences. As a result, cobamides mediate specific associations among microorganisms and can have substantially different effects on the growth and metabolism of different species. Therefore, cobamide sharing can serve as a model for the complexity of microbial interactions and provide a useful system to study the mechanisms that influence community composition and function. ADVANCES Our current understanding of the roles of cobamides in microbial communities is the result of multilayered approaches to studying cobamide biology. Historically, the differential effects of cobamides have been investigated using laboratory cultures of single species and the biochemical characterization of cobamide-dependent enzymes. However, it is only with comparative genomic analyses of thousands of microbial species that researchers have begun to fully recognize the prevalence of cobamide sharing among microorganisms. Several newly described cocultures of two to three microbial species bridge molecular analysis and community-wide studies, and these cocultures provide experimental systems for probing the mechanisms and dynamics of cobamide sharing. Integrating discoveries across these different scales of analysis is a valuable strategy for understanding the functions of important molecules in microbial communities. OUTLOOK The structural diversity, functional specificity, and widespread use of cobamides by microorganisms have led researchers to speculate that cobamides could be used as tools to manipulate microbial community composition and function to improve environmental or human health. Performing cobamide-based manipulations in a controlled manner requires a greater understanding of how specific cobamides affect particular members of a community or might disrupt existing microbial interactions. Further integrating molecular approaches with community-wide studies will pave the way for understanding complex microbial communities in increasing mechanistic detail and may enable potential applications of cobamides in human health, agriculture, and industrial production. Cobamides as models for studying microbial interactions. Cobamides are a class of enzyme cofactors that are used for a wide variety of metabolic functions. They contain a catalytic upper ligand (R) and a structurally variable region (shown in blue, red, or green) that influences organisms’ metabolism and growth. Studies of cobamide biology on multiple scales—from enzymes to microbial communities—have revealed that cobamides constitute an effective model system for studying the complexity of microbial interactions. Microbial communities are essential to fundamental processes on Earth. Underlying the compositions and functions of these communities are nutritional interdependencies among individual species. One class of nutrients, cobamides (the family of enzyme cofactors that includes vitamin B12), is widely used for a variety of microbial metabolic functions, but these structurally diverse cofactors are synthesized by only a subset of bacteria and archaea. Advances at different scales of study—from individual isolates, to synthetic consortia, to complex communities—have led to an improved understanding of cobamide sharing. Here, we discuss how cobamides affect microbes at each of these three scales and how integrating different approaches leads to a more complete understanding of microbial interactions.

中文翻译：

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分享维生素：Cobamides 揭示微生物相互作用

营养相互依赖 细菌和古细菌显示出广泛的营养专业性。并非每个生物体都可以合成必需成分，可能需要进行交易。以一个多样化且有趣的酶辅因子家族为例——含钴的 cobamides，其中包括维生素 B12——Sokolovskaya 等人。回顾了微生物之间对这套营养素的相互依赖性。许多过程都需要钴胺素，从碳源的分解代谢到核苷酸的生物合成，并且大多数微生物（从肠道中的微生物到海洋中的微生物）都需要钴胺素。cobamides 的可用性是零散的和特定于栖息地的，非特异性清除可能不足以获得生物体所需的特定 cobamide 结构。所以，各种互利共生已经进化为通过同样多样的微妙和不同的机制在生物体之间或真核生物和原核生物联盟之间传递和导入特定结构的钴胺素变体。科学，这个问题 p。48 背景 地球上几乎每一种植物、动物和环境都寄居着多种多样的微生物群落，这些微生物群落相互影响并影响它们的环境。社区内的微生物通过竞争资源或共享有价值的营养物质（例如我们在本评论中强调的钴胺素）在分子水平上相互作用。这种分子相互作用影响个体微生物的生理以及群落的整体功能。因此，研究微生物如何相互作用对于理解并可能干扰，影响人类和环境健康的微生物过程。Cobamides 是结构多样的含钴辅因子，其中最熟悉的是维生素 B12（也称为钴胺素）。自从 1948 年首次发现维生素 B12 可用于治疗恶性贫血症以来，微生物学家已经鉴定出十多种 cobamides——B12 和类似物——它们完全由细菌和古细菌产生。尽管维生素 B12 因其在人类健康中的作用而广受赞誉，但 B12 和其他钴胺素在微生物群落中也发挥着重要作用。微生物使用钴胺作为涉及氨基酸合成、碳代谢和许多其他功能的化学反应的催化剂。重要的是，生命各个领域的微生物都需要钴胺素，但大多数依赖于周围的物种来产生这种营养物质，这导致了依赖于钴胺素的相互作用网络。这些相互作用的细微差别源自 cobamides 的结构多样性，是生物体对特定 cobamides 有选择性，不同物种有不同的 cobamide 偏好。因此，cobamides 介导微生物之间的特定关联，并对不同物种的生长和代谢产生显着不同的影响。因此，cobamide 共享可以作为微生物相互作用复杂性的模型，并提供一个有用的系统来研究影响群落组成和功能的机制。进展我们目前对 cobamides 在微生物群落中的作用的理解是研究 cobamide 生物学的多层方法的结果。从历史上看，已经使用单一物种的实验室培养物和 cobamide 依赖性酶的生化特征研究了 cobamides 的不同作用。然而，只有通过对数千种微生物的比较基因组分析，研究人员才开始充分认识到微生物之间共存共酰胺的普遍性。几个新描述的两到三个微生物物种的共培养连接了分子分析和社区范围的研究，这些共培养提供了用于探索 cobamide 共享机制和动力学的实验系统。整合这些不同分析尺度的发现是理解微生物群落中重要分子功能的重要策略。前景结构多样性、功能特异性、微生物对cobamides的广泛使用使研究人员推测cobamides可以用作操纵微生物群落组成和功能以改善环境或人类健康的工具。以受控方式进行基于 cobamide 的操作需要更深入地了解特定 cobamide 如何影响社区的特定成员或可能破坏现有的微生物相互作用。进一步将分子方法与社区范围的研究相结合，将为了解复杂微生物群落的机制细节铺平道路，并可能使 cobamides 在人类健康、农业和工业生产中的潜在应用成为可能。Cobamides 作为研究微生物相互作用的模型。Cobamides 是一类酶辅因子，用于多种代谢功能。它们包含一个催化上配体 (R) 和一个影响生物体代谢和生长的结构可变区（以蓝色、红色或绿色显示）。从酶到微生物群落的多个尺度上的 cobamide 生物学研究表明，cobamides 构成了研究微生物相互作用复杂性的有效模型系统。微生物群落对地球上的基本过程至关重要。这些群落的组成和功能的基础是各个物种之间的营养相互依赖性。一类营养素，cobamides（酶辅因子家族，包括维生素 B12），被广泛用于各种微生物代谢功能，但这些结构多样的辅助因子仅由一部分细菌和古细菌合成。不同规模的研究进展——从个体分离株到合成联合体，再到复杂的社区——提高了对 cobamide 共享的理解。在这里，我们将讨论 cobamides 如何在这三个尺度上影响微生物，以及如何整合不同的方法来更全面地了解微生物相互作用。