微生物交叉喂养综述：胞外代谢如何组织群落互作

图示信息：FIG 1 Microbes release various molecules that promote cross-feeding. Microbially produced extracellular molecules such as quorum sensing signals, exoenzymes, siderophores, toxins, metabolites (e.g., sugars, organic acids, amino acids, etc.), biofilm matrix, nanowires, extracellular vesicles, and nanotubes can be consumed by neighboring microbes or can influence cross-feeding between cells. Extracellular Metabolism Promotes Microbial Cross-Feeding Microbiology and Molecular Biology Reviews March 2021 Volume 85 Issue 1 e00135-20 mmbr.asm.org 3

论文结果 / 观点：该图把群落互作落实到代谢物、电子或营养物交换，是理解共培养功能涌现的关键证据。

研究意义 / 边界：这张图用于支持作者的概念框架或案例归纳；实际迁移到其他系统时，仍需结合成员来源、环境条件、稳定性和功能验证。

来源：MMBR.00135-20.pdf，PDF 第 3 页；图像来自 PDF 内部可匹配 Figure caption 的图像块。

图示信息：FIG 2 Synthetic microbial consortia featuring essential cross-feeding interactions. (A) Bidirectional cross-feeding of CO2 and NH4 1 between Saccharomyces cerevisiae and Chlamydomonas reinhardtii (51). (B) Syntrophic cross-feeding of acetate, CO2, and H2 between Desulfovibrio vulgaris and Methanococcus maripaludis (61, 62). (C) Bidirectional cross-feeding of amino acids between Escherichia coli auxotrophs (64, 70). (D) Bidirectional cross-feeding of lysine and adenine between S. cerevisiae auxotrophs (75, 245). (E) Multidirectional cross-feeding of acetate, methionine, and NH4 1 between auxotrophic E. coli, Salmonella enterica, and Methylobacterium extorquens (74, 246). (F) Bidirectional cross-feeding of fixed carbon and cobalamin between Lobomonas rostrata and Mesorhizobium loti (78). (G) Bidirectional cross-feeding of organic acids and NH4 1 between E. coli and Rhodopseudomonas palustris (207). (H) Syntrophic cross-feeding of electrons between Geobacter metallireducens and Geobacter sulfurreducens (63). The “D” symbol indicates an auxotrophy for an incoming metabolite. Extracellular Metabolism Promotes Microbial Cross-Feeding Microbiology and Molecular Biology Reviews March 2021 V

论文结果 / 观点：该图把群落互作落实到代谢物、电子或营养物交换，是理解共培养功能涌现的关键证据。

研究意义 / 边界：这张图用于支持作者的概念框架或案例归纳；实际迁移到其他系统时，仍需结合成员来源、环境条件、稳定性和功能验证。

来源：MMBR.00135-20.pdf，PDF 第 5 页；图像来自 PDF 内部可匹配 Figure caption 的图像块。

图示信息：FIG 3 Cross-feeding of carbon waste metabolites creates a global carbon cycle. The indicated trophic categories only refer to possible effects on carbon transformation. For example, chemoheterotrophs are primarily responsible for the conversion of macromolecules from both microbes and multicellular organisms into diverse organic compounds that can serve as nutrients for other lifestyles but might also participate in the cycling of other elements. Acetogenesis arrows involve the excretion of acetate from the conversion of two CO2 to acetyl-CoA via energy-conserving Wood-Ljungdahl pathway activity, rather than referring to every lifestyle possible for a bacterium classified as an acetogen (247). Syntrophy arrows are for fermentative carbon transformations that require consumption by a partner to be thermodynamically feasible (31, 57, 58). The diazotrophy arrow represents one of the carbon transformations known to be carried out by nitrogenase in sufficient quantity to support the growth of a partner (236). In some cases, only certain organisms within a category might generate a given molecule. The figure does not necessarily capture every possible activity within a given lifestyle. The

论文结果 / 观点：该图把群落互作落实到代谢物、电子或营养物交换，是理解共培养功能涌现的关键证据。

研究意义 / 边界：这张图用于支持作者的概念框架或案例归纳；实际迁移到其他系统时，仍需结合成员来源、环境条件、稳定性和功能验证。

来源：MMBR.00135-20.pdf，PDF 第 6 页；图像来自 PDF 内部可匹配 Figure caption 的图像块。

图示信息：FIG 4 Cross-feeding and its outcomes are dynamic. (A) A high level of cooperation by one partner can lead to excessive and harmful reciprocation by another. In this case, when production rate exceeds consumption rate (blue arrows), a metabolite (blue dot) can accumulate to toxic levels, for example by acidifying the environment (207). The “conc” triangle illustrates the effect of the metabolite on the recipient, ranging from beneficial (blue) to detrimental (red) as the concentration increases. (B) Growth-independent cross-feeding can rescue partners from starvation. Maintenance metabolism alone can lead to metabolite excretion under nongrowing conditions (left). Consumption of the metabolite by a recipient can stimulate recipient growth and reciprocation, creating a positive feedback loop and lifting both partners out of starvation (30). (C) The level of privatization influences the affinity that each partner must have for a communally valuable metabolite for cooperative coexistence to result (225). (Top) Cross-feeding of an intracellularly generated metabolite (left: high privatization) and an extracellularly generated metabolite liberated by an exoenzyme (right: low privatization).

论文结果 / 观点：该图把群落互作落实到代谢物、电子或营养物交换，是理解共培养功能涌现的关键证据。

研究意义 / 边界：这张图用于支持作者的概念框架或案例归纳；实际迁移到其他系统时，仍需结合成员来源、环境条件、稳定性和功能验证。

来源：MMBR.00135-20.pdf，PDF 第 17 页；图像来自 PDF 内部可匹配 Figure caption 的图像块。