Pherribo Gordon J, Taga Michiko E
Department of Plant & Microbial Biology, University of California, Berkeley, Berkeley, CA 94720 U.S.A.
bioRxiv. 2023 Mar 1:2023.02.28.530524. doi: 10.1101/2023.02.28.530524.
The majority of microbes are auxotrophs - organisms unable to synthesize one or more metabolites required for their growth. Auxotrophy is thought to confer an evolutionary advantage, yet auxotrophs must rely on other organisms that produce the metabolites they require. The mechanisms of metabolite provisioning by "producers" remain unknown. In particular, it is unclear how metabolites such as amino acids and cofactors, which are found inside the cell, are released by producers to become available to auxotrophs. Here, we explore metabolite secretion and cell lysis as two distinct possible mechanisms that result in release of intracellular metabolites from producer cells. We measured the extent to which secretion or lysis of and amino acid producers can support the growth of engineered amino acid auxotrophs. We found that cell-free supernatants and mechanically lysed cells provide minimal levels of amino acids to auxotrophs. In contrast, bacteriophage lysates of the same producer bacteria can support as many as 47 auxotroph cells per lysed producer cell. Each phage lysate released distinct levels of different amino acids, suggesting that in a microbial community the collective lysis of many different hosts by multiple phages could contribute to the availability of an array of intracellular metabolites for use by auxotrophs. Based on these results, we speculate that viral lysis could be a dominant mechanism of provisioning of intracellular metabolites that shapes microbial community structure.
大多数微生物是营养缺陷型生物——即无法合成自身生长所需的一种或多种代谢物的生物。营养缺陷型被认为具有进化优势，然而营养缺陷型生物必须依赖其他能产生它们所需代谢物的生物。“生产者”提供代谢物的机制仍然未知。特别是，尚不清楚细胞内发现的氨基酸和辅因子等代谢物是如何由生产者释放出来以供营养缺陷型生物利用的。在这里，我们探讨代谢物分泌和细胞裂解这两种不同的可能机制，它们会导致生产者细胞释放细胞内代谢物。我们测量了氨基酸生产者的分泌或裂解能够支持工程化氨基酸营养缺陷型生物生长的程度。我们发现无细胞上清液和机械裂解的细胞为营养缺陷型生物提供的氨基酸水平极低。相比之下，相同生产者细菌的噬菌体裂解物每裂解一个生产者细胞能够支持多达47个营养缺陷型细胞生长。每种噬菌体裂解物释放出不同水平的不同氨基酸，这表明在微生物群落中，多种噬菌体对许多不同宿主的集体裂解可能有助于提供一系列细胞内代谢物以供营养缺陷型生物利用。基于这些结果，我们推测病毒裂解可能是塑造微生物群落结构的细胞内代谢物供应的主要机制。
