Mok Kenny C, Sokolovskaya Olga M, Deutschbauer Adam M, Carlson Hans K, Taga Michiko E
Department of Plant & Microbial Biology, University of California, Berkeley, Berkeley, CA 94720, U.S.A.
Present address: Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, U.S.A.
bioRxiv. 2025 Feb 20:2024.11.04.621602. doi: 10.1101/2024.11.04.621602.
Cobamides, the vitamin B (cobalamin) family of cofactors, are used by most organisms but produced by only a fraction of prokaryotes, and are thus considered key shared nutrients among microbes. Cobamides are structurally diverse, with multiple different cobamides found in most microbial communities. The ability to use different cobamides has been tested for several bacteria and microalgae, and nearly all show preferences for certain cobamides. This approach is limited by the commercial unavailability of cobamides other than cobalamin. Here, we have extracted and purified seven commercially unavailable cobamides to characterize bacterial cobamide preferences based on growth in specific cobamide-dependent conditions. The tested bacteria include engineered strains of , , and expressing native or heterologous cobamide-dependent enzymes, cultured under conditions that functionally isolate specific cobamide-dependent processes such as methionine synthesis. Comparison of these results to previous studies of diverse bacteria and microalgae revealed that a broad diversity of cobamide preferences exists not only across different organisms, but also between different cobamide-dependent metabolic pathways within the same organism. The microbes differed in the cobamides that support growth most efficiently, cobamides that do not support growth, and the minimum cobamide concentrations required for growth. The latter differ by up to four orders of magnitude across organisms from different environments and by up to 20-fold between cobamide-dependent enzymes within the same organism. Given that cobamides are shared, required for use of specific growth substrates, and essential for central metabolism in certain organisms, cobamide preferences likely impact community structure and function.
钴胺素，即维生素B（钴胺）家族的辅因子，被大多数生物体所利用，但仅由一小部分原核生物产生，因此被认为是微生物之间关键的共享营养素。钴胺素在结构上具有多样性，在大多数微生物群落中发现了多种不同的钴胺素。已经对几种细菌和微藻利用不同钴胺素的能力进行了测试，几乎所有的细菌和微藻都对某些钴胺素表现出偏好。这种方法受到除钴胺素之外其他钴胺素无法商业化获取的限制。在这里，我们提取并纯化了七种无法通过商业途径获得的钴胺素，以根据在特定钴胺素依赖条件下的生长情况来表征细菌对钴胺素的偏好。所测试的细菌包括表达天然或异源钴胺素依赖酶的工程菌株，在功能上分离特定钴胺素依赖过程（如甲硫氨酸合成）的条件下进行培养。将这些结果与之前对多种细菌和微藻的研究进行比较后发现，不仅在不同生物体之间，而且在同一生物体中不同的钴胺素依赖代谢途径之间，都存在广泛多样的钴胺素偏好。这些微生物在最能支持生长的钴胺素、不支持生长的钴胺素以及生长所需的最低钴胺素浓度方面存在差异。后者在来自不同环境的生物体之间相差多达四个数量级，在同一生物体中不同的钴胺素依赖酶之间相差多达20倍。鉴于钴胺素是共享的，是使用特定生长底物所必需的，并且对某些生物体的中心代谢至关重要，钴胺素偏好可能会影响群落结构和功能。
