Exploring the onset of B 12 -based mutualisms using a recently evolved Chlamydomonas auxotroph and B 12 -producing bacteria
Exploring the onset of B 12 -based mutualisms using a recently evolved Chlamydomonas auxotroph and B 12 -producing bacteria
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使用最近进化的营养缺陷型衣藻和生产 B 12 的细菌探索基于 B 12 的互利共生的开始
DOI：
10.1101/2022.01.04.474942
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发表时间：
2022
期刊：
影响因子：
--
通讯作者：
Bunbury F
中科院分区：
文献类型：
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作者：
Bunbury F
钴胺素（维生素B12）是多种真核生物（包括藻类等主要初级生产者）代谢反应的辅助因子，但只有原核生物才能产生它。许多细菌可以在藻类藻圈定居，形成稳定的群落，优先获得光合作用，并提供化合物，如B12。长期共存会导致基因丢失，导致藻类和细菌之间更大的相互依赖。在这项研究中，我们研究了最近进化的B12依赖型莱茵衣藻菌株metE7如何与某些细菌形成互利共生关系，包括根瘤菌Mesorhizobium loti，甚至是肠道细菌E的菌株。通过大肠杆菌工程改造产生钴胺素尽管metE7得到了B12生产者的支持，但它在共培养中的生长速度比B12独立的野生型慢，这表明高细菌B12供应可能是有利于B12营养缺陷型及其进化所必需的。此外，我们发现，一个E。释放更多B12的大肠杆菌菌株是一个更好的互利合作伙伴，尽管这种特性可能在隔离时成本更高，但更多的B12释放在共培养中提供了优势。我们假设，在适当的条件下，可以选择释放更多B12的细菌，特别是如果它们与B12依赖性藻类形成密切的相互作用。
Cobalamin (vitamin B12) is a cofactor for essential metabolic reactions in multiple eukaryotic taxa, including major primary producers such as algae, and yet only prokaryotes can produce it. Many bacteria can colonize the algal phycosphere, forming stable communities that gain preferential access to photosynthate and in return provide compounds such as B12. Extended coexistence can then drive gene loss, leading to greater algal–bacterial interdependence. In this study, we investigate how a recently evolved B12‐dependent strain ofChlamydomonas reinhardtii, metE7, forms a mutualism with certain bacteria, including the rhizobiumMesorhizobium lotiand even a strain of the gut bacteriumE. coliengineered to produce cobalamin. Although metE7 was supported by B12producers, its growth in co‐culture was slower than the B12‐independent wild‐type, suggesting that high bacterial B12provision may be necessary to favour B12auxotrophs and their evolution. Moreover, we found that anE. colistrain that releases more B12makes a better mutualistic partner, and although this trait may be more costly in isolation, greater B12release provided an advantage in co‐cultures. We hypothesize that, given the right conditions, bacteria that release more B12may be selected for, particularly if they form close interactions with B12‐dependent algae.