Minimal cobalt metabolism in the marine cyanobacterium Prochlorococcus
Minimal cobalt metabolism in the marine cyanobacterium Prochlorococcus
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DOI：
10.1073/pnas.2001393117
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发表时间：
2020-07-07
影响因子：
11.1
通讯作者：
Saito, Mak A.
中科院分区：
文献类型：
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作者：
Hawco, Nicholas J.;McIlvin, Matthew M.;Saito, Mak A.
尽管海水中钴的浓度非常低，原绿球藻属的蓝细菌在其基因组中保留了合成和使用含钴辅因子（钴胺素）的遗传机制。我们通过铁和钴限制条件下的一系列生长实验，探索了从赤道太平洋分离的原绿球藻（菌株 MIT9215）中的钴代谢。金属吸收率、钴胺素依赖性酶的定量蛋白质组学测量以及理论计算都表明，原绿球菌 MIT9215 可以在每个细胞少于 50 个钴原子的情况下维持生长，这比这些细胞的最低铁需求量低 100 倍（类似于每个细胞 5,100 个原子）。原绿球藻钴限制的定量描述用于解释赤道太平洋的钴分布，该海域表面浓度是全球测得最低的，但原绿球藻生物量很高。较低的最低钴配额可确保其他营养物质（尤其是铁）在钴完全耗尽之前耗尽，这有助于解释海洋蓝藻中钴依赖性代谢的持续存在。
Despite very low concentrations of cobalt in marine waters, cyanobacteria in the genus Prochlorococcus retain the genetic machinery for the synthesis and use of cobalt-bearing cofactors (cobalamins) in their genomes. We explore cobalt metabolism in a Prochlorococcus isolate from the equatorial Pacific Ocean (strain MIT9215) through a series of growth experiments under iron- and cobalt-limiting conditions. Metal uptake rates, quantitative proteomic measurements of cobalamin-dependent enzymes, and theoretical calculations all indicate that Prochlorococcus MIT9215 can sustain growth with less than 50 cobalt atoms per cell, similar to 100-fold lower than minimum iron requirements for these cells (similar to 5,100 atoms per cell). Quantitative descriptions of Prochlorococcus cobalt limitation are used to interpret the cobalt distribution in the equatorial Pacific Ocean, where surface concentrations are among the lowest measured globally but Prochlorococcus biomass is high. A low minimum cobalt quota ensures that other nutrients, notably iron, will be exhausted before cobalt can be fully depleted, helping to explain the persistence of cobalt-dependent metabolism in marine cyanobacteria.