Romine Margaret F, Rodionov Dmitry A, Maezato Yukari, Osterman Andrei L, Nelson William C
Pacific Northwest National Laboratory, Richland, WA, USA.
Sanford Burnham Prebys Medical Discovery Institute, La Jolla, CA, USA.
ISME J. 2017 Jun;11(6):1434-1446. doi: 10.1038/ismej.2017.2. Epub 2017 Feb 10.
Many microorganisms are unable to synthesize essential B vitamin-related enzyme cofactors de novo. The underlying mechanisms by which such microbes survive in multi-species communities are largely unknown. We previously reported the near-complete genome sequence of two ~18-member unicyanobacterial microbial consortia that maintain stable membership on defined medium lacking vitamins. Here we have used genome analysis and growth studies on isolates derived from the consortia to reconstruct pathways for biogenesis of eight essential cofactors and predict cofactor usage and precursor exchange in these communities. Our analyses revealed that all but the two Halomonas and cyanobacterial community members were auxotrophic for at least one cofactor. We also observed a mosaic distribution of salvage routes for a variety of cofactor precursors, including those produced by photolysis. Potentially bidirectional transporters were observed to be preferentially in prototrophs, suggesting a mechanism for controlled precursor release. Furthermore, we found that Halomonas sp. do not require cobalamin nor control its synthesis, supporting the hypothesis that they overproduce and export vitamins. Collectively, these observations suggest that the consortia rely on syntrophic metabolism of cofactors as a survival strategy for optimization of metabolic exchange within a shared pool of micronutrients.
许多微生物无法从头合成与维生素B相关的必需酶辅因子。这类微生物在多物种群落中生存的潜在机制在很大程度上尚不清楚。我们之前报道了两个由约18个成员组成的单蓝细菌微生物群落的近乎完整的基因组序列，这些群落在缺乏维生素的特定培养基上保持稳定的成员组成。在此，我们利用对群落分离株的基因组分析和生长研究，重建了八种必需辅因子的生物合成途径，并预测了这些群落中辅因子的使用情况和前体交换。我们的分析表明，除了两个嗜盐单胞菌属和蓝细菌群落成员外，所有其他成员至少对一种辅因子营养缺陷。我们还观察到多种辅因子前体的补救途径呈镶嵌分布，包括那些通过光解产生的前体。观察到潜在的双向转运体优先存在于原养型中，这表明了一种控制前体释放的机制。此外，我们发现嗜盐单胞菌属不需要钴胺素也不控制其合成，这支持了它们过量产生并输出维生素的假说。总体而言，这些观察结果表明，这些群落依赖辅因子的互养代谢作为一种生存策略，以优化在共享的微量营养素池中进行的代谢交换。
