Qabar Christine M, Baidoo Edward E K, Akyuz Turumtay Emine, Qayum Tariq M, Keasling Jay D, Madigan Cressida A, Portnoy Daniel A, Cox Jeffery S
Department of Plant and Microbial Biology, University of California Berkeley, Berkeley CA 94720, USA.
Joint BioEnergy Institute, Lawrence Berkeley National Laboratory, Emeryville CA 94608, USA.
bioRxiv. 2025 Jul 11:2025.07.11.664281. doi: 10.1101/2025.07.11.664281.
Isoprenoids are a diverse class of natural products that are essential in all domains of life. Most bacteria synthesize isoprenoids through either the methylerythritol phosphate (MEP) pathway or the mevalonate (MEV) pathway, while a small subset encodes both pathways, including the pathogen (Mm). It is unclear whether the MEV pathway is functional in Mm, or why Mm encodes seemingly redundant metabolic pathways. Here we show that the MEP pathway is essential in Mm while the MEV pathway is dispensable in culture, with the ΔMEV mutant having no growth defect in axenic culture but a competitive growth defect compared to WT Mm. We found that the MEV pathway does not play a role in or infection but does play a role in survival of peroxide stress. Metabolite profiling revealed that modulation of the MEV pathway causes compensatory changes in the concentration of MEP intermediates DOXP and CDP-ME, suggesting that the MEV pathway is functional and that the pathways interact at the metabolic level. Finally, the MEV pathway is upregulated early in the shift down to hypoxia, suggesting that it may provide metabolic flexibility to this bacterium. Interestingly, we found that our complemented strains, which vary in copy number of the polyprenyl synthetase , responded differently to peroxide and UV stresses, suggesting a role for this gene as a determinant of downstream prenyl phosphate metabolism. Together, these findings suggest that MEV may serve as an anaplerotic pathway to make isoprenoids under stress conditions.
类异戊二烯是一类多样的天然产物，在所有生命领域中都至关重要。大多数细菌通过甲基赤藓糖醇磷酸（MEP）途径或甲羟戊酸（MEV）途径合成类异戊二烯，而一小部分细菌同时编码这两条途径，包括病原体结核分枝杆菌（Mm）。目前尚不清楚MEV途径在Mm中是否起作用，或者Mm为何编码看似冗余的代谢途径。在这里，我们表明MEP途径在Mm中是必不可少的，而MEV途径在培养中是可有可无的，ΔMEV突变体在无菌培养中没有生长缺陷，但与野生型Mm相比存在竞争性生长缺陷。我们发现MEV途径在感染或感染过程中不起作用，但在过氧化物应激的存活中起作用。代谢物谱分析表明，MEV途径的调节会导致MEP中间体DOXP和CDP-ME浓度的补偿性变化，这表明MEV途径是有功能的，并且这两条途径在代谢水平上相互作用。最后，在向下转变为缺氧的早期，MEV途径被上调，这表明它可能为这种细菌提供代谢灵活性。有趣的是，我们发现我们的互补菌株，其聚异戊二烯合成酶的拷贝数不同，对过氧化物和紫外线应激的反应不同，这表明该基因在下游异戊烯基磷酸代谢中起决定作用。总之，这些发现表明MEV可能作为一种回补途径，在应激条件下合成类异戊二烯。
