共培养体系中伴生菌(Priestia endophytica)促进普通产酮古洛糖酸菌生长和2-酮基-L-古龙酸转化的作用机制

Mechanisms of Priestia endophytica promoting the growth and 2-keto-L-gulonic acid biotransformation of Ketogulonicigenium vulgare in the co-culture system

摘要:

目的 植物内生芽孢杆菌(Priestia endophytica，伴生菌) 1-112对普通产酮古洛糖酸菌(Ketogulonicigenium vulgare，产酸菌)生长及促进2-酮基-L-古龙酸(2-keto-L-glonic acid, 2-KLG)生物转化的作用尚不明确。本研究采用不同培养基培养该辅助菌株，旨在探究其对普通产酮古洛糖酸菌的作用机制。方法 采用不同培养基(基本培养基、混合培养基及发酵培养基)培养1-112，探究其对普通产酮古洛糖酸菌生长及2-KLG生物转化的影响。运用转录组学技术，分析经不同培养基培养的辅助菌株中差异表达基因(differentlly expressed genes, DEGs)及相关代谢通路，筛选共培养体系中的关键因素。评估关键因素对普通产酮古洛糖酸菌生长及2-KLG生物转化的影响，以明确其在共培养体系中的作用。结果 与发酵培养基培养伴生菌相比，基本培养基培养伴生菌丧失了促进K. vulgare转化2-KLG的能力，但仍能促进其生长，这提示伴生菌对K. vulgare的影响可分为促进生长与促进2-KLG转化2个相对独立的功能模块。转录组分析表明，与基本培养基培养相比，发酵培养基培养的伴生菌共有1 859个差异表达基因，这些基因显著富集在烟酸与烟酰胺代谢、碳代谢、精氨酸与脯氨酸代谢以及氨基酸的生物合成等关键代谢通路。进一步向基本培养基中添加关键因子(丝氨酸、甘氨酸、苏氨酸、脯氨酸、烟酸和生物素)进行验证发现，甘氨酸、脯氨酸、生物素和烟酸是伴生菌促进K. vulgare生长的关键因子，而甘氨酸、苏氨酸、生物素和烟酸则是促进K. vulgare转化2-KLG的关键因子。结论 通过比较不同培养基培养伴生菌对K. vulgare生长及2-KLG转化的影响发现，伴生菌通过不同机制分别促进K. vulgare的生长与2-KLG的转化。

Abstract:

Objective The effects of the helper strain (Priestia endophytica) 1-112 on the growth of Ketogulonicigenium vulgare and the biotransformation of 2-keto-L-glonic acid (2-KLG) remain unclear. In this study, we cultured the helper strain in different media to study the mechanisms of the growth- and 2-KLG biotransformation-promoting effects of the helper strain on K. vulgare.Methods We used different media (minimal, mixed, and fementation media) to culture the helper strain and investigated the effects of the strain on the growth and 2-KLG biotransformation of K. vulgare. The differently expressed genes (DEGs) and associated metabolic pathways in the helper strain cultured in different media were analyzed by transcriptomics to screen the key factors in the co-culture system. The effects of key factors on the growth and 2-KLG biotransformation of K. vulgare were evaluated to explore their roles in the co-culture system.Results Strain 1-112 cultured in the minimal medium lost or reduced the ability to promote 2-KLG production, while it retained the ability to promote the growth of K. vulgare. This result indicated that the helper strain promoted 2-KLG biotransformation through two distinct mechanisms. There were 1 859 DEGs in strain 1-112 cultured in fermentation medium in comparison with the minimal medium, and the DEGs were significantly enriched in the pathways such as nicotinate and nicotinamide metabolism, carbon metabolism, arginine and proline metabolism, and amino acid biosynthesis. In addition, the helper strain cultured in the minimal medium containing some key factors could restore the ability to promote 2-KLG production. Glycine, proline, biotin, and nicotinic acid were found to be essential for promoting K. vulgare growth, whereas glycine, threonine, biotin, and nicotinic acid played critical roles in enhancing 2-KLG biotransformation.Conclusion The helper strain promoted the growth and 2-KLG biotransformation of K. vulgare through different mechanisms.