Abstract

The low yield as bottleneck problem limits the application of microbial flocculant in water treatment. However, genetic information of microbial flocculant-producing strains can guide the regulation of microbial flocculant production, but it remains unknown. Agrobacterium tumefaciens F2 produced polysaccharide-based microbial flocculants in the fermentation medium but none in Luria Bertani medium; hence, the transcriptome was used to analyze the potentially associated genes with the production of microbial flocculants. Glucose, mannose, rhamnose, and galactose are the main sugar monomers, and genes (manA, glmM, manC, rfb genes, exo genes, etc.) with changed expression levels related to sugar monomers metabolism potentially participated in the biosynthesis of polysaccharide-based microbial flocculants. exoC, exoP, and manC were confirmed to participate in the biosynthesis via constructing the mutants F2-dexoC, F2-dexoP, and F2-dmanC. An exo_F2 gene cluster was annotated due to the high percentage of matches between the genome sequences of strains F2 and C58, and exo genes in their genome sequences showed the similarity of 86~92%. The hypothetical pathway for the biosynthesis of polysaccharide-based microbial flocculants in strain F2 was proposed, laying the basis for the production yield regulation.

Key points

• An exo _F2 gene cluster in the polysaccharide biosynthesis was annotated.

• exoC, exoP, and manC genes participated in the polysaccharide biosynthesis.

• A hypothetical biosynthesis pathway of polysaccharide in flocculant was proposed.

中文翻译：

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应用微生物学和生物技术揭示了根癌农杆菌F2中基于多糖的微生物絮凝剂的生物合成途径。

摘要

作为瓶颈问题的低产量限制了微生物絮凝剂在水处理中的应用。然而，微生物絮凝剂产生菌株的遗传信息可以指导微生物絮凝剂产生的调控，但是仍然未知。根癌土壤杆菌F2在发酵培养基中产生了基于多糖的微生物絮凝剂，而在Luria Bertani培养基中则没有。因此，转录组被用来分析与微生物絮凝剂产生相关的潜在基因。葡萄糖，甘露糖，鼠李糖和半乳糖是主要的糖单体，以及基因（manA，glmM，manC，rfb基因，exo与糖单体代谢相关的表达水平改变的基因等）可能参与了基于多糖的微生物絮凝剂的生物合成。exoC，exoP和manC通过构建突变体F2-d exoC，F2-d exoP和F2-d manC被证实参与了生物合成。一个外_F2基因簇是由于注释以匹配株F2和C58，以及基因组序列之间的高比例的外它们的基因组序列中的基因相似度为86〜92％。提出了F2菌株中基于多糖的微生物絮凝剂生物合成的假想途径，为调节产量提供了基础。

关键点

• 注释了多糖生物合成中的exo _F2基因簇。

•exoC，exoP和manC基因参与了多糖的生物合成。

•提出了絮凝剂中多糖的假设生物合成途径。