College of Petroleum & Gas Engineering, Liaoning Shihua University, Fushun, 113006, China.
College of Resource & Civil Engineering, Northeastern University, Shenyang, 110819, China.
Sci Rep. 2020 Feb 19;10(1):2918. doi: 10.1038/s41598-020-59114-z.
Microbial flocculant (MBF), an environmentally friendly water treatment agent, can be widely used in various water treatments. However, its use is limited by low yield and high cost. This problem can be solved by clarifying its biosynthesis mechanism and regulating it. Paenibacillus shenyangensis A9, a flocculant-producing bacterium, was used to produce polysaccharide-type MBFA9 by regulating the nitrogen source (nitrogen adequacy/nitrogen deficiency). In this study, RNA-Seq high-throughput sequencing technology and bioinformatic approaches were used to investigate the fermentation and biosynthesis of polysaccharide-type MBFA9 by regulating the nitrogen source (high nitrogen/low nitrogen) in the flocculant-producing bacteria Paenibacillus shenyangensis A9. Differentially expressed genes, functional clustering, and functional annotation of key genes were assessed. Then the MBFA9 biosynthesis and metabolic pathway were reconstructed. Our results showed that when cultured under different nitrogen conditions, bacterial strain A9 had a greater ability to synthesize polysaccharide-type MBFA9 under low nitrogen compared to high nitrogen conditions, with the yield of MBFA9 reaching 4.2 g/L at 36 h of cultivation. The quality of transcriptome sequencing data was reliable, with a matching rate of 85.38% and 85.48% when L36/H36 was mapped to the reference genome. The total expressed genes detected were 4719 and 4730, with 265 differentially expressed genes. The differentially expressed genes were classified into 3 categories: molecular function (MF), cell component (CC), and biological process (BP), and can be further divided into 22 subcategories. There were 192 upregulated genes and 73 downregulated genes, with upregulation being predominant under low nitrogen. UDP-Gal, UDP-Glc, UDP-GlcA, and UDP-GlcNAc, which are in the polysaccharide metabolic pathway, could all be used as precursors for MBFA9 biosynthesis, and murA, wecB, pgm, galU/galF, fcl, gmd, and glgC were the main functional genes capable of affecting the growth of bacteria and the biosynthesis of MBF. Results from this study provide evidence that high-level expression of key genes in MBFA9 biosynthesis, regulation, and control can achieve MBFA9 directional synthesis for large-scale applications.
微生物絮凝剂（MBF）是一种环保型水处理剂，可广泛应用于各种水处理中。然而，其产量低、成本高的问题限制了其应用。通过阐明其生物合成机制并进行调控，可以解决这一问题。产絮菌沈阳芽孢杆菌 A9 可通过调控氮源（氮充足/氮缺乏）来产生多糖型 MBFA9。本研究采用 RNA-Seq 高通量测序技术和生物信息学方法，研究了产絮菌沈阳芽孢杆菌 A9 通过调控氮源（高氮/低氮）发酵和合成多糖型 MBFA9 的过程。评估了差异表达基因、功能聚类和关键基因的功能注释，然后重建了 MBFA9 的生物合成和代谢途径。结果表明，在不同氮源条件下培养时，与高氮条件相比，细菌菌株 A9 在低氮条件下具有更强的合成多糖型 MBFA9 的能力，在培养 36 h 时 MBFA9 的产量达到 4.2 g/L。转录组测序数据质量可靠，L36/H36 与参考基因组的匹配率分别为 85.38%和 85.48%。共检测到 4719 个和 4730 个总表达基因，有 265 个差异表达基因。差异表达基因分为分子功能（MF）、细胞成分（CC）和生物过程（BP）3 类，可进一步细分为 22 个亚类。有 192 个上调基因和 73 个下调基因，低氮条件下基因上调占主导地位。UDP-Gal、UDP-Glc、UDP-GlcA 和 UDP-GlcNAc 是多糖代谢途径中的物质，都可以作为 MBFA9 生物合成的前体，murA、wecB、pgm、galU/galF、fcl、gmd 和 glgC 是影响细菌生长和 MBF 生物合成的主要功能基因。本研究结果为 MBFA9 生物合成、调控关键基因的高表达，以及实现 MBFA9 的定向合成以进行大规模应用提供了证据。
