State Key Laboratory of Materials-Oriented Chemical Engineering , Nanjing 211816 , China.
College of Food Science and Light Industry , Nanjing Tech University , Nanjing 211816 , China.
J Agric Food Chem. 2019 Apr 3;67(13):3711-3722. doi: 10.1021/acs.jafc.9b00332. Epub 2019 Mar 21.
Bacillus amyloliquefaciens NX-2S154 is a promising poly(γ-glutamic acid) (γ-PGA) producing strain discovered in previous studies. However, the wild-type strain contains an unknown endogenous plasmid, p2Sip, which causes low transformation efficiency and instability of exogenous plasmids. In our study, p2Sip is 5622 bp with 41% G+C content and contains four putative open reading frames (ORFs), including genes repB, hsp, and mobB and γ-PGA-synthesis regulator, pgsR. Elimination of p2Sip from strain NX-2S154 delayed γ-PGA secretion and decreased production of γ-PGA by 18.1%. Integration of a pgsR expression element into the genomic BamHI locus using marker-free manipulation based on pheS* increased the γ-PGA titer by 8%. pgsR overexpression upregulated the expression of γ-PGA synthase pgsB, regulator degQ, and glutamic acid synthase gltA, thus increasing the γ-PGA production in B. amyloliquefaciens NB. Our results indicated that pgsR from p2Sip plays an important regulatory role in γ-PGA synthesis in B. amyloliquefaciens.
解淀粉芽抱杆菌 NX-2S154 是先前研究中发现的一种有前途的聚（γ-谷氨酸）（γ-PGA）生产菌株。然而，野生型菌株含有一个未知的内源性质粒 p2Sip，这导致了外源质粒转化效率低和不稳定。在我们的研究中，p2Sip 长 5622bp，G+C 含量为 41%，包含四个假定的开放阅读框（ORFs），包括 repB、hsp、mobB 和 γ-PGA 合成调控因子 pgsR。从 NX-2S154 菌株中消除 p2Sip 会延迟 γ-PGA 的分泌，并使 γ-PGA 的产量降低 18.1%。使用基于 pheS*的无标记操作将 pgsR 表达元件整合到基因组 BamHI 位点，可使 γ-PGA 产量提高 8%。pgsR 的过表达上调了 γ-PGA 合酶 pgsB、调控因子 degQ 和谷氨酸合酶 gltA 的表达，从而增加了解淀粉芽抱杆菌 NB 中的 γ-PGA 产量。我们的结果表明，p2Sip 中的 pgsR 在解淀粉芽抱杆菌的 γ-PGA 合成中起着重要的调控作用。
