Dertli Enes, Mayer Melinda J, Colquhoun Ian J, Narbad Arjan
Department of Gut Health and Food Safety, Institute of Food Research, Norwich, Colney, NR4 7UA, UK.
Department of Food Engineering, Faculty of Engineering, Bayburt University, Bayburt, 69000, Turkey.
Microb Biotechnol. 2016 Jul;9(4):496-501. doi: 10.1111/1751-7915.12314. Epub 2015 Sep 24.
Lactobacillus johnsonii FI9785 has an eps gene cluster which is required for the biosynthesis of homopolymeric exopolysaccharides (EPS)-1 and heteropolymeric EPS-2 as a capsular layer. The first gene of the cluster, epsA, is the putative transcriptional regulator. In this study we showed the crucial role of epsA in EPS biosynthesis by demonstrating that deletion of epsA resulted in complete loss of both EPS-1 and EPS-2 on the cell surface. Plasmid complementation of the epsA gene fully restored EPS production, as confirmed by transmission electron microscopy and nuclear magnetic resonance (NMR) analysis. Furthermore, this complementation resulted in a twofold increase in the expression levels of this gene, which almost doubled amounts of EPS production in comparison with the wild-type strain. Analysis of EPS by NMR showed an increased ratio of the heteropolysaccharide to homopolysaccharide in the complemented strain and allowed identification of the acetylated residue in EPS-2 as the (1,4)-linked βGlcp unit, with the acetyl group located at O-6. These findings indicate that epsA is a positive regulator of EPS production and that EPS production can be manipulated by altering its expression.
约氏乳杆菌FI9785有一个eps基因簇，该基因簇是同聚胞外多糖（EPS）-1和作为荚膜层的杂聚EPS-2生物合成所必需的。该基因簇的第一个基因epsA是推定的转录调节因子。在本研究中，我们通过证明epsA的缺失导致细胞表面EPS-1和EPS-2完全丧失，显示了epsA在EPS生物合成中的关键作用。epsA基因的质粒互补完全恢复了EPS的产生，这通过透射电子显微镜和核磁共振（NMR）分析得到证实。此外，这种互补导致该基因表达水平增加两倍，与野生型菌株相比，EPS产量几乎增加了一倍。通过NMR对EPS的分析表明，互补菌株中杂多糖与同多糖的比例增加，并确定EPS-2中的乙酰化残基为（1,4）连接的βGlcp单元，乙酰基位于O-6位。这些发现表明epsA是EPS产生的正调节因子，并且可以通过改变其表达来操纵EPS的产生。
