粪肠球菌Gr17(Enterococcus faecalis Gr17)是从白酒酒醅中分离的高产细菌素的菌株,该研究以Gr17为研究对象,筛选可正向调控细菌素合成的营养胁迫条件,并初步探究该条件正向调控细菌素合成的具体机制。以MRS培养基为对照,测定在1/4 MRS、1/2 MRS和3/4 MRS的营养胁迫条件下,该菌生长及细菌素产量的变化,并采用实时定量聚合酶链式反应(real-time quantitative polymerase chain reaction,RT-qPCR)测定群体感应调控中与细菌素合成相关基因的表达水平。结果表明,随初始营养物质的减少,菌体生长密度减小。但发现1/4 MRS的胁迫条件下菌株细菌素产量显著上升。RT-qPCR结果显示,在1/4 MRS的胁迫条件下,细菌素结构基因ent I、ent J和ent Gr17,ABC转运系统调节基因AS-48E、AS-48F、AS-48G、AS-48H,自诱导肽基因AIP以及双组分调节基因hpk和rr的表达均显著上调(P＜0.05)。因此,营养胁迫对粪肠球菌Gr17的生长不利,但1/4 MRS的胁迫条件可正向调控细菌素合成,且受群体感应系统调控。该研究期望为营养胁迫对细菌素合成的调控机制相关研究提供参考。
Enterococcus faecalis Gr17, a high bacteriocin-producing strain, was isolated from fermented grains of Baijiu. To screen nutritional stress conditions that can positively regulate bacteriocin production and preliminarily explored the specific mechanism of the regulation, the growth and bacteriocin production of the strain under the nutritional stress of 1/4 MRS, 1/2 MRS and 3/4 MRS were measured, and MRS was served as control. Real-time quantitative polymerase chain reaction (RT-qPCR) was used to measure the expression level of genes related to bacteriocin synthesis in quorum sensing regulation. The results showed the cell growth density decreased with the decrease of initial nutrients, while bacteriocin production of strain Gr17 significantly enhanced under the stress condition of 1/4 MRS. RT-qPCR results showed that under the stress of 1/4 MRS, the expression of bacteriocin structural genes ent I, ent J and ent Gr17, ABC transport system regulatory genes AS-48E, AS-48F, AS-48G and AS-48H, self-induced peptide gene AIP and two-component regulatory genes hpk and rr were significantly increased (P<0.05). Therefore, although nutritional stress is unfavorable to the growth of E.faecalis Gr17, the stress condition of 1/4 MRS can enhance bacteriocin production and quorum sensing system is involved in the regulation. The results provide reference for the research on the regulation mechanism of bacteriocin synthesis under nutritional stress.
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