基于信号分子AI-2活性的发酵黏液乳杆菌2-1分泌胞外多糖的研究

Exopolysaccharides secretion of Limosilactobacillus fermentum 2-1 based on AI-2 activity

摘要:

【背景】 LuxS/自体诱导物-2 (autoinducer-2, AI-2)群体感应系统可以通过分泌信号分子调控菌体细胞环境适应的过程，胞外多糖在保护细胞免受外界环境的刺激、伤害等方面也有着至关重要的作用，但二者之间的相互关系并不明确。【目的】 探究不同培养条件下发酵黏液乳杆菌(Limosilactobacillus fermentum) 2-1的AI-2活性与胞外多糖产量的关系。【方法】 采用苯酚-硫酸法及哈维氏弧菌(Vibrio harveyi) BB170生物发光法测定不同培养条件下发酵黏液乳杆菌2-1胞外多糖产量和信号分子AI-2活性。【结果】 发酵黏液乳杆菌2-1在培养初期的细胞生长速率最快，随后菌体密度逐渐趋于稳定；信号分子AI-2活性在7 h时出现峰值，随后下降；胞外多糖产量先增加后减小，16 h时显著高于其他培养时间，达(204.30±15.98) mg/L。温度升高(44 ℃)或降低(23 ℃, 30 ℃)，菌株的菌体密度、信号分子AI-2活性和胞外多糖的产生都会受到抑制；酸性条件有利于发酵黏液乳杆菌2-1信号分子AI-2的分泌，但菌株的生长和胞外多糖产量受到抑制；菌株信号分子AI-2活性及胞外多糖产量与接种量在1%−3%范围内呈正相关；培养基碳源改变时，菌株菌体密度、信号分子AI-2活性及胞外多糖产量也随之改变。添加终浓度为100μmol/L的外源信号分子AI-2时，显著促进了发酵黏液乳杆菌2-1胞外多糖的产量(p<0.05)。【结论】 在一定条件下时，信号分子AI-2活性和胞外多糖产量之间呈正相关关系。

关键词:群体感应;信号分子AI-2;发酵黏液乳杆菌2-1;胞外多糖

Abstract:

[Background] The LuxS/autoinducer-2 (AI-2) quorum sensing system regulates bacterial adaptation to environmental changes by secreting signal molecules. Exopolysaccharides (EPS) play a crucial role in protecting cells from external environmental stress and damage. However, the relationship between the LuxS/AI-2 system and EPS production remains unclear. [Objective] To investigate the relationship between AI-2 activity and EPS production in Limosilactobacillus fermentum 2-1 cultured under different conditions. [Methods] The phenol-sulfuric acid method and Vibrio harveyi BB170 bioluminescence assay were employed to determine the EPS yield and AI-2 activity, respectively, of L.fermentum 2-1 cultured under different conditions. [Results] The cell growth of L.fermentum 2-1 was the fastest during the early stages of culture, after which the cell density gradually stabilized. The AI-2 activity peaked at the time point of 7 h and then decreased. The EPS production presented a trend of first rising and then declining, reaching the peak of (204.30±15.98) mg/L at the time point of 16 h, which was significantly higher than that at other time points. Both elevated (44 ℃) and declined (23 ℃, 30 ℃) temperatures inhibited the cell density, AI-2 activity, and EPS production. Acidic conditions favored AI-2 secretion but inhibited cell growth and EPS production. AI-2 activity and EPS production were positively correlated with inoculum size within the range of 1%−3%. Changes of the carbon source altered the cell density, AI-2 activity, and EPS production. Addition of exogenous AI-2 at a final concentration of 100 μmol/L promoted EPS production in L.fermentum 2-1 (P<0.05). [Conclusion] Under certain conditions, there is a positive correlation between AI-2 activity and EPS production in L.fermentum 2-1.

Key words:quorum sensing;signal molecule AI-2;Limosilactobacillus fermentum 2-1;exopolysaccharide