食源性致病菌群体感应信号分子的检测

群体感应(Quorum sensing,QS)在食物中毒导致的食源性疾病暴发机制和食物腐败变质中起主要作用,QS影响致病菌的细胞被膜形成和致病性。文中通过深入了解食源性致病菌的QS信号分子,综述了革兰氏阴性和革兰氏阳性菌产生的信号分子类型,同时介绍了检测QS信号分子的不同技术,并根据QS机制在食品中的影响提出了思考和建议,为监控食源性致病菌提供依据。     

肠杆菌科细菌群体感应系统的研究进展

细菌能够感受种群密度的变化,并通过调节自身某些基因的表达来作出应答,这种细菌种间和种内的沟通方式被称为群体感应(QS)。肠杆菌科细菌大多是食源性致病菌或食品腐败菌,且研究证明毒力因子的调控表达和食品的腐败变质均与QS密切相关。本文中,笔者综述了肠杆菌科成员中5种信号分子介导的群体感应系统,包括N-酰基高丝氨酸内酯(AHLs)介导的Ⅰ型QS系统、由自诱导物2(AI-2)介导的Ⅱ型QS系统、AI-3/肾上腺素/去甲肾上腺素介导的Ⅲ型QS系统、一种线型五肽(NNWNN) QS因子EDF(extracellular death factor)短肽介导的QS系统和吲哚介导的QS系统,并对其在毒力基因和食品腐败变质的调控机制中的研究进行了介绍。     

细菌生物被膜中群体感应调控机制及其控制研究展望

生物被膜(biofilm)是微生物聚集黏附在物体表面形成的多细胞结构,是引起微生物感染的主要原因,对食品工业和公共卫生安全造成巨大的威胁。群体感应(quorum sensing,QS)是调控生物被膜形成的重要因素,与生物被膜的抗生素耐药性、抗逆性密切相关。研究发现:针对QS系统的天然、合成化合物被称为群体感应抑制剂(quorum sensing inhibitors,QSI),可干扰QS信号,破坏生物被膜的形成,这种现象被称为群体淬灭(quorum quenching,QQ)。本文中,笔者就生物被膜组分、群体感应的调控机制及生物被膜的控制策略进行深入综述,旨在为食品加工程中细菌生物被膜的防控提供理论依据。     

群体感应系统介导细菌生物膜形成的研究进展

群体感应(QS)是微生物之间的通讯机制,通过信号分子调控基因表达,这种交流可使细菌表达不同的生理行为,包括病原微生物的毒性、对抗生素的形成、生物膜的形成与生长等。生物膜的形成对微生物的代谢、毒力因子的表达等密切相关。群体感应现象与生物膜的形成相互依赖,生物膜提供菌体聚集场所,避免群体感应信号分子的扩散,聚集菌体的群体感应现象为生物膜的形成提供基础。群体感应系统不仅可直接介导细菌生物膜的形成,还可调节胞内第二信使分子水平,间接调控生物膜的生成。本文中,笔者从直接和协同其他信号分子两方面对细菌生物膜形成机制研究进展进行综述,为在工业应用中降低细菌耐药性、指导食品生产安全、提高功能性生物膜产量等方面提供理论依据。     

信号分子调控细菌生物被膜形成的分子机制

细菌生物被膜(Bacterial biofilm,BF)是黏附于机体黏膜或生物材料表面、由细菌及其分泌的多聚糖、蛋白质和核酸等组成的被膜状生物群体,是造成持续性感染的重要原因之一。细菌在生长繁殖时会产生一些次级代谢产物,部分会作为生物信号分子在细胞内或细胞间传递信息,使细菌在多细胞水平协调统一相互配合,以完成一些重要的生理学功能,如生物发光、BF的形成、运动与固定态生活方式的转换等。信号分子在BF形成过程中起着重要的调控作用。文中从密度感应系统(Quorum-sensing systems,QS)、环二鸟苷酸(Cyclic diguanylate,c-di-GMP)、双组分系统(Two-component systems,TCS)和sRNA等方面介绍影响BF形成的相关信号分子,重点对BF形成过程中的信号分子调控机制进行概述,这对于深入揭示信号分子调控BF形成的机制十分必要。     

米曲霉来源的环二肽对荧光假单胞菌群体感应的抑制及其机制

荧光假单胞菌(Pseudomonas fluorescens)是一类重要的食品腐败菌,在乳制品、肉制品、水产品等食品中经常被检测到。细菌通过群体感应(quorum sensing,QS)系统来进行彼此之间的交流,腐败菌的一些特性也受到QS系统的调控。因此,以QS系统为靶点来控制食品的腐败,提高食品质量和安全性是一条潜在可行的途径。本研究中,笔者从米曲霉(Aspergillus oryzae) D01的次级代谢产物中分离得到了一种群体感应抑制剂——环二肽(L-苯丙氨酸-L-脯氨酸,cyclo-(L-phenylalanyl-L-prolyl)),并测定了其对荧光假单胞菌群体感应的抑制活性,并用分子对接的方法分析了其抑制机制。结果表明:当环二肽的质量浓度为60μg/m L时,细菌泳动运动、群集运动的区域直径比对照组分别减少了66. 62%和36. 92%;生物被膜含量比对照组减少了75. 86%。L-苯丙氨酸-L-脯氨酸能显著抑制荧光假单胞菌的QS表型——紫色素的产生、泳动和群集运动,胞外蛋白酶的产生和生物被膜的形成。分子对接分析表明,其抑制机制可能是由于环二肽与荧光假单胞菌的Lux I型蛋白竞争性结合,阻碍了信号分子产生并阻断了相关基因的表达所致。     

细菌群体感应及其干扰策略的研究进展

群体感应（QS）广泛存在于细菌中,是细菌根据细胞密度变化调控基因表达的一种机制。许多植物病原菌依赖QS调控致病基因和毒性因子的表达,导致植物发病,因此通过抑制QS效应就为控制细菌病害提供了一种有效的方法。目前发现许多途径可以干扰细菌的QS,如：产生可使信号分子降解的酶,产生病原菌信号分子的类似物与信号分子受体蛋白竞争结合来阻断病原菌的群体感应,利用QS中信号分子来诱发寄主抗性。系统阐述了细菌QS及其干扰策略。     

细菌群体感应信号分子的光电检测技术

群体感应（quorum sensing，QS）是一种依赖菌群密度的细菌交流系统。在探究细菌群体感应系统的调控机制中，对QS信号分子的鉴别和检测是不可或缺的环节，其对生命科学、药学等领域涉及细菌等微生物的相互作用、高效检测和作用机制解析等具有重要的参考意义。本文在总结不同类型细菌QS信号分子来源和结构的基础上，对QS信号分子的光电检测方法和技术进行了综述，重点对光电传感检测的敏感介质、传感界面、传感机制及测试效果进行探讨，同时关注了将微流控芯片分析技术应用于细菌QS信号分子原位监测的相关研究进展。     

群体感应信号分子AI-2研究进展

群体感应(QS)是细菌根据种群密度的变化调控基因表达,协调群体行为的机制。除具有种特异性的信号分子AI-1外,近年来发现一类新的信号分子AI-2在调控细菌基因表达中起重要作用。AI-2的结构和生物合成途径已被确定,其产生依赖于一种称为LuxS的蛋白。目前认为AI-2在细菌种间交流中起通用信号分子(universalsignal)的作用。了解细菌的QS调控过程以及种间细胞交流的新机制,有助于对细菌病害进行防治。     

群体感应抑制剂及其在食品保藏中的应用研究进展

细菌在生长过程中会合成并释放一种叫做信号分子的化学因子,作为细胞间或细胞内传递信息的介质。这种信号分子积累到一定水平,会对细菌生理性状的表达产生调控作用,即群体感应现象。细菌群体感应现象对食品腐败变质过程也有很大的影响。因此,研究群体感应抑制剂在食品保藏中的作用就显得尤为重要。本文中,笔者根据细菌分泌信号分子类型的不同,综述了不同细菌的群体感应抑制剂及其在食品保藏中的应用。     

Messing with bacterial quorum sensing.

Quorum sensing is widely recognized as an efficient mechanism to regulate expression of specific genes responsible for communal behavior in bacteria. Several bacterial phenotypes essential for the successful establishment of symbiotic, pathogenic, or commensal relationships with eukaryotic hosts, including motility, exopolysaccharide production, biofilm formation, and toxin production, are often regulated by quorum sensing. Interestingly, eukaryotes produce quorum-sensing-interfering (QSI) compounds that have a positive or negative influence on the bacterial signaling network. This eukaryotic interference could result in further fine-tuning of bacterial quorum sensing. Furthermore, recent work involving the synthesis of structural homologs to the various quorum-sensing signal molecules has resulted in the development of additional QSI compounds that could be used to control pathogenic bacteria. The creation of transgenic plants that express bacterial quorum-sensing genes is yet another strategy to interfere with bacterial behavior. Further investigation on the manipulation of quorum-sensing systems could provide us with powerful tools against harmful bacteria.     

Messing with Bacterial Quorum Sensing

Quorum sensing is widely recognized as an efficient mechanism to regulate expression of specific genes responsible for communal behavior in bacteria. Several bacterial phenotypes essential for the successful establishment of symbiotic, pathogenic, or commensal relationships with eukaryotic hosts, including motility, exopolysaccharide production, biofilm formation, and toxin production, are often regulated by quorum sensing. Interestingly, eukaryotes produce quorum-sensing-interfering (QSI) compounds that have a positive or negative influence on the bacterial signaling network. This eukaryotic interference could result in further fine-tuning of bacterial quorum sensing. Furthermore, recent work involving the synthesis of structural homologs to the various quorum-sensing signal molecules has resulted in the development of additional QSI compounds that could be used to control pathogenic bacteria. The creation of transgenic plants that express bacterial quorum-sensing genes is yet another strategy to interfere with bacterial behavior. Further investigation on the manipulation of quorum-sensing systems could provide us with powerful tools against harmful bacteria.     

Investigation of N-acyl homoserine lactone (AHL) molecule production in Gram-negative bacteria isolated from cooling tower water and biofilm samples

In this study, 99 Gram-negative rod bacteria were isolated from cooling tower water, and biofilm samples were examined for cell-to-cell signaling systems, N-acyl homoserine lactone (AHL) signal molecule types, and biofilm formation capacity. Four of 39 (10 %) strains isolated from water samples and 14 of 60 (23 %) strains isolated from biofilm samples were found to be producing a variety of AHL signal molecules. It was determined that the AHL signal molecule production ability and the biofilm formation capacity of sessile bacteria is higher than planktonic bacteria, and there was a statistically significant difference between the AHL signal molecule production of these two groups (p?<?0.05). In addition, it was found that bacteria belonging to the same species isolated from cooling tower water and biofilm samples produced different types of AHL signal molecules and that there were different types of AHL signal molecules in an AHL extract of bacteria. In the present study, it was observed that different isolates of the same strains did not produce the same AHLs or did not produce AHL molecules, and bacteria known as AHL producers did not produce AHL. These findings suggest that detection of signal molecules in bacteria isolated from cooling towers may contribute to prevention of biofilm formation, elimination of communication among bacteria in water systems, and blockage of quorum-sensing controlled virulence of these bacteria.     

细菌细胞间通讯的群感效应

自然界中的细菌大多数以生物膜的形式存在,这种存在方式增强了细菌对环境的适应性和病原菌的致病性。近年来研究表明,细菌群感效应(quorum—sensing)是调控生物膜形成和其它生物学功能的机制。细菌能够分泌特定的信号分子并感应它的浓度,当信号分子浓度达到阈值时,细菌就能够引发包括致病基因在内的相关基因的表达以适应环境的变化。由于生物膜的形成是病原菌致病性和其它要求一定细胞密度才能产生功能的基础,所以细菌群感效应的发现为防止病原菌的毒害作用提供了新的思路。     

细菌群体感应信号分子与抑制剂研究进展

具有群体感应系统的细菌通过相互交换一种自动诱导（autoinducer）信号分子来实现彼此问的信息交流。当信号分子积累到一定浓度时会改变细菌特定基因的表达,如生物膜的形成、生物发光行为、毒性基因的表达、孢子的形成等。近年来,人们发现了多种天然或者人工合成的群体感应抑制剂,可以干扰群感系统的信息回路。本文系统地阐述了细菌群体感应信息系统的划分、自体诱导分子及其抑制剂的研究进展。     

Food color ‘Azorubine’ interferes with quorum sensing regulated functions and obliterates biofilm formed by food associated bacteria: An in vitro and in silico approach

Quorum sensing (QS) plays a crucial role in different stages of biofilm development, virulence production, and subsequently to the growth of bacteria in food environments. Biofilm mediated spoilage of food is one of the ongoing challenge faced by the food industry worldwide as it incurs substantial economic losses and leads to various health issues. In the present investigation, we studied the interference of quorum sensing, its regulated virulence functions, and biofilm in food-associated bacteria by colorant azorubine. In vitro bioassays demonstrated significant inhibition of QS and its coordinated virulence functions in Chromobacterium violaceum 12472 (violacein) and Pseudomonas aeruginosa PAO1 (elastase, protease, pyocyanin, and alginate). Further, the decrease in the production EPS (49–63%) and swarming motility (61–83%) of the pathogens was also recorded at sub-MICs. Azorubine demonstrated broad-spectrum biofilm inhibitory potency (50–65%) against Chromobacterium violaceum, Pseudomonas aeruginosa, E. coli O157:H7, Serratia marcescens, and Listeria monocytogenes. ROS generation due to the interaction between bacteria and azorubine could be responsible for the biofilm inhibitory action of the food colorant. Findings of the in vitro studies were well supported by molecular docking and simulation analysis of azorubine and QS virulence proteins. Azorubine showed strong binding to PqsA as compared to other virulent proteins (LasR, Vfr, and QscR). Thus, it is concluded that azorubine is a promising candidate to ensure food safety by curbing the menace of bacterial QS and biofilm-based spoilage of food and reduce economic losses.     

The role of c-di-GMP signaling in an Aeromonas veronii biovar sobria strain

Aeromonas is a ubiquitous gram-negative bacterium that persists in the environment. It is shown that all isolates of persistent Aeromonas clones show strong biofilm formation ability. C-di-GMP regulates biofilm formation in many bacteria. To investigate the impact of c-di-GMP signaling, we introduced heterologous GGDEF and EAL domain proteins from Salmonella Typhimurium to an Aeromonas veronii biovar sobria strain. Overexpression of the GGDEF domain protein AdrA increased c-di-GMP concentration and biofilm formation and reduced motility. Production of the quorum-sensing signaling molecule C4-homoserine lactone and adhesion to aquatic plant duckweed and amoeba surfaces were enhanced. On the other hand, overexpression of the EAL domain protein YhjH decreased biofilm formation and increased motility.