群体感应调控下的乳酸菌细菌素合成

细菌素是一种在新陈代谢过程中由核糖体合成的具有抑菌作用的抗菌肽,因此被作为天然、无毒抗菌剂并广泛应用到食品行业中。群体感应是细菌细胞间通过对自诱导物浓度的感知,从而对基因表达进行调控的行为,现已证明乳酸菌的群体感应是细菌素合成的关键调控机制。作者主要综述了目前乳酸菌细菌素的研究现状、细菌素的系统分类、群体感应信号的转导机制及其对乳酸菌细菌素合成的调节,以促进对细菌素的研究及应用。     

共培养诱导乳酸菌细菌素合成的研究进展

乳酸菌细菌素是一种新型的生物防腐剂,具有来源广泛、成本较低、抑菌谱广、安全性高等特点,合成量低是细菌素在食品中应用受限的主要原因之一,共培养是提高乳酸菌细菌素合成量的有效途径之一,群体感应系统在共培养诱导细菌素合成过程中发挥关键的作用,群体感应系统包括信号分子和双组分调控系统(组氨酸蛋白激酶和反应调节蛋白)。因此,对调控机制的掌握显得尤为重要。文章论述了共培养中诱导菌与乳酸菌细菌素合成的关系、诱导因子/信号分子AI-2的特征、双组分调控系统及共培养诱导乳酸菌细菌素合成的分子机制。了解诱导机制及特征将有助于筛选和开发共培养诱导细菌素合成系统和新产品,提高细菌素合成量,近而对人体产生益生效应。     

乳酸菌合成细菌素的细胞通讯机制研究进展

乳酸菌细菌素作为一种天然抑菌物质,是化学防腐剂和抗生素的理想替代品。本文从细胞通讯的角度阐述乳酸菌合成细菌素的不同诱导信号来源及其诱导机制,细菌素的合成机制,共培养过程中的多细胞交流以及在复杂环境下的群体感应(QS)信号网络,系统地介绍乳酸菌产细菌素的通讯机制研究进展,为促进细菌素的研究和应用提供参考。     

黄曲霉群体感应研究进展

曲霉属真菌(Aspergillus)如黄曲霉、寄生曲霉侵染玉米、花生等富含油脂的作物种子后产生的黄曲霉毒素(aflatoxin)具有强致癌作用,严重威胁食品安全和人类健康。群体感应(quorum sensing,QS)曾经认为只存在于细菌中,但是在真菌中也存在QS系统,菌体的形态建成和次级代谢产物的产生都与细胞的群体密度有关。黄曲霉拥有类似群体感应的机制,菌核到分生孢子的转换受细胞密度和脂肪氧合酶调控。氧脂素作为信号分子通过密度依赖机制可抑制或促进黄曲霉的生长及黄曲霉毒素的生物合成,本文综述了黄曲霉群体感应及信号通路的研究进展,旨在从群体感应的角度抑制黄曲霉毒素的产生,为微生物与食品安全的研究提供指导。     

动物双歧杆菌细菌素bifidocin A群体感应合成调控行为分析

bifidocin A是由Bifidobacterium animalis BB04代谢合成的一种新型广谱高效细菌素。为探讨该细菌素的群体感应合成调控行为,本研究通过监测发酵过程中菌体生长及细菌素抑菌活性变化规律,分析菌体密度和细菌素合成的相关性;基于低产细菌素培养模型体系的构建,检测发酵上清液中是否存在群体感应自诱导肽,判断是否存在细菌素合成相关群体感应系统;并通过对发酵上清液中自诱导肽进行提纯和分子质量测定,初步明确其分子特性。结果表明,当菌体细胞达到活菌数为7.31（lg（CFU/mL））时,细菌素才开始合成;发酵过程中,菌体密度与细菌素的合成呈现正相关性;成功构建了低产细菌素培养模型体系,其培养条件为培养温度37?℃、培养基起始pH?5、培养基浓度1/10改良MRS（Man Rogosa Sharpe）培养基、接种量1%、培养时间24?h;基于此模型体系,确定发酵上清液中确实存在可以诱导细菌素合成的自诱导肽,细菌素bifidocin?A的合成是受群体感应系统调控的;通过对发酵上清液进行超滤管筛分、葡聚糖凝胶柱层析及高效液相色谱层析提纯,获得了高纯度自诱导肽样品;采用基质辅助激光解析电离飞行质谱测定其分子质量为3?587.253?Da。     

基于AHLs介导的革兰氏阴性菌群体感应调控及淬灭机制研究进展

革兰氏阴性细菌群体感应(QS)系统主要由N-酰基高丝氨酸内酯(AHLs)类信号分子介导。信号分子随着细菌密度的增加而逐渐积累,当信号分子浓度达到阈值时,同源受体结合信号分子并触发信号转导,导致细菌生物膜形成、生物发光、质粒接合转移和毒力因子等群体感应表型表达。目前革兰氏阴性菌群体感应淬灭作用的研究主要针对QS系统中合成酶(I)、AHLs信号和受体(R)三组分之一进行外部干预,进而实现抑制细菌表型的基因表达。本文首先介绍AHLs的结构、合成方式、QS系统及调控机制,然后,重点综述AHLs介导的群体感应淬灭作用(QQ)和AHLs内酯酶、酰基转移酶和氧化还原酶3类群体感应淬灭酶的来源、种类、信号分子类型及降解机理。本文为控制由AHLs介导的革兰氏阴性菌群体感应机制研究提供参考,也为实现通过群体感应淬灭作用控制革兰氏阴性菌导致的疾病提出一个新的思路。     

微生物共培养促进植物乳杆菌RX-8高效合成细菌素的调控机制

目的:植物乳杆菌RX-8是一株分离自中国传统泡菜的益生菌,该菌株具有产Ⅱb类细菌素植物乳杆菌素(Plantaricin)EF的优良特性,然而产量较低。目前采用与外源微生物共培养的方式提高细菌素产量,然而共培养体系中具体的调控机制尚不清楚。本研究通过敲除种内群体感应信号分子的关键基因plnA,构建种内群体感应缺失的共培养体系,探究微生物共培养对于细菌素高效合成的内在机制。方法:构建基因缺失突变菌株植物乳杆菌ΔRX-8,通过突变菌株和野生菌株与枯草芽孢杆菌1.8715在共培养过程中的生长差异、信号分子分泌量变化以及相关基因的表达量,探究种间群体感应系统促进细菌素高效合成的作用机制。结果:在敲除关键基因plnA后,共培养中突变菌株生长曲线上与野生菌株并无明显差异,而细菌素产量有所下降。与纯培养相比,共培养体系中群体感应信号分子AI-2的分泌量在前期显著增加,而后趋于一致,从菌株水平上看并无明显差异。纯培养体系中,突变菌株的双组分系统plnBCD基因表达量略低于野生菌株,细菌素合成基因plnEF的表达量同样有所下降,然而,并不影响种间信号分子AI-2合成的基因LuxS和pfs的相对表达量。结论:在种内信号分子缺失的共培养体系中,种间信号分子可以正常分泌,种间群体感应系统可以发挥作用,推测可能存在共用双组分系统,共同促进细菌素的高效合成。     

群体感应信号分子AI-2高产乳酸菌株筛选及特性研究

为深入研究乳酸菌的群体感应系统,对8株乳酸菌产群体感应信号分子自体诱导剂-2(Autoinducer-2,AI-2)情况进行了检测,7株乳酸菌中检测到明显的AI-2信号分子,且其中3株产生AI-2信号极强;对高产AI-2的菌株,通过RT-PCR对乳酸菌luxS基因和LDH基因的表达情况进行了检测,发现高产AI-2的乳酸菌其luxS基因表达较强,而LDH基因表达较弱;最后分析了酸性环境与乳酸菌信号分子AI-2产量的相关性,结果表明培养基酸性越强,乳酸菌产AI-2信号越强。luxS基因是AI-2信号合成的关键基因,AI-2信号分子提高了乳酸菌的耐酸性,有利于乳酸菌通过群体感应信号调控肠道内的酸碱平衡和菌群平衡。     

基于LuxS的群体感应系统在乳酸菌共培养中的研究

群体感应是微生物调控群体行为的重要方式,基于LuxS的群体感应系统广泛存在于各种属细菌中。AI-2作为LuxS系统的信号分子,在细胞交流中起到关键作用。LuxS系统在多种乳酸菌共同作用完成发酵任务以及某些乳酸菌行使益生功能中发挥了重要作用。文中综述了AI-2的合成途径、转导方式并重点阐述LuxS系统对乳酸菌共培养过程中蛋白表达和基因转录的影响。对LuxS系统进行深入研究,必将进一步揭示多种乳酸菌共同发酵以及其完成益生功能的机理,为从分子水平调控乳酸菌的发酵和益生行为提供了可能。     

酸胁迫条件对粪肠球菌Gr17代谢合成细菌素的影响

目的:粪肠球菌Gr17分离自中国传统发酵酸鱼，可以代谢合成新型广谱IIa类细菌素enterocin Gr17，有作为发酵食品功能性菌株的巨大应用潜力，然而该菌株应用于实际发酵环境时会面临各种胁迫条件，酸胁迫是其中主要的胁迫因素之一。本研究旨在探讨不同酸胁迫条件对菌株Gr17生长及代谢合成细菌素的影响。方法:在筛选可正向影响细菌素合成的酸胁迫条件参数基础上，测定该条件下细菌素生物合成相关基因的表达水平变化，分析其影响机制。结果:与正常生长条件pH 7.0相比，在pH 4.5~6.5的酸胁迫条件下，菌株Gr17的菌体密度会随pH值的下降而降低；pH 5.0～6.5的酸胁迫条件可明显正向提高细菌素的分泌合成量，其中pH 5.5的酸胁迫条件最为明显。在此条件下，细菌素生物合成相关ABC转运系统as-48H、as-48G、as-48F、as-48E基因表达在处理时间48 h内没有显著变化，种内群体感应调控系统自诱导肽基因entIP在8 h时表达量明显提高，双组分基因entPK、entR以及细菌素编码基因entGr17在12 h时表达量明显提高。结论:基于以上结果，推测pH 5.5的酸胁迫条件可以促进自诱导肽的分泌表达，正向调控种内群体感应系统，从而增加细菌素的合成。本研究结果对于从分子水平上全面揭示实际发酵环境中乳酸菌细菌素的合成调控行为，最大限度地提高产细菌素乳酸菌在发酵生产中的应用价值具有重要的科学和现实意义。     

乳酸菌细菌素研究进展及其在水产养殖和加工中的应用

乳酸菌细菌素是一种由乳酸菌在核糖体内合成、具有抑菌活性的多肽或蛋白质。由于乳酸菌通常被认为是安全的微生物,因此由它产生的细菌素受到了广泛地关注。目前由于大部分乳酸菌细菌素抑菌机理研究还不够深入,在一定程度上限制了它的发展和应用。本文对现有乳酸菌细菌素研究成果进行总结,并对细菌素进行了系统分类,阐述了各类乳酸菌细菌素对革兰氏阳性菌的作用机理,最后介绍了乳酸菌细菌素在水产养殖、水产品加工贮藏过程中的应用,旨在为乳酸菌细菌素的应用提供新的探索和基础理论依据。     

FUNDAMENTALS AND PERSPECTIVES FOR THE USE OF BACTERIOCINS PRODUCED BY LACTIC ACID BACTERIA IN MEAT PRODUCTS

Bacteriocins of lactic acid bacteria (LAB) are proteinaceous compounds that may present antimicrobial activity towards important foodborne pathogens and spoilage-related microflora. Due to these properties, bacteriocin-producing strains or purified bacteriocins have a great potential of use in biologically based food preservation systems. Despite the growing number of articles describing the isolation of bacteriocinogenic strains, genetic determinants for production, as well as the purification and biochemical characterization of these inhibitory substances, there are only limited reports of successful application of bacteriocins to meats.

This paper presents a critical review of the methods available for screening of bacteriocin-producing LAB strains from meats and also discusses the proposed mechanisms of action for LAB bacteriocins. Additionally, an overview of the Brazilian experience in the application of LAB bacteriocins to meats and meat products is given.     

FUNDAMENTALS AND PERSPECTIVES FOR THE USE OF BACTERIOCINS PRODUCED BY LACTIC ACID BACTERIA IN MEAT PRODUCTS

Bacteriocins of lactic acid bacteria (LAB) are proteinaceous compounds that may present antimicrobial activity towards important foodborne pathogens and spoilage-related microflora. Due to these properties, bacteriocin-producing strains or purified bacteriocins have a great potential of use in biologically based food preservation systems. Despite the growing number of articles describing the isolation of bacteriocinogenic strains, genetic determinants for production, as well as the purification and biochemical characterization of these inhibitory substances, there are only limited reports of successful application of bacteriocins to meats.

This paper presents a critical review of the methods available for screening of bacteriocin-producing LAB strains from meats and also discusses the proposed mechanisms of action for LAB bacteriocins. Additionally, an overview of the Brazilian experience in the application of LAB bacteriocins to meats and meat products is given.     

Lactobacillus salivarius: Bacteriocin and probiotic activity

Lactic acid bacteria (LAB) antimicrobial peptides typically exhibit antibacterial activity against food-borne pathogens, as well as spoilage bacteria. Therefore, they have attracted the greatest attention as tools for food biopreservation. In some countries LAB are already extensively used as probiotics in food processing and preservation. LAB derived bacteriocins have been utilized as oral, topical antibiotics or disinfectants. Lactobacillus salivarius is a promising probiotic candidate commonly isolated from human, porcine, and avian gastrointestinal tracts (GIT), many of which are producers of unmodified bacteriocins of sub-classes IIa, IIb and IId. It is a well-characterized bacteriocin producer and probiotic organism. Bacteriocins may facilitate the introduction of a producer into an established niche, directly inhibit the invasion of competing strains or pathogens, or modulate the composition of the microbiota and influence the host immune system. This review gives an up-to-date overview of all L. salivarius strains, isolated from different origins, known as bacteriocin producing and/or potential probiotic.     

Bacteriocin-based strategies for food biopreservation

Bacteriocins are ribosomally-synthesized peptides or proteins with antimicrobial activity, produced by different groups of bacteria. Many lactic acid bacteria (LAB) produce bacteriocins with rather broad spectra of inhibition. Several LAB bacteriocins offer potential applications in food preservation, and the use of bacteriocins in the food industry can help to reduce the addition of chemical preservatives as well as the intensity of heat treatments, resulting in foods which are more naturally preserved and richer in organoleptic and nutritional properties. This can be an alternative to satisfy the increasing consumers demands for safe, fresh-tasting, ready-to-eat, minimally-processed foods and also to develop "novel" food products (e.g. less acidic, or with a lower salt content). In addition to the available commercial preparations of nisin and pediocin PA-1/AcH, other bacteriocins (like for example lacticin 3147, enterocin AS-48 or variacin) also offer promising perspectives. Broad-spectrum bacteriocins present potential wider uses, while narrow-spectrum bacteriocins can be used more specifically to selectively inhibit certain high-risk bacteria in foods like Listeria monocytogenes without affecting harmless microbiota. Bacteriocins can be added to foods in the form of concentrated preparations as food preservatives, shelf-life extenders, additives or ingredients, or they can be produced in situ by bacteriocinogenic starters, adjunct or protective cultures. Immobilized bacteriocins can also find application for development of bioactive food packaging. In recent years, application of bacteriocins as part of hurdle technology has gained great attention. Several bacteriocins show additive or synergistic effects when used in combination with other antimicrobial agents, including chemical preservatives, natural phenolic compounds, as well as other antimicrobial proteins. This, as well as the combined use of different bacteriocins may also be an attractive approach to avoid development of resistant strains. The combination of bacteriocins and physical treatments like high pressure processing or pulsed electric fields also offer good opportunities for more effective preservation of foods, providing an additional barrier to more refractile forms like bacterial endospores as well. The effectiveness of bacteriocins is often dictated by environmental factors like pH, temperature, food composition and structure, as well as the food microbiota. Foods must be considered as complex ecosystems in which microbial interactions may have a great influence on the microbial balance and proliferation of beneficial or harmful bacteria. Recent developments in molecular microbial ecology can help to better understand the global effects of bacteriocins in food ecosystems, and the study of bacterial genomes may reveal new sources of bacteriocins.     

Bacteriocins: safe, natural antimicrobials for food preservation.

Bacteriocins are antibacterial proteins produced by bacteria that kill or inhibit the growth of other bacteria. Many lactic acid bacteria (LAB) produce a high diversity of different bacteriocins. Though these bacteriocins are produced by LAB found in numerous fermented and non-fermented foods, nisin is currently the only bacteriocin widely used as a food preservative. Many bacteriocins have been characterized biochemically and genetically, and though there is a basic understanding of their structure-function, biosynthesis, and mode of action, many aspects of these compounds are still unknown. This article gives an overview of bacteriocin applications, and differentiates bacteriocins from antibiotics. A comparison of the synthesis. mode of action, resistance and safety of the two types of molecules is covered. Toxicity data exist for only a few bacteriocins, but research and their long-time intentional use strongly suggest that bacteriocins can be safely used.     

安全的天然食品防腐剂细菌素

细菌素是细菌产生的可以杀死或抑制别的细菌生长的抗菌蛋白。许多乳酸菌(LAB)产生各种各样的细菌素，其中的尼生素是唯一的在食品中作为防腐剂广泛使用的细菌素。文章综述了以尼生素为重点对细菌素与抗生素的区别、活性细菌素分子的形成以及其在食品中的应用，并比较了这两种类型的分子的合成、作用模式、抵抗力和安全性。     

Pediocin PA-1的结构、生物合成与作用机制

乳酸菌素是乳酸菌通过核糖体合成机制产生的一类具有生物活性的蛋白质、多肽或前体多肽.最近将乳酸菌素分为三大类,其中Ⅱ a类类片球菌素是研究的热点,它的典型代表是Pediocin PA-1.Pedioein PA-1具有较强的抗单增李斯特菌特性和热稳定性,是一种具有广阔应用前景的食品添加剂.本文综述了Pediocin PA-1的结构、生物合成和作用机制,概述了国内外对Pediocin PA-1的研究进展和发展方向,以期对细菌素的深入研究和广泛应用起到抛砖引玉的作用.     

Application of bacteriocins in vegetable food biopreservation

Bacteriocins are generally recognized as "natural" compounds able to influence the safety and quality of foods. In the past years, a lot of works have been aimed to the detection, purification and characterisation of bacteriocins, as well as to their use in food preservation strategies. A list of review articles dealing with the application of bacteriocins to the protection of foods of animal origin is also available in literature, but it lacks for a summary on the utilization of bacteriocins in vegetable foods. These biopreservatives can be used in a number of ways in food systems and this paper mainly focuses on the state-of-the-art application of bacteriocins from lactic acid bacteria (LAB) to promote the microbial stability of both fermented and non-fermented vegetable food products using bacteriocinogenic strains as starter cultures, protective cultures or co-cultures and the employment of pure bacteriocins as food additives. In addition, applications of bacteriocins from non-LAB are also reviewed. The scopes of future directions of research are summarised.