RayFire Tools 组件分布和参数详解

1、Quorum- Sensing System in Microbes and Its ApplicationAbstract: Bacteria can coordinate group activities by cell -cell communicate with each other.Bacteria can sense the density change of their own population and other bacterial population around them according to the concentrationof given signal mo

2、lecules. The interbacterial communication system known as quorum sensing ( QS) utilizes hormones, such as acyl-homoserine lactone (AHL) , oligopeptideand furanosyl borate diester, to regulate bacterial gene expression Bacteria can adapt to the environment through opening interrelatedgenes expression

3、 when the signal molecules accumulate to the minimal threshold level. This regulation system is called quorum-sensing system in bacteria. Fungi also have signal molecules similar tobacteria to regulate some population level behaviors of fungus, and the system is also called quorum- sensing system in

4、 fungus. An in- depth study on quorum sensing system will help to understand the relations between the information exchangeand the behavior characteristics among one-celledmicrobes, and establish the connection between chemical signals and physiological behavior. It also has the practicalsignificanc

5、e of controlling some functions through artificial interference with or activation of the microbial quorum sensing system.Key Words:microbes;bacteria;fungus; quorum- sensing system; IntroductionIn 1970s, Nealson discovered the phenomenon ofbioluminescence controlled by the quorum sensing in marine b

6、acterium Vibrio fischeri and Hawaii Vibrio. Vibrio fischeri symbiosis with some marine fish, they provide light for marine fish , the intensity of light is closely related to Vibrio fischeri population density.( Bauer, W. D. and Robinson, J. B. 2002) Bacterial produce a signaling molecule (inducer)

7、and each bacterium also has a receptor for the inducer . When the inducer binds to the receptor, it activates the transcription ofcertain genes, including those responsible for the synthesis of theinducer itself.Quorum sensing is a cell-to-cell signaling mechanism in which bacteria coordinate the ex

8、pression of certain genes in response to their population density by producing small signal molecules (called auto inducers). (Brelles-Marino, G and Bedmar, E. J, 2001)In other words, cell density-dependentgene expression is denoted quorum sensing.Bacteria use quorum sensing to communicate both with

9、in and between species. Both species-specific and species-non specificautoinducers exist. These signals enable bacteria to distinguish low from high cell population density.The process of growth and development of a variety of quorum sensing is involved in the regulation of microorganisms, such as b

10、ioluminescence, antibiotic production, biofilm formation, and the generation of various enzymes. Quorum sensing is so closely related to human health effects, the Food and Drug.( Cha, C., Gao, et al.1998)QS system in bacterialQuorum Sensing in Gram-Negative Bacteria: The LuxI/LuxR ParadigmA typical

11、system in Gram-negative bacteria is LuxI / LuxR.(Fig1)It is regulated by two proteins called LuxI and LuxR. The LuxI protein is the autoinducer synthase, and it is responsible for production of the autoinducer signal molecule. The autoinducer is an acylated-homoserinelactone(AHL) .( Debler, E. W et

12、al2007)The family of N-acyl homoserine lactones is an importantclass of chemical signal molecules.(Parsek, M. R et al 2007) AHLs of different species differ in the carbon number of the acyl side chain,which usually contains between 4 and 14 carbons. It is free to diffuse out of the cell membrane. Th

13、e second protein, LuxR, is a regulatory protein that binds both the autoinducer and DNA.( Zhu, J et al2003)AHL is the main inducing factor in Gram-Negative Bacteria, and therefore it is the most in-depth research and comprehensive. Gram-negative bacteria that are unable to synthesize signal molecule

14、s are still able to perceive and respond to the AHL signal molecules.AHL generated within the cells to diffuse freely inside and outside the cell membrane, when accumulated to a certain concentration in the cytoplasm of binding several transcription factors regulating the expression of genes related

15、 to quorum sensing. Research shows that there are more than 50 kinds of Gram-negative bacteria which use this LuxI / LuxR systems to communicate between cells.( Williams, P, 2001)Fig1 : The LuxI/LuxR systeminGram-negativeGram-Positive Quorum Sensing :Peptide Signals Like Gram-negative bacteria, quor

16、um sensing also occurs in Gram-positive bacterial species. Quorum sensing in gram-positive bacteria regulates a number of physiological activities, including those involving pathogenesis and biofilm formation. Gram-positive bacteria communicate using polypeptides as autoinducers (AIP)for signaling.(

17、Fig2)Typically, the peptide signal molecule is secreted by a dedicated ATP-binding cassettetransporter.Most of the peptide are modified after processing the precursor peptide (add lactone, thiolactone ring, lanthionine or isoprene, etc.) after the formation of the amino acid residues 5-17 room chang

18、es.(Kapellos, G. E2007)After AIP produced and accumulated to a certain concentration in the cells, you can interact with the cell membrane as a signal molecule tyrosine kinase receptor molecules in the group dual signal transduction systems.AIP binding activates the receptor kinase activity of the d

19、ual system, so that the receptor phosphorylation and phosphorylation of the receptor to the cytoplasm pass regulator, through phosphorylation of the transcription regulator can activate the expression of related genes , AIP stimulates more molecules and result quorum sensing.(Pinto, U. M2007)Fig2 :A

20、 General Model for Gram-Positive Quorum SensingQS system in FungiIn recent years, research shows that there are also similar pheromone bacterial signaling molecules in fungus, and fungal mediated regulation of certain physiological behavior, and this process is also known fungal quorum sensing syste

21、m.Ethanol and benzene color alcohol farnesol are found in Human opportunistic pathogen Candida albicans,which were the first quorum sensing signal molecules founded in Fungi.(Li man ,et,al2007) The study found there are three kinds of quorum sensing signal molecules in Candida albicans: farnesol (E-

22、farnesol), p-hydroxyphenyl ethanol (tyrosol) and musk oleic acid (farnesoic acid).Among those, farnesol molecule is common.Itnot only can inhibit Candida albicans yeast-type transition from a mycelium nature, but also to induce gene expression in anti-oxidation effect against oxidative stress. Farne

23、sol concentration increases with cell density and growth, but the exact mechanism of Candida white farnesol sensor unclear. Farnesol affects Candida albicans biofilm formation, such as acacia was added to the medium the alcohol can effectively inhibit the formation of C. albicans biofilms.Other fung

24、i have been reported to have quorum sensing signal molecules, such as Cryptococcus neoformans has a molecule containing a signal peptide of 11 amino acids, which can promote the growth of fungi on a solid medium. These have shown that quorum sensing systems in fungi also play an important role, but

25、the current research is still in its infancy, and its mechanism for signaling molecules most fungi remains unclear.ApplicationSince QS system and its pathogenicity have a certain relationship in bacterial, then the signal molecules produced by bacteria could become a potential early diagnosis of bac

26、terial infection biomarkers. We can use a variety of signals with different chemical structures of molecules, with different sensing system to detect these signaling molecules. Therefore, the detection signal QS molecule may be a method of early diagnosis of bacterial infections.(Winzer, K.et al.200

27、1)Conventional antibiotics kill bacteria by interfering with essential functions like DNA, RNA and proteinsynthesis. The antibiotic resistance of the "super bacteria" appear, leading to an urgentneed to develop newAntibacterial drugs. Quorum quenching is a promising approach

28、.Some chemicals andenzymes have been identified. These include halogenated furanones fromthe seaweed Delisea pulchra, whichare structural mimics of quorum-sensing signals.Enzymes such as AHL-lactonase.(Xu, F and Byun, T et al 2003)Synthetic AHL and AIP analogues have been developed to compete with q

29、uorum-sensingsignals. These components have been tested, and has a good effect on antibiosis.( Francesco, B.2007).ConclusionsQuorum-sensing systems have been widelyadapted for a variety of uses by bacteria.We need to learn more about how quorumsensing is used by bacteria to commu

30、nicate both within and between species.We need to understand thevariety of signals produced and how information contained within those signals.The phenomenonof quorum sensing and how bacteria talk to each other is a fascinatingone,its study could revealthe secret between bacteria.Refe

31、rencesBauer, W. D., and Robinson, J. B., 2002.Disruption of quorum sensing by other organisms.Curr.Opin.Biotechnol, 13: 234-237.Brelles-Marino, G., and Bedmar, E. J, 2001.Detection, purificationand characterisation of quorum-sensing signal moleculesin plant-associated bacteria. Biotechnology, 91: 19

32、7-209.Cha, C., Gao, P, Chen, Y. C., Shaw, P. D., and Farrand, S. K.,1998. Production of acyl-homoserine lactone quorum-sensingsignals by gram-negative plantassociated bacteria. Mol. Plant-Microbe. Interact., 11: 1119-1129.Debler, E. W., Kaufmann, G. F., Kirchdoerfer, R. N., Mee, J. M.,Janda, K. D.,

33、and Wilson, I. A., 2007. Crystal structures of aquorum-quenching antibody. J. Mol. Biol., 368: 1392-1402.Francesco, B., Marian, G. and Natalio, K., 2007. Quorum sensingsystems .Theor. Comp. Sci., 371: 20-33.Gao, M., Teplitski, M., Robinson, J. B., and Bauer, W. D., 2003.Production of substances by M

34、edicagotruncatula that affectbacterial quorum sensing. Mol. Plant Microbe. Interact. 16:827-834.Kapellos, G. E., Alexiou, T. S., and Payatakes, A. C., 2007.Hierarchicalsimulator of biofilm growth and dynamics ingranular porous materials. Adv. Water Res., 30: 1648-1667Li man, Qiujian 2007.Quorum sensing system in Fungus. Microbiology China.Parsek, M. R., Val, D. L.,