Quorum sensing是一種細菌會偵測族群密度而改變性狀的現象，藉由分泌一些被稱為autoinducer的信號分子並偵測其濃度來達成。Autoinducer-2 (AI-2)是一種通用於多種細菌間的信號分子，由LuxS所合成，只要具有luxS基因都有可能分泌AI-2。Lactobacillus casei ATCC 334是一株基因體全定序的乳酸菌，具有luxS基因，也可偵測到AI-2活性。為了研究AI-2在Lactobacillus casei ATCC 334會控制哪些性狀，以直接添加AI-2的方式來做研究。所以我們純化了LuxS的重組蛋白，以之合成AI-2並純化之。以GC-MS及NMR氫原子光譜確認了合成的AI-2與文獻中記載的一樣。以AI-2測試是否會影響乳酸菌的biofilm、抑菌力、抗氧化力三種性狀，結果是不會影響。

Quorum sensing is a phenomenon with which bacteria detect high population density and change their phenotype. Bacteria secrete some signal molecules called autoinducer, then detect autoinducer concentration to achieve quorum sensing. Autoinducer-2 (AI-2) is a signal molecule in common use among many bacterial species, and it is synthesized by LuxS . If there is a luxS gene in a bacterial genome, the bacteria may secrete the AI-2. Lactobacillus casei ATCC 334 is a lactic acid bacteria of which the genome has been sequenced completely. It has luxS gene, and AI-2 activity can be detected . In order to study which phenotype is controlled by AI-2 in Lactobacillus casei ATCC 334, we directly added AI-2 to incubate Lactobacillus casei ATCC 334. We purified recombinant protein LuxS and used it to synthesize AI-2 for purification. We used GC-MS and NMR proton spectrum to determine whether the enzyme product was AI-2. We tested the effects of AI-2 on three phenotypes：biofilm、antibacterial ability and antioxidative ability. There is no significant difference.

1. Redfield, R.J., Is quorum sensing a side effect of diffusion sensing? Trends Microbiol, 2002. 10(8): p. 365-70.
2. Williams, P., et al., Look who's talking: communication and quorum sensing in the bacterial world. Philos Trans R Soc Lond B Biol Sci, 2007. 362(1483): p. 1119-34.
3. Nealson, K.H., Autoinduction of bacterial luciferase. Occurrence, mechanism and significance. Arch Microbiol, 1977. 112(1): p. 73-9.
4. Bassler, B.L., M. Wright, and M.R. Silverman, Multiple signalling systems controlling expression of luminescence in Vibrio harveyi: sequence and function of genes encoding a second sensory pathway. Mol Microbiol, 1994. 13(2): p. 273-86.
5. Winzer, K., K.R. Hardie, and P. Williams, Bacterial cell-to-cell communication: sorry, can't talk now - gone to lunch! Curr Opin Microbiol, 2002. 5(2): p. 216-22.
6. Nealson, K.H., T. Platt, and J.W. Hastings, Cellular control of the synthesis and activity of the bacterial luminescent system. J Bacteriol, 1970. 104(1): p. 313-22.
7. Fuqua, W.C., S.C. Winans, and E.P. Greenberg, Quorum sensing in bacteria: the LuxR-LuxI family of cell density-responsive transcriptional regulators. J Bacteriol, 1994. 176(2): p. 269-75.
8. Eberhard, A., Inhibition and activation of bacterial luciferase synthesis. J Bacteriol, 1972. 109(3): p. 1101-5.
9. Eberhard, A., et al., Structural identification of autoinducer of Photobacterium fischeri luciferase. Biochemistry, 1981. 20(9): p. 2444-9.
10. Swift, S., et al., Quorum sensing in Aeromonas hydrophila and Aeromonas salmonicida: identification of the LuxRI homologs AhyRI and AsaRI and their cognate N-acylhomoserine lactone signal molecules. J Bacteriol, 1997. 179(17): p. 5271-81.
11. Lynch, M.J., et al., The regulation of biofilm development by quorum sensing in Aeromonas hydrophila. Environ Microbiol, 2002. 4(1): p. 18-28.
12. Swift, S., et al., Quorum sensing-dependent regulation and blockade of exoprotease production in Aeromonas hydrophila. Infect Immun, 1999. 67(10): p. 5192-9.
13. Zhang, L., et al., Agrobacterium conjugation and gene regulation by N-acyl-L-homoserine lactones. Nature, 1993. 362(6419): p. 446-8.
14. Piper, K.R., S. Beck von Bodman, and S.K. Farrand, Conjugation factor of Agrobacterium tumefaciens regulates Ti plasmid transfer by autoinduction. Nature, 1993. 362(6419): p. 448-50.
15. Papagianni, M., Ribosomally synthesized peptides with antimicrobial properties: biosynthesis, structure, function, and applications. Biotechnol Adv, 2003. 21(6): p. 465-99.
16. Cheigh, C.I. and Y.R. Pyun, Nisin biosynthesis and its properties. Biotechnol Lett, 2005. 27(21): p. 1641-8.
17. Baranova, I.P. and N.S. Egorov, [Biosynthesis and properties of the polypeptide antibiotic nisin]. Nauchnye Doki Vyss Shkoly Biol Nauki, 1973. 112(4): p. 106-15.
18. Kuipers, O.P., et al., Autoregulation of nisin biosynthesis in Lactococcus lactis by signal transduction. J Biol Chem, 1995. 270(45): p. 27299-304.
19. Dodd, H.M., et al., Molecular analysis of the regulation of nisin immunity. Microbiology, 1996. 142 ( Pt 9): p. 2385-92.
20. Ji, G., R.C. Beavis, and R.P. Novick, Cell density control of staphylococcal virulence mediated by an octapeptide pheromone. Proc Natl Acad Sci U S A, 1995. 92(26): p. 12055-9.
21. Ji, G., R. Beavis, and R.P. Novick, Bacterial interference caused by autoinducing peptide variants. Science, 1997. 276(5321): p. 2027-30.
22. Dunman, P.M., et al., Transcription profiling-based identification of Staphylococcus aureus genes regulated by the agr and/or sarA loci. J Bacteriol, 2001. 183(24): p. 7341-53.
23. P, M.D., et al., Structure, activity and evolution of the group I thiolactone peptide quorum-sensing system of Staphylococcus aureus. Mol Microbiol, 2001. 41(2): p. 503-12.
24. Tortosa, P. and D. Dubnau, Competence for transformation: a matter of taste. Curr Opin Microbiol, 1999. 2(6): p. 588-92.
25. De Keersmaecker, S.C., K. Sonck, and J. Vanderleyden, Let LuxS speak up in AI-2 signaling. Trends Microbiol, 2006. 14(3): p. 114-9.
26. Surette, M.G., M.B. Miller, and B.L. Bassler, Quorum sensing in Escherichia coli, Salmonella typhimurium, and Vibrio harveyi: a new family of genes responsible for autoinducer production. Proc Natl Acad Sci U S A, 1999. 96(4): p. 1639-44.
27. Kaper, J.B. and V. Sperandio, Bacterial cell-to-cell signaling in the gastrointestinal tract. Infect Immun, 2005. 73(6): p. 3197-209.
28. Duerre, J.A. and C.H. Miller, Cleavage of S-ribosyl-L-homocysteine by extracts from Escherichia coli. J Bacteriol, 1966. 91(3): p. 1210-7.
29. Duerre JA, B.D., Salisbury L, Structure elucidation of a carbohydrate derived from S-ribosylhomocysteine by enzymatic cleavage. Fed Proc, 1971. 30: p. 1067.
30. Vendeville, A., et al., Making 'sense' of metabolism: autoinducer-2, LuxS and pathogenic bacteria. Nat Rev Microbiol, 2005. 3(5): p. 383-96.
31. Gordon, R.K., et al., S-adenosylmethionine and its sulfur metabolites. Methods Enzymol, 1987. 143: p. 191-5.
32. Chen, X., et al., Structural identification of a bacterial quorum-sensing signal containing boron. Nature, 2002. 415(6871): p. 545-9.
33. Miller, S.T., et al., Salmonella typhimurium recognizes a chemically distinct form of the bacterial quorum-sensing signal AI-2. Mol Cell, 2004. 15(5): p. 677-87.
34. Winzer, K., et al., LuxS: its role in central metabolism and the in vitro synthesis of 4-hydroxy-5-methyl-3(2H)-furanone. Microbiology, 2002. 148(Pt 4): p. 909-22.
35. Sun, J., et al., Is autoinducer-2 a universal signal for interspecies communication: a comparative genomic and phylogenetic analysis of the synthesis and signal transduction pathways. BMC Evol Biol, 2004. 4: p. 36.
36. Erkki Honkanen, T.P.a.T.H., The aroma of finnish wild raspberries, Rubus idaeus, L. Zeitschrift f□r Lebensmitteluntersuchung und -Forschung A, 1980. 171(3): p. 180-182.
37. H. Idstein, P.S., Volatile constituents from guava (Psidium guajava, L.). J. Agric. Food Chem, 1985. 33: p. 138-143.
38. R.G. Buttery, G.R.T., L.C. Ling, Furaneol: odor threshold and importance to tomato aroma. J. Agric. Food Chem, 1995. 43: p. 1638-1640.
39. C.H.T. Tonsbeek, E.B.K., A.S.M. Van der Zijden, J.A. Losekoot, Components contributing to beef flavour; natural precursors of4-hydroxy-5-methyl-3(2H)-furanone in beef broth. J. Agric. Food Chem, 1969. 17: p. 397-400.
40. Cerny, C. and T. Davidek, Formation of aroma compounds from ribose and cysteine during the Maillard reaction. J Agric Food Chem, 2003. 51(9): p. 2714-21.
41. Mottram, D.S. and I.C. Nobrega, Formation of sulfur aroma compounds in reaction mixtures containing cysteine and three different forms of ribose. J Agric Food Chem, 2002. 50(14): p. 4080-6.
42. Hauck, T., et al., Alternative pathway for the formation of 4,5-dihydroxy-2,3-pentanedione, the proposed precursor of 4-hydroxy-5-methyl-3(2H)-furanone as well as autoinducer-2, and its detection as natural constituent of tomato fruit. Biochim Biophys Acta, 2003. 1623(2-3): p. 109-19.
43. Tavender, T.J., et al., LuxS-independent formation of AI-2 from ribulose-5-phosphate. BMC Microbiol, 2008. 8(1): p. 98.
44. Hauck, T., et al., Formation of 5-methyl-4-hydroxy-3[2H]-furanone in cytosolic extracts obtained from Zygosaccharomyces rouxii. J Agric Food Chem, 2003. 51(5): p. 1410-4.
45. Frias, J., E. Olle, and M. Alsina, Periodontal pathogens produce quorum sensing signal molecules. Infect Immun, 2001. 69(5): p. 3431-4.
46. DeLisa, M.P., et al., DNA microarray-based identification of genes controlled by autoinducer 2-stimulated quorum sensing in Escherichia coli. J Bacteriol, 2001. 183(18): p. 5239-47.
47. Yuan, L., J.D. Hillman, and A. Progulske-Fox, Microarray analysis of quorum-sensing-regulated genes in Porphyromonas gingivalis. Infect Immun, 2005. 73(7): p. 4146-54.
48. Joyce, E.A., et al., LuxS is required for persistent pneumococcal carriage and expression of virulence and biosynthesis genes. Infect Immun, 2004. 72(5): p. 2964-75.
49. Sperandio, V., et al., Quorum sensing controls expression of the type III secretion gene transcription and protein secretion in enterohemorrhagic and enteropathogenic Escherichia coli. Proc Natl Acad Sci U S A, 1999. 96(26): p. 15196-201.
50. Petersen, F.C., et al., LuxS-mediated signalling in Streptococcus anginosus and its role in biofilm formation. Antonie Van Leeuwenhoek, 2006. 90(2): p. 109-21.
51. Lebeer, S., et al., Functional analysis of luxS in the probiotic strain Lactobacillus rhamnosus GG reveals a central metabolic role important for growth and biofilm formation. J Bacteriol, 2007. 189(3): p. 860-71.
52. Doherty, N., et al., Functional analysis of luxS in Staphylococcus aureus reveals a role in metabolism but not quorum sensing. J Bacteriol, 2006. 188(8): p. 2885-97.
53. Shao, H., R.J. Lamont, and D.R. Demuth, Autoinducer 2 is required for biofilm growth of Aggregatibacter (Actinobacillus) actinomycetemcomitans. Infect Immun, 2007. 75(9): p. 4211-8.
54. Gonzalez Barrios, A.F., et al., Autoinducer 2 controls biofilm formation in Escherichia coli through a novel motility quorum-sensing regulator (MqsR, B3022). J Bacteriol, 2006. 188(1): p. 305-16.
55. Bassler, B.L., E.P. Greenberg, and A.M. Stevens, Cross-species induction of luminescence in the quorum-sensing bacterium Vibrio harveyi. J Bacteriol, 1997. 179(12): p. 4043-5.
56. Schauder, S., et al., The LuxS family of bacterial autoinducers: biosynthesis of a novel quorum-sensing signal molecule. Mol Microbiol, 2001. 41(2): p. 463-76.
57. De Keersmaecker, S.C., et al., Chemical synthesis of (S)-4,5-dihydroxy-2,3-pentanedione, a bacterial signal molecule precursor, and validation of its activity in Salmonella typhimurium. J Biol Chem, 2005. 280(20): p. 19563-8.
58. Semmelhack, M.F., et al., Boron binding with the quorum sensing signal AI-2 and analogues. Org Lett, 2004. 6(15): p. 2635-7.
59. Frezza, M., et al., Ac2-DPD, the bis-(O)-acetylated derivative of 4,5-dihydroxy-2,3-pentanedione (DPD) is a convenient stable precursor of bacterial quorum sensing autoinducer AI-2. Bioorg Med Chem Lett, 2007. 17(5): p. 1428-31.
60. Meijler, M.M., et al., Synthesis and biological validation of a ubiquitous quorum-sensing molecule. Angew Chem Int Ed Engl, 2004. 43(16): p. 2106-8.
61. Turovskiy, Y. and M.L. Chikindas, Autoinducer-2 bioassay is a qualitative, not quantitative method influenced by glucose. J Microbiol Methods, 2006. 66(3): p. 497-503.
62. McKenzie, K.M., et al., A furanosyl-carbonate autoinducer in cell-to-cell communication of V. harveyi. Chem Commun (Camb), 2005(38): p. 4863-5.
63. Zhu, J. and D. Pei, A LuxP-based fluorescent sensor for bacterial autoinducer II. ACS Chem Biol, 2008. 3(2): p. 110-9.
64. Sperandio, V., et al., Bacteria-host communication: the language of hormones. Proc Natl Acad Sci U S A, 2003. 100(15): p. 8951-6.
65. Miller, C.H. and J.A. Duerre, S-ribosylhomocysteine cleavage enzyme from Escherichia coli. J Biol Chem, 1968. 243(1): p. 92-7.
66. Ljungh, A. and T. Wadstrom, Lactic acid bacteria as probiotics. Curr Issues Intest Microbiol, 2006. 7(2): p. 73-89.
67. Wells, J.M. and A. Mercenier, Mucosal delivery of therapeutic and prophylactic molecules using lactic acid bacteria. Nat Rev Microbiol, 2008. 6(5): p. 349-62.
68. http://microbialgenomics.energy.gov/ Microbial Genomics Research U.S. Department of Energy Office of Science Office of Biological and Environmental Research Sequencing and exploiting entire genomes of microorganisms having potential usefulness in DOE mission-related research.
69. Frees, D., F.K. Vogensen, and H. Ingmer, Identification of proteins induced at low pH in Lactococcus lactis. Int J Food Microbiol, 2003. 87(3): p. 293-300.
70. Azcarate-Peril, M.A., et al., Microarray analysis of a two-component regulatory system involved in acid resistance and proteolytic activity in Lactobacillus acidophilus. Appl Environ Microbiol, 2005. 71(10): p. 5794-804.
71. Di Cagno, R., et al., Cell-cell communication in sourdough lactic acid bacteria: a proteomic study in Lactobacillus sanfranciscensis CB1. Proteomics, 2007. 7(14): p. 2430-46.
72. Tannock, G.W., et al., Ecological behavior of Lactobacillus reuteri 100-23 is affected by mutation of the luxS gene. Appl Environ Microbiol, 2005. 71(12): p. 8419-25.
73. Jelcic, I., et al., Repression of the locus of the enterocyte effacement-encoded regulator of gene transcription of Escherichia coli O157:H7 by Lactobacillus reuteri culture supernatants is LuxS and strain dependent. Appl Environ Microbiol, 2008. 74(10): p. 3310-4.
74. Mahmoud Ghannoum, G.A.O.T., Microbial biofilms 2004.
75. Drider, D., et al., The continuing story of class IIa bacteriocins. Microbiol Mol Biol Rev, 2006. 70(2): p. 564-82.
76. Quadri, L.E., Regulation of antimicrobial peptide production by autoinducer-mediated quorum sensing in lactic acid bacteria. Antonie Van Leeuwenhoek, 2002. 82(1-4): p. 133-45.
77. Merritt, J., et al., LuxS controls bacteriocin production in Streptococcus mutans through a novel regulatory component. Mol Microbiol, 2005. 57(4): p. 960-9.
78. Sztajer, H., et al., Autoinducer-2-regulated genes in Streptococcus mutans UA159 and global metabolic effect of the luxS mutation. J Bacteriol, 2008. 190(1): p. 401-15.
79. Gatof, D. and D. Ahnen, Primary prevention of colorectal cancer: diet and drugs. Gastroenterol Clin North Am, 2002. 31(2): p. 587-623, xi.
80. Marnett, L.J., Oxy radicals, lipid peroxidation and DNA damage. Toxicology, 2002. 181-182: p. 219-22.
81. Bruce, W.R., A. Giacca, and A. Medline, Possible mechanisms relating diet and risk of colon cancer. Cancer Epidemiol Biomarkers Prev, 2000. 9(12): p. 1271-9.
82. Lin, M.Y. and C.L. Yen, Antioxidative ability of lactic acid bacteria. J Agric Food Chem, 1999. 47(4): p. 1460-6.
83. Lin, M.Y. and F.J. Chang, Antioxidative effect of intestinal bacteria Bifidobacterium longum ATCC 15708 and Lactobacillus acidophilus ATCC 4356. Dig Dis Sci, 2000. 45(8): p. 1617-22.
84. Jiang, T., A. Mustapha, and D.A. Savaiano, Improvement of lactose digestion in humans by ingestion of unfermented milk containing Bifidobacterium longum. J Dairy Sci, 1996. 79(5): p. 750-7.
85. Annuk, H., et al., Characterization of intestinal lactobacilli as putative probiotic candidates. J Appl Microbiol, 2003. 94(3): p. 403-12.
86. Sambrook, J. and D.W. Russell, Molecular cloning : a laboratory manual. 3rd ed. 2001, Cold Spring Harbor, N.Y.: Cold Spring Harbor Laboratory Press.
87. Semmelhack, M.F., et al., An expeditious synthesis of DPD and boron binding studies. Org Lett, 2005. 7(4): p. 569-72.
88. Zhu, J., et al., S-Ribosylhomocysteinase (LuxS) is a mononuclear iron protein. Biochemistry, 2003. 42(16): p. 4717-26.
89. Turcotte, C., et al., A rapid turbidometric microplate bioassay for accurate quantification of lactic acid bacteria bacteriocins. Int J Food Microbiol, 2004. 90(3): p. 283-93.
90. Huang, D., B. Ou, and R.L. Prior, The chemistry behind antioxidant capacity assays. J Agric Food Chem, 2005. 53(6): p. 1841-56.
91. Oyaizu, M., Antioxidative activity of browning products of glucosamine fractionated by organic solvent and thin-layer chromatography. Journal of the Japanese Society for Food Science and Technology, 1988. 35(11): p. 771-775.