N-Acyl homoserine lactone

N-Acyl homoserine lactones (Abbreviated as AHLs or N-AHLs) are a class of signaling molecules involved in bacterial quorum sensing. Quorum sensing is a method of communication between bacteria that enables the coordination of group-based behavior based on population density. They signal changes in gene expression, such as switching between the flagella gene and the gene for pili for the development of a biofilm.

General chemical structure of an N-acyl homoserine lactone

Formation

Bacterial signalling

In bacterial signalling, N-AHLs are produced within the bacterial cell and released into the environment. N-AHLs produced by different bacteria differ in the length of the R-group side-chain. Chain lengths vary from 4 to 18 carbon atoms and in the substitution of a carbonyl at the third carbon.[1]

Edman degradation

Homoserine lactone is also a product of the proteolytic reaction of cyanogen bromide (CNBR) with a methionine residue in a protein. This reaction is important for chemical sequencing of proteins, as the Edman degradation process is unable to sequence more than 70 consecutive residues.

In biology

General principles

The production signaling molecules are produced within the cell and are released into the environment. The resulting concentration of signaling molecules in the environment is dependent upon population density. Once the population density has reached a particular threshold, gene expression can begin. This allows bacteria to coordinate group-based behavior. It has also been suggested that N-AHLs alter local surface tension enough to create Marangoni flows which facilitate swarming and colony motility. [2]

History

Homoserine lactones were first discovered at Cornell University.[3]

Notes

Kumari, A.; Pasini, P.; Deo, S. K.; Flomenhoft, D.; Shashidhar, S.; Daunert, S. (2006). "Biosensing Systems for the Detection of Bacterial Quorum Signaling Molecules". Analytical Chemistry. 78 (22): 7603–7609. doi:10.1021/ac061421n. PMID 17105149.
Daniels, R.; Reynaert, S.; Hoekstra, H.; Verreth, C.; Janssens, J.; Braeken, K.; Fauvart, M.; Beullens, S.; Heusdens, C.; Lambrichts, I.; De Vos, D.E.; Vanderleyden, J.; Vermant J.; Michiels, J. (2006). "Quorum signal molecules as biosurfactants affecting swarming in Rhizobium etli" (PDF). PNAS. 103 (40): 14965–14970. Bibcode:2006PNAS..10314965D. doi:10.1073/pnas.0511037103. PMC 1595459. PMID 16990436.
Eberhard, A.; Burlingame, A. L.; Eberhard, C.; Kenyon, G. L.; Nealson, K. H.; Oppenheimer, N. J. (1981). "Structural identification of autoinducer of Photobacterium fischeri luciferase". Biochemistry. 20 (9): 2444–2449. doi:10.1021/bi00512a013. PMID 7236614.

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[Kumari2006-1] Kumari, A.; Pasini, P.; Deo, S. K.; Flomenhoft, D.; Shashidhar, S.; Daunert, S. (2006). "Biosensing Systems for the Detection of Bacterial Quorum Signaling Molecules". Analytical Chemistry. 78 (22): 7603–7609. doi:10.1021/ac061421n. PMID 17105149.

[Daniels2006-2] Daniels, R.; Reynaert, S.; Hoekstra, H.; Verreth, C.; Janssens, J.; Braeken, K.; Fauvart, M.; Beullens, S.; Heusdens, C.; Lambrichts, I.; De Vos, D.E.; Vanderleyden, J.; Vermant J.; Michiels, J. (2006). "Quorum signal molecules as biosurfactants affecting swarming in Rhizobium etli" (PDF). PNAS. 103 (40): 14965–14970. Bibcode:2006PNAS..10314965D. doi:10.1073/pnas.0511037103. PMC 1595459. PMID 16990436.

[Eberhard1981-3] Eberhard, A.; Burlingame, A. L.; Eberhard, C.; Kenyon, G. L.; Nealson, K. H.; Oppenheimer, N. J. (1981). "Structural identification of autoinducer of Photobacterium fischeri luciferase". Biochemistry. 20 (9): 2444–2449. doi:10.1021/bi00512a013. PMID 7236614.