Quorum sensing

Event Date: 
Wednesday, June 24, 2015 - 19:15 - 20:00
University of New South Wales

The role of quorum sensing in chitin biodegradation


The 1011 ton global annual turnover of chitin has generated extensive interest in the regulation of chitin processing enzyme production in bacteria. Some bacteria regulate chitinase production by N-Acyl-L-homoserine lactone (AHL) mediated quorum sensing. In this study, a description of bacterial community succession during chitin particle colonisation and depolymerisation in activated sludge is presented. It was discovered that Betaproteobacteria and Bacteroidetes lineages dominate chitin colonisation in sludge and that AHLs bind to chitin at concentrations that upregulate AHL dependent transcription in bacterial cells associated with the chitin surface. There was no requirement for high cell density (a quorum) at the chitin surface. Further, N-Acetyl glucosamine (GlcNAc), the monomer of the chitin polymer, is shown to inhibit AHL dependent gene transcription representing a previously unrecognised mechanism by which the chitinase reaction product negatively regulates chitinase production. Evidence is presented supporting a role for both competitive inhibition at the AHL binding site of LuxR type transcriptional regulators and catabolite repression. The quorum sensing inhibitor activity of GlcNAc adds to its list of possible therapeutic benefits. 

JAMS Meeting Report – April 2012
by Thomas Jeffries
There was a good turnout on ANZAC day eve for three interesting talks, pizza and free local beer.
Kicking off the evening was John Lee, from the University of Georgia, with his ambitiously titled talk “Bioluminescence: The First 3000 Years”.  After a historical introduction to the long running observation of bioluminescence, via the discovery in 1672 that oxygen was necessary for bacterial luminescence, John told us how it was determined that bioluminescence is an enzyme mediated chemical reaction involving “luciferase” and "luciferine". In the modern age of biochemistry it was determined that ATP is the substrate in this reaction.  Following the elucidation of the structure of firefly luciferase in 1959, modern techniques (i.e. picosecond dynamic fluorescence spectroscopy and NMR) have allowed researchers to uncover the enzymes and processes involved in bioluminescence.  One of the most important of these enzymes Green-fluorescent protein (GFP) was discovered in jellyfish by Shimomura (who evidently has a lab at his house!) and led to his Nobel prize in 2008.  Due to GFP’s widespread use in research, it is regarded as one of the most important proteins in science.

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