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Post by aqt on Jan 13, 2009 13:59:45 GMT -5
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Post by aqt on Jan 13, 2009 15:51:12 GMT -5
quorum sensing
Mechanism Bacteria that use quorum sensing constantly produce and secrete certain signaling molecules (called autoinducers or pheromones). These bacteria also have a receptor that can specifically detect the signaling molecule (inducer). When the inducer binds the receptor, it activates transcription of certain genes, including those for inducer synthesis. There is a low likelihood of a bacterium detecting its own secreted inducer. Thus, in order for gene transcription to be activated, the cell must encounter signaling molecules secreted by other cells in its environment. When only a few other bacteria of the same kind are in the vicinity, diffusion reduces the concentration of the inducer in the surrounding medium to almost zero, so the bacteria produce little inducer. However, as the population grows the concentration of the inducer passes a threshold, causing more inducer to be synthesized. This forms a positive feedback loop, and the receptor becomes fully activated. Activation of the receptor induces the up regulation of other specific genes, causing all of the cells to begin transcription at approximately the same time. This coordinated behavior of bacterial cells can be useful in a variety of situations. For instance, the bioluminescent luciferase produced by V. fischeri would not be visible if it were produced by a single cell. By using quorum sensing to limit the production of luciferase to situations when cell populations are large, V. fischeri cells are able to avoid wasting energy on the production of useless products.
Examples
Vibrio fischeri Quorum sensing was first observed in Vibrio fischeri, a bioluminiscent bacterium that lives as a mutualistic symbiont in the photophore (or light-producing organ) of the Hawaiian bobtail squid. When V. fischeri cells are free-living (or planktonic), the autoinducer is at low concentration and thus cells do not luminesce. However, when they are highly concentrated in the photophore (about 1011 cells/ml) transcription of luciferase is induced, leading to bioluminescence.
aqt
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Post by aqt on Jan 13, 2009 16:07:37 GMT -5
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Post by aqt on Jan 13, 2009 16:09:39 GMT -5
web photo of vibrio like organism attached to a spherical bacterial cell
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Post by aqt on Jan 13, 2009 16:10:12 GMT -5
my photo of what I found on bedsheets aqt
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Post by aqt on Jan 13, 2009 16:22:39 GMT -5
web shot of vibrio
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Post by aqt on Mar 11, 2009 10:04:21 GMT -5
The SXT element is a Vibrio cholerae-derived ICE (integrating and conjugative element), which has also been referred to as a conjugative transposon transposon /trans·po·son/ (trans-po´zon) a small mobile genetic (DNA) element that moves around the genome or to other genomes within the same cell, usually by copying itself to a second site but sometimes by splicing itself out of its (1) or a constin (2). ICEs excise from the chromosomes of their hosts, transfer to a new host through conjugation, and then integrate into the chromosome againwww.thefreelibrary.com/Vibrio+cholerae+SXT+element,+Laos-a0129363013 VIBRIO LIKE ELEMENT PER SILENTSUPERBUG CLUES aqt
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Post by aqt on Mar 11, 2009 11:48:20 GMT -5
Bioinformatics analyses show the presence of a novel insertion sequence-like element in the CTXPhi phage of Vibrio cholerae. The solitary open reading frame ... www.ncbi.nlm.nih.gov/pubmed/16539534
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Post by aqt on Mar 11, 2009 12:08:56 GMT -5
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Post by aqt on Mar 11, 2009 12:10:25 GMT -5
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Post by aqt on Mar 11, 2009 12:19:36 GMT -5
Another vibrio-like organism, Helicobacter pylori causes duodenal and gastric ulcers and gastric cancer. It is also reclassified into the class Epsilonproteobacteria family Helicobacteraceae www.textbookofbacteriology.net/cholera.html
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Post by aqt on Mar 11, 2009 12:25:34 GMT -5
This analysis in Choromobacterium violaceum has revealed four prophage and 12 insertion sequences, suggesting genetic exchange with several other bacterial ...www.ncbi.nlm.nih.gov/pubmed/15100989Choromobacterium violaceum is a vibrio like element
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Post by aqt on Mar 24, 2010 15:54:43 GMT -5
quorum sensing for sure could be vibrio gene/chromosome/enzyme/protein? ?? aqt
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Post by Dave B on Oct 28, 2016 9:13:30 GMT -5
Hi there, I was wondering if anyone can help me. I have been trying to get the vibrio harveyi bioluminescne assay off the ground and I can't get it to work. The positive control isn't lighting up the samples. Is there anyone on this board that has sucessfully carried out the assay and if so could I bounce some questions off you?
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