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Topic: Quorum sensing

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	Terry's LJ
		In a process termed quorum sensing, bacteria use diffusible chemical signals to coordinate cell density-dependent gene expression.
		Quorum sensing is required for P. aeruginosa virulence in animal models.
		Curiously, quorum sensing-deficient variants, most of which carry a mutation in the gene encoding the central quorum sensing regulator lasR, are frequently isolated from acute and chronic infections.
	tdj.livejournal.com (1748 words)

	Quorum sensing - Wikipedia, the free encyclopedia
		Quorum sensing is the ability of bacteria to communicate and coordinate behavior via signaling molecules.
		The purpose of quorum sensing is to coordinate certain behaviour or actions between bacteria of the same kind, depending on their number.
		Quorum sensing was first observed in Vibrio fischeri, a bioluminiscent bacterium that lives as a symbiont in the light-producing organ of the Hawaiian bobtail squid.
	en.wikipedia.org /wiki/Quorum_sensing (716 words)

	Bonnie L. Bassler
		Quorum sensing, which involves the production, release, and subsequent detection of chemical signaling molecules called autoinducers, allows bacteria to regulate gene expression in response to changes in cell-population density.
		Processes controlled by quorum sensing are usually ones that are unproductive when undertaken by an individual bacterium but become effective when undertaken by the group.
		Our study of quorum sensing is providing insight into intra- and interspecies communication, population-level cooperation, and the design principles underlying signal transduction and information processing at the cellular level.
	www.hhmi.org /research/investigators/bassler.html (1392 words)

	DIALOGS WITH BACTERIA: QUORUM SENSING (Site not responding. Last check: 2007-10-13)
		This new branch of microbiology, quorum sensing, discovered by Bonny Bassler, professor of microbiology from Princeton, is dedicated to studying this phenomenon.
		This pathfinder addresses a broad audience, from undergraduate students to scholars who are interested in investigating quorum sensing either for their class projects or choosing the topic for their scientific research.
		This article describes the history of quorum sensing as a new branch of microbiology, and examines what the study of this phenomenon promises for the future of mankind.
	library.albany.edu /science/newinsci_quorum_sensing.htm (2921 words)

	Quorum Sensing
		The observation that stationary phase cultures of rhizobia capable of free-living nitrogen fixation contain non-growing cells may reflect a quorum sensing phenomenon leading to cessation of growth as the cells think they are within a nodule.
		Quorum sensing was first described in the bioluminescent bacterium Vibrio fischeri in which luminescence is expressed at high cell densities such as those found in the light organs of bioluminescent fishes.
		In a quorum sensing regulatory system, the bacterium produces an autoinducer molecule (AI) that is secreted to the surrounding medium.
	web.umr.edu /~djwesten/quorum_sensing.html (1406 words)

	Anamesa
		Quorum sensing uses small molecules as “votes.” Bacteria release small molecules derived from proteins or intermediates of cellular metabolism into their environment, in effect, creating a ‘chemical bath.’ Sensors detect and register these molecules as they accumulate in the environment.
		Quorum sensing thus ensures that the energetically expensive process of light production is initiated only when it promises to be effective, only when the bacteria are in sufficient numbers.
		Some quorum sensing systems use molecules that are specific to the species, and some systems use molecules sensed by many different species; it is the second type that allows cooperation in mixed communities.
	homepages.nyu.edu /~cts233/bacterial.html (801 words)

	quorum sensing
		fisheri, (2) bioluminescence is regulated by cell density or quorum sensing and is essentially a "social behavior" in bacteria, (3) quorum sensing is regulated by a diffusible factor.
		Quorum sensing has been identified in a large number of bacteria, both gram negative and gram positive, and regulates a plethora of responses.
		Regulation by quorum sensing may either be by activation or by repression of target pathways.
	plantbio.berkeley.edu /~courses/pmb148/quorum_sensing.htm (1640 words)

	CiteULike: Transition to Quorum Sensing in an Agrobacterium Population: A Stochastic Model. (Site not responding. Last check: 2007-10-13)
		Quorum sensing, which allows bacteria to activate genetic programs cooperatively, provides an instructive and tractable example illuminating the causal relationships between the molecular organization of gene networks and the complex phenotypes they control.
		Thus, we demonstrate that the transition to quorum sensing requires a much higher threshold cell density in liquid medium than in biofilm, and on this basis we hypothesize that in Agrobacterium quorum sensing serves as the detector of biofilm formation.
		Simulating the transition to quorum sensing in a liquid medium and biofilm, we explain the experimentally observed gradual manifestation of the quorum-sensing phenotype by showing that the transition of individual model cells into the "on" state is spread stochastically over a broad range of autoinducer concentrations.
	www.citeulike.org /article/339198 (625 words)

	Quorum Sensing
		Interference with quorum sensing is an novel approach to controlling bacterial growth and exoproduct expression, without resorting to conventional antibiotics.
		But furanone inhibitors of quorum sensing are being used to prevent experimental fouling of immersed polymers by marine biofilms.
		Quorum sensing provides an explanation for why some disease-causing virulence factors are not expressed during the early stages of encounter with the human host, allowing the bacterial fox to sneak under the chicken wire of the human defence system.
	e-tiology.com /quorum.htm (1081 words)

	Quorum-sensing bacteria discovery
		This discovery could be the first step toward human intervention in these signaling pathways, a phenomenon known as quorum sensing, either by thwarting activities of harmful bacteria or facilitating activities of helpful ones.
		Among human pathogens that use quorum sensing to estimate their population densities are Pseudomonas aeruginosa, which can cause serious infections, particularly in burn victims, and Yersinia pestis, the bubonic plague bacterium that killed millions during the Middle Ages.
		But the idea of bacterial quorum sensing, which came under serious consideration only in the last decade, is still as much theory as established fact, Winans cautioned.
	www.news.cornell.edu /Chronicle/02/7.11.02/quorum-sensing.html (785 words)

	Pharmainfo.net - Quorum Sensing- Communication Between Bacteria (Site not responding. Last check: 2007-10-13)
		Nowadays we use the term 'Quorum Sensing' (QS) to describe the phenomenon whereby the accumulation of signalling molecules enable a single cell to sense the number of bacteria (cell density).
		Quorum sensing is a cell density dependent gene regulation that allows bacterial cells to express certain or specific genes only when they reach high cell density.
		The bacteria are able to sense their cell density by monitoring the autoinducer concentration.
	www.pharmainfo.net /exclusive/reviews/quorum_sensing-_communication_between_bacteria (2951 words)

	Acyl-homoserine lactone quorum sensing in Gram-negative bacteria: A signaling mechanism involved in associations with ... (Site not responding. Last check: 2007-10-13)
		Acyl-homoserine lactone quorum sensing in Gram-negative bacteria: A signaling mechanism involved in associations with higher organisms -- Parsek and Greenberg 97 (16): 8789 -- Proceedings of the National Academy of Sciences
		Acyl-HSL quorum sensing is commonly found in Gram-negative bacteria that interact with plant and animal hosts.
		Quorum sensing and motility mediate interactions between Pseudomonas aeruginosa and Agrobacterium tumefaciens in biofilm cocultures.
	www.pnas.org /cgi/content/full/97/16/8789 (3953 words)

	Quorum sensing research
		The ability of bacterial cells to communicate with one another and thus spawn disease and develop resistance to antibiotics is the focus of a four-year research grant by USC scientists in public health and chemistry.
		The intricate chemistry of quorum sensing relates to the spread of disease, the resistance of infections in medicine, and the recently discovered high diversity of bacteria within certain natural environments.
		Common bacteria living on the surface of the intestines likely communicate with intestinal tissue using quorum sensing, and are thought to aid the intestines in protecting against pathogenic bacteria.
	www.sc.edu /usctimes/articles/2005-08/quorum_sensing.html (505 words)

	Quorum sensing in Vibrio cholerae - Nature Genetics
		Quorum sensing ensures that a sufficient number of bacteria are present to coordinate a virulence response that will overwhelm the host defenses
		As the bacterium multiplies, the quorum sensing signal molecules accumulate and activate the two quorum sensing systems, which inactivate LuxO.
		Incorporation of quorum sensing into a global network of regulatory responses may be required to increase selectivity and efficiency of a bacterium's response to the stresses it encounters in its growth environment.l
	www.nature.com /uidfinder/10.1038/ng1002-217 (1529 words)

	Quorum sensing in yeast (Site not responding. Last check: 2007-10-13)
		While quorum sensing is a well-established mode of intercellular communication in bacteria, its role in fungal systems is still emerging.
		Interestingly, these molecules elicited different effects in the yeast strain, Candida albicans, suggesting that these newly identified fungal quorum sensing signals are species-specific.
		"The ability of these quorum sensing molecules to stimulate growth or alter morphology could be important in pathogen virulence where the infecting organism is initially present in only small numbers of cells," adds Dr. Fink.
	www.eurekalert.org /pub_releases/2006-04/cshl-qsi041606.php (153 words)

	Talking to Themselves: Autoregulation and Quorum Sensing in Fungi -- Hogan 5 (4): 613 -- Eukaryotic Cell (Site not responding. Last check: 2007-10-13)
		Quorum sensing in bacteria: the LuxR-LuxI family of cell density-responsive transcriptional regulators.
		Quorum sensing in the dimorphic fungus Candida albicans is mediated by farnesol.
		Cell cycle dynamics and quorum sensing in Candida albicans chlamydospores are distinct from budding and hyphal growth.
	ec.asm.org /cgi/content/full/5/4/613 (4291 words)

	Quorum Sensing and the Lifestyle of Yersinia (Site not responding. Last check: 2007-10-13)
		Bacterial cell-to-cell communication ('quorum sensing') is mediated by structurally diverse, small diffusible signal molecules which regulate gene expression as a function of cell population density.
		AHL-dependent quorum sensing is highly conserved in both pathogenic and non-pathogenic members of the genus Yersinia.
		However the role of AHL-dependent quorum sensing in Yersinia pestis remains to be determined.
	www.horizonpress.com /cimb/abstracts/v8/01.html (188 words)

	Bugging the Bugs
		Using a chemical strategy dubbed quorum sensing, the bacteria manage to assess their own population size and distinguish themselves from all other kinds of bacteria.
		Besides its role in bioluminescence, quorum sensing is used by many kinds of bacteria to mastermind behaviors ranging from mating to releasing toxins and triggering disease, an activity known as virulence.
		Bassler's fascination with bacterial communication, quorum sensing, and luminescence began in 1990, while she was a graduate student.
	publications.nigms.nih.gov /findings/oct04/bugging.html (2174 words)

	Institute for Cellular Engineering
		Of these most widely studied is luxI/luxR quorum sensing system in Vibrio fischeri which uses 3-oxo-hexanoyl-homoserine lactone (3-oxo-C6-HSL) as the signal molecule.
		Based on quorum sensing mechanism, we have designed a two species synthetic ecosystem in which each one of the species requires a certain threshold density of the other for their survival, but the growth is independent.
		To capture intercellular signaling via the quorum sensing systems, the specific growth rate of each species is assumed to be nonlinearly dependent on the cell densities of the other species such that cell growth is severely retarded when the cell density of the other population is below a threshold value.
	www.umass.edu /ice/conference2006/abstracts/quorumsensing.html (417 words)

	OPED31 Quorum Sensing
		The larger the number of bacteria present the higher the level of the chemical, and this is detected by the surface receptors.
		One potential difficulty with this new approach is that if the quorum sensing systems are different among different bacteria then drugs developed would only work against a specific bacterium.
		However, some promising research at Princeton University has suggested that a single quorum sensing mechanism may be in use by most bacteria, and that bacteria have both a species-specific and a universal mechanism.
	www.sibelle.info /oped31.htm (485 words)

	Quorum Sensing
		They showed a segment on "Quorum Sensing" that, with a few changes in language, was an excellent explanation of "Smart Mobs".
		Quorum sensing is a biology term which describes what happens when enough of any one kind of bacteria get together.
		Biologists are actively exploring quorum sensing behavior, just as sociologists are actively exploring smart mob behavior.
	www.bizmediascience.com /2007/01/quorum_sensing.html (1083 words)

	Tiny Conspiracies - quorum sensing in bacteria Natural History - Find Articles
		By means of a process called quorum sensing, bacteria are able to detect when they are assembled in large numbers as opposed to when they are essentially alone.
		The phenomenon of quorum sensing was first discovered in two species of bioluminescent marine bacteria, Vibrio fischeri and V. harveyi.
		The squid senses the intensity of light from the sky and regulates its light organ accordingly, so that the animal, seen from below, more or less matches the background.
	www.findarticles.com /p/articles/mi_m1134/is_4_110/ai_74693738 (925 words)

	Homogenization (Site not responding. Last check: 2007-10-13)
		This phenomenon, called quorum sensing, apparently enables colonies to grow to sufficient size undetected by the immune system of the host organism.
		Using this model we show that quorum sensing works because of a biochemical switch between two stable steady solutions, one with low levels of autoinducer and one with high levels of autoinducer.
		movie is shown the growth of a colony with quorum sensing.
	www.math.utah.edu /~keener/research/quorum.html (292 words)

	Hebrew University researcher develops compounds to control bacteria
		By altering the molecular structure in these compounds, Jabbour was able to show that it is possible to control the quorum sensing responses in order to "deceive" the bacteria.
		Control over quorum sensing provides a promising avenue for future treatment of bacterial pathogenic activity without having to resort to antibiotic drugs with their accompanying disadvantages.
		On the other hand, enhancing quorum sensing could prove useful in agriculture, biotechnology and the food industry, where increasing bacterial activity would be beneficiary.
	www.eurekalert.org /pub_releases/2005-06/thuo-hur060205.php (462 words)

	Making sense of quorum sensing
		In the last decade or so, bacterial quorum sensing has been an important area of research.
		In case of a quorum formation, the bacterial cells move around by chemotaxis — in directions guided by other cells which produce and release chemoattractants.
		With a better understanding of quorum sensing and its associated mechanisms, scientists can block the process, or enhance it — depending which is favourable — paving the way for new therapies or drugs to various diseases.
	www.nus.edu.sg /corporate/research/gallery/research86.htm (685 words)

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