PowerPoint Presentation On Quorum Sensing

PPT On Quorum Sensing

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Quorum Sensing Presentation Transcript:

1. Introduction To Quorum Sensing
- Cell to cell communication among procaryotes occurs by the exchange of small molecule often termed signal or signaling molecule. The exchanging of signaling molecule is essential in the co-ordination of gene expression of microbial population Quorum sensing is a type of decision-making process used by decentralized groups to coordinate behavior. Many species of bacteria use quorum sensing to coordinate their gene expression according to the local density of their population.

2. Quorum sensing was firstly discovered in the marine bioluminescent bacteria Vibrio fischeri , which produce light only if cells are at high density. It has been discovered that intercellular communication play an essential role in the regulation of gene whose products are needed for establishment of virulence, symbiosis , Biofilm production, plasmid transfer &morphological differentiation in a wide range of microbes.

3. Quorum Sensing
Fuqua et al. (1994) introduced the term quorum sensing to describe cell-cell signaling in bacteria Early 1990’s – homologs of LuxI were discovered in different bacterial species V. fischeri LuxI-LuxR signaling system becomes the paradigm for bacterial cell-cell communication

4. Methods & Mechanism
 For a molecule to classed as a quorum sensing signal there are number of important criteria that need to be met → The production of the quorum sensing signal should takes place during specific stage of growth or in response to particular environment changes. The quorum sensing should accumulate in extra cellular environment & be recognized by a specific bacterial receptor.

5. The accumulation of a critical threshold concentration of the quorum sensing signal should be stimulate a response. The cellular response should extend beyond the physiological changes required to metabolized.

6. MECHANISM OF QUORUM SENSING IN GRAM-VE BACTERIA
For quorum sensing bacteria produce certain signaling compounds called as Auto inducer. Eg. N- acyl homoserin lactos (AHL) They have a receptor that detect AHL. AHL binds with the receptor it activate transcription of certain genes & also those for inducer synthesis.

7. Mechanism
When only few bacterias are present then concentration of AHL decreases or if number of bacteria are present then concentration of AHL increases. When many kinds of bacterias are present concentration of inducer AHL posses the threshold. It causes a +ve feed back loop & receptor become active.

8. MECHANISM
Species of gram –ve bacteria signaling transfer a series of AHL & it’s concentration exceed a threshold i.e. the cell population over a certain no., the promoter plux transcription is activates.

 9. Quorum Sensing in Gram-Positive Bacteria Gram-positive bacteria utilizes modified oligopeptides as signaling molecules – secreted via an ATP-binding cassette (ABC) transporter complex Detectors for these signals are two-component signal transduction systems

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