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Quorum sensing- Howdy Bacteria!

Submitted by on November 8, 2012 – 5:07 PM

The society we live in comprises of a social structure and social policies which are encapsulated in the mode of life, hem of geographical territories, relationships, civil rights, religious duties and cultural boundaries. This encasement complements human as its building block. Once we are well aware of this social cooperation, we dwell better in life.

Recent studies and developments have concluded that not only humans are threaded into a social network; almost all species in the animal kingdom are involved one way or the other into a complex social behavior. This distinctive sense of communication and cooperation is also found in insects such as honey bees and ants. These creatures are a perfect example of the social networking. Though they do not generate tweets or update their statuses on Facebook, they have a much specialized mode of communication called Quorum sensing.

Apart from eukaryotes, bacterial cells also use Quorum sensing as a very intense communication system. Every bacterial cell has an inducer to give out the signals and a receptor to receive them. The signaling molecule or the inducer binds to the receptor and activates the transcription of certain genes. This includes the formation of more inducers. The process can only be initiated in high density population of bacteria. As soon as the threshold is reached in a bacterial population or colony, the whole process works as a social networking website, signaling even more bacterial cells. Sequentially, this helps the bacterial population to respond to environmental changes such as the invasion of immune system, toxins, antibiotics, etc. It results in increased aggressiveness, increased resistance and increased mobility. This increased commitment amongst the bacterial colonies may eventually show progressive inflammatory infection due to decreased responsiveness of bacterial cells to the immune system invasions.

According a recent study conducted at Linköping University, Sweden, it has been noted that a protein named IQGAP has been identified as a recipient of bacterial message as well as a transmitter. Hence, it is a “double agent” in the communication. The team headed by Dr. Elena Vikström used the gram negative pathogen Pseudomonas aeruginosa. It was postulated that this bacteria uses N-acylhomoserine lactones (AHL) which acts as a communication molecule and aids in quorum sensing. This results in a well organized determination of pathogenicity and production of biofilms. By appointing mass spectroscopy, the researchers studied this by forming a relationship among the AHL of Pseudomonas aeruginosa and the epithelial cells of the human intestines. According to Dr. Vikström, “The protein can both listen in on the bacteria’s communication and change the functions in its host cells”. When the message is sent out from the site of wound, the bacterial colonies are sprung into action, functioning like a multicellular organism. The team also found that the eukaryotic cells also respond to the quorum sensing. This process is called inter-kingdom signaling which acts through multi-signaling pathway. This study clearly proved that the quorum sensing mobility was dose and time dependant, while the infection propagation is at its height.

Apart from Pseudomonas aeruginosa, the mechanism of quorum sensing has also been observed in Vibrio fischeri, Escherichia coli, Salmonella enteric, Acinetobacter sp., Aeromonas sp., etc. Blocking the quorum sensing i.e. quorum inhibition may be a potential target of anti-bacterial chemotherapeutic drugs in the future. According to another study performed by Dr. Thomas Bjarnsholt at Centre for Biomedical Microbiology, BioCentrum, Technical University of Denmark, garlic is believed to experimentally block quorum sensing in Pseudomonas aeruginosa. This can be done by a process called Quorum Inhibition which works by disrupting the signaling process. Other similar researches have come to the surface that may prove productive in formulation of compounds that can disrupt the bacteria’s ability to communicate, and thereby killing its ability to turn pathogenic. Ultimately, the human body is saved from the perils of cell damage, inflammation, toxicity, or other detrimental effects of the bacteria. This gives the body enough time to eradicate the quorum sensing naturally through normal immune system functions. The Quorum Inhibition will drastically reduce the bacterial resistance.

Article by : Mehreen Khan, Pharm D. She works as a medical writer/editor at Genesis Communications, Pakistan. She has recently graduated from Baqai Medical University, Karachi, Pakistan and holds managing experience of 13 peer-reviewed scientific journals at Bentham Science Publishers, an international publishing company. She loves to blog on medical topics. Mehreen is the Managing Editor at JPMS Medical Blogs. She can be reached at [email protected]

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