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cancer
December 2009 
Quorum Signaling and Iron Scavenging
Posted on Nov 3rd, 2009
by 
Bird
Bird
Quorum signaling and iron scavenging are instrumental in virulence, and it seems at least some pathogens have coordinated these important processes through the use of a single molecule with dual functions. Against a backdrop of ever-increasing antibiotic resistance, insight into integrated systems such as these could prove invaluable.
... Microorganisms secrete a multitude of small molecule natural products. Probably the most famous of these is antibiotics. For nearly a century, mankind has manipulated bacteria to produce vast quantities of such molecules for use in the fight against infectious disease. However, some have questioned whether growth inhibitory concentrations of antibiotics are ever reached in the environment and whether antibiotics themselves could not be better described as bacterial communcation molecules. Many antibiotics, when given at subinhibitory concentrations, greatly alter bacterial expression patterns while have no effect on bacterial growth --characteristics that are reminiscent of more conventional QS molecules.
... For any population, reaching a high density confers multiple advantages, but is also associated with several costs. There is inherent safety in numbers, yet if individuals do not work together, competition threatens viability and scarce resources are wasted. Bacteria at high density are no different. Thus, the ability to evolve diffusible QS signals that have far-reaching effects in both distance and scope would have been as vital for organisms to compete in a primoridial world as it is today. In a world initially devoid of oxygen, iron was an abundant primitive terminal electron acceptor for cellular respiration. The appearance of oxygen introduced the need to solubilize iron oxides and protect against ensuing oxidative damage. As more species arose, so too did the need to compete with others for metabolites and niches ... It is now known that some bacterial communication molecules do more than just interact with regulatory proteins to initiate changes in gene expression. They can also sequester limited resources, intercalculate into membranes or kill other organisms. In this way, QS molecules can have a direct role in community protection and nutrient scavenging.
As research in this area develops, we predict that new meanings for the communication signals will be discovered. Contextual information can largely affect the interpretation of a word, and thus it will also be important to examine how the environment influences which role of a QS molecule prevails. Only when we fully understand the nuances of bacterial language will we be able to decipher the message and manipulate bacteria to our advantage.
"More than a signal: non-signaling properties of quorum sensing molecules"
Jeffrey W. Schertzer, Megan L. Boulette and Marvin Whiteley in
Trends in Microbiology, vol 7 no 5
... Microorganisms secrete a multitude of small molecule natural products. Probably the most famous of these is antibiotics. For nearly a century, mankind has manipulated bacteria to produce vast quantities of such molecules for use in the fight against infectious disease. However, some have questioned whether growth inhibitory concentrations of antibiotics are ever reached in the environment and whether antibiotics themselves could not be better described as bacterial communcation molecules. Many antibiotics, when given at subinhibitory concentrations, greatly alter bacterial expression patterns while have no effect on bacterial growth --characteristics that are reminiscent of more conventional QS molecules.
... For any population, reaching a high density confers multiple advantages, but is also associated with several costs. There is inherent safety in numbers, yet if individuals do not work together, competition threatens viability and scarce resources are wasted. Bacteria at high density are no different. Thus, the ability to evolve diffusible QS signals that have far-reaching effects in both distance and scope would have been as vital for organisms to compete in a primoridial world as it is today. In a world initially devoid of oxygen, iron was an abundant primitive terminal electron acceptor for cellular respiration. The appearance of oxygen introduced the need to solubilize iron oxides and protect against ensuing oxidative damage. As more species arose, so too did the need to compete with others for metabolites and niches ... It is now known that some bacterial communication molecules do more than just interact with regulatory proteins to initiate changes in gene expression. They can also sequester limited resources, intercalculate into membranes or kill other organisms. In this way, QS molecules can have a direct role in community protection and nutrient scavenging.
As research in this area develops, we predict that new meanings for the communication signals will be discovered. Contextual information can largely affect the interpretation of a word, and thus it will also be important to examine how the environment influences which role of a QS molecule prevails. Only when we fully understand the nuances of bacterial language will we be able to decipher the message and manipulate bacteria to our advantage.
"More than a signal: non-signaling properties of quorum sensing molecules"
Jeffrey W. Schertzer, Megan L. Boulette and Marvin Whiteley in
Trends in Microbiology, vol 7 no 5
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