Biolog Phenotype MicroArray
     Serious Technology for Serious Microbiology January 2012
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Phenotype MicroArrays Used to Study Intrinsic Mechanisms of Antibiotic Resistance

Phenotype MicroArray
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What do MDR's , nitric oxide, hydrogen sulfide, and proteases, have in common? They are all enlisted to resist antibiotics by increasing drug efflux, mitigating oxidative stress caused by many classes of antibiotics, repairing oxidative damage due to antibiotic exposure. As cells strive to restore homeostasis they produce antioxidant cytoprotective gasotransmitters (NO and H2S) to mitigate oxidative stress and use proteolysis to degrade accumulating hydroxylated misfolded proteins. Three new papers and a "Perspectives" article, illustrate the use Phenotype MicroArray technology in the study of these intrinsic antibiotic resistance mechanisms.
 
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  Antioxidant Strategies to Tolerate Antibiotics
Convergent antioxidant strategies are triggered by the starvation-signaling stringent response and by several classes of antibiotics. The review highlights the similarities of these tolerance mechanisms and proposes potential antibiotic potentiation strategies.
 
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 H2S: A Universal Defense Against Antibiotics in Bacteria
Shatalin, Nudler, and colleagues found that cystathionine b-synthase (CBS), cystathionine g-lyase (CSE), and 3-mercaptopyruvate sulfurtransferase (3MST) contribute to H2S production in many bacterial species. They hypothesized that H2S could act as a cytoprotective gasotransmitter. Using Phenotype MicroArrays, they found that as predicted the 3MST, CBS, and CSE mutants were hyper sensitive to a wide array of diverse antibiotics. This is the second gasotransmitter (the other one being NO) involved in antibiotic resistance that these authors have discovered with the aid of Phenotype MicroArray technology.
 
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 Membrane Proteases and Aminoglycoside Antibiotic Resistance
In order to understand the tobramycin sensitivity of the amgRS mutant, Manoil and colleagues identified seven amgRS regulated genes that represent redundant functions responsible tobramycin resistance. The E. coli homologues of two of these genes are involved in proteolysis. To further explore the role of proteolysis in antibiotic resistance, 61 protease mutants were screened for tobramycin sensitivity. Two of these mutants are sensitive and regulate the FtsH membrane protease. The ftsH mutant itself is also sensitive. These four mutants were characterized using Phenotype MicroArrays revealing protection not only against tobramycin but also other classes of antibiotics, osmolarity, and pH.
 
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 Differential Gene Expression by RamA in Ciprofloxacin-Resistant Salmonella Typhimurium
In the study of ramA mediated antibiotic resistance, Meng and colleagues used Phenotype MicroArrays to characterize ramA overexpressing and ramA deletion mutants. Overexpression of ramA upregulated the MDR efflux pump AcrAB-TolC and led to resistance to antibiotics and other toxic agents. Additionally, PM uncovered that the ramA deletion mutant had increased ability to use 10 carbon sources and 10 phosphorus sources. Several PM findings were independently verified.
 
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Phenotype MicroArray Technology
Biolog's Phentoype MicroArray technology enables researchers to evaluate nearly 2000 phenotypes of a microbial cell in a single experiment. This integrated system of cellular assays, instrumentation and bioinformatics software provides cellular knowledge that complements molecular information, helping you interpret and find the relevant aspects in massive amounts of gene expression or proteomics data. Through comprehensive and precise quantitation of phenotypes, researchers are able to obtain an unbiased perspective of the effect on cells of genetic differences, environmental change, exposure to chemicals or drugs, and more.
 
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