http://precedings.nature.com/users/b2a2c9bc416deea7641f17448bfae04c/ Documents posted by jaison jacob Nature Publishing Group en Nature Precedings http://precedings.nature.com/images/header_logo.gif http://precedings.nature.com http://dx.doi.org/10.1038/npre.2009.3118.1 Small colony variants (SCVs) are bacterial subpopulation that grow slowly and form smaller colonies. They have been described for a wide range of bacterial species, but most extensively studied for Staphylococci. They are considered as mutants that are auxotrophic to hemin, thiamine or thymidine. In the presence of auxotrophic agents, they revert to normal growth. They are tolerant to many antibiotics and are implicated in chronic and persistent infections. In this presentation, it is proposed that most of them are normal senescent bacteria that do not revert in the presence of auxotrophic agents. SCVs can explain the concentration dependent killing property, long post-antibiotic effect and increased resistance to aminoglycosides. http://dx.doi.org/10.1038/npre.2009.3118.1 Wed, 22 Apr 2009 16:46:09 UTC Small Colony Variants and Senescent Bacteria doi:10.1038/npre.2009.3118.1 2009-04-22 Jaison Jacob Nature Precedings 2009-04-22T16:46:09Z Presentation Microbiology Pharmacology http://creativecommons.org/licenses/by/3.0/ http://precedings.nature.com/documents/1411/version/2 Persisters are a small subpopulation of bacteria that survive a lethal concentration of antibiotic without antibiotic resistance genes. Isolation of persisters from normally dividing population is considered difficult due to their slow growth, low numbers and phenotypic shift i.e. when re-grown in antibiotic free medium, they revert to parent population. Inability to isolate persisters is a major hindrance in this field of research. Here we reject the ‘phenotypic shift’ phenomenon exhibited by persisters. Persisters, on the other hand, exhibit a heritable phenotype and can be easily isolated from a normally dividing population that allows their selective growth. Rather than a single subset, they comprise many distinct subgroups each exhibiting different growth rates, colony sizes, antibiotic tolerance and protein expression levels. Clearly, they are one of the sources of bacterial heterogeneity and noise in protein expression. Existence of persisters in normally dividing population can explain some of the unsolved puzzles like antibiotic tolerance, post-antibiotic effect and viable but non-culturable bacterial state. We hypothesize that persisters are aging bacteria. http://precedings.nature.com/documents/1411/version/2 Mon, 06 Apr 2009 19:29:19 UTC Persisters show heritable phenotype and generate bacterial heterogeneity and noise in protein expression hdl:10101/npre.2009.1411.2 2009-04-06 Jaison Jacob Nature Precedings 2009-04-06T19:29:19Z Manuscript Microbiology http://creativecommons.org/licenses/by/3.0/