Transcript persisters
Genetic and environmental conditions influencing persistence Hannes Luidalepp Institute of Technology University of Tartu August 2011 Overview • Persisters • Method to follow cell division • My results Bacterial “lifecycle” in lab Resistance • Including whole population • Genetically determined • • • • Pumping out antibiotics Degradation of antibiotics Altering the target etc Persistence • Part of the population is insensitive – persisters • Medically important – chronical and persistent infections • Genetically identical to the mother cells • Phenotypical property Persisters • frequency usually 10-4-10-6 • mainly originate from stationary phase Keren, et al 2004 • common to all bacterial species investigated (also to fungi and cancer cells) High persistence (Hip) mutants • persister frequency usually at least 100x higher (also some clinical isolates of C. candida, P. aeruginosa) • most common mutant is hipA7 (point mutations in hipA gene) • hipA is a toxin from hipBA antitoxin-toxin pair Persisters - dormant cells Balaban, et al 2004 Persisters Type I persister: originate from stationary phase Type II persisters: originate from growth phase Balaban, et al 2004 Physiology of persisters • Gene expression arrays different toxin/antitoxin genes, other unrelated genes • Mutant collection screens different unrelated genes • Over-expression studies all toxic stuff will increase persistence Method to follow cell division Roostalu, et al 2008 Cell division • LB medium • 24h stationary phase culture diluted into fresh media • Two population dividing non-dividing Age of the culture and persistence Growth resumption dynamics Length of antibiotic treatment Persister dynamics in mutants Growth resumption of sucB mutant Other TCA cycle mutants Summary • Growth resumption depends on: – media – age of the culture • Level of persisters depends on growth resumption Mutants and persistence – Mutants show different persister formation dynamics – Difference from wild type might be observed only in certain conditions Medical applications – To make cell to wake up faster Allison et al., 2011 Kim et al., 2011 – To make cell permanently dormant Acknowledgments People from Tanel Tenson’s lab Specially Arvi Jõers and Niilo Kaldalu