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Genetic and environmental conditions influencing persistence

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

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Genetic and environmental conditions influencing persistence

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  1. Genetic and environmental conditions influencing persistence Hannes Luidalepp Institute of Technology University of Tartu August 2011

  2. Overview • Persisters • Method to follow cell division • My results

  3. Bacterial “lifecycle” in lab

  4. Resistance • Including whole population • Genetically determined • Pumping out antibiotics • Degradation of antibiotics • Altering the target • etc

  5. Persistence • Part of the population is insensitive – persisters • Medically important – chronical and persistent infections • Genetically identical to the mother cells • Phenotypical property

  6. Persisters • frequency usually 10-4-10-6 • mainly originate from stationary phase • common to all bacterial species investigated (also to fungi and cancer cells) Keren, et al2004

  7. 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

  8. Persisters - dormant cells Balaban, et al2004

  9. Persisters Type I persister: originate from stationary phase Type II persisters: originate from growth phase Balaban, et al2004

  10. 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

  11. Method to follow cell division Roostalu, et al 2008

  12. Cell division • LB medium • 24h stationary phase culture diluted into fresh media • Two population dividing non-dividing

  13. Age of the culture and persistence

  14. Growth resumption dynamics

  15. Length of antibiotic treatment

  16. Persister dynamics in mutants

  17. Growth resumption of sucB mutant

  18. Other TCA cycle mutants

  19. Summary • Growth resumption depends on: • media • age of the culture • Level of persisters depends on growth resumption

  20. Mutants and persistence • Mutants show different persister formation dynamics • Difference from wild type might be observed only in certain conditions

  21. Medical applications • To make cell to wake up faster Allison et al., 2011 Kim et al., 2011 • To make cell permanently dormant

  22. AcknowledgmentsPeople fromTanel Tenson’s labSpecially Arvi Jõers and Niilo Kaldalu

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