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1. MIC 329The Gram-positive World* *(Well, really a talk about my favorite Gram (+) organism, Bacillus subtilis)
6. The ongoing schism of the genus Bacillus Geobacillus
7. Why study Bacillus subtilis? Best-characterized Gram-positive bacterium
Biochem., metabolism well-studied
Good genetic system (transformation, transduction)
Advanced molecular biology techniques
Entire genome sequenced / annotated
Easy to grow, manipulate in culture
Widely used in industry, agriculture
?Simple? model for cellular differentiation
9. B. subtilis spore anatomy
10. Endospores are resistant to: Heat (both wet and dry)
Ultraviolet (UV) radiation
Extreme desiccation (including vacuum)
Chemicals (organic solvents, oxidizing agents, etc.)
12. Abundance of spores in extreme locales
13. Solar UV:
~10 J /m2 sec UV-B (noon)
~25 J/m2 sec UV-A (noon)
Avg. -7 to +46 ?C (air)
~70-80 ?C (surfaces)
Avg. 13%-30% RH
Avg. 28 cm rainfall / year
14. Spores are 1-2 orders of magnitude more UV resistant than vegetative cells
16. DNA Protective Factors in Spores Spore coat proteins
Spore pigment in coat
Dipicolinic acid in core
SASP in core
21. Spore photochemistry is due to SASP-DNA interaction SASP are Small, Acid-soluble Spore Proteins
SASP are synthesized at Stage III of sporulation
SASP bind to DNA and shift its conformation from B to A
UV irradiation of SASP-DNA complexes results in formation of SP and not T<>T
23. The UV photochemistry of DNA in vegetative cells and spores is different
26. SP is repaired in germinating spores by SP lyase and NER
27. Spores of B. subtilis DNA repair mutants respond differently to lab UV and Solar UV
28. Do spores exposed to solar UV accumulate different types of DNA damage(s)?
29. Probing DNA damages with EndoV and alkali
32. SP is repaired in germinating spores by SP lyase and NER
33. SP lyase-mediated DNA repair in B. subtilis Encoded by splB gene.
Synthesized at Stage III of sporulation, packaged in the dormant spore.
Active during spore germination.
Direct reversal of SP to thymines in situ.
?Dark repair? process.
34. Organization and expression of the splAB operon in B. subtilis
35. ?Radical SAM? Model for SP repair
36. CONCLUSIONS In the laboratory:
Spores are highly UV resistant.
SP is the major DNA damage.
CPD, ss, ds breaks negligible at biol. relevant UV doses.
SP lyase > NER during germination.
37. Survival and persistence of bacterial endospores in extreme environments Patricia Fajardo Mario Pedraza
Lilian Chooback Roberto Rebeil
Heather Glanzberg Paul Riesenman
Jocelyn Law Tony Slieman
Rachel Mastrapa Yubo Sun
Heather Maughan Yaming Xue