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Lecture 8: Bacterial Differentiation: Sporulation

Lecture 8: Bacterial Differentiation: Sporulation. Reading assignments in Text: Lengeler et al. 1999 Lecture 8 Text: pages 586-601 Sporulation Text: pages 627 Secondary metabolism Lecture 7 Text: pages 792-799 Gut bugs Text: pages 276-277, 800 Bacterial Lux

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Lecture 8: Bacterial Differentiation: Sporulation

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  1. Lecture 8: Bacterial Differentiation: Sporulation Reading assignments in Text: Lengeler et al. 1999 Lecture 8 Text: pages 586-601 Sporulation Text: pages 627 Secondary metabolism Lecture 7 Text: pages 792-799 Gut bugs Text: pages 276-277, 800 Bacterial Lux Text: pages 498-499 Quorum sensing Text: pages 801 Bacteria and plants Text: pages 865-868 Agrobacterium Text: pages 275 Toxic oxygen Text: pages 807 Nitrogen cycle Text: pages 851-862 Rhizobia and Cyanobacteria

  2. Lecture Overview Metabolism GROWTH Bacterial populations (lab conditions) Bacteria as single cells (“cell cycles”) Differentiation Symbiosis Sporulation

  3. Bacillus subtilis growth and sporulation Log(N) 3 4 inoculate 2 time 1 1 log growth, symmetric cell division 2 Gain motility Quorum sensing 3 Gain genetic competence 4 Sporulate, asymmetric cell div ~7 hours VII stages B Gene (A, B, C …) Genetics: III Stage (0, I, II, III, IV, V, VI) Relatives: B. cereus, B. anthracis >200 genes/proteins Spo

  4. B. subtilis sporulation stages 2 chromosomes, axial fibers 0 I 2 cells, cell wall II Engulfment III Double membrane D M Cortex IV Coat V-VI Spore maturation Mother cell lysis (DNA) VII

  5. Bacillus subtilis engulfment SpoIIIE-GFP fusion protein (pink) Membranes (red) DNA (blue)

  6. Sigma factor saga s A Log/ veg. Growth s H s s s s 0 E E F F Active s I G II Inactive III s K Active IV V-VI ? Signals Check-points VII ? decision Inactive ? activation

  7. Deciding to sporulate s s 3 ? A H 2 1 1 Starvation: 2 Cell density: Ok ? Trouble ahead ! 3 Chromosomes: ? sporulate What is monitored? [GTP] = (C, N, P) Not ppGpp “quorum sensing” peptides Food low, [cell] low Food low, [cell] high 2 undamaged, complete, and polar placement.

  8. Decision committee ~~~~~~~ ~P Inputs 1, 2, 3, ? Spo0F Spo0B ~P relay Spo0A~P Spo0A (+ feed back ) TGNCGAA ~P relay genes (+ feedback) s s s H E F New genes mRNA DNA “developmental switch” (inactive, “in waiting”) Histidine Kinases KinA, KinB New genes: Asymmetric division

  9. Activating the sigma factors Spo0A~P DNA SpoIIAA SpoIIAB SpoIIE Anti-sigma (ATP) SpoIIAA SpoIIAB Released in “daughter” forespore compartment (ADP) Anti-Anti-sigma Many genes s s s E F F New genes mRNA SpoIIGA, SpoIIR proteases Pro- cut off Active Sigma Mother Daughter Pro-Sigma Protein

  10. Sigma-K activation in mother cell Split gene 42 kb Recombinase gene Joined gene protein Pro-sigma-K sigma-K Pro- Mother Daughter

  11. Sigma factor summary s A Log/ veg. Growth s H s s s s 0 E E F F Active s I G II Inactive III s K Active IV V-VI Signals Check-points VII decision Inactive activation

  12. B. subtilis versus E. coli s s s 5 Smaller cells Spores Fewer ribosomes Compact DNA Cyclopropane fatty acids Hard cortex Programmed mother cell death Cell death Genetic competence (sex) Hypervariation ?

  13. Other sporulating bacteria Crystal toxin Bacillus thuringiensis Neurotoxins 1 gram kills a billion hamsters Clostrium botulinum “Jurassic Park” experiment Endospores 2 cells make 1 spore Exospores 1 cell makes 1 spore (not as durable) Streptomyces coelicolor Gram(+), fungus-like myceleum, antibiotics Myxococcus xanthus Gram(-), wolf-pack gliding, social interactions

  14. Streptomyces coelicolor “smell like soil”

  15. Myxococcus xanthus Germinate starvation Travel 3 Fruiting Body (exospores) 2 Aggregate 1 “wolf pack” “big stomach” feeding behavior, ~105 cells Type IV pili S-motility A-motility Slime jets A-signal (Quorum sensing) C-signal (contact, packing, alignment) Ripple /waves Motto Eat together, spore together, move together

  16. Stigmatella aurantiaca fruiting body on a piece of decaying forest wood (scanning electron micrograph)

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