Lecture Overview Bacterial populations (lab conditions) Metabolism GROWTHGROWTH Bacteria as single cells (“cell cycles”) Differentiation Symbiosis Sporulation
Bacillus subtilis growth and sporulation time Log(N) inoculate 1 log growth, symmetric cell division 1 2 Gain motility 2 3 Gain genetic competence 3 4 Sporulate, asymmetric cell div 4 Relatives: B. cereus, B. anthracis ~7 hours VII stages Genetics: Spo >200 genes/proteins III Stage (0, I, II, III, IV, V, VI) B Gene (A, B, C …) Quorum sensing
Activating the sigma factors E SpoIIAASpoIIAB F DNA New genes mRNA Spo0A~P Anti-sigma (ATP) SpoIIAASpoIIAB F Anti-Anti-sigma (ADP) Released in “daughter” forespore compartment Pro-Sigma Protein SpoIIE Pro- cut off Active Sigma MotherDaughter Many genes SpoIIGA, SpoIIR proteases
Sigma-K activation in mother cell Split gene 42 kb Recombinase gene Joined gene Pro-sigma-K protein Mother Daughter sigma-K Pro-
Sigma factor summary I Log/ veg. Growth A 0 H II K IV VII V-VI E F E F Inactive Active G Inactive III Active decision activation Signals Check-points
B. subtilis versus E. coli s 5 Spores Smaller cells Fewer ribosomes Compact DNA Hard cortex Cyclopropane fatty acids Programmed mother cell death Cell death Genetic competence (sex) Hypervariation ?