Lecture 8: Bacterial Differentiation: Sporulation

Reading assignments in Text: Lengeler et al. 1999

Lecture 8Text: pages 586-601 SporulationText: pages 627 Secondary metabolism

Lecture 7Text: pages 792-799 Gut bugsText: pages 276-277, 800 Bacterial LuxText: pages 498-499 Quorum sensingText: pages 801 Bacteria and plantsText: pages 865-868 AgrobacteriumText: pages 275 Toxic oxygenText: pages 807 Nitrogen cycleText: pages 851-862 Rhizobia and Cyanobacteria

Lecture Overview

Bacterial populations (lab conditions)

Metabolism

GROWTH

Bacteria as single cells (“cell cycles”)

DifferentiationSymbiosis

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 …)

Quorumsensing

0

B. subtilis sporulation stages

M D

2 chromosomes, axial fibers

I 2 cells, cell wall

II Engulfment

III Double membrane

IV Cortex

V-VI Coat

VII Spore maturationMother cell lysis (DNA)

Bacillus subtilis engulfment

SpoIIIE-GFP fusion protein (pink) Membranes (red) DNA (blue)

Sigma factor saga

I

Log/ veg.Growth

A

0

H

II

K

IV

VII

V-VI

E F E F

Inactive

Active

G

Inactive

IIIActive

? decision

? activation

? Signals Check-points

Deciding to sporulate

A

H

?

sporulate

1

1 Starvation: What is monitored? [GTP] = (C, N, P)

2 Cell density:

2?

“quorum sensing” peptides

Food low, [cell] low

Food low, [cell] high

Ok ?

Trouble ahead !

3

3 Chromosomes: 2 undamaged, complete, and polar placement.

Not ppGpp

Decision committee

Histidine Kinases KinA, KinB

Spo0F

Spo0B

Spo0A

~P relay

Inputs1, 2, 3, ?

~~~~~~~

Spo0A~P

~P

TGNCGAA

DNA New genes mRNA

New genes:

H

~P relay genes (+ feedback)

(+ feed back )

“developmental switch”E F

(inactive, “in waiting”)

Asymmetric division

Activating the sigma factors

E

SpoIIAA SpoIIAB F

DNA New genes mRNASpo0A~P

Anti-sigma (ATP)

SpoIIAA SpoIIAB F

Anti-Anti-sigma (ADP)Released in “daughter”forespore compartment

Pro-Sigma Protein

SpoIIE

Pro- cut offActive Sigma

Mother Daughter

Many genes

SpoIIGA, SpoIIRproteases

Sigma-K activation in mother cell

Split gene42 kb

Recombinase gene

Joined gene

Pro-sigma-Kprotein

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

IIIActive

decision

activation

Signals Check-points

B. subtilis versus E. coli

s5

Spores Smaller cellsFewer ribosomesCompact DNA

Hard cortex Cyclopropane fatty acids

Programmed mother cell death

Cell death

Genetic competence(sex)

Hypervariation ?

Other sporulating bacteria

Bacillus thuringiensis Crystal toxin

Clostrium botulinum Neurotoxins 1 gram kills a billion hamsters

“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

Streptomyces coelicolor

“smell like soil”

Myxococcus xanthus

1 “wolf pack” “big stomach” feeding behavior, ~105 cells

S-motility Type IV pili

A-motility Slime jets

starvation

A-signal (Quorum sensing)

2 Aggregate

Ripple /waves

Travel

Germinate

C-signal(contact, packing, alignment)

Motto Eat together, spore together, move together

3 Fruiting Body(exospores)

Stigmatella aurantiaca fruiting bodyon a piece of decaying forest wood (scanning electron micrograph)