Methylobacterium extorquens: Metabolic superstar

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Methylobacterium extorquensMetabolic superstar
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Meet Methylobacterium extorquens
methylotroph grows on one-carbon compounds
e.g., methanol (CH3OH) also grows on
multicarbon compounds e.g., succinate
(C4H4O42-) natural habitat leaf surfaces
pink!
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Why is M. extorquens a metabolic superstar?
Talented - ability to use C1 fuel is
unusual Versatile - can switch between C1,
C2, C3, and C4 fuels Full of potential - may
become a model system for understanding
metabolic transitions in other organisms - may
become genetically engineered to convert
methanol into valuable materials (e.g., plastics)
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The M. extorquens genome is sequenced.What more
do we need to know?
Genome all the genes Central dogma of
biology
DNA RNA Proteins
substrates
products
The genes indicate a cells metabolic
potential (Which reactions can occur?)
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Genes alone tell us littleabout metabolic
transitions
DNA RNA Proteins
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The big question
How does M. extorquens sense changes in fuel
availability and respond appropriately? An
inappropriate response might lead to a buildup of
formaldehyde, which is toxic.
methanol (CH3OH)
formaldehyde (HCHO)
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Multiple measurements forunderstanding metabolic
transitions
proteomics, enzyme activity assays
microarrays
genomics
DNA RNA Proteins
flux rates
substrates
products
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My focus flux ratesthrough biochemical pathways
CH3OH
OUTSIDE OF CELL
INSIDE OF CELL
CH3OH
HCHO
H4MPT
H4F
HCHO
Serine
CH2H4F
CH2H4MPT
Biomass
HCOOH
CO2
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14C assay measuresbiomass and CO2 production
(radioactive)
Add
CH3OH
OUTSIDE OF CELL
INSIDE OF CELL
CH3OH
HCHO
H4MPT
H4F
HCHO
Serine
CH2H4F
CH2H4MPT
Biomass
HCOOH
CO2
C.J. Marx et al., PLoS Biol 3(2) e16, 2005
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Deuterium assay measures short and long
routes of biomass production
Add
CD3OD
OUTSIDE OF CELL
INSIDE OF CELL
CD3OD
DCDO
H4MPT
H4F
DCDO
CD2H4MPT
Serine (D2) Serine (D)
CD2H4F
CDHH4F
DCOOH
CO2
Biomass
C.J. Marx et al., PLoS Biol 3(2) e16, 2005
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Conclusion(adapted from A.L. Webber T. Rice
1971)
I dont know how they do it Switching fuels
like a hybrid. And when they change, They really
change. If the levels of succinate Start to
fall, Theyll shift to methanol Yes, now we
have their genome, But I dont see what it tells
us. Its the genes its just the genes. And the
genes dont change When the fuels do, So how do
the cells respond? We need more clues!
Measure pathway flux Measure RNA Check
metabolites Do enzyme assays! Hey, M.
extorquens, soon well know What youre all
about Dont you think its rather daunting? All
this work, all this data. No other group would
take this on. So well be first to get
results And get our grant renewed When its
reviewed. Theyll think were shrewd Or else
were screwed.
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Id like to thank the Academy
Current Lidstrom lab members/collaborators Gundula
Bosch, Ph.D. Mila Chistoserdova, Ph.D. Xiaofeng
Guo Marina Kalyuzhnaya, Ph.D. George Kosaly,
Ph.D. Mary Lidstrom, Ph.D. Jonathan Miller Betsy
Skovran, Ph.D. Tim Strovas Dan Yates
Former lab members Kelly FitzGerald, Ph.D. Chris
Marx, Ph.D. Yoko Okubo, Ph.D. Steve Van Dien,
Ph.D. Julia Vorholt, Ph.D.
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The End
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