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Folate Production and Lysis. Victoria. System Design. Lysis. Folate is released into large intestine where it is eventually absorbed. Overproduction of folate in e coli. Folate Production. Biosynthetic pathway of folate. folE. folB. folK. folP. folB. folA. DHFR. Bermingham et al.

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Folate Production and Lysis


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Presentation Transcript
system design
System Design

Lysis

Folate is released into large intestine where it is eventually absorbed

Overproduction of folate in e coli

biosynthetic pathway of folate
Biosynthetic pathway of folate

folE

folB

folK

folP

folB

folA

DHFR

Bermingham et al.

6 enzymatic steps final reduction step
6 enzymatic steps + final reduction step
  • GTPCH1 - GTP Cyclohydrolase I (folE)
  • DHPP -7,8-Dihydroneopterin triphosphate pyrophosphohydrolase
  • DHNA - 7,8-Dihydroneopterin aldolase (folB)
  • HPPK - 6-Hydroxymethyl-7,8-dihydropterin pyrophosphokinase (folK)
  • DHPS - Dihydropteroate synthase (folP)
  • FPGS - Folylpoly-g-glutamate synthetase (folC)
  • DHFR – dihydrofolate reductase (folA)
    • Reduces 7,8-dihydrofolate  5,6,7,8-tetrahydrofolate
paba glutamate
PABA & glutamate
  • For B.Subtilis – pabA, pabB, pabC were used to make PABA from chorismate

Zhu et al

controlled lysis
Controlled Lysis
  • Prophage
  • the T4 holin + the T7 lysozyme
  • the ldcA deletion
folate release
Folate Release

Pulse release

population

Time

Continuous release

plyst t4 gene t morita
pLysT – T4 gene t (Morita)
  • Produces T7 lysozyme which degrades petidoglycan, but won’t lyse the cell until the expression of T4 holin (expressed by gene t) which creates a break in the membrane, allowing the T7 to reach the peptidoglycan layer.
  • Requires IPTG to trigger expression of the plasmid.

Morita et al. Programmed Escherichia coli Cell Lysis by Expression of Cloned T4 Phage Lysis Genes. Biotechnol. Prog. 2001, 17, 573-576

ldca deletion
ldcA deletion
  • ldcA encodes a cytoplasmic L,D-carboxypeptidase which creates peptide bonds in the peptidoglycan layer between the inner and outer membranes.
  • Normally, the murein (peptidoglycan) is continuously recycled into a pentapeptide and replaced.
  • Deleting ldcA results in the accumulation of a tetrapeptide instead of a pentapeptide, causing a weakened cell wall, and resulting in spontaenous autolysis during the stationary growth phase.
  • Can the E.coli reach a stationary growth phase in the intestine?
  • The E.coli would become more and more fragile as time goes on since it’s still recycling the good murein but not replacing it, so eventually it would lyse?

Templin et al. A defect in cell wall recycling triggers autolysis during the stationary growth phase of Escherichia coli. The EMBO Journal Vol.18 No.15 pp.4108–4117, 1999