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In This Article

  • Summary
  • Abstract
  • Introduction
  • Protocol
  • Representative Results
  • Discussion
  • Acknowledgements
  • Materials
  • References
  • Reprints and Permissions

Summary

Here we present a protocol for the use of pre-existing antibiotic resistance-cassette deletion constructs as a basis for making deletion mutants in other E. coli strains. Such deletion mutations can be mobilized and inserted into the corresponding locus of a recipient strain using P1 bacteriophage transduction.

Abstract

A first approach to study the function of an unknown gene in bacteria is to create a knock-out of this gene. Here, we describe a robust and fast protocol for transferring gene deletion mutations from one Escherichia coli strain to another by using generalized transduction with the bacteriophage P1. This method requires that the mutation be selectable (e.g., based on gene disruptions using antibiotic cassette insertions). Such antibiotic cassettes can be mobilized from a donor strain and introduced into a recipient strain of interest to quickly and easily generate a gene deletion mutant. The antibiotic cassette can be designed to include flippase recognition sites that allow the excision of the cassette by a site-specific recombinase to produce a clean knock-out with only a ~100-base-pair-long scar sequence in the genome. We demonstrate the protocol by knocking out the tamA gene encoding an assembly factor involved in autotransporter biogenesis and test the effect of this knock-out on the biogenesis and function of two trimeric autotransporter adhesins. Though gene deletion by P1 transduction has its limitations, the ease and speed of its implementation make it an attractive alternative to other methods of gene deletion.

Introduction

A common first approach to study the function of a gene is to perform knock-out mutagenesis and observe the resulting phenotype. This is also termed reverse genetics. The bacterium E. coli has been the workhorse of molecular biology for the last 70 years or so, due to the ease of its culturing and its amenability to genetic manipulation1. Several methods have been developed to produce gene deletions in E. coli, including marker exchange mutagenesis2,3 and, more recently, recombineering using the λ Red or Rac ET systems4,

Protocol

1. Strains and Plasmids

  1. Bacterial strains
    1. Use the E. coli strains BW251135, JW4179 (BW25113 tamA::kan)7, BL21(DE3)20, and BL21ΔABCF21. See Table of Materials for further information.
  2. Bacteriophages
    1. Use the phage P1vir for the general transduction. Store the phage as a liquid stock with .......

Representative Results

Generation of a tamA Knock-out of BL21ΔABCF:

The strategy outlined above has previously been used to produce a derivative strain of BL21(DE3), a standard laboratory strain used for protein production, which is optimized for outer membrane protein production and called BL21ΔABCF21. This strain lacks four genes coding for abundant outer membrane proteins and, consequently, is able to produce.......

Discussion

P1 transduction is a fast, robust, and reliable method for generating gene deletions in E. coli. This is demonstrated here by transducing a tamA deletion mutant from a Keio donor strain to a BL21-derived recipient. The major stages in the transduction process are the production of the transducing lysate, the transduction itself, the excision of the Kan resistance cassette, and the verification of the knock-out by PCR. In total, the process takes approximately 1 week and requires no molecular biology met.......

Acknowledgements

Keio collection strains were obtained from the National BioResource Project (NIG, Japan): E. coli. We thank Dirk Linke (Department of Biosciences, University of Oslo) for his continuing support. This work was funded by the Research Council of Norway Young Researcher grant 249793 (to Jack C. Leo).

....

Materials

NameCompanyCatalog NumberComments
Strains
E. coli BW25113NIGME6092Wild-type strain of Keio collection
E. coli BL21(DE3)Merck69450-3Expression strain
E. coli BL21DABCFAddgene102270Derived from BL21(DE3)
E. coli JW4179NIGJW4179-KCtamA deletion mutant
P1 virNIGHR16Generally transducing bacteriophage
Plasmids
pCP20CGSC14177conditionally replicating plasmid with FLP
pASK-IBA2IBA GmbH2-1301-000expression vector
pEibD10N/AN/Afor production of EibD; plasmid available on request
pET22b+Merck69744-3expression vector
pIBA2-YadAN/AN/Afor production of YadA; plasmid available on request
Chemicals
Acetic acidThermoFisher33209
AgarBD Bacto214010
AgaroseLonza50004
AmpicillinApplichemA0839
AnhydrotetracyclineAbcamab145350
anti-collagen type I antibody COL-1SigmaC2456
Bovine collagen type ISigmaC9791
Calcium chlorideMerck102382
ChloroformMerck102445
Di-sodium hydrogen phosphateVWR28029
DNA dyeThermoS33102
DNA molecular size markerNew England BioLabsN3232S
DNase ISigmaDN25
dNTP mixNew England BiolabsN0447
ECL HRP substrateAdvanstaK-12045
EDTAApplichemA2937
GlycerolVWR24388
goat anti-mouse IgG-HRPSanta Cruzsc-2005
goat anti-rabbit IgG-HRPAgriseraAS10668
HEPESVWR30487
Isopropyl thiogalactosideVWR43714
KanamycinApplichemA1493
LysozymeApplichemA4972
Magnesium chlorideVWR25108
Manganese chlorideSigma221279
N-lauroyl sarcosineSigmaL9150
Skim milk powderSigma70166
Sodium chlorideVWR27808
tamA forward primerInvitrogenN/ASequence 5'-GAAAAAAGGATATTCAGGAGAAAATGTG-3'
tamA reverse primerInvitrogenN/ASequence 5'-TCATAATTCTGGCCCCAGACC-3'
Taq DNA polymeraseNew England BiolabsM0267
Tri-sodium citrateMerck106448
TryptoneVWR84610
Tween20SigmaP1379
Yeast extractMerck103753
Equipment
Agarose gel electrophoresis chamberHoeferSUB13
Bead beaterThermoFP120A-115
CCD cameraKodak4000R
Electroporation cuvettesBio-Rad165-2089
Electroporation unitBio-Rad1652100
Gel imagerNippon GeneticsGP-03LED
Incubating shakerInfors HTMinitron
IncubatorVWR390-0482
MicrocentrifugeEppendorf5415D
Microwave ovenSamsungCM1099A
PCR machineBiometraTpersonal
PCR stripsAxygenPCR-0208-CP-C
pH meterHanna InstrumentsHI2211-01
PVDF membraneThermoFisher88518
SDS-PAG electrophoresis chamberThermoFisherA25977
Tabletop centrifugeBeckman CoulterB06322
Vortex mixerScientific IndustriesSI-0236
Water bathGFLD3006
Wet transfer unitHoeferTE22

References

  1. Blount, Z. D. The unexhausted potential of E. coli. eLife. 4, e05826 (2015).
  2. Hamilton, C. M., Aldea, M., Washburn, B. K., Babitzke, P., Kushner, S. R. New method for generating deletions and gene replacements in Escherichia coli.

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