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Appl. Environ. Microbiol., 05 1996, 1500-1506, Vol 62, No. 5
MJ Laine, H Nakhei, J Dreier, K Lehtila, D Meletzus, R Eichenlaub and MC Metzler
In this paper we describe transformation of Clavibacter michiganensis
subsp. sepedonicus, the potato ring rot bacterium, with plasmid vectors.
Three of the plasmids used, pDM100, pDM302, and pDM306, contain the origin
of replication from pCM1, a native plasmid of C. michiganensis subsp.
michiganensis. We constructed two new cloning vectors, pHN205 and pHN216,
by using the origin of replication of pCM2, another native plasmid of C.
michiganensis subsp. michiganensis. Plasmids pDM302, pHN205, and pHN216
were stably maintained without antibiotic selection in various strains of
C. michiganensis subsp. sepedonicus. We observed that for a single plasmid,
different strains of C. michiganensis subsp. sepedonicus showed
significantly different transformation efficiencies. We also found
unexplained strain-to-strain differences in stability with various plasmid
constructions containing different arrangements of antibiotic resistance
genes and origins of replication. We examined the effect of a number of
factors on transformation efficiency. The best transformation efficiencies
were obtained when C. michiganensis subsp. sepedonicus cells were grown on
DM agar plates, harvested during the early exponential growth phase, and
used fresh (without freezing) for electroporation. The maximal
transformation efficiency obtained was 4.6 x 10(4) CFU/microgram of pHN216
plasmid DNA. To demonstrate the utility of this transformation system, we
cloned a beta-1,4-endoglucanase-encoding gene from C. michiganensis subsp.
sepedonicus into pHN216. When this construction, pHN216:C8, was
electroporated into competent cells of a cellulase- deficient mutant, it
restored cellulase production to almost wild-type levels.
Copyright © 1996, American Society for Microbiology
Stable transformation of the gram-positive phytopathogenic bacterium Clavibacter michiganensis subsp. sepedonicus with several cloning vectors
Department of Biology, University of Turku, Finland.
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