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J. Bacteriol., 03 1995, 1336-1347, Vol 177, No. 5
U Gerischer and LN Ornston
Bacteria containing spontaneous null mutations in pcaH and -G, structural
genes for protocatechuate 3,4-dioxygenase, were selected by exposure of an
Acinetobacter calcoaceticus strain to physiological conditions in which
expression of the genes prevents growth. The parental bacterial strain
exhibits high competence for natural transformation, and this procedure was
used to characterize 94 independently isolated spontaneous mutations. Four
of the mutations were caused by integration of a newly identified insertion
sequence, IS1236. Many (22 of 94) of the mutations were lengthy deletions,
the largest of which appeared to eliminate at least 17 kb of DNA containing
most of the pca-qui-pob supraoperonic gene cluster. DNA sequence
determination revealed that the endpoints of four smaller deletions (74 to
440 bp in length) contained DNA sequence repetitions aligned imprecisely
with the sites of mutation. Analysis of direct and inverted DNA sequence
repetitions associated with the sites of mutation suggested the existence
of DNA slippage structures that make unhybridized nucleotides particularly
susceptible to mutation.
Copyright © 1995, American Society for Microbiology
Spontaneous mutations in pcaH and -G, structural genes for protocatechuate 3,4-dioxygenase in Acinetobacter calcoaceticus
Department of Biology, Yale University, New Haven, Connecticut 06520- 8103.
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