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Journal of Bacteriology, December 2001, p. 6822-6831, Vol. 183, No. 23
Department of Molecular, Cellular, and
Developmental Biology, Yale University, New Haven, Connecticut
06520-8103
Received 17 July 2001/Accepted 20 September 2001
The genus Acinetobacter encompasses a heterogeneous
group of bacteria that are ubiquitous in the natural environment due in part to their ability to adapt genetically to novel challenges. Acinetobacter sp. strain ADP1 (also known as strain BD413)
is naturally transformable and takes up DNA from any source. Donor DNA
can be integrated into the chromosome by recombination provided it
possesses sufficient levels of nucleotide sequence identity to the
recipient's DNA. In other bacteria, the requirement for sequence
identity during recombination is partly due to the actions of the
mismatch repair system, a key component of which, MutS, recognizes
mismatched bases in heteroduplex DNA and, along with MutL, blocks
strand exchange. We have cloned mutS from strain ADP1 and
examined its roles in preventing recombination between divergent DNA
and in the repair of spontaneous replication errors. Inactivation of
mutS resulted in 3- to 17-fold increases in transformation efficiencies with donor sequences that were 8 to 20% divergent relative to the strain ADP1. Strains lacking MutS exhibited increased spontaneous mutation frequencies, and reversion assays demonstrated that MutS preferentially recognized transition mismatches while having
little effect on the repair of transversion mismatches. Inactivation of
mutS also abolished the marker-specific variations in
transforming efficiency seen in mutS+
recipients where transition and frameshift alleles transformed at
eightfold lower frequencies than transversions or large deletions. Comparison of the MutS homologs from five individual
Acinetobacter strains with those of other gram-negative
bacteria revealed that a number of unique indels are conserved among
the Acinetobacter amino acid sequences.
0021-9193/01/$04.00+0 DOI: 10.1128/JB.183.23.6822-6831.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Functions of the Mismatch Repair Gene
mutS from Acinetobacter sp. Strain
ADP1

*
Corresponding author. Mailing address: Department of
Molecular, Cellular, and Developmental Biology, Yale University, P.O. Box 208103, New Haven, CT 06520-8103. Phone: (203) 432-3498. Fax: (203)
432-3350. E-mail: nicholas.ornston{at}vale.edu.
Publication 29 from the Biological Transformations Center in the
Yale Institute for Biospherics Studies.
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