Activation of a cryptic streptomycin-resistance gene in the Bacteroides erm transposon, Tn4551.
Bacteroides compound transposons encoding erm resistance are highly homologous but previous studies have shown some divergence of Tn4551. Results presented here describe a novel Tn4551 streptomycin-resistance gene, aadS, that was phenotypically silent in wild-type Bacteroides. However, aadS expression could be activated by a trans-acting chromosomal mutation. The aadS-encoded peptide displayed significant homology to Gram-positive streptomycin-dependent adenyltransferases, and enzymatic analysis confirmed the production of this activity. Examination of the nucleotide sequence showed that 200 bp upstream of aadS, the DNA base composition changed abruptly from 31% G+C to 48% G+C. These two regions were demarcated by a DNA sequence with homology to the recombination hot spots reported for Tn21 and the Bacteroides ermFU gene and to sequences at the ends of the chromosomal Bacteroides conjugal element, XBU4422.
Smith
C J
CJ
Department of Microbiology and Immunology, School of Medicine, East Carolina University, Greenville, North Carolina 27858.
Owen
C
C
Kirby
L
L
D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics*; D001439:Bacteroides / Q000187:drug effects / Q000235:genetics*; D001483:Base Sequence; D004251:DNA Transposable Elements; D004269:DNA, Bacterial; D004352:Drug Resistance, Microbial / Q000235:genetics; D015964:Gene Expression Regulation, Bacterial; D008969:Molecular Sequence Data; D009154:Mutation; D009713:Nucleotidyltransferases / Q000235:genetics* / Q000378:metabolism; D010957:Plasmids; D015183:Restriction Mapping; D017385:Sequence Homology; D013307:Streptomycin / Q000494:pharmacology*; D015533:Transcriptional Activation
D001426:Bacterial Proteins; D004251:DNA Transposable Elements; D004269:DNA, Bacterial; C076999:AadS protein, Bacteroides erm transposon, Tn4551; D009713:Nucleotidyltransferases; D013307:Streptomycin