A regulatory cascade involving AarG, a putative sensor kinase, controls the expression of the 2'-N-acetyltransferase and an intrinsic multiple antibiotic resistance (Mar) response in Providencia stuartii.
A recessive mutation, aarG1, has been identified that resulted in an 18-fold increase in the expression of beta-galactosidase from an aac(2')-lacZ fusion. Transcriptional fusions and Northern blot analysis demonstrated that the aarG1 allele also resulted in a large increase in the expression of aarP, a gene encoding a transcriptional activator of aac(2')-Ia. The effects of aarG1 on aac(2')-Ia expression were mediated by aarP-dependent and -independent mechanisms. The aarG1 allele also resulted in a multiple antibiotic resistance (Mar) phenotype, which included increased chloramphenicol, tetracycline and fluoroquinolone resistance. This Mar phenotype also resulted from aarP-dependent and -independent mechanisms. Sequence analysis of the aarG locus revealed the presence of two open reading frames, designated aarR and aarG, organized in tandem. The putative AarR protein displayed 75% amino acid identity to the response regulator PhoP, and the AarG protein displayed 57% amino acid identity to the sensor kinase PhoQ. The aarG1 mutation, a C to T substitution, resulted in a threonine to isoleucine substitution at position 279 (T279I) in the putative sensor kinase. The AarG product was functionally similar to PhoQ, as it was able to restore wild-type levels of maganin resistance to a Salmonella typhimurium phoQ mutant. However, expression of the aarP and aac(2')-Ia genes was not significantly affected by the levels of Mg2+ or Ca2+, suggesting that aarG senses a signal other than divalent cations.
Veterans Affairs Medical Center and Department of Medicine, Case Western Reserve University School of Medicine, Cleveland, OH 44106, USA. pxr17@po.cwru.edu
P N
PN
Rather
M R
MR
Paradise
M M
MM
Parojcic
S
S
Patel
D000123:Acetyltransferases / Q000235:genetics / Q000378:metabolism*; D000483:Alleles; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D015152:Blotting, Northern; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D004352:Drug Resistance, Microbial / Q000235:genetics; D018432:Drug Resistance, Multiple / Q000235:genetics*; D029968:Escherichia coli Proteins; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D008826:Microbial Sensitivity Tests; D008969:Molecular Sequence Data; D009154:Mutation; D010957:Plasmids / Q000235:genetics; D011494:Protein Kinases / Q000235:genetics* / Q000378:metabolism; D011532:Providencia / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D017422:Sequence Analysis, DNA; D015534:Trans-Activators / Q000378:metabolism; D014158:Transcription, Genetic
C093833:AarP protein, Providencia stuartii; D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; C080002:MarA protein, E coli; C079792:PhoQ protein, Bacteria; D012333:RNA, Messenger; D015534:Trans-Activators; D000123:Acetyltransferases; C443113:aminoglycoside 2'-N-acetyltransferase; D011494:Protein Kinases; C114822:AarG protein, Providencia stuartii