Mutant alleles of tRNAThr genes suppress the hisG46 missense mutation in Salmonella typhimurium

Kupchella, Eugene; Koch, Walter; Cebula, Thomas A.

doi:10.1002/em.2850230202

Cited by 33 publications

(9 citation statements)

References 44 publications

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“…1, were used to detect mutations in gyrA. Colony hybridization was performed as described previously (19). Briefly, colonies were grown on BHI agar plates overnight and transferred to paper filters.…”

Section: Methodsmentioning

confidence: 99%

Single-Nucleotide Polymorphism Mutation Spectra and Resistance to Quinolones in Salmonella enterica Serovar Enteritidis with a Mutator Phenotype

Levy

Sharma

Cebula

2004

Antimicrob Agents Chemother

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Resistance to quinolone antibiotics has been associated with single-nucleotide polymorphisms (SNPs) in the quinolone resistance-determining region (QRDR) of gyrA. Mutations in the gyrA gene were compared by using mutant populations derived from wild-type Salmonella enterica serovar Enteritidis and its isogenic mutS::Tn10 mutator counterpart. Spontaneous mutants arising during nonselective growth were isolated by selection with either nalidixic acid, enrofloxacin, or ciprofloxacin. QRDR SNPs were identified in approximately 70% (512 of 695) of the isolates via colony hybridization with radiolabeled oligonucleotide probes. Notably, transition base substitution SNPs in the QRDR were dramatically increased in mutants derived from the mutS strain. Some, but not all, antibiotic-resistant mutants lacking QRDR SNPs were resistant to tetracycline and chloramphenicol, consistent with alterations in nonspecific efflux pumps or other membrane transport mechanisms. Changing the selection conditions shifted the mutation spectrum. Selection with ciprofloxacin was least likely to yield a mutant harboring either a QRDR SNP or chloramphenicol resistance. Selection with enrofloxacin was more likely to yield mutants containing Ser833Phe mutations, whereas selection with ciprofloxacin or nalidixic acid favored recovery of Asp873Gly mutants. Fluoroquinolone-resistant Salmonella strains isolated from veterinary or clinical settings frequently display a mutational spectrum with a preponderance of transition SNPs in the QRDR, the pattern found in vitro among mutS mutator mutants reported here. Both the preponderance of transition mutations and the varied mutation spectra reported for veterinary and clinical isolates suggest that bacterial mutators defective in methyl-directed mismatch repair may play a role in the emergence of quinolone and fluoroquinolone resistance in feral settings.

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Section: Methodsmentioning

confidence: 99%

Single-Nucleotide Polymorphism Mutation Spectra and Resistance to Quinolones in Salmonella enterica Serovar Enteritidis with a Mutator Phenotype

Levy

Sharma

Cebula

2004

Antimicrob Agents Chemother

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“…After overnight growth, the colonies were lifted onto Whatman no. 541 filter paper and processed as described previously (Kupchella et al, 1994). Oligonucleotide probes were labelled using T4 polynucleotide kinase and [$#P]ATP (Sambrook et al, 1989) and were used to hybridize bacterial DNA affixed to the filters.…”

Section: Methodsmentioning

confidence: 99%

Evolution of multi-gene segments in the mutS–rpoS intergenic region of Salmonella enterica serovar Typhimurium LT2 a aThe GenBank accession number for the sequence reported in this paper is AY050714.

Kotewicz

Levy

et al. 2002

Microbiology

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The nucleotide sequence of the 126 kb region between the mutS and rpoS genes of Salmonella enterica serovar Typhimurium LT2 (S. typhimurium) was compared to other enteric bacterial mutS-rpoS intergenic regions. The mutS-rpoS region is composed of three distinct segments, designated HK, O and S, as defined by sequence similarities to contiguous ORFs in other bacteria. Inverted chromosomal orientations of each of these segments are found between the mutS and rpoS genes in related Enterobacteriaceae. The HK segment is distantly related to a cluster of seven ORFs found in Haemophilus influenzae and a cluster of five ORFs found between the mutS and rpoS genes in Escherichia coli K-12. The O segment is related to the mutS-rpoS intergenic region found in E. coli O157 :H7 and Shigella dysenteriae type 1. The third segment, S, is common to diverse Salmonella species, but is absent from E. coli. Despite the extensive collinearity and conservation of the overall genetic maps of S. typhimurium and E. coli K-12, the insertions, deletions and inversions in the mutS-rpoS region provide evidence that this region of the chromosome is an active site for horizontal gene transfer and rearrangement.

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“…The photomutagenicity of TBZ was more evident in WP2uvrA/pKM101, whose mutational target is the trpE65 ochre mutation (TAA), than in TA100, which has the hisG46 missense mutation (CCC) as a target for mutation. The hisG46 missense mutation, which substitutes a proline triplet in place of a leucine triplet (CTC), can be reverted to histidine prototorophy by any of several point mutations occurring at G:C basepairs [Levin and Ames, 1986] or by T:A3 G:C transversions in tRNA genes [Kupchella et al, 1994], with the former responsible for more than 90% of spontaneous mutations at the hisG46 locus [Levin and Ames, 1986]. Since trpE65 carries an ochre (TAA) mutation, strains that carry trpE65 can be reverted to Trp ϩ prototorophy by base substitutions either at the ochre site or at ochre suppressor sites, i.e., on tRNA genes, including tyrT, tyrU, lysT, glnU, and gluT [Miller, 1992].…”

Section: Discussionmentioning

confidence: 99%

Photomutagenicity of thiabendazole, a postharvest fungicide, in bacterial assays

Watanabe-Akanuma¹,

Ohta

Yamagata

2003

Environ and Mol Mutagen

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We investigated the photomutagenicity of thiabendazole (TBZ), a postharvest fungicide commonly used on imported citrus fruits. Using UVA light (320-400 nm), we irradiated bacterial cultures with or without TBZ in a 24-well multiplate. UVA-irradiation without TBZ was not mutagenic to the tester strains, nor was unirradiated TBZ. TBZ was strongly photomutagenic in Escherichia coli WP2uvrA and WP2uvrA/pKM101 strains, weakly photomutagenic in Salmonella typhimurium TA100 and TA98, and not photomutagenic in S. typhimurium TA1535 and TA1538. The photomutagenicity of TBZ was more evident in WP2uvrA/pKM101, which carries the trpE65 ochre mutation (TAA), than in TA100, which carries the hisG46 missense mutation (CCC). In E. coli WP3101-WP3106 and the corresponding pKM101-containing strains, photoactivated TBZ induced predominantly G:C-->A:T transitions and A:T-->T:A transversions. In the plasmid-containing strains only, TBZ induced a moderate number of A:T-->G:C transitions and a few A:T-->C:G and G:C-->T:A transversions. The observation that UVA-irradiated TBZ mutated both G:C and A:T basepairs may explain why WP2uvrA/pKM101 was more sensitive to its mutagenicity than TA100. TBZ that was irradiated before it was added to the WP2uvrA/pKM101 cells was not photomutagenic, which suggests that the photomutagenic products of TBZ were unstable or rapidly reacted with other molecules before being incorporated into cells.

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Mutant alleles of tRNA^Thr genes suppress the hisG46 missense mutation in Salmonella typhimurium

Cited by 33 publications

References 44 publications

Single-Nucleotide Polymorphism Mutation Spectra and Resistance to Quinolones in Salmonella enterica Serovar Enteritidis with a Mutator Phenotype

Single-Nucleotide Polymorphism Mutation Spectra and Resistance to Quinolones in Salmonella enterica Serovar Enteritidis with a Mutator Phenotype

Evolution of multi-gene segments in the mutS–rpoS intergenic region of Salmonella enterica serovar Typhimurium LT2 a aThe GenBank accession number for the sequence reported in this paper is AY050714.

Photomutagenicity of thiabendazole, a postharvest fungicide, in bacterial assays

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