An inducible tellurite-resistance operon in Proteus mirabilis

Abstract

Tellurite resistance (Te r ) is widespread in nature and it is shown here that the natural resistance of Proteus mirabilis to tellurite is due to a chromosomally located orthologue of plasmid-borne ter genes found in enteric bacteria. The P. mirabilis ter locus (terZABCDE) was identified in a screen of Tn5lacZ-generated mutants of which one contained an insertion in terC. The P. mirabilis terC mutant displayed increased susceptibility to tellurite (Te s ) and complementation with terC carried on a multicopy plasmid restored high-level Te r . Primer extension analysis revealed a single transcriptional start site upstream of terZ, but only with RNA harvested from bacteria grown in the presence of tellurite. Northern blotting and reverse transcriptase-PCR (RT-PCR) analyses confirmed that the ter operon was inducible by tellurite and to a lesser extent by oxidative stress inducers such as hydrogen peroxide and methyl viologen (paraquat). Direct and inverted repeat sequences were identified in the ter promoter region as well as motifs upstream of the 235 hexamer that resembled OxyR-binding sequences. Finally, the 390 bp intergenic promoter region located between orf3 and terZ showed no DNA sequence identity with any other published ter sequences, whereas terZABCDE genes exhibited 73-85 % DNA sequence identity. The ter operon was present in all clinical isolates of P. mirabilis and Proteus vulgaris tested and is inferred for Morganella and Providencia spp. based on screening for high level Te r and preliminary PCR analysis. Thus, a chromosomally located inducible tellurite resistance operon appears to be a common feature of the genus Proteus.

The role of TerW protein in the tellurite resistance of uropathogenic Escherichia coli

“…The real time PCR assay also confirmed that the ter gene cluster in E. coli KL53 and its regulatory region are not inducible by potassium tellurite and/or hydrogen peroxide (Vavrova et al 2006). This observation is in contrast to the regulation of the ter operon in the urinary pathogen Proteus mirabilis, in which transcription is induced by oxidative stress (Toptchieva et al 2003).…”

“…Promoter strength was measured with a fluorimetric assay. GFPuv reporter was chosen because tellurite toxicity prevented the use of the lacZ fusion as a reporter for regulatory studies (Toptchieva et al 2003). E. coli BL21(DE3) containing pBAD-GFPuv with the araBAD promoter, PBAD, from the arabinose operon, and the corresponding regulatory gene, araC, were used as positive and negative controls for fluorimetry that were dependent on arabinose addition/non-addition to the growth medium, respectively.…”

“…(Jobling & Ritchie 1987); it has also been found on the plasmid pHH1508a (IncHII) from Klebsiella aerogenes (Walter & Taylor 1989), the large conjugative plasmid pR478 (IncHI2) from Serratia marcescens (Whelan et al 1997) and the chromosomes of Proteus mirabilis (Toptchieva et al 2003) and Escherichia coli O157:H7 (Perna et al 2001). Several enteric pathogens share a similar locus of ter genes, which provides the high level resistance that is currently used for the isolation and identification of many pathogens, including the emergent enterohemorrhagic E. coli O157:H7 strain (Zadik et al 1993).…”

The phrA gene of Rhodobacter sphaeroides encodes a photolyase and is regulated by singlet oxygen and peroxide in a σ E-dependent manner

“…Toptchieva et al (2003) found that intrinsic tellurite toxicity prevented the use of the lacZ fusion as a reporter for regulatory studies in Proteus mirabilis. Since tellurite oxidizes thiol groups, it contributes to oxidative stress and might affect the b-galactosidase enzyme in a similar way as ROS.…”

Comprehensive Characterization of the Contribution of Individual SigB-Dependent General Stress Genes to Stress Resistance ofBacillus subtilis

“…PF02342), which are important for tellurite resistance. These proteins might be implicated in oxidative stress response for two reasons: (i) the toxicity of tellurite could be related to its oxidizing capacity (53,55) and (ii) the ter operon of Proteus mirabilis is induced by oxidative stress caused by H 2 O 2 or methyl viologen (54).…”