An arsenic (ars) four-gene operon, containing genes encoding a putative membrane permease (ArsP), a transcriptional repressor (ArsR), an arsenate reductase (ArsC) and an arsenical-resistance membrane transporter (Acr3) was first identified in urease-positive thermophilic Campylobacter (UPTC) isolate, CF89-12. UPTC CF89-12 and some other Campylobacter lari isolates contained their ars four-genes, similarly, differing from that in the reference C. lari RM2100 strain. Two putative promoters and a putative terminator were identified for the operon in UPTC CF89-12. In vivo transcription of the operon was confirmed in the UPTC cells. PCR experiments using two primer pairs designed in silico to amplify two arsR and arsC-acr3 segments, respectively, generated two amplicons, approximately 200 and 350 base pairs, with all 31 of 31 and 19 of 31 C. lari isolates (n = 17 for UPTC; n = 14 for UN C. lari), respectively. An inverted repeat forming a dyad structure, a potential binding site for a transcriptional repressor, was identified in the promoter region. Within the deduced 61 amino acids sequence of the putative arsR open reading frame from the UPTC CF89-12, a metal binding box and a DNA-binding helix-turn-helix motif were identified. The UPTC CF89-12 and some other UPTC isolates isolated from natural environment were resistant to arsenate.

Department of Bacteriology Northem Ireland Public Health Laboratory Belfast UK

Faculty of Pharmaceutical Sciences Hokuriku University Kanazawa Japan

Laboratory of Molecular Biology Graduate School of Environmental Health Sciences Azabu University Sagamihara 252 5201 Japan

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