Molecular analysis and characterisation of the full-length flagellin C gene (flaC) from Campylobacter lari

A degenerate polymerase chain reaction (PCR) primer pair (f-ClflaC/r-ClflaC) was constructed in silico to amplify flaC and its adjacent genetic loci from Campylobacter lari isolates. Approximately 1.45 kbp amplicons, including the sequences encoding the flaC structural gene of 750 bp, putative promoter, rho-independent intrinsic terminator regions and partial sequences of two putative open reading frames (ORFs), immediately upstream and downstream of the gene, were identified in 16 C. lari isolates (four urease-negative [UN] C. lari; 12 urease-positive thermophilic campylobacters [UPTC)]). All 16 flaC structural genes commenced with an ATG start codon and terminated with a TAA stop codon and probable ribosome-binding sites were identified in all 16 isolates. These probably indicate a monocistronic operon structure for the flaC gene in C. lari isolates. In addition, the putative flaC gene ORFs were deduced to be similar in 747 bp among all 26 thermophilic Campylobacter isolates examined, resulting in a similar calculated molecular weight of approximately 26.6-26.9 kDa. The flaC from C. lari was different from the flaA-like sequence and the shorter flaA of UPTC isolates found previously. Reverse transcription PCR and Northern blot hybridisation analyses identified flaC transcription in C. lari cells. The transcription initiation site for the flaC gene was also determined by primer extension analysis. A dendrogram constructed, based on the nucleotide sequence information of flaC from 17 C. lari isolates, demonstrated that the C. lari isolates were genetically variable and formed two minor clusters for UN C. lari and UPTC.