2 TYPES OF 16S RIBOSOMAL-RNA GENE ARE FOUND IN CAMPYLOBACTER-HELVETICUS - ANALYSIS, APPLICATIONS AND CHARACTERIZATION OF THE INTERVENING SEQUENCE FOUND IN SOME STRAINS

In the recently described species Campylobacter helveticus, two sizes of PCR amplicon were detected with primers homologous to conserved reg ions of the 16S rRNA gene. A conventionally sized gene was sequenced f rom the type strain, NCTC 12470, placing the new species as phylogenet ically related to C. upsaliensis and the thermotolerant campylobacters . This nucleotide sequence enabled PCR primers to be designed for use in rapid molecular identification of C. helveticus and its closest phy logenetic relative, C. upsaliensis. When this assay was employed to ch aracterize 22 'C. upsaliensis-like' isolates, twelve were identified a s C. helveticus and nine as C. upsaliensis, in agreement with data obt ained with a C. helveticus-specific DNA probe. A 550 bp amplicon inter nal to the 16S rRNA gene of C. helveticus was used to determine restri ction fragment length polymorphisms (RFLPs) in genomic Southern blots, confirming that the copy number of the C. helveticus gene was three, and identifying nine 16S rRNA gene profiles. In 5/12 C. helveticus iso lates identified by PCR, an enlarged amplicon was detected. The enlarg ed 16S rRNA gene of one of these strains, NCTC 12838, was sequenced an d shown to contain an atypical intervening sequence (IVS) of 148 nucle otides. The position and size of such an IVS was inferred in the other four isolates by PCR with primers 5' and 3' to its position in NCTC 1 2838. This is a first report of an IVS in the 16S rRNA gene of a eubac terium.