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Research has been conducted on the DNA inversion frequency. The effect of the 626-bp 5' conserved regions on this inversion based on the homologous recombination has been investigated and the results suggest that the Chi-like site disruption may affect the frequency of DNA inversion.

The invertible regions from type A strain 23D type B strain 84-107 Campylobacter fetus were cloned and sequence to determine whether the invertible region has genes which have a role in the expression, antigenic variation or secretion of C. fetus S-layer proteins (SLPs). Since each DNA sequence predicted four genes (sapCDEF), three of which are homologous to genes encoding type I secretion proteins, a mutation in sapD was formed. It was demonstrated that this mutant did not produce or secrete SLPs. Coexpression of the sapA and sapCDEF genes in Escherichia coli revealed that the sapCDEF genes are enough to permit secretion of SapA from the bacterial cell.

Reports that Campylobacter fetus, a spiral gram-negative bacterial pathogen, uses multiple loci for DNA inversion within the 5' conserved regions of sap homologs. Effect of mutations on sap inversion frequencies; Movement of the KpnI and NotI sites relative to the sapA promoter; Rearrangement in the FCR downstream of the antibiotic cassettes.