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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.

Research was conducted to study the use of a shuttle vector and expression of tetO in Campylobacter fetus and to test whether C. fetus possesses recA. Chromosomal DNA was harvested from plate cultures while degenerate polymerase chain reaction primers were designed based on the conserved amino acid sequences of RecA. Results suggested that the rearrangement of SLP gene cassettes will occur by a site-specific mechanism different from previously described RecA-independent programmed DNA inversion mechanisms.