Campylobacter species are becoming increasingly significant to the health of humans. Campylobacters are notably difficult to isolate, maintain and manipulate and the use of molecular biology techniques is very limited. As a result few genes have been identified from this bacterium and little is known of its association with humans or animal disease in comparison to other enteric pathogens. A specifically targeted strategy employing the polymerase chain reaction with degenerate oligonucleotide primers (PCRDOP) was used to successfully clone portions of the C. upsaliensis flagellin genes, fla1 and fla2. Sequence analysis showed that the C. upsaliensis flagellin gene fragments were highly similar to the flagellin genes of C. jejuni and C. coli, although it contained a region of DNA extra to that of the other species. An alternative strategy was attempted to identify genes encoding potentially exported proteins using the transposon, TnPhoA. This technique resulted in the cloning of portions of the gene homologues of the a subunit of ATP synthase (uncB), an ATP-dependent protease (sms), two cytochromes (clpA and clpB), a cytochrome oxidase bd (cydA) and polyphosphate kinase (ppK). This is the first report of the identification of cytochrome bd in a campylobacter species. Campylobacters were previously thought to possess cytochromes of the b and c types only, and not the a or d types. The cytochrome bd is often hidden in other species when using traditional methods for identification of bacterial cytochromes involving spectrophotometry. A defined mutant in the putative cydA gene was engineered using a novel strategy for the transformation of campylobacters. The phenotype was investigated and revealed severe growth restrictions at low oxygen tensions.