Ten isolates of an unknown Campylobacter species were isolated from cloacal swabs obtained from captive adult whooping cranes (Grus americana). All isolates were identified as Campylobacter based on generic PCR and grouped with other Campylobacter species based on 23S rRNA gene sequence. None of the isolates could be identified by species-specific PCR for known taxa, and all ten isolates formed a robust clade that was very distinct from known Campylobacter species based on 16S rRNA, rpoB and cpn60 gene sequences. The results of 16S rRNA gene nucleotide sequence (<or=92% sequence similarity to recognized Campylobacter species) and genomic DNA (no detectable relatedness) analyses were consistent with novel species status. Cells of the Campylobacter from whooping cranes were uniflagellar and typically sigmoid to allantoid in shape (0.48 microm wide and 2.61 microm long), but also spheroid to coccoid (0.59 microm wide and 0.73 microm long). The bacterium was oxidase-positive, able to reduce nitrite, able to grow at 3 degrees and 42 degrees C, and grew anaerobically, as well as in an atmosphere devoid of H2, and on MacConkey agar. It was not alpha-haemolytic and was negative for hippurate and indoxyl acetate hydrolysis and alkaline phosphatase. It also was susceptible to cephalotin and was unable to grow on nutrient agar, on a medium containing 3.5% NaCl or in ambient O2. The bacterium was unable to grow at 25 degrees C and growth was negative or very restricted at 30 degrees C. Fluorescent amplified fragment length polymorphism analysis indicated that nine of the recovered isolates were genetically distinct. A species-specific primer set targeting the cpn60 gene was developed. The name Campylobacter canadensis sp. nov. is proposed for the novel species, with the type strain L266T (=CCUG 54429T=LMG 24001T).