The microbial ecology of Campylobacter jejuni in New Zealand within a spatial-temporal framework : a thesis presented in partial fulfilment of requirements for the degree of Doctor of Philosophy in Veterinary Science at Massey University, Manawatu, New Zealand
Campylobacter jejuni (C. jejuni) is an important cause of gastroenteritis internationally; it is a
complex bacterium carried by multiple hosts, showing phenotypic and genotypic variation. This
thesis systematically examines the molecular ecology and evolution of C. jejuni in New Zealand
from the levels of population movement, phenotype, genome and metabolism.
First, the demographic history of cattle, sheep and poultry importations into New Zealand (1860-
1979) was quantified. Australia was the most common reported source of cattle sheep and poultry,
with large numbers of cattle and sheep being imported in the 1860s, and large numbers of poultry
imported from the 1960s onwards. This suggests the population structure of cattle and sheep and
the microbial organisms they carried may exhibit a founder effect.
The second level investigated the phenotypes of related sequence types (ST) with generalist and
specialist lifestyles and compared them at 42°C and 22°C on the basis of carbon source utilisation
in Biolog phenotypic microarrays. The isolates utilised a total of 29 carbon sources in a pattern
that clustered them together on the basis of ST at 42°C more than lifestyle and host. At 22°C they
utilised a limited palette of carbon sources (9) related to the tricarboxylic acid cycle (TCA).
The third level, used genomic comparisons to identify a putative new species C. sp. nov. 4 spp.
in the Australian purple swamphen (Porphyrio porphyrio melanotus). Overall, the pattern of
relationship between isolates associated with the pukeko (Porphyrio porphyrio melanotus), takahe
(Porphyrio hochstetteri) and the Australian swamphen isolates suggested a recent common ancestor
and then divergence after separation. Despite high levels of recombination in C.jejuni, the genomes
grouped by clonal complex and ST, this suggests there are factors restricting regular recombination
between more distant C. jejuni STs. The draft genomes for the wild-bird and agricultural-related
isolates clustered by lineages in a host(s).
The fourth level involved the comparison of C. jejuni metabolic pathways (subsystems) to identify
host association. Type VI secretion system, Coenzyme A biosynthesis and Campylobacter spp. iron
metabolism were identified as important pathways in distinguishing between wild-bird and livestock