The presence of Helicobacter species in Australian marsupials was examined systematically using microscopy, culture, and PCR in different regions of the gastrointestinal tract (GIT) and in the liver of brushtail possums (BTPs) (Trichosurus vulpecula), a common Australian marsupial that feeds on eucalyptus leaves. The spatial distribution of Helicobacter species in the GIT sections also was examined microscopically in silverstained sections and by fluorescent in situ hybridization (FISH) using a Helicobacter genus-specific probe. Helicobacter species were found colonizing the lower bowel of all BTPs studied. Good agreement was observed between the detection of Helicobacter species using culture and PCR, which was supported by the microscopic examination of silver-stained sections and FISH. The lower bowel of BTPs were colonized by one to three morphologically different (a comma-shaped species with no apparent flagella, a fusiform-shaped species entwined with periplasmic fibers and a bipolar sheathed flagella, and an S-shaped species with bipolar sheathed flagella) and potentially novel Helicobacter species, as well as in one case with a potentially novel Campylobacter species, which was a tightly coiled rod with bipolar unsheathed flagella. The isolation and characterization of these Helicobacter species in BTPs provides important information regarding the specific natural niche of these bacteria and their corelationship within their host, and it increases our understanding of the ecology of Helicobacter species.Helicobacter spp. have been shown to naturally colonize the stomach and intestines of most animals and the liver of some animals (4,5,6,8). The genus Helicobacter is, in general, classified into two groups, gastric and enterohepatic Helicobacter spp. Gastric Helicobacter spp. have been found to colonize the stomach of humans, dogs, cats, cheetahs, rhesus monkeys, ferrets, sheep, cattle, whales, and dolphins, while enterohepatic Helicobacter spp. are more commonly found colonizing animals such as mice, rats, and hamsters (4, 28). At the commencement of the current study, no information concerning Helicobacter spp. in one of the major classes of Mammalia, the Marsupialia, was known. The common brushtail possum (BTP; Trichosurus vulpecula) is the largest tree-dwelling marsupial herbivore and feeds on a variety of leaves, particularly eucalyptus (17). Physiologically the BTP is a cecum fermenter, having a simple stomach and a well-developed cecum and proximal colon (15).The aim of this study was to investigate the presence of spiral (Sp)-shaped and fusiform (F)-shaped Helicobacter spp. colonizing the mucus layer of different regions of the gastrointestinal tract (GIT) as well as the liver of BTPs using microscopy, culture, and PCR. Spiral-and fusiform-shaped isolates were characterized and identified using morphological appearance, Helicobacter genus-specific PCR, and 16S rRNA gene sequence comparisons. The spatial distribution of Helicobacter species in GIT sections was examined microscopically in silverstai...

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