Abstract:
Duvaucel’s gecko is an endemic New Zealand lizard that has been relegated to offshore islands due to the effects of habitat loss and predation by introduced mammals. The main approach used to manage this threatened species involves the translocation of animals between offshore islands, with the purpose of increasing genetic diversity and generating self-sustaining wild populations. Prior to translocation, geckos are required to undergo testing for certain microorganisms, including Salmonella, to minimise the risk of spreading potential pathogens between islands. However, a current lack of knowledge about baseline health parameters, including what constitutes a ‘typical’ gut microbial community, makes it difficult to conduct disease screening in a targeted and cost-effective way. Microbial community structure and composition in the gut have a demonstrated effect on a wide range of health parameters in various vertebrate species, however few gut microbiota studies have focussed on reptiles. The first part of this study used 454 pyrosequencing to target the bacterial 16S rRNA genes in the Duvaucel’s gecko gut, providing the first investigation into the structure and composition of the gut microbiota in this species. The results from this investigation suggested that the gut microbiota of the Duvaucel’s gecko is broadly similar to those of other reptile groups which have been sampled to date, and indicated that a ‘core’ bacterial community exists among conspecifics. Although there was no evidence of sexual asymmetry, pre-quarantine and post-quarantine Duvaucel’s gecko gut samples showed significant differences in microbial composition, which is likely attributable to factors associated with captivity, such as an artificial diet. The most common bacterial phyla recovered across all samples were Proteobacteria (class Gammaprotoeobacteria), Firmicutes and Bacteroidetes. The second part of this study used PCR to evaluate the recovery of Salmonella cells from Duvaucel’s gecko cloacal swabs, and examined the distribution of Salmonella sequences obtained from the 16S rRNA-gene based pyrosequencing of the Duvaucel’s gecko gut microbiota. PCR with Salmonella-specific primers was successfully able to identify Salmonella in geckos which had already tested positive for Salmonella using traditional (cultivation-based) testing methods, and it was found that these samples also exhibited a high number of Salmonella-affiliated 16S rRNA gene sequences. The sensitivity of the methods used in this study to recover Salmonella genomic DNA was estimated to be in the range of 1-2 CFU per mL, or per swab. It is hoped that this research will aid in the conservation of this threatened species by providing valuable information about the ‘core’ bacterial community, which will allow for the identification of allochthonous, potentially pathogenic bacteria, if they arise.