ABSTRACT
Koalas are eucalyptus folivore specialists that are heavily reliant on their gut microbiome to breakdown their high fibre, low protein diet. Koalas in NSW, QLD and the ACT are also now endangered due to severe population declines, partly driven by a chlamydia epidemic that is underpinned by koala retrovirus. Here I will discuss our recent work investigating the koala gut microbiome; its role in koala health, nutrition and ecology. In doing so, I will also outline a SNP based method for determining which species of eucalypts koalas have eaten from their scats that has proven essential to our microbiome studies. We have shown that koalas eating different eucalypts have different microbiomes and this is likely because their microbiomes’ influence diet selection. Further, we have demonstrated that the gut microbiome is maternally inherited through pap feeding and this could contribute to geographic differences in microbiome composition and dietary preferences. We are also developing faecal inoculation therapies to assist in preventing gut dysbiosis when koalas are treated with antibiotics for chlamydia infection. I will then proceed to outline our work on koala retrovirus (KoRV), which is ubiquitous throughout koala populations and is the most recently endogenized (incorporated into the host’s germline) retrovirus known. Only KoRV subtype A has been incorporated into the koala’s genome, while another 12 exogenous subtypes exist that we have shown are primarily transmitted from mother to joey. Both KoRV-A and the exogenous subtypes appear to cause neoplasia (cancer) and we have found compelling evidence that they also cause immune suppression that leaves koalas more susceptible to secondary diseases such as chlamydia. However, our improved understanding of the virus provides hope that targeted management actions could improve koala resilience. For instance, the different exogenous subtypes are geographically restricted, viral titre in the blood is influenced by stress hormone levels and koalas on the sunshine coast have evolved the ability to supress KoRV in the testes via the piRNA mechanism.

BIOGRAPHY
Michaela Blyton completed her PhD at ANU in 2013 on the sociobiology, molecular ecology and pathogen transmission dynamics of mountain brushtail possums. Since then, she has undertaken postdoctoral positions studying the ecology and genetics of E. coli at ANU, the gut microbiome and nutritional ecology of koalas at Western Sydney University and koala retrovirus at the University of Queensland. She is now the group leader of the MMEOW (microbiology and molecular ecology of wildlife) team within the Australian Centre for Ecogenomics (ACE) at the University of Queensland. Her research uses molecular and genomic techniques combined with field-based studies to investigate host-microbe interactions and how they impact the health, ecology and conservation of wildlife.