A Gut Feeling

Crucial work to understand the gut bacteria of koalas is raising the possibility of a new treatment for koalas, which could enhance survival rates of this vulnerable species.

When koala, Bingara Liz was admitted to the Port Macquarie Koala Hospital, she was in a bad way. Suffering from a severe case of chlamydia, her eyes were red and almost swollen shut. She was put on a course of intravenous and topical antibiotics to treat the infection. 

Liz is just one of many koalas (Phascolarctos cinereus) treated in wildlife hospitals every year. The Australian Koala Foundation estimates perhaps 20,000 koalas have been treated in facilities like the Koala Hospital since the mid- 1990s. As few as one fifth survive their treatment. 

“They’ll be on the antibiotic and the chlamydia will be starting to clear up but then the animal crashes,” says Dr Michaela Blyton, a research fellow at Western Sydney University’s Hawkesbury Institute for the Environment. “The assumption has always been that the antibiotic treatment has wiped out their useful gut bacteria and they’re not digesting appropriately, they stop eating, and they just go downhill.” 

Research from Blyton, and her colleague, Dr Ben Moore could lead to a new treatment for koalas to counter the harmful effects of the antibiotics, boosting their chance of survival. 

With the animal listed as threatened or vulnerable in New South Wales, Queensland and the Australian Capital Territory, the survival rate of koala hospital patients is critical to the species’ success in those states. 

Moore and Blyton have been profiling the diversity, abundance and activity of koala intestinal bacteria revealing an astonishing, complex relationship between koalas, their food and their microbes. They found that the microbial community of a koala’s intestine can be artificially altered. 

Moore started down the unusual path of examining koala faeces because he noticed that when koalas overbrowsed manna gum (Eucalyptus viminalis), their preferred food tree, most individuals didn’t switch to feeding on the less preferred messmate (E. obliqua) trees nearby. 

He realised that even though koalas can survive on both manna gum and messmate leaves, they seemed to be selective about the exact species of gum leaf they ate, creating a situation where koalas could be surrounded by edible gum leaves, yet starve to death. Moore wondered whether their microbiome played a role. 

He and Blyton designed an experiment to test whether koala feeding had any relationship to their gut bacteria. Along with collaborators, they captured koalas from a manna gum forest and kept them for two months, collecting their faeces and running DNA sequencing on it to identify the resident bacterial species and their functions. 

By night, the marsupials were given an abundance of messmate leaves; by day, they were offered manna gum to ensure they would still feed. For nine days, the animals were also administered two daily probiotic pills. Some were dosed with the bacteria extracted from the faeces of messmate-eating koalas living in the wild that had been previously caught and fitted with radio tracking collars, others were inoculated with their own manna-gum-conditioned bacterial community. 

Need to know

  • Researchers have profiled the gut bacteria of koalas    
  • Research found that gut bacteria communities can be artificially altered
  • Probiotic pills for sick koalas could be derived from this work

When Blyton looked at the results of the DNA sequencing she found that five out of six koalas’ microbiomes were changed by their messmate diet and probiotic course. “Some shifted a lot, while others shifted a bit: their microbiomes became more similar to those of the messmate-eating donors,” she says. 

Curiously, the researchers also found that the degree of change in the microbiome determined how much messmate they ate. 

“The more the microbiome shifted, the more messmate an animal was willing to eat,” says Blyton. 

The researchers are now exploring the possibilities for koala microbiome manipulation in more depth. 

While Bingara Liz survived, many koalas don’t. The researchers say their work could lead to a koala-specific probiotic pill to help maintain the delicate balance of intestinal flora during and after a course of antibiotics. 

“It’s important in terms of conservation biology, not just helping a few little animals that are sick on the sidelines,” says Moore. “There’s enough seriously threatened koala populations in New South Wales and Queensland where a substantial part of the population is coming into care. Losing those animals from the population is actually dooming the survival of those populations in the wild. We need to get them out of the hospital and back into those wild populations.” 

Meet the Academic | Dr Ben Moore

Ben Moore is an ecologist broadly interested in plant-animal interactions, chemical ecology and the causes and consequences of variation in plant chemistry. He is particularly interested in the chemical, nutritional and physiological ecology of Australian marsupials, like the koala, that feed on Eucalyptus. What adaptations and strategies have these animals adopted that allow them to survive on this challenging diet? How is climate and landscape change altering the ecology of these interactions? And how does the quality of Eucalyptus as food for herbivores vary across the landscape and through time?

Ben completed his honours degree in zoology at the University of Melbourne and then obtained his PhD from the Australian National University (Canberra).  He then spent 2.5 years at James Cook University in Townsville and 5 years at the James Hutton Institute in Aberdeen, Scotland.


This research was supported by the Australian Government through the Australian Research Council.

Future-Makers is published for Western Sydney University by Nature Research Custom Media, part of Springer Nature.