One of the Australian native, critically endangered lizard species: Lister’s gecko. Credit: Parks Australia
Bacteria responsible for the deaths of critically endangered species.
With the destruction of wild populations, Lister’s gecko exists and the blue-tailed deer only feeds in captivity. Researchers from the University of Sydney have discovered a bacterium that could cause their potential extinction.
Native reptile populations on Christmas Island have deteriorated sharply with two species, Lister’s gecko and the blue-tailed skin, which have completely disappeared from the wild. Although previously the main driver for this decline was probably the invasion by invasive species and destruction of habitats, a silent killer now threatens to wipe out the species completely.
Those bred in captivity on Australian territory in the Indian Ocean are also mysteriously dying, putting the two species – which number only about 1,000 each – at risk of extinction. Veterinary scientists from the University of Sydney, the Australian Register of Wildlife Health and the Taronga Conservation Society Australia have now discovered the cause of these deaths: a bacterium, Enterococcus lacertideformus (E. lacertideformus).
Infected goat showing severe head and face swelling associated with Enterococcus lacertideformus infection. Credit: Jessica Agius
The bacterium was discovered in 2014 after reptiles in captivity had facial distortions and lethargy, and some even died. Samples were collected and analyzed using microscopy and genetic testing. The findings of the researchers, published in Boundaries in microbiology, will inform antibiotic trials on the reptiles to see if the infection can be treated.
The bacterium grows in the animal’s head, then in its internal organs, before eventually causing death. It can be spread by direct contact – also through reptiles’ mouths, or by reptiles that bite each other – often during fights during the breeding season.
“This means that healthy animals in captivity should not be kept from infected animals and that they should also be kept away from areas where infected animals were,” said Jessica Agius, co-principal researcher and PhD candidate at the Sydney School of Veterinary Science, said.
PhD researcher Jessica Agius critically threatened lizards in the field on Christmas Island to find out if they were infected with Enterococcus lacertideformus. Credit: Jessica Agius
Agius and the research team not only identified the bacterium but also decoded its genetic structure through the entire genome sequence.
Specific genes have been identified that are likely related to the bacterium’s ability to infect the host, invade the tissue, and evade the immune system.
“We also found that the bacterium can surround itself with a biofilm – a ‘community of bacteria’ that can help it survive,” Agius said.
‘To understand how E. lacertideformus producing and maintaining the biofilm can provide insights into how to treat other species of biofilm-forming bacteria. ”
The search for the genetic code suggests that the killer bacterium is susceptible to most antibiotics.
Professor David Phalen, research leader and me. Agius’s PhD supervisor, said: ‘This indicates that infected animals can be treated successfully. This is what we need to determine now. ”
In another effort to protect the endangered reptiles on Christmas Island, a population of bluegrass has been established on the Cocos Islands. Agius played a critical role in the translocation and tested reptiles on the Cocos Islands to make sure they were free of E. lacertideformus.
“It is critical that we act now to ensure that these native reptiles survive,” Agius said.
Reference: “Genomic insights into the pathogenicity of a new biofilm formation Enterococcus sp. Bacteria (Enterococcus lacertideformus) Identified in reptiles ”by
Jessica Esther Agius, David Norton Phalen, Karrie Rose and John-Sebastian Eden, March 2, 2021, Boundaries in microbiology.
DOI: 10.3389 / fmicb.2021.635208
Statement: The authors thank the Westmead Institute for Medical Research, Sydney School of Veterinary Science – University of Sydney, Australian Registry of Wildlife Health – Taronga Conservation Society Australia, and Christmas Island National Park – Parks Australia for their logistical and financial support.