What Rottnest's salt lakes hold: scientists map full genetic code of island bacteria

A team at Murdoch University in Perth has finished reading the full genetic code of bacteria drawn from the salt lakes of Wadjemup, the Western Australian island better known to the world as Rottnest. The work, completed in mid-2026 and reported on 20 July, gives researchers their sharpest look yet at how microbes survive in brine dense enough to float a human and hostile enough to kill almost everything else.

The island's fame rests on the quokka, the small marsupial whose selfie-friendliness has produced a decade of tourism marketing. Underneath that story sits a quieter one about water: a string of shallow lakes along the island's centre and northern end, scoured out by wind, lined by gypsum and salt-encrusted clay, and ten times saltier than the sea. Microbial life in those lakes has been studied in patches for years. What changed this summer is the depth of the read.

What the sequencing actually captured

According to the researchers, the new work produced complete, closed genomes rather than partial drafts, meaning every letter of the organisms' DNA was assembled, end to end. That distinguishes the project from earlier surveys, which tended to recover fragments and stitch them later. Closed genomes matter for one practical reason: they make it possible to identify, with confidence, the full set of genes an organism carries, including the metabolic machinery it uses to keep its interior isotonic with the brine outside.

For halophiles, the obligate salt-lovers that dominate these lakes, the core trick is pumping potassium into the cell to match the osmotic pressure of the surrounding water. The genetic inventory from Wadjemup now maps the versions of those pump proteins, and the enzymes that let the bacteria run their central metabolism at molar salt concentrations, more completely than any prior dataset from the island.

Why a small island's salt pans matter

Rottnest is not unique in hosting hypersaline lakes. Comparable systems exist along Western Australia's coastline, in the salt flats of Tunisia and the Dead Sea works of Jordan and Israel, and in the engineered salterns of Mexico and California. What makes the Wadjemup lakes a useful natural laboratory is geography: they sit on an island, in a managed reserve, with relatively few outside inputs, so the chemistry and the resident communities are mostly shaped by evaporation and rain rather than by industrial runoff. Closed genomes from such a clean baseline provide a reference other systems can be compared against.

The structural interest goes beyond local curiosity. Salt lakes hold a meaningful slice of Earth's microbial biomass, and they are also one of the most plausible terrestrial analogue sites for how life might persist elsewhere. Closed genomes from Wadjemup add to the catalogue of strategies extremophiles use to keep their proteins folded and their metabolism running at ionic strengths that denature most life on Earth.

The honest limits of the dataset

The sequencing is comprehensive within the samples collected. It does not, by itself, establish what those bacteria are doing in the lake every hour of the day. Microbial communities fluctuate with temperature, rainfall, brine concentration, and seasonal algal blooms, and a genome read at one moment captures potential more than behaviour. The Murdoch team have also signalled that functional follow-up will be needed, including stress tests on isolates in the lab and time-series sampling across seasons, before the genetic inventory can be tied to measurable rates of nitrogen cycling, carbon turnover, or pigment production in the lakes themselves.

It is also worth noting what the work does not cover. The dataset captures the culturable and most readily sequenced fraction of the community. The bulk of microbes in hypersaline systems globally is still invisible to short-read sequencers, and reading those genomes will require the same long-read, single-molecule methods that produced the closed genomes from the culturable side. For now, the picture is sharply detailed where it lands, and silent where the methods cannot reach.

What the finding changes

Practically, very little moves next week. The first downstream users will be the Australian extremophile community, which gains a reference dataset against which to compare other sites. The wider significance is cumulative rather than singular: a credible set of closed genomes from a clean site, available to other labs to query, adds one more well-described point to what is still a sparsely sampled map of salt-lake biology. Over time, that kind of catalogue is what makes larger claims, about how halophile metabolism compares across continents, or how the Wadjemup communities shift as the climate dries and the lakes concentrate further, answerable.

Monexus framed this as a baseline-data story rather than a discovery story, which is what the sequencing actually supports; a closed genome is a reference, not a revelation.