In a diagonal swathe from Ruapehu to White Island, the Earth’s surface stretches and seethes, steaming with the sulphurous breath of the thousands of hot springs that pockmark the Taupō Volcanic Zone.
The springs have a pH of one, or almost 10. They are 100ºC, or 20ºC—or, in the case of one called Inferno Crater, flip from 30ºC to 80ºC once a month. They are blood red, iceberg blue, snot green, and muddy brown. They are stream-side pools locals like to swim in, beautiful silica-fringed terraces, and stinky black holes in the ground.
And, strangely, almost all of them are heaving with life.
We know this only because new gene-sequencing technology has, just in the past five years, made it possible to quickly and cheaply identify the microscopic creatures living there, in some of the most changeable and extreme environments on Earth.
For the past two years, microbiologists from the University of Waikato and GNS Science have been picking their way between boiling mud pools to take samples from 1012 hot springs across the volcanic zone. Matthew Stott leads GNS’s Extremophiles team, and conceived the ‘1000 Springs’ project along with the university’s Craig Cary.
“Conveying how exciting this is can be difficult for microbiologists, because you’re trying to explain something that’s invisible to the naked eye,” Stott tells me, as he shows me around a spring at Wairakei Terraces, five minutes down the road from the GNS campus outside Taupō. “We just have to infect people with our enthusiasm.”
As we watch superheated water boil out of the ground and flow down a series of sculpted terraces, he bombards me with a series of mind-boggling facts: There are more micro-organisms living in a handful of soil than there are people on Earth; you are only 10 per cent human (the rest of the cells in your body belong to bacteria using you as a host); the living things you can see make up only half of all life on this planet. Stott’s interest is in the other half.
“Micro-organisms don’t have an issue with oceans, or mountain ranges. They can float in the air, they can cross continents inside rain clouds and hitch rides on the backs of birds… everything is everywhere, the environment selects,” he says.
Hot springs are wildly divergent in acidity and temperature and surrounded by toxic gases. Extremophiles (literally, ‘extreme-lovers’) have adapted over millennia to take advantage of the particular conditions in each spring. Because the Taupō Volcanic Zone has one of the highest concentrations of geothermal activity in the world—surpassed only by America’s Yellowstone National Park—Stott reasoned it was likely these rare conditions had brought about some rare forms of life.
“Is there a spring out there that has bacteria that haven’t been seen anywhere else in the world? Is there a spring that has the closest thing to alien life that can be found on Earth? We just don’t know. And yet we have been making decisions about which springs to protect and which to develop, without even knowing what’s in there.”
To find out more about what lurks in New Zealand’s hot springs, I tag along with the extremophiles team on a field visit to Whakarewarewa Village in Rotorua. It’s a hot sunny day in late spring. We walk over the bridge where children used to dive for pennies, past the marae and the church and the small wooden houses straddling steaming fumaroles, and down to a sludgy-looking series of pools beside the stream, overlooked by a carpark and the hotel balconies of the Holiday Inn.
It seems an unlikely location for a frontier of science.
Whakarewarewa has been a tourist magnet since the late 1800s, when the Tūhourangi people—already well-known guides to the famous Pink and White Terraces —settled there after the 1886 eruption of Mt Tarawera, and continued their tradition of welcoming visitors. Now busloads of tourists roll up every day to be guided through the thermal valley by their Tūhourangi/Ngāti Wahiao hosts, who still use the heated waters for cooking and bathing.
Stott and his team are on a tour of a different sort—prospecting for new forms of life. PhD student and lead field researcher Jean Power perches on the edge of a gently steaming shallow spring, demonstrating how to collect samples. The main data collection finished last April, but she’s returning now to train a masters student and re-sample a few springs.
Using a long metal pole with a plastic bottle clasped at its end, she scoops water from the centre of the pool, filling containers that will be taken back to the GNS lab at Wairakei for analysis of both the water’s physical properties and the life it contains.
Power also measures the water temperature, and draws a rough map of the spring on her tablet. She’s done the same thing almost a thousand times over the past two years, missing only 36 out of the 1012 springs sampled during the project.
This one is tame by comparison with some of the places the work has taken her—flying in by helicopter to White Island, sampling springs along the edge of Lake Rotomahana from a boat, and scooping water from the catchment pool of the Pohutu geyser as it blew. (For health and safety reasons, they decided not to sample from the geyser itself, instead collecting the water as it landed.)
The ground around many springs is unstable—shot through with subterranean channels, eroded by acids. Stott and Power must test every patch of ground with a pole before they set foot there; others they can’t safely visit at all.
There’s also deadly gas. As we walk around Whakarewarewa, our conversation is punctuated by the soft beeps of Stott’s gas monitor, scanning for unsafe levels of carbon monoxide, carbon dioxide and poisonous hydrogen sulphide. Some springs can be visited only on windy days, when the breeze can transport toxins away.
“If someone starts mumbling, it’s time to get out of there,” says Stott. “That’s the first sign they’re being affected by gas.”
So far so good: Stott’s team surveyed more than a thousand hot springs with the only casualty being a mobile phone that wound up taking a bath in hot acid.
“Geothermal environments are inherently unpredictable,” he says. “You can never be entirely sure what’s going to happen.”
The study of extremophiles is relatively recent. Fifty years ago, it was believed that life couldn’t survive in water hotter than 73ºC. In the mid-1960s, a professor at the University of Indiana called Thomas Brock began studying the microbial ecology of Yellowstone’s famous thermal springs.
He realised the received wisdom was wrong. In one pool, Octopus Spring, he observed colonies of bright-pink, stringy bacteria, even though it reached temperatures of 88ºC. Brock decided to dip microscope slides into every bubbling pool he could find.
Although the hot water looked empty, under the microscope “the results were dramatic,” he later wrote. “Virtually every slide, from every boiling or superheated pool, had heavy bacterial growth.”
Since then, scientists have found microbes thriving in an asphalt lake, inside freezing stones in Antarctica, and feeding on nuclear waste.
Bacillus infernus—the ‘bacterium from hell’—lives more than two kilometres underground where temperatures are 75ºC and breathes iron instead of oxygen; while ‘snottites’ eat sulphur and excrete potent sulphuric acid, forming a microbial mat with the consistency of mucus that hangs from cave ceilings like a stalactite.
Thomas Brock’s Yellowstone discoveries kick-started the study of extremophiles—but it was one particular species he found there that made him famous.
In 1966, Brock and his student Hudson Freeze isolated a new kind of thermophile from Mushroom Spring, a bacterium they named Thermus aquaticus. In the 1980s, another scientist, Kary Mullis, needed an enzyme that could work at high temperatures for his pioneering technique Polymerase Chain Reaction (PCR)—essentially a way to ‘photocopy’ DNA. He found the enzyme he was looking for in Thermus aquaticus, calling it Taq Polymerase.
PCR has revolutionised modern molecular biology. It’s used in biomedical research, genetics and forensics, and has generated billions of dollars—as well as a Nobel Prize for Mullis—in the 30 years since it was made possible by an accidental discovery in a hot spring.
The possibilities aren’t lost on Matthew Stott. “It’s the best way to justify this research. We could find the next Taq Polymerase!”
In a neat twist, the advances in genomics ushered in by Thermus aquaticus have enabled Stott and Cary’s study of New Zealand’s hot springs. They’ve been able to piggyback off investment by governments and the healthcare industry in mapping the human genome, which has made gene sequencing exponentially faster and cheaper. The cost of sequencing a human genome has plummeted from about US$10 million to a few thousand dollars in just six years.
“It’s incredibly dynamic. We’ve gone from one person being able to sequence one gene in, say, four months, to doing millions in this project over two years,” says Stott.
“We couldn’t have done it even five years ago—we would have been able to look at half the number of springs and spent three times as much money.”
Back in Wairakei, a moustachioed microbial ecologist from Canada called Carlo Carere shows me around the GNS extremophiles lab. It looks pretty much as you’d expect—microscopes, computers, a minus-80ºC freezer, and fridges with stickers reminding staff not to keep their lunch in with the microbes. Rows of test tubes oscillate in unison, the rhythm of the machines competing with poppy music videos playing on someone’s laptop.
Here’s how the 1000 Springs project works: water samples collected in the field are rushed back to the lab the same day. The water is analysed for pH, conductivity, turbidity, dissolved gases and compounds, before the extremophiles are filtered out.
Until recently, the only way to identify micro-organisms and find out what they could do was to isolate them, coax them to grow in the lab, and test them—a time-consuming process with a low chance of success, as the vast majority of bacteria are difficult or impossible to cultivate.
Now, scientists use a Polymerase Chain Reaction machine (thanks, Thermus aquaticus) to copy extremophile DNA, which they send away to be sequenced.
“We sequence the gene that is present in all of life, and then compare that code to a global database which will show us where it sits in the tree of life,” Carere tells me. “It’s very powerful. You can look at 3000 different species and say, what are these capable of, and how are they similar and how are they different.”
As the data come in, the team updates the project’s website. Clever interactive diagrams help to visualise the extremophile ecosystem at each site, allowing landowners, iwi, tourism operators and the public to learn about their local springs.
Regional councils, too, can use the data to assess planning proposals—though Stott’s keen to stress it’s not about blocking development.
“The data might show there are 30 similar springs, so maybe we can afford to lose one,” he says. “We’re not making a judgment on conservation—we’re just giving people what they need to make informed decisions about their resources.”
The next step for the scientists is to analyse the data. It’s early days, but it’s already clear just how special some of these springs are.
“There’s one at Ngatamariki, over the hill here, it’s like the Amazon of microbiology in New Zealand,” says Stott.
“You’d walk right past it because it looks ugly, but the organisms in there are just phenomenal, unheard of—it’s an amazing place. We could work in there for the rest of our lives and there’d still be more work to do.”
Even in the small spring by the stream at Whakarewarewa, Stott estimates 90 per cent of the microbes are new to science. “Not just new species, but whole new phyla,” he says.
We humans belong to the phylum ‘chordates’, which includes everything with a spinal cord—from geckos to kereru to humpback whales.
“We’ve found micro-organisms that are so mysterious we don’t know what they are beyond the fact they’re bacteria. So that would be the equivalent of looking at some animal and saying, ‘Well, it’s got a spinal cord—that’s new.’”
The GNS team hasn’t found the next Taq Polymerase yet, but has identified several species of bacteria that can break down sugar at high temperatures, which could be useful in biofuels production. They’re also hopeful they’ll find an extremophile that produces heat-stable antibiotics, says Stott.
“Bacteria are usually in competition with each other and often generate compounds to beat up their mates. We spend a lot of money keeping medicines cool—so our hypothesis is that if you can get temperature-stable anti-microbial agents from thermophiles, you could make stable medicines that could be put in the back of a truck and driven into a developing country that doesn’t have reliable refrigeration.”
One of the perks of finding new lifeforms is that you get to name them, although you can’t go calling your microbe ‘Supermanii’: the taxonomic authorities encourage you to reference attributes, function or location. So for Limisphaera ngatamarikiensis (‘soil-dwelling sphere from Ngatamariki’), the GNS team agreed on the name with the landowners of the spring where they found it.
But it’s safe to say there won’t be any extremophiles named Stott any time soon. “Generally only dead people and emeritus scientists get species named after them, and I’m none of those things yet!”
Being able to point to potential industrial applications helps researchers to secure funding, but extremophiles also invite speculation on some of the biggest questions in science.
All microbiologists are on the lookout for LUCA, Stott tells me, as we crouch on the rocks at Whakarewarewa, peering into a pool lined with beautiful blue-black microbial sludge. That would be our ‘Last Universal Common Ancestor’—the single living cell from which all life on Earth evolved. (Luca also happens to be the name of Stott’s son, but he insists he didn’t realise the connection until later: “I would so not get away with that!”)
Scientists believe life began about 3.8 million years ago, and that first spark probably happened around a deep-sea thermal vent or a freshwater hot spring.
“That first organism needed to be able to deal with the conditions that were prevalent at that time—hydrogen sulphide, acid, carbon monoxide, and very little oxygen,” says Stott. In other words, it was probably an extremophile.
And if life can survive in a White Island crater that’s 99ºC with a pH of -0.8 (bacteria from 10 different phyla have been identified at that site), it begs the question… Where else might we find it?
In the icy iron-red gullies of Mars? In the liquid methane lakes of Titan, one of Saturn’s moons? Or in an underground ocean on Jupiter’s moon Europa?
“It’s inconceivable that there’s no life on other planets,” says Stott. “Just look at the conditions that micro-organisms can deal with here. I can’t believe that we’re alone.”
But he’s happy to leave that question to the exobiologists.
“Sure, we’d all like to explore Mars, but we’re still making incredible discoveries here on Earth. We’re in the middle of Rotorua—and there’s life here that no one’s documented before. There are so many amazing things to discover right here in our backyard.”