Hunting for the tardigrade: one small step toward sequencing the DNA of every living thing on Earth | Biology

Witek Morek takes a closer look at an old brick and stone wall at the Cambridgeshire campus of the Wellcome Sanger Institute.

“We’re going to use a very advanced tool designed by bioengineers and evolved over millions of years – the human hand – and grab some moss, put it in an envelope,” he said.

This is the tardigrade hunt, the first small step in a huge, ambitious scientific undertaking: the genetic sequencing of all life on Earth.

Accompanied by Prof. Mark Blaxter, who leads the center’s Tree of Life program, Morek, a postdoctoral researcher and tardigrade specialist, continues to collect the leaves from a walnut tree in the green center, before returning to the lab with his samples.

In 1998, a millimeter-long nematode worm became the first animal to have its entire genome sequenced. The human genome began to be sequenced five years later, although it was not completely completed until 2021.

The genome is the instructions for making an animal, written in a chemical code known as DNA. Genomics looks beyond genes to all the DNA found between genes. Establishing “reference genomes” for species can help scientists better study biological and evolutionary biology, as well as identify new drugs and compounds.

Sequencing genomes took years. Blaxter sequenced 18 genomes in 25 years of study in his early work. Now, the Tree of Life program has 48 episodes each week, thanks to advances in programming technology. 2,600 genomes have been sequenced so far, from whales to fungi, with a particular focus on British and Irish species.

And now it’s the turn of the little tardigrades – the famous winner of last year’s Guardian invertebrate of the year competition.

About 1,500 species of tardigrade – the name means “slow ladder” – have been identified around the world so far. They are indestructible, able to survive extreme heat, extreme cold and even a spell in space. This is due to their ability to disintegrate and dry animation, until they are rehydrated.

Morek begins the sequencing process by placing the moss and lichen samples he has collected in a beaker of water. After thirty minutes, the tardigrades move.

He puts small pieces of moss under a microscope and immediately sees a tardigrade. It shakes the fat baby’s legs. This “moss piglet” is a metamorphosed, medium-sized tardigrade, about 350 micrometers long (a human fur is 50 micrometers wide). Freshly eaten: A Morek can see the contents of its intestines.

Morek, who has collected about 20 of the 50 tardigrades in the British catalog (“a huge underestimation” of the species’ total, he says), will have to see its eggs to identify the true species. Some tardigrades have smooth eggs; some have mushroom, conical or needle-like faces.

Tardigrades can be “voracious predators, chasing nematodes and eating them like spaghetti”, says Morek. But he also revealed how they can show parental care. Sometimes the mother discards the cuticle (her skin) containing the eggs safely inside the scaly skin. But it keeps the cuticle attached to the legs until the eggs hatch.

Morek made a temporary slide – placing the tardigrade in the middle of the glass – to confirm its taxonomy as closely as possible. It should be temporary because the water will evaporate and the tardigrade can be crushed by the glass.

The tardigrade is kept alive and transferred in a barcoded plastic tube. This is frozen for sequence over time – stored in special double-door freezers set at -71C.

There are four high-quality tardigrade genomes in the public database, Morek is working on another 14, and there are about 50 in the freezer waiting to be sequenced.

Before extracting the DNA for sequencing, Witek must “disrupt” his specimen. He can cut a 200 micrometer tardigrade by hand or use a type of fusion inside a block of ice when it freezes.

A tardigrade has a small amount of DNA, 200 to 500 picograms (one picogram is one third of a gram). In the old days, researchers would have to clone 1,000 tardigrades to get enough DNA, a difficult process that was impossible with rare or hard-to-find species. Another strategy is to use a single female to produce large numbers of genes.

But the Wellcome Sanger Institute uses a different approach: a multimodal picogram input sequence protocol.

In this way, genomic DNA and RNA are extracted from the tardigrade and separated into two tubes. Researchers then use polymerase chain reaction (PCR) to amplify these fragments to create enough material.

The quality of the DNA produced is checked and the samples are given to the center’s scientific team. After sequencing, the data is available in the center’s computer cluster. The chain itself is a million strings long of the four types of bases found in the DNA molecule: adenine, cytosine, guanine and thymine (ACTG).

Fortunately for tardigrade researchers, tardigrade genomes are small – 30 times smaller than the human genome. Although the PCR process is complex, scientists need little data to assemble the tardigrade genome.

For Morek, sequencing the tardigrades will help reveal how the species are related. Amazingly, some tardigrades are separated by 550m of evolutionary years.

But genome sequencing may also reveal that tardigrades’ superpowers – such as resistance to cold (cryobiosis), resistance to lack of oxygen (anoxybiosis) and the ability to repeatedly survive extinction (anhydrobiosis) – can help us.

“And, because most of the things that live on this planet are small, like tardigrades, this new method of genetic sequencing promises to open the gates to the sequencing of all life,” Blaxter said. “These genomes will open up new ideas and opportunities in biomedicine and biotechnology.”

By sequencing, scientists can identify the genes and proteins required for these processes. If a certain protein is important for anhydrobiosis, can we use it to produce dry vaccines, or add it to plants to make them drought resistant?

“There are many research questions,” said Morek. “The more we know, the more questions we ask. It’s a never-ending story.”

Invertebrate of the year is here for 2026

The tardigrade won last year, but who will win in 2026? The whistle blew to launch the third invertebrate competition of the year.

We, creatures with backbones, are a minority in the animal world. People, dogs, cows, birds, fish – we may think we are the rulers of the planet but we are not. We make about five percent of the animals on earth; but on the other hand there are at least 1.3 million species of invertebrates to choose from.

We want you to nominate your favorite invertebrate in the Guardian’s most popular annual event celebrating the wonder and importance of the world’s invertebrates. Without the unseen activities of our untold neighbors – snails, spiders, sponges, corals, bivalves, wasps and crabs – the great edifice that is human civilization would crumble.

These are our pollinators, soil builders, breeders, water cleaners, predator cleaners and pest controllers. A few invertebrates may wreak havoc on the human world but as the famous biologist EO Wilson put it: “The truth is that we need invertebrates but they don’t need us.”

Please select your favorite invertebrate here. Our writers will shortlist 10 and enter their details and on August 17th we will announce your favourite.