Native American scientist Robin Wall Kimmerer tells the story of mosses, the first plants to develop the ability to live on land. Unlike other plants they can survive long periods of drought in a condition of dessication – dry, brittle, brown – then spring back to life as soon as a drop of rain hits the ground.
I pray to the small things
who shape the world with invisible wisdom
teach me all I need to know
In Gathering Moss Native American professor of biology Robin Wall Kimmerer speaks of the resilience of mosses. These ancient bryophytes, the first plants to develop the ability to live on land, are simple yet tough. Kimmerer tells the story of how they developed 350 billion years ago from algae who were either left stranded in pools or attempted to colonise the ‘shady crevices of the rocky shore’.
To survive they developed a ‘new architecture’: stems to hold them upright, root-like rhizoids to anchor them to the soil, tiny leaves one cell thick to photosynthesise (but only when damp as they lack the vascular system of later plants wherein water is carried by phloem and xylem).
As algal eggs usually float in water one of their biggest challenges was reproduction. In a ‘huge innovation’ they developed the female structure of the archegonium to protect the egg and the male antheridia filled with sperm. Water on mosses carries the sperm to the egg and fertilisation brings into being a sporophyte to ‘create and disperse the next generation’.
Mosses played a leading role in the development of life on Earth. As they evolved and spread across the land their photosynthesis removed carbon dioxide from the atmosphere and replaced it with oxygen. This caused a drop in global temperatures and the first glaciations. The weathering of rock and death of mosses provided soil for vascular plants as homes to the creatures who left the seas.
Considering their longevity it is little wonder mosses are so resilient. Unlike other plants and trees they can survive long periods of drought and even a complete lack of water in a condition of dessication – dry, brittle, brown – then spring back to life as soon as a drop of rain hits the ground.
MOSS PIGS IN SPACE
In the ‘microscopic forest’ of mosses Kimmerer notes an equally resilient creature can be found. Tardigrades (from tardigradum ‘slow walker’ also known as ‘moss pigs’ and ‘water bears’) are tiny animals 0.3mm to 1.2mm long with ‘translucent and pearly white’ bodies composed of a chitin and protein cuticle, ‘eight stumpy legs’, ‘long black claws’, round heads, and ‘sucking mouthparts’ with a ‘stylet like a hypodermic needle’ that pierces moss cells and sucks out the contents.
Like mosses they can endure drought and dessication by entering a state of anabiosis ‘lack of life’. Shrinking to one eighth of their size, pulling in their legs, they form ‘barrel-shaped miniatures of themselves called tuns’. When water returns, with their mossy homes, they revive and resume their shape.
In their tun state tardigrades are able to endure a number of extremes. For a few minutes some can survive temperatures of 151°C and – 272°C, the low pressure of a vacuum, high pressures of 600 MPa, and 6000 gy of radiation. They are the only animal to have endured being blasted unprotected into outer space, surviving both the vacuum and the UV rays of the sun (which did take its toll on some).
Their ability to survive radiation has its basis in a protein which protects their DNA. This has the potential to ‘benefit people undergoing radiation therapies’ and ‘may one day protect workers from radiation in nuclear facilities or possibly help us to grow crops in extreme environments, such as the ones found on Mars.’
With the earliest fossils dating to 530 million years ago tardigrades have survived five mass extinctions. However, they are not extremophiles, beings who not only endure but love and thrive in extreme conditions.
Extremophiles include archaea, bacteria, algae, lichens, and fungi. Archaea and bacteria are the oldest living beings on earth, dating to 3.5 billion years ago, long before the Great Oxygenation Event. Many cannot survive oxygenated conditions. They are found deep in the earth’s crust, in polar ice, the depths of the ocean, volcanoes, hydrothermal vents, geysers, and hot springs.
Extremophiles are able to endure extremes of temperature, salinity, acidity, alkalinity, and radiation. The most thermophilic is an archaea named Pyrolobus fiimarii which grows happily at 113°C. Dunaliella salina, a green halophilic alga, thrives at 25 – 33 % salinity and can survive in saturated sodium chloride. Acidophilic fungi such as Ferroplasma acidarmanus have been found growing near pH 0 ‘in a brew of sulfuric acid and high levels of copper, arsenic, cadmium, and zinc.’
Unsurprisingly, humans have subjected extremophiles to extremes of radiation. The aptly named Deinococcus radiodurans possesses the ability to endure ‘up to 20 kGy of gamma radiation and up to 1,000 joules per square meter of UV radiation’ and can repair its genome after it is blown apart. Countless extremophiles have been blasted naked into space to test the limits of their endurance.
These small creatures share the ability to exist in extremis ‘in the furthest reaches’ or ‘at the point of death’. As scientists learn more about them through experiments the limits of possibility are expanded along with the potential to exploit their capacities.
The possibilities of using extremophiles at very high temperatures and levels of acidity in the production of biofuels and bioplastics and in biomining are currently under investigation. Scientists at the Department of Energy aim to augment D. radiodurans to clean up toxic and radioactive spills. The chances of their survival on space shuttles, Mars, and Europa are being tested.
In medicine, biotechnologist James A. Coker says ‘microorganisms, including extremophiles, are producers of a host of antibiotics, antifungals, and antitumor molecules. In truth, this should come as little surprise, as microorganisms have been killing each other and fighting for survival for billions of years. After that long a time, it should be clear that microorganisms have perfected the art of warfare, but it is up to us to take advantage of it.’
These actions are symptomatic of a civilisation which is itself in extremis. Having destroyed the fragile atmospheric balance that has provided the conditions for life as we know it since the last Ice Age and initiated the sixth mass extinction, scientists search for increasingly extreme solutions, forgetting that the manipulation and exploitation of nature is how we ended up in this situation.
In Gathering Moss Kimmerer talks about how modern scientists have lost touch with indigenous beliefs in plants and animals as teachers. In her work as an Associate Professor of Environment and Forest Biology she strives to combine her ancestral teachings with her scientific research.
This involves treating mosses not as objects of study but as persons and listening rather than imposing theories. For example when she was investigating why Tetraphis reproduces in two ways – gemmae (clonal) and spores (sexual) she listened to what each family of individual shoots had to say. Fastidiously she tracked the changes of hundreds of colonies over several years by marking them with cocktail sticks.
Slowly she discovered that low-density patches produced gammae. When new shoots grew and conditions became more crowded there was a shift from gammae to female shoots with scattered males. ‘The colony has transformed itself from the vibrant green of gemmiferous shoots to the rusty colour of spore production.’ As the crowding increased there was another shift to all male shoots without a female in sight. Tetraphis revealed itself as a hermaphrodite. This brought about the death of the moss and the exposure of old wood where the ‘little green eggs’ of gammae were sown for ‘the next wave’.
Kimmerer’s patient listening paid off. Tetraphis, her teacher, revealed to her the mysteries of its reproduction. Going out into nature, spending hours with a plant on hands on knees, is a far cry from abducting it from its home to a laboratory, subjecting it to brutal tests, and analysing the results.
Surely if such methods were applied more broadly in science we might learn more about resilience from the extremophiles whose abilities we employ (unpaid and unacknowledged) in extreme biotechnologies and run less risk of hastening the ‘point of death’ we are desperately striving to avoid?
James A. Coker, ‘Extremophiles and biotechnology: current uses and prospects’, PMC, (2016)
Jason Bittel, ‘Tardigrade protein helps human DNA withstand radiation’, Nature.com, (2016)
Lynn Rothschild, ‘Life in Extreme Environments’, National Space Society, (2002)
Rachel Courtland, ‘‘Water bears’ are first animal to survive space vacuum’, New Scientist, (2008)
Robin Wall Kimmerer, Gathering Moss, (Oregon State University Press, 2003)
Tim Radford, ‘All hail the humble moss, bringer of life and oxygen to Earth’, The Guardian,(2016)
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