What On Earth Are Microbes?
You’ve all heard of various kinds of microbes like bacteria, algae, fungi and protozoa. For two billion years, microbes were the ONLY life form on our planet! They have the ability to inhabit every possible ecological niche. But despite these amazing facts, exploration of the world of microbes, so essential to life on earth, has only just begun. Microbes are everywhere, and without them, we and all of the abundant life we love so much, would be – nowhere!
There is bacteria on your fingertips. There are microbes in the stomachs of tigers and birds and lizards. And you can find the minuscule creature that I want to introduce you to, in a puddle of water. This microscopic being has really captured my imagination. It’s got a funny name: the tardigrade, or in Latin, Tardigrada. The name tardigrade means “slow walker,” and they are also known as water bears and moss piglets because of the way they look and move!
Tardigrades are tiny, only about one millimetre long when fully grown. They usually live in water. They have four pairs of stout legs, and short, plump, segmented bodies. They have four to eight “claws” at the end of each leg! Tardigrades are part of an ancient group of microbes with fossils dating from 530 million years ago, in earth’s Cambrian period! The first tardigrade was discovered in 1773, with more than 500 new tardigrade species found since then.
Okay, now for the really incredible news about our friend, the moss piglet/water bear/tardigrade. Because of their ability to thrive in extreme conditions that would kill most life on earth, scientists put tardigrades in a class of animals called “extremophiles,” meaning “love (philia) of extremes.” They live everywhere, from high in the Himalaya to the deepest ocean trenches, from polar regions to the equator. The most convenient way to find our moss piglet is by soaking a bit of lichen or moss in spring water. Once collected, they are easy to view under a very low-power microscope. So they are accessible to students and amateur scientists like you!
These little creatures can survive temperatures close to absolute zero (00 Kelvin or – 2730 C!) and as high as 1510 C. They can withstand 1,000 times more radiation than any other animal, including solar, gamma, and ionic radiation. They can survive for nearly 10 years without food and water, drying out to the point where they are three per cent or less of water, only to succeed, in the right conditions, in rehydrating, foraging for food, and reproducing! Yes, there are male and female water bears. Newly hatched moss piglets measure just 0.05 mm. In 2007, they were exposed to the vacuum of space for 10 days in low earth orbit, and returned alive, making them the first known animal to survive in space.
Aren’t tardigrades fascinating? Our study of them, and their role in our biosphere, has only just begun. Dr. E.O Wilson – the expert on ants (and so much more!) whom I have mentioned here before – has said that if he could begin all over again, he would devote all his years of study to microbial life. He is awed by the sheer fecundity (ability to reproduce in large numbers) of it – in a single pinch of soil, there may be 10 billion microscopic organisms belonging to thousands of different species, many as yet unidentified. Though many people think of microbes as our enemy, causing sickness and spoiling food, they are truly vital to earth’s biodiversity. They photosynthesize on a huge scale, providing up to half of the oxygen in the atmosphere! And they decompose dead animals and plants that would otherwise be an enormous burden on the ecosystem.
So thank you, water bears, and all of your microbial relatives. What would we and the tigers and the trees be, without you?
Author: Jennifer Scarlott, First appeared in: Sanctuary Cub, May, 2013.