The tiny eight-legged creatures are so resilient, they can even survive in outer space - and that's not all. Tardigrades are simply tremendous.
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Tardigrades, or moss bears as they are sometimes called, are only about half a millimeter (0.02 inches) long. With their thick legs and round bodies, they look a bit like microscopic caterpillars.
But looks can be deceiving. While caterpillars are relatively fragile creatures, some tardigrades have survived in temperatures close to absolute zero (-272 degrees Celsius, or -458 degrees Fahrenheit), while others have survived scorching heat of as much as 150 degrees Celsius (300 degrees Fahrenheit).
They can also survive high levels of radiation, water pressure in the deepest abysses of our oceans, and in the vacuum of outer space. And as if that wasn't enough, they can also survive without food or water for more than 30 years - yes, years!
Now, to be clear: tardigrades aren't extremophiles - they don't thrive under particularly hostile conditions, like some bacteria that really come into their own in highly acidic or near boiling water, or in rocks buried deep underground.
It's just that many things that kill almost anything else won't kill them. Thanks to this extraordinary resilience, the tiny critters are among a small group of species that have survived all five mass extinction events in the history of our planet.
So where can you find such an extraordinary creature? Well, since very little can kill them, pretty much everywhere, really.
They have been found high up in the Himalayas, as well as deep down in the ocean; in frozen puddles in Antarctica, also in marshes at the equator; and there are probably a ton of them in the rain gutter of your house.
They particularly like to live in moss (hence the name moss bear), where as many as 200 of them can be found in one square centimeter.
They may be tiny - but given their resilient nature, tardigrades are likely to outlive us. And considering the havoc we've been wreaking on the planet, that could turn out to be their most impressive accomplishment of all.
World Health Day 2015 is about highlighting food security. So what's the role of microorganisms in our food? We take a look at mold, bacteria and viruses that can spoil your appetite - but are also be useful.
Image: imago/Gerhard Leber
Ewww!
Just scrape the mold off, right? Wrong. A moldy old sandwich like this one is anything but harmless. While there are some harmless kinds of mold - like on Camembert cheese - many molds are toxic. Furthermore, mycelium spores can trigger allergies. Through contact with highly toxic types of mold, humans with weakened immune defenses could even die as a result of an extended exposure.
Image: imago/imagebroker
Mold as a biocatalyst
Mold can also be useful: Fungi is able to break down carbon hydrates, fats and proteins - more efficiently than any other organism. Industry makes use of a genetically modified Aspergillus niger fungus, which produces enzymes that can be used in food processing and production of detergents - like a living factory.
Image: BASF
Salami tactics
"Botulus" is Latin for "sausage." If mistakes are made in the production of sausage, or if meat or vegetables get contaminated during canning, this can cause botulism. The bacteria Clostridium botulinum causes this life-threatening poisoning.
Image: picture-alliance/dpa
Life without oxygen
Clostridium botulinum thrives in anaerobic, or oxygen-free, environments. It produces the nerve agent botox - used among cosmetic surgeons to help smooth skin. But in food, it leads to paralysis. At first, certain body parts get paralyzed, resulting in symptoms like slurred speech. But later, also the muscles responsible for breathing and heartbeat freeze up - eventually resulting in death.
Image: picture alliance/OKAPIA
Fresh vegetables not always healthy
Fenugreek sprouts were a favorite among Germans trying to eat healthy - until 2011. That year, seeds contaminated with the bacteria Escherichia coli (EHEC) caused an outbreak that killed 53 people - hundreds more were sickened. EHEC produces a toxin that destroys intestinal wall cells, and later attacks brain and kidney cells. Cooking raw vegetables and meat kills the harmful bacteria.
Image: picture-alliance/dpa
A useful relative
But not all varieties of E. coli are dangerous. Inside the human large intestine, the bacteria are usually responsible for producing vitamin K - important for the development of bones and cells, and for blood coagulation. In biotechnology, the bacteria play a role in producing insulin and growth hormones. They can even be used for turning microalgae into alcohol-based biofuel.
Image: Harvard’s Wyss Institute
Bacteria preserves foods
Thousands of years ago, humans learned to use lactic acid bacteria - for the production of yoghurt, kefir, sourdough bread and cheese. Raw milk warmed to 20 degrees Celsius is heaven for bacteria: Within 10 hours, the milk will go sour. Milk fermented with the help of bacteria, however, can stay edible for much longer.
Image: ZDF
Too much of a good thing
One of the many varieties of lactic acid bacteria are streptococci, which play a role in producing sauerkraut and fermented milk products. Although streptococci are everywhere - on humans, animals and plants - some of them are unhealthy. Some strains of strep can trigger tooth decay or sepsis, commonly known as blood poisoning.
Image: picture-alliance/OKAPIA
Dangerous diarrhea
Rod-shaped bacteria like Campylobacter and Salmonellae cause illness and death the world over. Undercooked beef, pork or chicken containing Campylobacter is a common cause of diarrhea wordwide. Typhus is the most dangerous form of salmonellae, triggering high fever, weak heartbeat and constipation. Every year, about 32 million people are sickened from typhus - mainly by drinking impure water.
Also viruses can contaminate food
Norovirus or stomach flu is transmitted person-to-person through traces of vomit or feces. Just 100 tiny norovirus particles are enough to infect someone. The virus can easily pass into the food chain via infected drinking water.