Extremophiles: life in extreme places

Underwater volcanoes, arctic tundra and the reactor at Chernobyl- what do these places have in common? As strange as it might seem, they are the ideal living conditions for several different microorganisms. Think humans are the best at colonising Earth? Think again.

Deadly Radiation Levels: Chernobyl

The exploded reactor at Chernobyl (source)

About 70 miles away from Kiev in Ukraine lies the ruined reactor of the Chernobyl nuclear power plant and the eerie abandoned city of Prypiat.  In April 1986 during a security test at the plant, a huge explosion tore through the nuclear reactor, throwing its 1200 tonne cover high into the air, carrying with it a cloud of radioactive graphite dust and exposing the surrounding areas with lethal levels of radiation. To this day the clean-up of the fallout from this incident continues and a 2,600 exclusion zone has been put in place where no people live except for about 170 samosely – or settlers - who remained behind after the incident. Nobody is quite sure how many people died as a result of the power plant disaster, but estimates go as high as tens of thousands.

Given the catastrophic nature of this incident and the hostility of the area around the plant, it’s pretty surprising that it has been discovered in the last few years that black pigmented fungi grow and actually thrive on the walls of the broken down reactor. Normally gamma radiation (the most harmful form of radiation, the type given off by unshielded nuclear reactors and exploded atom bombs) causes irreparable damage to the DNA of living organisms, rendering them unable to function or reproduce.

The iconic radiation warning at Prypiat (source)

Turns out that the amazing ability these fungi have to thrive in these conditions is down to melanin- the same stuff that gives us moles and freckles. Along with many other organisms, some fungi produce melanin, which gives them a characteristic black colour. Scientists believe that these fungi use melanin to convert the deadly gamma radiation from the crippled reactor to energy they can use to grow. Lab tests with one such fungus, called Cryptococcus neoformans (I’m trying to spare the meaningless unpronounceable Latin names, but apparently us microbiologists are sticklers for it – sorry) showed that it grew three times faster than normal at 500 times the normal radiation found on Earth’s surface.

So, that’s the crazy radiation-munching fungi dealt with – let’s move on to heat, and another awesome environment.

Extreme Temperature and Pressure: Deep Sea Hydrothermal Vent Fields

A black smoker. I'd make a joke but it wouldn't be clever or funny (source)

Hydrothermal vent fields are probably some of the most hostile places on earth and they are freaking awesome. Uhh… that wasn’t very scientific – they are quite interesting. Better? Anyway, hydrothermal vents are holes in the Earth’s crust in volcanic regions which spew mineral rich water heated by molten rock. When this material hits the cold water some of it solidifies creating a chimney through which dissolved minerals issue like white and black smoke. These chimneys, not surprisingly, are called black smokers and white smokers. 

The water in these places can reach temperatures up to 400 degrees and the pressure is several times that of the surface, but amazingly they are some of the most life-filled places in the deep sea.  Discovered in 1970, these vents are relatively new to science, but in spite of this over 300 species have been identified in vent fields – more than 280 of which were completely new to science. The combined biomass (the total mass of living things) in these vent fields is estimated to be the same as the rainforest.

The thriving life in these hydrothermal vent fields is made up of bacteria, tubeworms, crabs, slugs, fish and many more. Like all life on this planet, the smallest lifeforms make it all possible. One of the components of the ‘smoke’ spewing out of the vents is hydrogen sulphide – a gas with a characteristic rotten egg smell which is toxic to most life in high levels. This gas is the primary food source for the microorganisms that live there. These microorganisms make up the bottom rung of the food chain, allowing more complex life to survive by feeding on them. These microbes have to be specially adapted to live in such a place, as high temperature and pressure destroy the structure of cells and damage the proteins that make them work – in fact it is temperature and pressure that are used to sterilise laboratory and medical equipment through a process known as autoclaving.The types of microbes that survive down here are ones whose internal components are highly resistant to such damage.

M. kandleri - fascinating AND pretty (source)

One of these microbes, called Methanopyrus kandleri  (sorry!) is the world record holder for life at high temperatures.  M. kandleri is an archaeon – a member of the archea which are similar to bacteria but are quite different at a genetic level and often to live in extreme and methane gas rich environments – either producing it or using it as an energy source. M. kandleri was discovered on the wall of a black smoker vent and grows happily at 110°C and can survive up to 130°C. Science classifies this awesome little bug as a hyperthermophile, meaning ‘extremely high temperature lover’.

Sub-zero Temperatures: Arctic Permafrost

Whenever people think of inhospitable conditions the Arctic tundra is probably pretty high on the list. I keep thinking of arctic explorers fighting their way through blizzard in huge fur coats with their big bushy beards caked with snow… but maybe that’s just me. One critter that loves to live in the arctic permafrost is the fetchingly-named Planococcus halocryophilus. This one is an extreme survival double-whammy. It is capable of growing at ultra-low temperatures and ultra-high salt concentrations.

P. halocryophilus in the flesh... or whatever they are made of (source)

P. halocryophilus was discovered in 2011 in the Canadian High Arctic where scientists believe they grow in the permafrost – the frozen soil on the surface of the Arctic. These bugs are reported to live in tiny regions of highly salty water in the permafrost, which creates a particularly demanding environment of high salinity (salt content) and sub-zero temperatures. P. halocryophilus has been shown to grow happily at the ambient permafrost temperature of -16°C and survive up to -25°C and has been referred to as a ‘cold temperature champion’.

Normally bacteria are killed by extremely low temperature when water inside the cells freezes or the temperature slows or stops the chemical processes that keep them alive. When water freezes it tends to form crystals which tear through cell walls and render them useless. Cold-loving bacteria (cryophiles) protect themselves by producing their own kind of antifreeze inside and out which prevents them from freezing solid or being killed by ice crystals. P. halocryophilus is able to survive at such low temperatures by doing just that, as well as being highly adapted to be cold-resistant.

So, if you didn’t before, you now know about three of the world champions of survival, and yes, they are all microbes – in microbiology these are called ‘extremophiles’. “That’s all very well” you might be saying, “but so what?” – which is a fair question. Probably the most fascinating thing about these extremophiles is the fact that they provide us with a window to other worlds. I know, right? I made that sound super dramatic. What I am talking about here is xenobiology – the study of extra-terrestrial life. I’m not talking about the E.T., X-files, take-a-deep-breath-here-comes-the-probe type of extra-terrestrial life, I’m talking about microbes. Some of these extreme environments on earth closely mirror what conditions might be like on other planets and studying the life that thrives in them tells us about the possibility of life on other planets. Microbiologists believe in aliens – who knew?  

As with every article I post here, this one has been thoroughly researched and a list of sources can be provided for anyone who is curious – just check out the contact page.