Scientists Are Discovering That Life Can Exist In Some of the Most Inhospitable Locales on Earth

Scientists have been finding new forms of life that thrive in locations that just a few short years ago, consensus dictated was impossible. Over the course of scientific attempts to estimate just when life originated on Earth, new discoveries and proposals have had one thing in common; they have pushed the origin of life farther back in time. One recent estimate studies the Hadean Eon 4.5 to 3.8 billion years ago when during a period 3.9 million years ago, referred to as the Late Heavy Bombardment in which many experts had believed that the Earth had been completely sterilized comes a new theory that many microbes alive at the time could very well have survived.

This theory has lead lead to the belief that: "These new results push back the possible beginnings of life on Earth to well before the bombardment period 3.9 billion years ago," said CU-Boulder Research Associate Oleg Abramov. "It opens up the possibility that life emerged as far back as 4.4 billion years ago, about the time the first oceans are thought to have formed."

Hydrothermal vents may have provided sanctuaries millions of years ago for extreme, heat-loving microbes known as hyperthermophilic bacteria. And those "few particularly tough species of bacteria and archaea, a lesser-appreciated but equally-vast branch of the organismal tree" exist in the most inhospitable locations on Earth. It must be noted that archaea are just as complicated organisms as bacteria, and that bacteria do not possess a cell nucleus. Also: "One thing bacteria and archaea have in common, however, is the lack of a nucleus or other membrane-bound cellular substructures. Only eukaryotic cells, which compose the bodies of plants, animals and fungi, have such structures." They differ from each other profoundly, but not in ways that lend themselves to such hierarchical judgments.When we speak of microbial life we are treading through unknown territory: "Less than 1 percent of Earth's microorganisms have been identified, and most of those won't even grow in a lab.... In some cases, the bugs are labeled as being uniquely durable, but the labels almost certainly won't stick. Hardly a month passes without some newly characterized species setting a new microbial benchmark. Indeed, the very concept of species might not apply. Bacteria and archaea exchange genes "horizontally," without the need for reproduction.

Now for a journey that will introduce us to some of the organisms that live in the most inhospitable places found on Earth known as extremophiles. An extremophile (from Latin extremus meaning "extreme" and Greek philiā (φιλία) meaning "love") is an organism that thrives in and even may require physically or geochemically extreme conditions that are detrimental to the majority of life on Earth.

Our first stop on our tour of life forms living under extreme conditions is Greenland where

Herminiimonas glaciei (pictured above and to the left) is found living two miles beneath the surface of a glacier. Herminiimonas glaciei has very long flagella which aids it on its treks through the nearly solid ice. One of the creatures most astonishing abilities is to lay dormant for approximately 120,000 years. A similar microbe, Chryseobacterium greenlandensis, lives in the same environment and could exceed a period of well over a million years.

Our next form of extreme condition life form is Pyrodictium abyssi which is referred to as a thermophile and are found around the nutrient abundant borders of deep sea volcanic aperturial vents such as pictured directly below.

The pressures at these depths were the vents are found are overwhelming; consequently P. abyssi form as tube-like structures that are highly resistant to heat and pressure. A second view of a deep ocean volcanic vent and P. abyssi is pictured immediately below.
Deinococcus peraridilitoris is closely related to Deinococcus radiodurans which bears the distinction of being the "toughest bacterium on Earth by the Guinness Book of World Records." Deinococcus peraridilitoris has been found to be able to "withstand cold, vacuum, drought and radiation. Key to its survival are multiple copies of its genome; when one is damaged, the necessary sections can be copied from the other." Deinococcus peraridilitoris is pictured below along with a picture of the dry Chilean desert in which it is found.
Haloquadratum walsbyi, pictured above, a "square and ultra flat archaeon" found in the highly saline area of the salt flats region near the Red Sea survives by achieving "the highest surface-to-volume ratio of any creature on Earth."

In search of the highest radiation resistant bacteria on Earth? Halobacterium NRC-1, pictured below, proves to fill that niche remarkably well. It can withstand18,000 grays of radiation, an incredibly high amount of radiation and possesses the ability to repair it's own DNA.

Ferroplasma acidophilum has the remarkable ability to thrive in areas where the pH is rated at zero; quite a remarkable feat. One of it's most notable distinctions is that it uses iron "as the central structural element of nearly all its proteins." It is pictured below on the left with the toxic conditions found in a gold mine shown on the right.

The last example of an extremeophile is Desulforudis audaxviator which exists by itself, unlike other extremophiles which exist in groups or colonies. Pictured below, "D. audaxviator, which was discovered in a South African mine shaft, two miles beneath Earth's surface" ... uses "radioactivity from uranium-containing rocks as energy, it can harvest or metabolize every nutrient it needs from surrounding rock and gas — the world's only known single-species ecosystem."

As we have seen, extremophiles are a collection of microbial organisms that display an amazing flexibility to survive in extreme environments - niches that are extraordinarily hot, or cold, or dry, or under immense pressures - that would be completely inhospitable to complex organisms. A consensus of scientists have concluded over the past few decades that life may have actually begun on Earth in heat vents far under the ocean's surface. Extremophiles are present in numerous and diverse genetic lineages of both bacteria and archaeans. The domain Archaea contains renowned examples, but extremophiles are present in numerous and diverse genetic lineages of both bacteria and archaeans. Furthermore, it is erroneous to use the term extremophile to encompass all archaeans, as some are mesophilic (an organism that grows best in moderate temperature, neither too hot nor too cold, typically between 15 and 40 °C (77 and 104 °F) We have also learned that there are many different classes of extremophiles, each corresponding to the way its environmental niche differs from mesophilic conditions. These classifications are not exclusive. Many extremophiles, therefore fall under multiple categories.