Survival in secret

Microbial life under extreme environmental conditions

Hei e source near the city of Beppu in Japan Kai Mangelsdorf, GFZ Potsdam
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Whether in the deep sea, at boiling hot springs or even in the dark interior of the earth - for humans, survival at such extreme locations is hardly possible. But some microbes and multicellulars seem to feel really comfortable at over 100 ° C or more than 250 times the atmospheric pressure. Although research on these survivors is still in its infancy, it already seems clear that they could be of great benefit in both medicine and business.

In many habitats that have long been regarded as hostile to life, scientists have provided evidence of the existence of life in recent years. But what is an extreme habitat anyway? Examples include the deep sea, hot springs, geysers or the Arctic and Antarctic polar zones, which are characterized by physical extremes such as special pressure and temperature conditions. Furthermore, they contain chemical extremes, for example, characterized by high dryness, high salt content, high acid or base concentrations or oxygen-depleted conditions. This applies above all to deserts, salt lakes, hot springs as well as to the free oxygen depleted deep underground of the earth.

Specialists for the extreme

Organisms that inhabit these habitats are referred to as extremophiles, which is derived from the Greek word "philos" for loving and can be translated roughly as "the extraordinary loving". The vast majority of extremophiles are microorganisms - that is, protozoa. However, there are also some multicellulars among them, such as the Himalayan ridge or the Antarctic krill. Depending on the main feature of their preferred habitat, they are termed thermophiles (temperatures higher than 60 ° C), psychrophiles (temperatures lower than 15 ° C), halophiles (high salt concentrations), alkaliphiles (base concentrations higher than pH 9), acidophiles (acid concentrations lower than pH 3) and piezophiles (high pressures), just to name a few of the categories.

Sampling under exclusion of oxygen © Kai Mangelsdorf, GFZ Potsdam

However, the word loving does not apply to all organisms in the extreme habitats. Because not all find there their optimal growth conditions, but are simply survivors. They tolerate certain conditions better than others and can thereby conquer a niche - but they would flourish under other conditions much better. Such organisms are therefore called tolerants. But how do the organisms manage to adapt to the extreme living conditions?

Protection of cell structures

In order to protect their cells and maintain their cell mechanisms, they have developed a variety of mechanisms. Proteins and DNA strands in thermophilic organisms are protected by special structural changes from decomposition at elevated temperatures. Another aspect is the compression of the cell membranes at elevated ambient pressure. Solidification has an extremely detrimental effect on the vital exchange processes of the cell with the environment. display

With a trick, organisms can survive under high-pressure conditions: they incorporate components with a higher space requirement into their cell membrane and thus counteract the ambient pressure. GFZ Potsdam

The biogeochemists at the GeoForschungsZentrum Potsdam are also concerned with the adaptation of cell membranes of organisms from the deep underground of the earth to the increasing ambient pressure at depth. They were able to show that the organisms living under high-pressure conditions incorporate a higher proportion of membrane components with a higher space requirement into the cell membranes. This leads to a loosening of the membranes and thus counteracts the increased ambient pressure.

Life on Mars?

But in addition to purely scientific curiosity, the scientists are also driving the search for life on other planets. For example, if the conditions of life on the surface of Mars are too hostile to life as we know it, then below the surface of Mars there could exist a lifeworld that could be associated with comparable to the deep biosphere of the earth. According to the current state of science, at least liquid water seems to be an indispensable prerequisite for life. The recent discovery of ice caps on Mars indicates the possible existence of liquid water in the subsurface. It is also believed that Jupiter's moon Europa has an ocean below a thick layer of ice. A life uncoupled from the solar energy as at the hot springs of the deep sea is quite conceivable there.

However, the study of extremophiles also awakens economic interests. New natural products and the organisms themselves are of great benefit to agriculture, the chemical industry, biotechnology, medicine and microbiological remediation of polluted areas. But even if life in extreme habitats is already the subject of intense research, the discovery of these fascinating new worlds of life is only just beginning.


GFZ, Section 4.3: Organic Geochemistry

(Kai Mangelsdorf, GFZ Potsdam, 05.04.2007 - AHE)