Life in extreme environments

Abstract

Each recent report of liquid water existing elsewhere in the Solar System has reverberated through the international press and excited the imagination of humankind. Why? Because in the past few decades we have come to realize that where there is liquid water on Earth, virtually no matter what the physical conditions, there is life. What we previously thought of as insurmountable physical and chemical barriers to life, we now see as yet another niche harbouring 'extremophiles'. This realization, coupled with new data on the survival of microbes in the space environment and modelling of the potential for transfer of life between celestial bodies, suggests that life could be more common than previously thought. Here we examine critically what it means to be an extremophile, and the implications of this for evolution, biotechnology and especially the search for life in the Universe.

Growth of non-phototrophic microorganisms using solar energy through mineral photocatalysis

“…Non-phototrophic autotrophs and heterotrophs exist in abundance in both ancient and modern environments 40,41 . On early anoxic Earth, metal sulfide photocatalysis might have provided an energy-yielding pathway to support microbial growth.…”

EST-analysis of the thermo-acidophilic red microalga Galdieriasulphuraria reveals potential for lipid A biosynthesis and unveils the pathway of carbon export from rhodoplasts

“…In contrast, the presently known upper temperature limit for eukaryotic microorganisms is 62°C, and most metazoans (multicellular eukaryotes) are unable to grow above 50°C (Tansey and Brock, 1972;Rothschild and Mancinelli, 2001). Surprisingly, photosynthetic prokaryotes, such as the cyanobacteria, are completely absent from hot acidic waters (Brock, 1973).…”

“…Surprisingly, photosynthetic prokaryotes, such as the cyanobacteria, are completely absent from hot acidic waters (Brock, 1973). Instead, thermo-acidophilic photosynthetic unicellular red algae of the Cyanidiales are the principal photosynthetic organisms found in these ecological niches (Doemel and Brock, 1970;Rothschild and Mancinelli, 2001;Donachie et al, 2002). The three species belonging to the Cyanidiales (Cyanidium, Cyanidioschyzon, and Galdieria) can grow at pH 0 and temperatures up to 57°C (Doemel and Brock, 1971;Brock, 1978) and they are found globally in hot, acidic habitats.…”

Genomics of Adaptation to Multiple Concurrent Stresses: Insights from Comparative Transcriptomics of a Cichlid Fish from One of Earth’s Most Extreme Environments, the Hypersaline Soda Lake Magadi in Kenya, East Africa

“…This unusually stressful environment poses several physiological challenges. High alkalinity, salinity, and temperature can cause degradation of cellular biomolecules such as proteins (Rothschild and Mancinelli 2001). Likewise, high osmotic and ionic gradients brought about by high salinity need to be counteracted to avoid effects on cell structure and function (Gonzalez 2012).…”

“…Likewise, high osmotic and ionic gradients brought about by high salinity need to be counteracted to avoid effects on cell structure and function (Gonzalez 2012). High pH often negatively affects nitrogen waste excretion, whereas intense ultraviolet radiation and ROS have detrimental effects on several cellular components including lipid peroxidation, protein carbonylation, and degradation of genetic material (DNA and RNA) (Rothschild and Mancinelli 2001). Surprisingly, despite these stressful conditions, A. grahami maintains viable populations in Lake Magadi, which do not show signs of reduced genetic diversity (Seegers et al 1999;Wilson et al 2000Wilson et al , 2004Kavembe et al 2014).…”