For Three Billion Years, Microorganisms Were
the Only Inhabitants of the Earth
4
Jean-Claude Bertrand, Ce ´line Brochier-Armanet, Manolo Gouy,
and Frances Westall
Abstract
Microorganisms were the sole inhabitants of our planet for almost 3 billion years. They
have survived the intense geological upheavals that have marked the history of the Earth.
They profoundly shaped their environment, thus participating in a true co-evolution
between the biosphere and the geosphere. Through their activity, they also created
favourable conditions for the emergence of multicellular aerobic organisms (particularly
with an intense production of oxygen released into the atmosphere).
Among past microorganisms, LUCA occupied a central position in the evolutionary
history of life. The possible origin and the large uncertainties about the nature of LUCA are
discussed: where and when did LUCA live? Was it a hyperthermophilic, thermophilic or
mesophilic organism? How did its genome look like?
Scenarios and hypotheses regarding the emergence and the relationships of the three
domains of life – Archaea, Bacteria and Eucarya – as well as the transition from a
prokaryotic to eukaryotic cell organisation are discussed in the light of the most recent
data. Possible major steps in the evolution of microorganisms are deduced from genomic
investigations and from the geological record (fossils, isotopic ratios, biomarkers).
Although the early steps of microbial metabolic evolution are still hotly debated, it is
possible to speculate on the occurrence of the first living entities, from the primordial
metabolisms to the advent of photosynthesis.
Keywords
Early evolution Evolution of the Earth Evolutionary scenarios of life Fossils Geological
record History of life on Earth LUCA Tree of life
4.1
From The ‘RNA World’ to the Last
Common Ancestor of All Living
Beings: LUCA
This chapter will not present the various hypotheses that
have been proposed to explain the terrestrial or extraterrestrial origin of life. The plot will begin with the appearance of
the last common ancestor of all living beings. The Earth was
formed about 4.5 billion years ago, and life must have
emerged before 3.5 billion years (Ga) ago because the oldest
fossil and isotopic traces of life have been found in South
Africa and in Australia in particularly well-preserved rocks
dated circa 3.5 Ga (that is to say, a billion years after the
J.-C. Bertrand*
Institut Me ´diterrane ´en d’Oce ´anologie (MIO), UM 110, CNRS 7294
IRD 235, Universite ´ de Toulon, Aix-Marseille Universite ´,
Campus de Luminy, 13288 Marseille Cedex 9, France
e-mail: Jean-claude.bertrand@univ-amu.fr
C. Brochier-Armanet M. Gouy (*)
Laboratoire de Biome ´trie et Biologie E ´ volutive, UMR CNRS 5558,
Universite ´ Claude Bernard Lyon 1, 69622 Villeurbanne Cedex, France
F. Westall
Centre de Biophysique Mole ´culaire, CNRS,
45071 ORLEANS Cedex 2, France
* Chapter Coordinator
J.-C. Bertrand et al. (eds.), Environmental Microbiology: Fundamentals and Applications: Microbial Ecology,
DOI 10.1007/978-94-017-9118-2_4, # Springer Science+Business Media Dordrecht 2015
75
the Only Inhabitants of the Earth
4
Jean-Claude Bertrand, Ce ´line Brochier-Armanet, Manolo Gouy,
and Frances Westall
Abstract
Microorganisms were the sole inhabitants of our planet for almost 3 billion years. They
have survived the intense geological upheavals that have marked the history of the Earth.
They profoundly shaped their environment, thus participating in a true co-evolution
between the biosphere and the geosphere. Through their activity, they also created
favourable conditions for the emergence of multicellular aerobic organisms (particularly
with an intense production of oxygen released into the atmosphere).
Among past microorganisms, LUCA occupied a central position in the evolutionary
history of life. The possible origin and the large uncertainties about the nature of LUCA are
discussed: where and when did LUCA live? Was it a hyperthermophilic, thermophilic or
mesophilic organism? How did its genome look like?
Scenarios and hypotheses regarding the emergence and the relationships of the three
domains of life – Archaea, Bacteria and Eucarya – as well as the transition from a
prokaryotic to eukaryotic cell organisation are discussed in the light of the most recent
data. Possible major steps in the evolution of microorganisms are deduced from genomic
investigations and from the geological record (fossils, isotopic ratios, biomarkers).
Although the early steps of microbial metabolic evolution are still hotly debated, it is
possible to speculate on the occurrence of the first living entities, from the primordial
metabolisms to the advent of photosynthesis.
Keywords
Early evolution Evolution of the Earth Evolutionary scenarios of life Fossils Geological
record History of life on Earth LUCA Tree of life
4.1
From The ‘RNA World’ to the Last
Common Ancestor of All Living
Beings: LUCA
This chapter will not present the various hypotheses that
have been proposed to explain the terrestrial or extraterrestrial origin of life. The plot will begin with the appearance of
the last common ancestor of all living beings. The Earth was
formed about 4.5 billion years ago, and life must have
emerged before 3.5 billion years (Ga) ago because the oldest
fossil and isotopic traces of life have been found in South
Africa and in Australia in particularly well-preserved rocks
dated circa 3.5 Ga (that is to say, a billion years after the
J.-C. Bertrand*
Institut Me ´diterrane ´en d’Oce ´anologie (MIO), UM 110, CNRS 7294
IRD 235, Universite ´ de Toulon, Aix-Marseille Universite ´,
Campus de Luminy, 13288 Marseille Cedex 9, France
e-mail: Jean-claude.bertrand@univ-amu.fr
C. Brochier-Armanet M. Gouy (*)
Laboratoire de Biome ´trie et Biologie E ´ volutive, UMR CNRS 5558,
Universite ´ Claude Bernard Lyon 1, 69622 Villeurbanne Cedex, France
F. Westall
Centre de Biophysique Mole ´culaire, CNRS,
45071 ORLEANS Cedex 2, France
* Chapter Coordinator
J.-C. Bertrand et al. (eds.), Environmental Microbiology: Fundamentals and Applications: Microbial Ecology,
DOI 10.1007/978-94-017-9118-2_4, # Springer Science+Business Media Dordrecht 2015
75