Hydrothermal vents and the origin of life

William Martin

University of Düsseldorf, Germany

Abstract

Darwin was not primarily concerned with microbes, and it is arguably true that the most incisive insights that we have obtained into the evolutionary process since the New Sysnthesis have concerned the evolution of microbes. As recently as 10 years ago, it was widely held that some eukaryotes primitively lacked mitochondria and were true intermediates in the prokaryote-to-eukaryote transition. That idea focussed much research on anaerobic and parasitic eukaryotes, which turned out to have mitochondria that were either previously overlooked or not recognized as such. Today, mitochondria, including their manifestations among anaerobic forms — hydrogenosomes and mitosomes —, are known to be ubiquitous among eukaryotes, at odds with older theories that held eukaryotes to be direct descendants of a prokaryote via direct filiation, but consistent with the predictions of theories that apporach the origin of mitochondria from the standpoint of a symbiosis between prokaryotes. This view has it that eukaryotes thus arose from prokaryotes, hence the origin of life boils down to the origin of prokaryotes, among which two main groups — the archaebacteria and the eubacteria — are recognized. And whence did prokaryotes arise? Submarine hydrothermal vents are geochemically reactive habitats that harbour rich microbial communities. There are striking parallels between the chemistry of the H2–CO2 redox couple that is present in hydrothermal systems and the core energy metabolic reactions of some modern prokaryotic autotrophs. The biochemistry of these autotrophs might, in turn, harbour clues about the kinds of reactions that initiated the chemistry of life. Hydrothermal vents are now a point where microbiology and geology meet, thereby breathing new life into research into one of biology’s most important questions — the origin of life.

Selected references:
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