Early bioenergetic evolution

ITQB Seminar

Title: Early bioenergetic evolution

Speaker: William F. Martin

Affiliation: Institute of Molecular Evolution, University of Düsseldorf, Germany

Abstract:

The talk aims to outline an energetically feasible path from a particular inorganic setting for the origin of life to the first free-living cells. The sources of energy available to early organic synthesis, early evolving systems and early cells stand in the foreground, as do the possible mechanisms of their conversion into harnessable chemical energy for synthetic reactions. With regard to the possible temporal sequence of events, the focus is on: i) alkaline hydrothermal vents as the far from equlibrium setting, ii) the Wood-Ljungdahl (acetyl-CoA) pathway as the route that could have underpinned carbon assimilation for these processes, iii) biochemical divergence, within the naturally-formed inorganic compartments at a hydrothermal mound, of geochemically confined replicating entities with a complexity below that of free-living prokaryotes, and iv) acetogenesis and methanogenesis as the ancestral forms of carbon and energy metabolism in the first free-living ancestors of the eubacteria and archaebacteria, respectively. In terms of the main evolutionary transitions in early bioenergetic evolution the focus is on: i) thioester dependent substrate level phosphorylations, ii) harnessing of naturally existing proton gradients at the vent-ocean interface via the ATP-synthase, iii) harnessing of Na+ gradients generated by H+/Na+ antiporters, iv) flavin based bifurcation-dependent gradient generation, and finally v) quinone based (and Q-cycle dependent) proton gradient generation. Of those five transitions, the first four are posited to have taken place at the vent. Ultimately all of these bioenergetic processes depend, even today, upon CO2 reduction with low potential ferredoxin (Fd), generated either chemosynthetically or photosynthetically, suggesting a reaction of the type “reduced iron  reduced carbon” at the beginning of bioenergetic evolution.

References:

Sousa FL, Thiergart T, Landan G, Shijulal N, Pereira IAC, Allen JF, Lane N, Martin WF: Early bioenergetic evolution. Phil Trans Roy Soc Lond B. in press (2013).
Lane N, Martin WF: The origin of membrane bioenergetics. Cell 151:1406–1416 (2012).

Martin WF: Hydrogen, metals, bifurcating electrons, and proton gradients: The early evolution of biological energy conservation. FEBS Lett. 586:485–493 (2012).
Martin W, Baross J, Kelley D, Russell MJ: Hydrothermal vents and the origin of life. Nature Rev. Microbiol. 6:805–814 (2008).

Martin W, Russell MJ: On the origin of biochemistry at an alkaline hydrothermal vent. Phil. Trans Roy. Soc. Lond. B 367:1887–1925 (2007).