We announce with great pleasure the confirmed visiting lecturer at the third SiSB:

William F. Martin

Professor Martin is involved in the fields of evolutionary biology and biocheimistry. His interests include investigation of plastid, mitochondria and hydrogenosomes evolutionary past. His group uses different laboratory experiments and computational methods to elucidate the origin of eucaryotes and even go a step further, to the very source of life itself. He has published over 250 papers cited nearly 25 000 times.

Find out more on professor Martin here.

Abstract of professor Martin's Lecture

Physiology, anaerobic mitochondria, endosymbiosis and complexity

Chloroplasts and mitochondria have conserved their prokaryotic biochemistry, but their genomes are reduced, and most organelle proteins are encoded in the nucleus. Endosymbiotic theory posits that bacterial genes in eukaryotic genomes entered the eukaryotic lineage via organelle ancestors. It predicts episodic influx of prokaryotic genes into the eukaryotic lineage, with acquisition corresponding to endosymbiotic events. Lateral gene transfer theories of the "you are what you eat" variety predict a constant flux of prokaryotic genes into eukaryotic genomes. Genome data can discriminate between endosymbiotic theory and LGT theory. By clustering and phylogenetic analysis of all eukaryotic gene families having prokaryotic homologues we show (1) that gene transfer from bacteria to eukaryotes is episodic and coincides with the origin of chloroplasts and mitochondria, (2) that gene inheritance in eukaryotes is vertical, sparse gene distributions stemming from differential loss, and (3) that continuous, lineage-specific lateral gene transfer does not contribute to long-term gene content evolution in eukaryotic genomes. The origin of eukaryotes was the origin of vertical lineage inheritance, and sex was required to keep vertically evolving lineages viable by rescuing the incipient eukaryotic lineage from Muller’s ratchet. Coding sequences in eukaryotic genomes that share more than 70 % amino acid sequence identity to prokaryotic homologs are typically assembly or annotation artifacts. The origin of mitochondria was the decisive incident that precipitated symbiosis-specific cell biological problems, the solutions to which were the salient features that distinguish eukaryotes from prokaryotes: A nuclear membrane, energetically affordable protein polymerization in the cytosol, and a cell cycle involving reduction division and reciprocal recombination (sex). Even the eukaryotic endomembrane system originated from mitochondria via outer membrane vesicles (OMVs) released by the mitochondrial ancestor within the cytosol of its archaeal host at eukaryote origin. Confined within the host's cytosol, OMVs accumulated naturally, fusing either with each other or with the host's plasma membrane. This matched the host's archaeal secretory pathway for cotranslational protein insertion with outward bound mitochondrial-derived vesicles consisting of bacterial lipids, forging a primordial, secretory endoplasmic reticulum as the cornerstone of the eukaryotic endomembrane system. In terms of physiology, eukaryotes as a group are less diverse than a typical Rhodobacter species, and endosymbiosis is why. In terms of cell biology, eukaryotes are fundamentally different from prokaryotes, and mitochondria are why.

Gould SB et al. (2016) Bacterial vesicle secretion and the evolutionary origin of the eukaryotic endomembrane system. Trends Microbiol. 24:525–534 (2016).

Ku C, Martin WF (2016) A natural barrier to lateral gene transfer from prokaryotes to eukaryotes revealed from genomes: The 70% rule. BMC Biology. 14:89 (2016).

Garg S Martin WF (2016) Mitochondria, the cell cycle and the origin of sex via a syncytial eukaryote common ancestor. Genome Biol. Evol. 8:1950–1970 (2016).

Ku C et al. (2015) Endosymbiotic origin and differential loss of eukaryotic genes. Nature 524:427–432.

Martin WF, Garg S, Zimorski V (2015) Endosymbiotic theory for eukaryote origin. Phil Trans Roy Soc Lond B 370: 20140330 (2015).

Müller M et al. (2012) Biochemistry and evolution of anaerobic energy metabolism in eukaryotes. Microbiol. Mol. Biol. Rev. 76:444–495.

Lane N, Martin W (2010) The energetics of genome complexity. Nature 467:929–934.