Cellular Evolution and Ubiquity of Life: Eukaryogenesis
Seckbach, J.
Department of Biological Sciences. Louisiana State University, Baton Rouge, La. 70803 USA
The question of the origin of living organisms is still not resolved. The first cells were unicellular bacteria (Monera), and those prokaryotic cells evolved into the eukaryotic protistan organisms. This eukaryogensis took place via endosymbiotic association, or via autogenous gradual processes, or by both of these pathways.
Life as we do not know it, is everywhere on Earth and one can detect microorganisms in very extreme habitats. Thus, one can discover microbial life in environments of high pressure, hypersalinity, and various levels of temperature (from psychrophiles to hyperthermophiles growing at 110°C). Likewise, several genera of bacteria and a few algal genera have been observed in hot springs in very acidic habitats (pH of 2 to 4) and others were observed at very alkalophilic areas.
The first considered eukaryotes are the unicellular organisms that do not possess some organelles (Archaeprotistae, e.g., the amitochondria or those lacking chloroplast cells). We have been investigating the Cyanidiaceae, a cosmopolitan algal group thriving in acid hot springs. The Cyanidiacean have three genera that show a gradual and stepwise interspecies evolution, from Cyanidioschyzon via Cyanidium to Galdieria and from latter one to the more advanced unicellular red algae. Cyanidioschyzon represent one of the most primitive Eukaryotes (as has been shown ultrastructurally, biochemically, and molecular biologically). This algal group serves as a model for Eukaryogenesis from the Cyanobacteria to Rhodophyta.
Seckbach, J. (1994) In: Evolutionary Pathways and Enigmatic Algae: Cyanidium caldarium (Rhodophyta) and Related Cells, J. Seckbach (ed.), Kluwer Publisher (the Netherlands).
Seckbach, J. (1997) Search for Life in the Universe with Terrestrial Microbes. In: Astronomical and Biochemical Origins and the Search for Life in the Universe (C.B. Cosmovice, S. Bowyer and D. Werthimer, (eds.) published by Editrice Compositiori. (Italy).
I thank Drs. Jack R.Van Lopik and Russell L. Chapman (both from LSU at BR, LA. 70803 USA) for warm hospitality and for presenting the chair in Sea Grant Research.
| LOCATION |
DATE |
TIME |
| Lecture Hall I |
Tuesday, April 7 |
04:30 pm |