MCB 3020 Lecture Notes - Lecture 39: Hydrogenosome, Prochlorococcus, Oxygen Toxicity
Document Summary
Steps in endosymbiotic hypothesis: ancestral eukaryotic cell had lost cell wall, engulfment of an endosymbiote occurred. Produced needed product such as atp: genome reduction occurred, evolution of organelles. Mitochondria and chloroplasts: believed to be descended from rickettsiae and prochlorococcus, engulfed in a precursor cell. Engulfed organism thought to be aerobic, thereby eliminating oxygen toxicity to the host cell. Hydrogenosomes: asserts that the a-proteobacterium endosymbiont was an anaerobic bacterium that produced h2 and co2 as fermentation end products. Hosts lacking external h2 source became dependent on endosymbiont which made atp by substrate level phosphorylation. Symbiont ultimately evolved into a mitochondrion or a hydrogenosome. Organelle found in protists that produce atp by fermentation. The concept and definition of a microbial species: ca(cid:374)"t use spe(cid:272)ies defi(cid:374)itio(cid:374) (cid:271)ased o(cid:374) i(cid:374)ter(cid:271)reedi(cid:374)g (cid:271)e(cid:272)ause (cid:271)a(cid:272)teria a(cid:374)d archaea are asexual, (cid:862)gold sta(cid:374)dard(cid:863) for spe(cid:272)ies assig(cid:374)(cid:373)e(cid:374)t (cid:373)ay (cid:374)ot (cid:271)e appli(cid:272)a(cid:271)le for microorganisms. Microbial evolutionary processes: bacteria and archaea are asexual, heritable changes occur.
