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MIMM 211 Lecture 3 CLASSIFICATION OF MICROBES Traditional (before 1866) o Plants and Animals Haeckel's Proposal (After 1866) o Plants, Animals, Microorganisms Edouard Chatton (1937) o Eukaryotes and Prokaryotes o Roger Stainer and C.B. Van Niel supported Chatton's proposal RECENT CLASSIFICATIONS Whitaker's Five Kingdoms (1959) o Monera, Protista, Fungi, Plantae, Animalia o Wrong Carls Woesse's THREE KINGDOMS-- or THREE DOMAINS (1977) o Bacteria, Archaea, and Eukarya o Used molecular approach, 16S ribosomal RNA gene used (Ubiquitous) 16S could not be easily transferred during horizontal gene transfer (HGT) ENDOSYMBIOTIC THEORY OF EVOLUTION Theory developed by Lynn Margulis (1981) Prokaryotes o No organelles Eukaryotes o Organelles Plants have mitochondria and chloroplasts Most others only have mitochondria o Has nuclear envelope Mitochondria and Chloroplasts o Almost the same size o Contain circular DNA (active genome) o Contain 70s ribosome (instead of 80s in eukaryotes) o Have double membrane (like gram negative bacteria), but no cell envelope o Divide by binary fission (reproduce separately from host) Mitochondria descend from gram-negative proteobacteria Rickettsia prowazekii o Obligate intracellular parasite, cannot live outside host Chloroplasts descend from cyanobacteria Prochloron Theory: o o o o o o Prokaryotes first appeared 3.5 mya Eukaryotes, 1 mya Primitive Eukaryote engulfed prokaryote Continued to develop a mutually beneficial symbiotic relationship for 1 bya Prokaryote is in a stable, sheltered, nutrient-rich environment Eukaryote gets ATP from photosynthesis and respiration RECENT EXAMPLE Aphids and endosymbiont (200 mya) o Endosymbiont kept cell envelope o Endosymbiont can't survive outside host o Aphid dies is endosymbiont is killed by antibiotic o Endosymbiont closely related to e. coli