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Unformatted text preview: Prokaryotic Domains: Bacteria & Archaea Bacteria, Archaea, and Eukarya: The Three Domains of Life Bacteria Eukarya Archaea Common ancestor of all species living today Introduction to Prokaryotes • Only 5000 species of bacteria and Archaea have been named and described; potentially millions exist • Bacteria and Archaea live almost everywhere, from below the Earth’s surface to on Antarctic sea ice • Microbiology is the study of microbes, microscopic organisms What is a prokaryote? Basic structure : • cell enclosed by: • nucleoid contains: • lacks a: • cytoplasm composed of cytosol & ribosomes Features of prokaryotes • cell wall – rigid • capsule – polysaccharide layer • ribosomes – sites for production of proteins • flagella – locomotion • reproduction: Bacteria and Archaea • are haploid and reproduce by fission —the splitting of a cell into two daughter cells • Bacterial cells can transfer copies of plasmids , extracellular loops of DNA conjugation: • plasmid or genes from main bacterial chromosome transferred from one bacteria to another genetic recombination separate from reproduction but some form colonies prokaryotes are usually single cells Bacteria and Archaea: Why Separate Domains? Bacteria • cell walls made of: • plasma membranes like eukaryotes; glycerol bonded to straight chain fatty acids • RNA polymerase: simple, • Translation : begins with formylmethionine, different from Archaea and Eukarya Archaea archaea = ancient (incorrect!)archaea = ancient (incorrect!...
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- Fall '10