Chapter 27: Bacteria and Archaea
Chapter 27: Bacteria and Archaea BYS 120
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This 5 page Class Notes was uploaded by Amelia Notetaker on Tuesday December 1, 2015. The Class Notes belongs to BYS 120 at University of Alabama - Huntsville taught by Dr. Luciano Matzkin in Fall 2015. Since its upload, it has received 13 views. For similar materials see Organismal Biology in Biological Sciences at University of Alabama - Huntsville.
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Date Created: 12/01/15
Chapter 27 Lecture Notes Prokaryotes o Earth's first organisms were likely prokaryotes o Unicellular o Cell wall Cell wall of prokaryotes o Bacterial cell walls contain peptidoglycan Sugar polymers cross-linked by polypeptides Peptidoglycain testing o Grew strains used to classify bacteria by cell wall composition o For bacteria Gram positive: bacteria have simpler walls with a large amount of peptidoglycain Gram negative: bacteria have less peptidoglycain and an outer membrane that's toxic Made up of lipopolysaccarides outer membrane Motility o Many bacteria have ability to move toward or away from stimulus (taxis) o Chemitaxis: movement toward or away from chemical stimulus o Most motile bacteria propel themselves by flagellum Flagellum of bacteria, archaea and eukaryotes are composed with a different protein, this suggests o It evolved independently Origins of prokaryotic flagellum o Flagellum is composed of different proteins and likely evolved indepedently o Flagella proteins are modified versions of proteins that perform other tasks in bacteria o Likely evolved as existing proteins Inside prokaryotes o Lack organelles o Some species can contain infoldings of plasma membrane DNA structure o Prokaryote genome is much smaller o Circular chromosomes o Chromosomes are not surrounded by membrane (no nucleus) o Some species of bacteria also have smaller rings of DNA called plasmids Reproduction o Reproduce through binary fission Splits into 2 o Reproduce only 1-3 hours, some every 20 minutes Genetic diversity o Prokaryotes have a great amount of genetic variation o 3 factors contribute to this genetic diversity Rapid reproduction Mutation Genetic recombination Mutation rates o Mutation rate is not dramatically high e coli per gene is 10^-7 o Rapid reproduction allows from the occurrence of many mutation events Given 1 hour if you start with one cell, after one day you'll have 16 million cells o High diversity from mutation allows for rapid evolution Genetic recombination o Combining DNA from 2 sources o Contributes to bacterial diversity o DNA from different individuals can be brought o Horizontal gene transfer: between different species gene exchange occurs Transformation o Uptake of DNA from surroundings o Could be from its own species or another o Could be incorporated into the genome o Antibiotic resistance Transduction o Movement of gene between bacteria by phages Conjugation o Transfer of genetic material How prokaryotic cells evolve o DNA transfer is one way o A donor cell attaches to a recipient by a pelis, pulls it closer, and transfers DNA o Piece of DNA called the fertility factor (f factor) F factor o Cells containing the f plasmid function as DNA donors during conjugation o The f factor is transferable during conjugation o The f factor can be built in the chromosome (raises frequency of recombination of Hfr recombinant) Metabolic diversity o Prokaryotes can inhabit a incredibly diverse set of environments o Phototrophs: get energy from the light o Chemotrophs: get energy from chemical reactions o Autotrophs: energy from a carbon source, like CO2 o Heterotrophs: energy from organic compounds Prokaryotes metabolism and oxygen o Obligate aerobics require O2 for cellular respiration o Obligate anaerobics: powered by O2 and use of fermentation for anaerobic respiration o Faculative anaerobes can survive with or without oxygen Prokaryotic metabolism and Nitrogen o Prokaryotes can metabolize Nitrogen in a variety of ways Nitrogen Is essential for amino acids and nucleic acids o In nitrogen fixation some prokaryotes convert atmospheric nitrogen (N2 and ammonia (NH3)) Cooperation o In cyanobacteria, Amabaena, photosynthetic cells, and Nitrogen fixing cells called heterocysts exchange metabolic products o Biofilms Surface-locating colonies Found of the surface of teeth Phylogeny of prokaryotes o Traditionally, prokaryotes were characterized by how they look, grow, and what type of media you can grow them on o Majority of them cannot be cultured in a lab o New molecular techniques have made it possible to sequence genes and even genomes from unaltered species o Metagenomics: multiple genomes are sequenced and then separated using computer algorithms Archaea o Extreme habitats: halophiles, live in high saline environments o Extreme temperatures: termophiles, live in very hot environments Even high pressure o Methanogens: live in swamps, marshes, Gastrointestinal tracts and produce methane as a waste product Poisoned by oxygen Important for sewage treatment Bacteria o Diverse mututional types Pathogens to beneficial types Proteobacteria o Gram-negative o Include photo-autotrophs, chemo-autotrophs, and heterotrophs o Alpha proteobacteria: living ancestor of mitochondrion Chlamydia o Parasites that live within animal cells o Not always an STD Spriochetes o Helical heterotrophs o Tyeponema pallium: syphillis and lime disease A bacteria contains an antibiotic resistance gene in plasmid R and F. how does it transfer genes to other bacteria? o Conjugation Cyanobacteria o Generate oxygen o Photo-autotrophs Gram-positive bacteria o Smallest known cells. o Anthrax, strep throat, and staph Nutrient cycling o Prokaryotes play a major role in recycling of chemicals elements Ecological interactions o Can live with large organisms in symbiosis o Mutualism, commensalism, and parasitic (pathogens)