BIOL 102 Lecture Notes Ch. 27 (Bacteria and Archaea)
BIOL 102 Lecture Notes Ch. 27 (Bacteria and Archaea) BIO 102
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This 3 page Class Notes was uploaded by Zach Notetaker on Tuesday September 20, 2016. The Class Notes belongs to BIO 102 at University of South Carolina taught by Mihaly Czako in Fall 2016. Since its upload, it has received 17 views.
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Date Created: 09/20/16
BIOL 102 Lectures Notes 9/13/16 Ch. 27 Bacteria and Archaea Prokaryotes found in every possible habitat… Ex) Utah’s Great Salt Lake pink color comes from living prokaryotes o Thrive almost everywhere o Mostly microscopic o LOTS OF THEM o Divided into two domains: bacteria and archaea Earth’s early organisms were likely prokaryotes o unicellular, but some form special colonies o variety of shapes o common shapes: spheres (coccus/cocci), rods (bacillus, bacilli), and spirals Cell Surface Structures: o Cell walls maintains cell shape, protects cell, prevents bursting in hypotonic environment o Eukaryote cell walls made of cellulose or chitin o Bacterial cell walls contain peptidoglycan: network of sugar polymers crosslinked by polypeptides o Scientists use gram stain to classify bacteria by cell wall composition Grampositive: bacteria w/ simpler walls and a large amount of peptidoglycan Gramnegative: bacteria w/ less peptidoglycan and an outer membrane that can be toxic to humans o Archaea contain polysaccharides and proteins BUT lack peptidoglycan; stain mostly Gramnegative (BUT staining doesn’t correlate w/ taxonomic subdivisions) Antibiotics target peptidoglycan and damage bacterial cell walls o Gramnegative bacteria more likely to be antibiotic resistant o Polysaccharide or protein layer called capsule covers many prokaryotes Many prokaryotes form metabolically inactive endospores, can remain viable in harsh conditions for centuries Some prokaryotes have fimbriae allow them to stick to their substrate or other individuals in a colony o Pili/pilus (sex pili) longer than fimbrae and allow prokaryotes to exchange DNA Many bacteria exhibit taxis ability to move toward or away from stimulus o Chemotaxis movement toward or away from chemical stimulus o Most propel themselves by flagella scattered about surface or concentrated at one or both ends Flagella of bacteria, archaea, and eukaryotes composed of different proteins and likely evolved independently Internal Organization and DNA in Prokaryotic cells: o usually lack complex compartmentalization o specialized membranes that perform metabolic functions usually infoldings in plasma membrane o less DNA than eukaryotic genome o mostly circular chromosomes not surrounded by membrane, located in nucleoid region o some species have smaller rings of DNA called plasmids Reproduction: o prokaryotes reproduce quickly binary fission (can divide every 13 hours) o Key features: small, binary fission, SHORT generation times o Considerable genetic variation: 3 factors: Recombination: combining of DNA from 2 sources, contributes to diversity DNA from different individuals brought together by transformation, transduction, and conjugation movement of genes among individuals from different species horizontal gene transfer o Transformation: prokaryotic cell can take up an incorporate foreign DNA from surrounding environment o Transduction: movement of genes between bacteria by bacteriophages (viruses that infect bacteria) o Conjugation and Plasmids: process where genetic material is transferred between prokaryotic cells (equivalent to mating or sexual reproduction in bacteria, DNA transfer is one way donor cell attached to recipient by pilus, pulls it closer, and transfers DNA piece of DNA called F factor is required for the production of pili o R Plasmids and Antibiotic Resistance: R plasmids: carry genes for antibiotic resistance antibiotics kill sensitive bacteria, but NOT bacteria w/ specific R plasmids Thru natural selection, fraction of bacteria w/ genes for resistance increases in population exposed to antibiotics antibiotic resistant strains are becoming more common Metabolic diversity of prokaryotes: o photoautotrophs energy from light o chemoautotrophs energy from inorganic chemicals o photoheterotroph energy from light but needs organic compounds to live o chemoheterotroph energy from organic compounds Oxygen in Metabolism: o Obligate aerobes require Oxygen for cellular respiration o Obligate anaerobes poisoned by O2 and use fermentation or anaerobic respiration o Facultative anaerobes can survive W/OUT Oxygen Nitrogen fixation: convert atmospheric nitrogen (N2) to ammonia (NH3) o nitrogen essential for production of amino acids and nucleic acids Bacteria o (subgroup Alpha Proteobacteria) Rhizobium forms root nodules in legumes and fixes atmospheric N2 Agrobacterium produces tumors in plants and is used in genetic engineering o (subgroup Gamma Proteobacteria) Escherichia coli resides in the intestines of mammals and isn’t normally pathogenic Extremophiles: archaea that live in extreme environments o Extreme halophiles: live in highly saline environments o Extreme thermophiles: thrive in very hot environments Methanogens: live in swamps and marshes & produce methane as waste product o strict anaerobes & are poisoned by Oxygen gas Symbiosis: two species live close together (larger host and smaller symbiont) Mutualism: both symbiotic organisms benefit Commensalism: one organism benefits while neither harming nor helping the other in any major way Parasitism: organism called parasite harms BUT doesn’t kill host o Parasites that cause disease are called pathogens Exotoxins: secreted by pathogenic prokaryotes and causes disease even if prokaryotes that produce them are not present Endotoxins: released only when bacteria die and their cell walls break down (outer membrane of Gramnegative bacteria) Bioremediation: use of organisms to remove pollutants from environment o bacteria can be engineered to produce vitamins, antibiotics, and hormones
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