Chapter 3: Prokaryotic Profiles: The Bacteria and Archaea
Chapter 3: Prokaryotic Profiles: The Bacteria and Archaea 2420
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This 3 page Class Notes was uploaded by Siân L'Roy on Saturday August 20, 2016. The Class Notes belongs to 2420 at Tarrant County College District taught by Mark Pulse in Summer 2016. Since its upload, it has received 9 views. For similar materials see Microbiology in Biology at Tarrant County College District.
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Date Created: 08/20/16
Prokaryotic Profiles: The Bacteria and Archaea Cells can be physically classified according to their shape and divisional arrangement o Common shapes include: Coccus (plural: cocci)= spherical; round; e.g. Staphyloccus areus Bacillus (plural: bacilli)= rod; e.g. Bacillus anthracis Coccobacillus (plural: coccobacilli)= shortened rod; e.g. Bordentella pertussis (whooping cough); E. coli Vibrio (plural: vibrios)= curved rod; e.g. Vibrio cholera Spirillum (plural: spirilla)= spiraled rod; e.g. Spirillum minor Spirochete= corkscrew shaped; e.g. Borrelia burgdorferi o Bacteria often vary in shape (pleomorphic) o Bacteria multiple (grow) by binary fission (cellular division); cells divide without completely separating o Binary fission can occur in one or more planes; results in the following arrangements: Diplo(one planed; paired arrangement; Neisseria sp.); move left, right or up, down Strepo (one planed; chain arrangement; Streptococcus sp.); move left, right and up, down Tetrads (two planed; four cell, cubed arrangement; Merisopedia sp.) Sarcina (three planed; eight cell, cubed arrangement; Sarina sp.); move left, right, up, down, and behind Staphlo (multi planed; cluster arrangement; Staphylococcus sp.); move left, right, up, down and diagonally Common prokaryotic cellular structures include: o Selectively permeable cytoplasmic membrane o Rigid cell wall and outer membrane (Gram negative) o Protective capsule or slime layer o External flagella or pili projections o Intracellular chromosomal and plasmid DNA o Intracellular storage and gas vesicles(inclusion bodies) o Internal endospores in Clostridium and Bacillus sp. o 70S, cytoplasmic ribosomes Cytoplasmic (inner) membrane specifics: o Comprised of phospholipids; polar (hydrophilic) o Phospholipids are in a bilayer arrangement (selective barrier);70% Prokaryotic Profiles: The Bacteria and Archaea o Proteins associated with membrane are classified as sensors or carriers (channels); 30% o Functions include: Synthesis of cell wall components Transportation of substances in and out of a cell (secretion) Generation of cellular energy (ATP; sugar) Rigid cell is important in maintaining cell shape and preventing cellular lysis Main component of cell wall is peptidoglycan polymer (NAM and NAG sugars) o Bilayered sugar backbone (Nacetylglucosamine and Nacetylmuramic acid) connected by tetrapetide (four amino acids) linkage Thickness, position, and overall composition varies between Gram (+) and Gram () bacteria o Gram (+): Cell wall is 20 to 80 nm across (thick) 60% to 90% of wall is peptidoglycan with teichoic acid projections (attachments) External to cytoplasmic (inner) membrane; lack of out membrane and periplasmic membrane Needs to be crossed linked o Gram (): Cell wall comprised of 10% to 20% peptidoglycan without teichoic acid (thin) Composition is complex; contains a mixture of polysaccharides, proteins, and lipids Cell wall is positions between an outer membrane and inner cytoplasmic membrane Outer membrane is made up of lipopolysaccharide (LPS); lipid A component and O polysaccharide Periplasmic spaces exists between wall and each membrane; site for specific enzymatic activity and transportation; gellike structure; each protein has specific function o AcidFast Bacteria: Cell wall is thick and contains 60% lipids in its structures Capsules and slime layers are gellike layers externally present on some bacteria; can provide the following functions: o Enable adherence of bacteria to specific surfaces like teeth, rocks, and prosthetic devices Prokaryotic Profiles: The Bacteria and Archaea o Enable adherence of bacteria to one another that result in the formation of biofilm communities o Important in immune evasion mechanisms Protein Flagella are important appendages involved in cellular motility; three major components of a flagellum are: o Basal body: Anchors flagellum to cell wall and membranes o Fillagment: ‘Tail’ portion extending into the environment o Hook: Portion connecting the filament to the basal body Pili are important appendages for attachment(fimbriae), motility (twitching and/or gliding) and transfer of DNA material (conjunction) Important internal structures of prokaryotic cells are: o Chromosomal DNA: Supercoiled, circular DNA; forms visible nucleoid within the cell o Plasmids: Extrachromosomal DNA; also supercoiled and circular; 0.1 to 10% of chromosomal DNA size; the cell can be packaged with several plasmids at one time o Ribosomes: Composed of ribosomal proteins and ribosomal RNA; nonfixed (free) and involved in protein synthesis o Storage granules and vesicles: Membrane bound structures involved in storing excess molecules for future use and store gas for cellular buoyancy; Similar to inclusion body o Endospores: Dormant cell produced in response to environmental stresses (pH, dehydration); very resist to various stresses and can exist for years Internally formed by a process known as sporulation Once conditions are favorable, endospore will absorb water and go through germination
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