Week 2 of BISC 300
Week 2 of BISC 300 BISC300
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This 15 page Class Notes was uploaded by Jj Lynch on Saturday February 20, 2016. The Class Notes belongs to BISC300 at University of Delaware taught by Carlton Cooper in Summer 2015. Since its upload, it has received 28 views. For similar materials see Microbiology in Biological Sciences at University of Delaware.
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Almost no time left on the clock and my grade on the line. Where else would I go? Jj has the best notes period!
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Date Created: 02/20/16
Wednesday Notes • 1673, Anton Van Leuwenhoek made first and simplest microscope o discovered single-celled organisms in pond water (Animalcules) • People believed Spontaneous Generation- living organisms come from non- living matter o Ie/ dead bodies --> maggots o Grain + sweaty clothes --> mice • John Needham boiled mutton to “kill all organisms”, let it cool and waited for microbes to form o Claimed the microbes were proof of spontaneous generation o Mutton was exposed to air though • Spallazani repeated experiment but covered mutton o No microbes formed o Concluded microbes came from air • Redi used gauze to cover meat in jar to prove flies cause maggots o Gauze caught fly eggs and maggots grew from those o Flies could smell meat through gauze o 3 jar was sealed with lid, no eggs, no maggots • Louis Pasteur created flask that let air in but no microbes to prove spontaneous generation, broth never grew microbes though • Essential bacterial structures (all have them) o Cell wall, cell membrane, cytoplasm, nuclear material • Accessory structure (some have them) o Capsule, flagella, pili, spore, • Spore has a compound, heat shock proteins (hold proteins together) and a dehydrating agent to keep heat (boiling) from destroying bacteria’s proteins (?? NOT 100% SURE ABOUT THIS) • Gram stain developed in 1884 by Hans Christian Gram o Looked at lung that had pneumonia, saw certain bacteria had certain color (????) • 2 groups for bacteria o Gram + (thick cell wall) stains purple o Gram – (thin cell wall) stains pink • Bacteria also divided into groups by shape Friday Notes • Gram stain: o Crystal violet (all purple cells) à iodine (all purple) à alcohol (G+ = purple G- = no color) à safranin ( G+ = purple G- = red) • Color dependent on cell wall o Bacterial cell wall made of peptidoglycan • For G-: The iodine forms a complex, the alcohol dehydrates the cell, dye gets trapped in plasma membrane, makes cell colorless (?? NOT 100% SURE ABOUT THIS) • G + bacterium: o NAG and NAM peptidoglycans alternate in cell wall (this happens in G– too) o Have “chaperone proteins” called Teichoic acid, support the large cell wall o Lipoteichoic acid attaches cell wall to plasma membrane • G – bacterium: o Has outer membrane o Lipoproteins connect cell wall to outer membrane • Outer membrane- lipoproteins, phospholipid bilayer, lipopolysaccharides (toxic to humans, cause inflammation) • Sight of selectivity is in plasma membrane • Cell wall provides structure and shape o Survival in hypotonic environment too § Ie/ penicillin kills bacteria by destroying cell wall. Bacteria lyse • Prokaryotes: o Outer membrane protects from antibodies • Bacteria can be good in one part of the body and bad in another o Ie/ E. Coli • G – have pili and flagella, G + just flagella • Capsule and slime layers made of polysaccharides and/or polypeptides o Capsules are organized and attached securely to cell wall o Slime layers are unorganized and not as securely attached • Pili are hair-like proteins on cell for movement and genetic exchange (conjugation) o Gives them toxin production and antibiotic resistance • To see if something is a pathogen: o Take microorganism from dead animal o Grow it in pure culture and identify it o Inject it into healthy animal o If it dies remove the microorganism and see if it’s the same one that killed the first animal Chapter 3 Textbook Notes • Variety of shapes and sizes in bacteria o Cocci- spherical § Single or characteristic arrangement (ie/ Diplococci- divided cocci remain together to form pairs) o Rod/ Bacilli- rod shaped § Various ones differ in length-to-width ratio § Single or in chains o Vibrius- comma shaped o Spirilla- rigid, spiral § May have tufts or flagella at one or both ends o Spirochets- flexible, spiral § Unique, internal flagella arrangement • Pleomorphic- variable in shape and lacking a single, characteristic form • Range in bacteria size: .3 um – 7 um (???) • Small size utilizes large surface area to volume ratio o Bacteria can be large if it maximizes this ration (ie/ convolutions in plasma membrane) • Cell envelope- plasma membrane, cell wall, capsule/slime layer • Bacteria don’t have membrane bound organelles, interior morphology is simple • Genetic material in nucleoid region • Ribosomes and larger masses are called inclusions • Flagella fro locomotion • Plasma membrane selectively permeable • Respiration, photosynthesis, and synthesis of lipids and cell wall parts occur in plasma membrane • Model for membrane is Fluid Mosaic Model o Lipid bilayer, proteins float within • Membrane lipids are amphipathic (polar and non- polar ends) • Peripheral membrane proteins- loosely connected to membrane and soluble in aqueous solution • Integral membrane proteins- insoluble in aqueous solution, amphipathic (hydrophobic regions are buried within bilayer) o Ie/ transport proteins or electron transport chain • Membrane is actually a patchwork of different lipidmicrodomains • Lipid composition of bacterial membrane varies with temperature o Lower temp = more unsaturated fatty acids o Higher temp = more saturated fatty acids • Bacterial membranes lack sterols but have hopanoids- sterol-like molecules made from same precursors as steroids, stabilize the membrane • Macroelements- C, O, H, N, S, and P. Found in macromolecules o Also K, Ca, Mg, and Fe • Micronutrients/ Trace elements- Mn, Zn, Cb, Cu, nickel • Growth Factor- molecules needed for survival, obtained from the environment o Amino acids, purines and pyrimidines, vitamins • Bacteria take in dissolved materials up the concentration gradient • Passive Diffusion- (simple diffusion) molecules move from higher to lower concentration (down the gradient) o Large gradient needed for good uptake o If not used up, rate of nutrient absorption decreases as more nutrients accumulate in cell o Small, non-polar substances • Large and/or polar ones move through transport proteins o Channels- proteins for pores for substances o Carriers- proteins carry nutrients across membrane • Facilitated Diffusion- movement across membrane with help from channels or carriers o Rate of diffusion increases more rapidly at lower molecule concentration than passive o With carrier the rate reaches a limit, all carriers saturated o No energy required o Not major uptake method for bacteria, live in nutrient low environments • Energy dependent transport more important uptake • Active Transport- molecules move from lower to higher concentrations through input of energy o Primary- uses carriers called primary active transporters. Energy comes from ATP hydrolysis § Uniporters move single molecule (ie/ ATP-binding cassete (ABC) transporters) o Secondary- uses potential energy of ion gradients to transport § Cotransporters, 2 substances move simultaneously § Symport- same direction § Antiport- different directions (ie/ electron transport and oxidative phosphorylation) • Usually have more than 1 transport system for a nutrient • Group translocation- molecule is chemically modified when brought into cell • Siderophores- organic, bind to ferric iron and bring it into cell o Bacteria secrete them to gain iron when iron is scarce in environment • Cell wall can protect cell from toxins and pathogens as well as give a bacteria pathogenicity • Not all bacteria fit the model of being typical Gram + or Gram – • Gram + and – bacteria have different Periplasmic space (space between the plasma membrane and the outer one (for G -) or the space between the plasma membrane and cell wall (G +) • Peptidoglycan has many identical subunits, each contain 2 sugar derivatives (N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM)) and amino acids • Peptidoglycans form peptidoglycan sacculus by linking the sugars in their subunits together, making strands that can be covalently bonded to other strands • Sacculus strong but elastic, responds to osmotic pressure o Also porous • Gram + have more cross-linking of strands than Gram – • Teichoic acids are polymers of glycerol or ribotol bonded together by phosphate groups o Covalently bonded to peptidoglycan • Lipoteichoic acids covalently bind to plasma membrane • Teichoic acids have negative charge, make cell wall negative • May make up 50% of cell wall mass • Exoenzymes-degrade polymeric nutrients that are too large to pass across plasma membrane • Gram – cell walls much more complex • Much larger periplasmic space, much thinner peptidoglycan layer • Outer membrane linked to cell by Braun’s lipoprotein • Lipopolysaccharides (LPS) have lipid and carbohydrate: lipid A, core polysaccharide, and O side chain • Lipid A has 2 glucosamine sugar derivatives, each has 3 fatty acids and a phosphate or pyrophosphate o Can act as a toxin (endotoxin) • Fatty acids embed in outer membrane, rest of LPS is on membrane surface • Core polysaccharide has 10 sugars • O side chain (O antigen) is polysaccharide chain that extends from core o Causes immune response in host to produce antibodies that will respond to that chain, then the bacteria may change the antigenic nature of the O chain • LPS gives negative charge to bacteria’s surface, stabilizes outer membrane, creates permeability barrier, and protects from pathogenic bacteria • Outer membrane more permeable than plasma o Because of Porin proteins- form a trimer in the membrane • Bacteria without cell walls stain Gram – • Crystal violet dye in staining is positive and attracted to negative cell • The iodine interacts with the crystal violet to make an insoluble complex so the dye is retained • The alcohol shrinks the pores of Gram + peptidoglycan to prevent dye loss o Dye is lost from Gram – • Safranin stains the colorless cells • Penicillin inhibits the enzyme that makes cross-links between peptidoglycan strands • Protoplasts have lost their cell wall (Gram +), spheroplasts have lost the peptidoglycan sacculus (Gram -) o Osmotically sensitive • Only bacteria synthesizes peptidoglycan • Capsules help bacteria resist phagocytosis by phagocytes • Slime layers have been seen to allow some bacteria to glide, facilitating mobility • Both capsules and slime layers are glycocalyx because they consist of a network of polysaccharides that extend from the cell o Allows attachment to solid surfaces (ie/ tissue) • S-layer- composed of protein or glycoprotein o Adheres to outer membrane in Gram -, peptidoglycan in Gram + o Protect against changing pH, osmotic stress, enzymes and other bacteria o Maintain shape and envelope rigidity and may give adhesion • Protoplast-plasma membrane and everything within • Homologues of eukaryotic actin and intermediate filaments and microtubules have been found in bacteria • Bacterial cytoskeleton are involved in cell division, localizing proteins, cell shape • Bacteria also has some unique cytoskeletal proteins o FtsZ, MreB, and CreS (crescentin) o FtsZ like tubulin, forms ring in center of dividing cell to separate daughter cells o MreB determines cell shape in rods o CreS promotes curved shape, is similar to lamin and keratin • Some bacteria have internal membranous structures o Photosynthetic bacteria or bacteria with high respiratory activity o Ie/ thylakoids in photosynthetic cyanobacteria • These structures could be spherical vesicles, flat vesicle, or tubular membranes • Connected to plasma membrane • Functions are to serve larger membrane surface in metabolism • Inclusions are formed by aggregation of substances (ie/ granules, crystals, globules) o Often used for storage or to reduce osmotic pressure • Glycogen inclusions, polyhydroxyalkonate granules, sulfur globules, and polyphosphate granules are the most common storage ones • Polyphosphate granules store phosphate needed for synthesis of important cell molecules (ie/ nucleic acids) • Some inclusions are microcompartments (large polyhedrons, consist of one or more different proteins, hold enzymes) o Ie/ Carboxysomes- in cyanobacteria, polyhedral coat has 6 different proteins, 100nm in diameter, holds enzyme carbonic anhydrase to make carbonic acid into CO2, holds RubisCO to turn CO2 into sugar • Some inclusions used for bacterial movement o Gas vacuoles give buoyancy, have small and hollow gas vesiacles o Magnetosomes orient themselves in Earths magnetic field • Bacterial cytoplasm packed with ribosomes, or has them loosely attached to membrane o Membrane ribosomes make proteins for envelope, free ones make proteins fro cytoplasm • Ribosomes of the three domains are similar • Bacterial ones are 70S, made of 50S and 30S subunits o S = Svedberg unit (measure of sedimentation velocity in a centrifuge, faster a particle travels=higher Svedberg) o Related to particle’s molecular weight, volume and shape: heavier and compact have larger S • Most bacteria have singular circular chromosome • They are longer than length of cell, must be tightly packed o Nucleoid-associated proteins (NAP) cause chromosome to bend anf fold o Condensins further compact it during cell division • A few bacteria have membrane enclosed DNA regions, most do not • Some bacteria have plasmids-small, double stranded DNA molecules that can exist independently of the chromosome, most are circular o Usually less than 30 genes, not essential, usually contain a selective advantage o Replication not linked to cell cycle • Episomes- plasmids that have integrated into the chromosome • Plasmids not always equally divided during cell division • Curing-loss of a plasmid • Fimbriae and Pili- slender tubes composed of protein subunits , are 3-10 nm in diameter and up to several micrometers long o Attach cells to solid surface • Sex pili are larger (diameter 9-10nm), genetically determined by conjugative plasmids, required for conjugation • Many bacteria use flagella to move, they can also use them to attach to surfaces o Are slender, rigid, 20nm wide, 20 um long • Monotrichous-one flagellum (polar if on an end) • Amphitrichous-one flagellum at each pole • Lopotrichous- cluster of flagella at one or both ends • Peritrichous- flagella evenly spread over whole surface • Flagellum has 3 parts o Filament extends from cell surface to tip, composed of flagellin, is an example of self assembly o Basal body is embedded in cell envelope, most complex part o Hook connects filament to basal body • Chemotaxis- movement toward chemical attractants and away from repellants o Also thermotaxis, phototaxis, aerotaxis, and osmotaxis • Swimming is done with flagella, rotates (a run is a smooth swimming movement, a tumble reorients the cell) o Direction of rotations determines whether run or tumble happens o The flagellar motor has a rotor and stator o Power supplied by difference is charge and pH across plasma membrane (proton motive force PMF) speed proportional to PMF o Bacteria can swim from 20-90 um per second • Most swarming bacteria (bacteria that move in unison across surface) have peritrichous flagella • Spirochetes have multiple flagella on each side of the cell that intertwine and wrap around the cell and remain in the periplasmic space (periplasmic flagella) o Rotate to cause cork-screw shaped outer membrane and rotate to move • Twitching and gliding involve IV pili and/or slime, the pili are on one or both poles • Twitching motility- short, intermittent jerking. Pili extend and retract pulling cell forward. Powered by ATP hydrolysis • Gliding motility is smooth and could be 2-600um per second, more than one mechanism for it exists • Social (S) motility-large groups of cells move together and coordinately , uses IV pili • Adventurous (A) motility- single cell moving independently • Chemical attractants and repellants are detected by chemoreceptors o In plasma membrane in Gram – • Concentrations of attractants and repellants dictate bacteria motion • Endospores are resistant to heat, UV, gamma, chemical disinfectants and desiccation o core has ribosomes and nucleoid etc. but lower water content, then inner membrane, core wall, cortex (peptidoglycan), outermembrane, and the coat and exosporium o all these layers prevent DNA damage • Bacteria that form endospores are pathogenic
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