Microbiology.docx

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Department
Microbiology
Course
MICR 2420
Professor
Emma Allen- Vercoe
Semester
Fall

Description
9/16/2013 6:50:00 AM Viruses  Some viruses envelop themselves in host membrane as a form of camo.  Tegument is a package of proteins and enzymes a virus may use for quicker infection time and less lag Filamentous Virus (helical capsid)  Genomes are too large and cannot be packed into an icosahedral  Some of the material is packed outside and these viruses are fairly flexible (such as ebola) Multiple Helical Packages  Collection of helical genome segments  Constantly transforming and evolving (influenza) Complex Viruses  Bacteriophages  Land and eject genetic material into bacteria Asymmetrical Viruses  Vaccinia poxvirus (chicken pox)  No symmetrical capsid and it stabilized by covalent connection of two strands (in a circle)  No capsid, DNA is enclosed by a core envelope surrounded by a membrane that comes from the host  Contain a large number of accessory proteins (enzymes and regulatory proteins). Viral Genomes  Efficiently packed into an mRNA like structure  Use different starts to produce different proteins  Long Terminal Repeats (LTR) – signatures of viruses that represent scars on the host genome  Viruses are made of at least a capsid and nucleic acid HERVs  Human endogenous Retroviruses  Make up 8% of the human genome (Recognized by LTR)  HERVs are the remains of ancient viruses that once infected the germline and incorporated themselves into our genome  Over the millennia they have become degraded and non-functional (Or have they?)  Not entirely junk DNA  Recent onset psychosis and multiple sclerosis patience show evidence of transcription of HERV genes  MS Patients in particular respond well to interferon beta therapy which suppresses retroviral replication Viroid  Extremely simple and no protective capsid  Usually RNA molecules that infect plants  Some have catalytic activity (Cleave very specific RNA sequences to interfere with transcription and translation; may be useful in medicine) Prions  Consist of proteins only  Not Viruses or cells  They contact and force normal proteins to change their confirmation Bacteria Prokaryotes  Free living organisms that may live in ecosystems  Stressful environments that includes predation, osmotic stress (membranes), nutrient limitation, temperature/pH fluctuations  Prokaryotes (Including bacteria and archaea) share traits such as a thick, complex outer envelope; a compact genome; and tightly coordinated cell functions Mollicutes  Contain DNA, Ribosomes, Cytoplasm and Plasma membrane and are the most basic of all bacteria  Don‟t require lots of energy to survive and are very small and compact and can fit through small spaces  Needs a Eukaryotic host to keep it safe  Complicated diet because they have small genomes so cannot synthesize everything they need to survive  Cell Wall o Peptidoglycan (Murein) Polymer of sugars and amino acids o Sugars are N-Acetyl Glucosamine and N-acetyl muramaic acid o Walking Pneumonia (Mycoplasma pneumonia, mycoplasma genitalium, TB)  Gram Positive Bacteria (“Fuzzy” type) o Contains, DNA, Ribosomes, Cytoplasm, Plasma membrane and a thick cell wall (20-80nm) o Strong teichoic acid threads through peptidoglycan layers adding strength o Guaranteed against osmotic lysis o Available in gram stain purple o Must be kept away from Lysozyme (attacks P.glycan very fast and degenerates bacteria)  Coccus = round (Staphylococcus aureus), Bacillus = rod shaped (Bacillus cereus)  Gram Negative Bacteria o Contains: DNA, ribosomes, cytoplasm, plasma membrane, Thin cell wall (only 1-2 sheets of p.glycan), outer membrane that contains lipopolysaccharide) o Lipopolysaccharide, used for serotyping. Lipid A portion is an endotoxin strong activator of the innate immune system, causes dangerous infections. o More evolved and able to defend itself against many toxic molecules o Built in periplasmic space used for storage o Guaranteed against osmotic Lysis o Gram stained red and different shapes o Toxic if not handled correctly o Usually requires a bigger genome to make a more complex double membrane (energetically expensive to maintain) o Iodine is used in gram staining to: create a complex with the crystal violet to make a larger compound  Added Extras S-Layer o S-Layer addition outside of the peptidoglycan or lipopolysaccharide layer o Bacterial Chainmail, a crystalline layer of thick glycoprotein or protein o Highly ordered, can flex to allow movement of molecules o S-Layers are biomaterials of the future: Self assemble and act as a scaffold for building synthetic plasma membranes for all kinds of applications o Can also act as a template for building inorganic nanocrystal super-lattices for „molecular electronics‟  Capsule o Sometimes called the „slime layer‟ available for G+ and G- o Consists of slippery coat of loosely bound polysaccharides o Difficult to stain and thus appear as clear halos around cells o May exist with S-layer and if so it is found outside of the S- layer o Important role in pathogens for preventing phagocytosis/activation of the innate immune system. o Bacillus anthracis (anthrax-causing) has a large capsule outside of its s-layer  Thylakoids o Only found in G- phototrophs o Specialist systems of extensively folded lamellae (sheets) of membrane o Packed by photosynthetic proteins and electron carriers o Maximize Photosynthetic capability of the cell o Porochlorococcus marinus is the most plentiful organism on earth and responsible for production of ~50% of atmospheric Oxygen.  Carboxysomes o Enzymes used to fix CO2 found in gram negatives o Found in all cyanobacteria and some chemotrophs that fix CO2 o Have a characteristic polyhedral shape  Gas Vesicles o Aquatic phototrophs and some aquatic heterotrophs o Thin balloons made of hydrophobic protein o Allow microbes to maintain a set buoyancy optimal to its preferred conditions in the water column  Storage Granules o During optimal growth periods bacteria store excess energy in the form of storage granules o Consume them later o Stored as glycogen, polyhydroxybutyrate (PHB) or poly-3- hydroxyalkanoate (PHA) o Some store sulfur in granules in the cytoplasm or outside as decorations on their membranes  Polyhydroxybutyrate (PHB) o Used in biodegradable plastics because it is: Water insoluble, biocompatible (used in surgery doesn‟t cause infection), non- toxic, high tensile strength (like polypropylene), Heavier than water (Will sink to the bottom of a water column where it is more efficiently biodegraded).  Magnetosomes o Only available for Gram negative, aquatic species o Membrane bound crystals of magnetite (Fe3O4) o Allow a motile bacterium to orient itself with the earth‟s magnetic field (Magnetotaxis) o Prefer to live in anaerobic conditions, they need to determine whether they are up or down and want to swim down where it is less toxic. o Bacterial magnetite nanocrystals have many advantages over nanocrystals synthesized in lab  Narrow size distribution (25-55nm)  Uniform Morphology  High Purity  Presence of a membrane (lipids and proteins) o Currently of great interest as a way to deliver targeted drugs (Cancer Therapy; delivery to a tumour site)  Pili o Available fir G+ and G- o Used for Bacterial adhesion o Can be Long or short, flexible or brittle, curly ot straight, singular or twisted in rope-like bundles o Some are Used in bacterial sex ( conjugation) o Some are used in specialist type of bacterial motility (twitching motility) , grappling hooks only expressed by pathogenic bacteria. o Pathogens often use pili to attach to host cells and initiate disease o Pili are a therapeutic target for strategies to prevent infection  Stalks o Membrane-embedded extension of the cytoplasm of some squatic bacteria o Only G-  Tip of stalks secretes secretion factors “Holdfasts”  Act as antenna to seek out nutrients (particularly Phosphates) Allow bacterium to remain in a favourable location  Rotary Flagella o Organelles of motility o Available for both G+ and G- o Rigid long helical protein structures o Anchored in the cell membrane (G+) or outer membrane (G-) o Work together with chemoreceptors to propel bacterium in optimal directions using runs and tumbles o Uses a motor that runs at almost 100% efficiency that drives the rotation of the flagellar propeller o Turns at 1000rpm and can switch spin direction almost instantaneously o Fuelled by an ionic gradient (PMF) across the membrane  Chemotaxis Archaea (Archaeon)  Look like Bacteria but they are not  Can be found in many environments and extreme conditions  Grow within a wider range of temperature and other environmental conditions than either bacteria or eukaryotes  Thermophiles o Pyrococcus furiosus: a therhmophile as well as a barophile o Can only survive at temps >70C o Anaerobe metabolises sulfur to H2S o Lives in deep sea thermal vents  Psychrophiles o Largely uncultured:
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