Microbiology Week 7 Lecture Notes
Microbiology Week 7 Lecture Notes 101.0
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This 7 page Class Notes was uploaded by Isabel Markowski on Saturday October 31, 2015. The Class Notes belongs to 101.0 at University of Wisconsin - Madison taught by a professor in Fall 2015. Since its upload, it has received 37 views. For similar materials see General Microbiology in Microbiology at University of Wisconsin - Madison.
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Date Created: 10/31/15
Microbiology 101 Week 7 Lecture Notes Transgenic Plants 0 Plants with engineered genes Examples 0 Goden Rice Gene products from other organisms Rice endosperm produces 0390 this Enzyme 1 Enzyme 2 Enzyme 3 GGDP gt Phytoene gt Lycopene gt BCarotene geranyl geranyl diphosphate o RoundUp Plants 0 Engineeredherbicide resistance 0 Bacillus Thuringiensis and BT Toxin o Crystalline proteins quotBt toxin 0 Protein toxic to insects protect plant 0 Now over 100 varients I Each one specific gt one group of insects 0 Requirements for toxin to work I Ingestion I Solubilized toxin large so must be dissolved insect gut alkaline pH I Activation activated by proteases I Then 0 Toxic monomer can bind to receptor in gut cells gt cell death 0 Leads to septicemia blood stream infection 0 Agricultural use of BT toxin I Spraypowderorganic I BT cotton corn rice engineered to resist certain insect group Control of Microbial Growth Terminology o Sterilization kills ALL viable organisms 0 Includes viruses bacterial endospores the hardy ones 0 GOLD STANDARD OF CONTROL KING 0 Disinfection removal of microbes from inanimate surface 0 Antisepsis removal of microbes from living surface 0 Sanitation reducing populations to safe level 0 Decontamination treatment make objects safe to handle Microbial Susceptibility to control measures 0 Varies 0 Most resistant prions infectious proteins ex Mad Cow bacterial endospores 0 Moderate resistance naked viruses protist cysts some fungal spores 0 Less resistant most vegetative bacterial cells enveloped viruses most fungal spores fungal and protest vegetative cells Physical Controls 0 Temperature 0 High temperatures very effective I Killing endospores sterilization requires temps above 100 C with increased pressure autoclave machine 0 Mild heating Pasteurization I Mild heating then immediate cooling I Kill specific pathogensspoilage organisms I Reduce overall microbes doesn t affect food I First purpose prevent spoilage of wine I NOT STERILIZATION TECHNIQUE I Protocols 5 UltraHigh Temperature Shortest time amp higher temp Batch Pasteurization Flash Pasteurization 0 Heat at 66 C for 30 min I Pass through tube shorter time amp higher temp 0 Low temperatures I Generally nonlethal microbistatic frozen not microbicidal dying I Microbes can survive low temps for long time I Freezing may kill if ice crystals form but don t count on it I Freezing storage in lab common usually add cryoprotectant o Irradiation o Damages proteins and DNA 0 UV Radiation only surfaces are affected 0 Ionizing radiation gamma or xrays kills microbes in food etc I Doesn t make food radioactive I Also for surgical instruments etc o Drying o Lowers water activity 0 Methods 1 Directly remove water evaporationheating 2 Add high concentrations of solutes sugar salt Chemical Controls 0 Must consider type of microbe presence organic matter toxicity to nontarget organisms corrosiveness o In food 0 Acids lactic acid bacteria acetic acid bacteria 0 Alcohols yeasts 0 Sugar and salt affect osmotic conditions 0 Other chemicals preservatives o In agriculture commercial and industrial settings 0 Chemical biocides large quantities are used 0 At least 10000 different chemicals 0 Usually general biocide ex Lysol I Broad acting in cell many cellular targets 0 Dissolve membranes denature proteins chemically modify proteins damage DNA etc I Broad range of susceptible organisms o Toxic many life forms not just microbes 0 Common biocides I Phenolics Lysol I Alcohols isopropanol rubbing alcohol I Aldehydes o lnOn Humans 0 Have to be safe to apply on body 0 Antisepsis removal pathogens from living tissues I Usually with broad range biocides I Not necessarily sterilization o Antibiotics are narrow range chemicals selectively remove specific organisms 0 Usually ONE specific target in cell 0 Target NOT found in all species Principles of Antimjcrobigls Selective Toxicitv 0 Target phylogenetic groups ex bacteria but not archaea 0 Goal to kill target with no effects on nontargeted organisms o Antibiotics o Produced by microbes 1 Bacteria Actinomycetes ex Streptomyces others ex bacillus pseudomonas etc 2 Fungi penicillium 0 Spectrum of activity broad range vs narrow ex tetracycline broad isoniazid narrow Antifungals Antibacterial Antiviral Eukaryotes Bacteria Obligater Viruses Parasitic i i Bacteria E Isoniazid Tetracycline E 0 Structural classes can be any of variety of chemical structure I Generally very complex 0 Testing for Antibiotic Susceptibility Method 1 Method 2 o MIC minimal inhibitory concentration 0 Disc Diffusion assay inoculate nutrient agar minimal amount to be effective plate with culture insert antimicrobial discs on 0 Growth tubes with different amounts of surface incubate test organism shows antibiotic pgml susceptibility by zones of inhibition no bacterial growth around discs o The bigger the zone the more sensitive the bacteria Antibacterial Antibiotics 0 Target essential cellular structures and functions most successful antibiotic 0 Target either one protein or one essential structure 0 Advantage eukaryote cells very different than bacteria 0 Major targets common Cell wall synthesis peptidoglycan and Protein synthesis ribosome Mior Antibacterial Antibiotics o Blactam antibiotics target cell wall synthesis most common 0 Fluoroquinolones target DNA structurereplication o Macrolides target protein synthesis Cell Wall Synthesis Peptidoglycan synthesis 0 Subunits made in cytoplasm attached to bactoprenol to ferry to nucleus 0 Transpeptidases and transglycosidases make and break bonds 0 Bactoprenol lipid ferries subunit across BLactams inhibit transpeptidases o Bind transpeptidase enzymes and inhibit their function 0 Transpeptidases first called penicillin binding proteins PBP original Blactams the penicillins o Blactam ring 4member ring with N TR 0 Fleming Increase levelproduction WWII treat wounded soldiers DNA ReplicationStructure Quinolone Antibiotics o Affect topoisomerases Gram proteins related to structure and DNA gyrases Gram o Nalidixic Acid a quinolone purple rings 0 Fluoroquinolone Topoisomerasesgyrases coilinguncoiling of DNA structure 0 If inhibited by quinolones cell death Other Targets Protein Synthesis 0 Ribosome 0 Many antibiotics macrolides tetracycline RNA Polymerase o Rifampicins important treatment of tuberculosis Metabolic Pathways o Bacteria make muchown stuff vitamins acids etc 0 Ex sulfa drugs target folic acid synthesis Membrane Function 0 NOT common target 0 Bacterial membranes and eukaryotic membranes too similar Antivirals o Viruses mostly use host machinery for replication 0 Hard to affect virus without affecting host 0 Often very specific 0 Target one specific protein in one specific virus 0 Common examples 0 Nucleoside analogs affect viral polymerases o Protease inhibitors affect viral proteases Antifungals 0 Close relatives to animals more similar to eukaryotes more difficult to develop antifungals 0 Example General cell walls made of chitin but fewer opportunities for antifungals than antivirals Antibiotics NonTarget Effects o Toxicity to host side effects ex damage kidneys hearing 0 Allergies o Alteration of normal microbiota antibiotics affect ALL bacteria 0 Microbiota shift diseases 0 Ex Clostridium difficile Cdif infection after antibiotic treatment disrupts normal intestinal microbiota Antibiotics Overuse A Intrinsic Resistance 0 Inappropriate prescription 0 Use in agriculture 0 Use in animal hobbies pets aquaria o Relaxed regulations OTC o Consequence 0 Increased levels of resistance 0 Mechanisms of antibiotic resistance 0 Lack target ex lack peptidoglycan Not permeable capsules outer membrane 0 Pump antibiotic out efflux pump transport small molecules out of cell B quotSituationalquot Resistance 0 Microbe isn t growing ex cyst or endospore o Microbe growing in location that s not easily accessible to antibiotic ex brain 0 Microbe growing in biofilm ex C Acquired Resistance polysaccharlde matrix deters diffu5on Sensitive cell changed to resistant cell from 0 Growth in biofilms helps sensitive mutation in gene or acquisition of new gene cells resist killing resist then horizontal gene transfer regenerate Mutation or 0 Also on implants and medical devices ConjugationTransductionTransformation Molecular Mechanisms of Antibiotic Resistance BLactams o Mutation o Porin gene reduced permeability o Transpeptidase gene reduced binding 0 Mutation increase production of efflux pump gene regulation 0 Gene Acquisition 0 Gene encoding degradative enzyme Blactamase destroy antibiotics I Blactamase breaks bond of Blactam ring of penicillin disable I Narrow spectrum broad spectrum and extended spectrum I Penicillin resistance 0 Gene encoding new transpeptidase MecA aren t inhibited by antibiotics 0 Gene encoding efflux pump acquires from horizontal gene transfer
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