Review Test 2 PDF

Section II exam review Andrei Kouranov Content: 1. Microbial growth curve 2. Microbial growth requirements 3. Methods of microbial growth control 4. Microbial genetics 5. Viruses & viral life cycles 6. Parasitic molecules - Prions Microbial Growth Curve Growth Curve in a Bacterial Cu...

Section II exam review Andrei Kouranov Content: 1. Microbial growth curve 2. Microbial growth requirements 3. Methods of microbial growth control 4. Microbial genetics 5. Viruses & viral life cycles 6. Parasitic molecules - Prions Microbial Growth Curve Growth Curve in a Bacterial Culture Plateau phase Microbial Growth Requirements Figure 6.2 Using a Liquid Thioglycolate Growth Medium to Identify the Oxygen Requirements of Organisms Thioglycolate media test A. Anaerobe most likely facultative B. Microaerophilic (grow best in the presence of small amount of oxygen) C. Obligate anaerobe D. Obligate aerobe E. Facultative anaerobe Two particular enzymes are utilized to alter toxicity of oxygen. Superoxide dismutase changes converts toxic forms of oxygen to less toxic hydrogen peroxide 2 HO2 → O2 + H2 O2 Peroxidase or Catalase converts hydrogen peroxide to water and oxygen 2 H2 O2 → 2 H2 O + O2 Figure 6.4 Five Categories of Microbes Based on Temperature Ranges for Growth Majority of pathogens are mesophiles with optimal temperature 37 oC. The high temperature limit 42 -45 oC that causes enzymes denaturation. Growth Requirements (11 of 17) Physical Requirements pH Organisms sensitive to changes in acidity Hydrogen ions interfere with H bonding. Neutrophiles grow best in a narrow range around neutral pH. Acidophiles grow best in acidic habitats. Alkalinophiles live in alkaline soils and water. Osmotic Pressure Osmophiles: live in habitats with high solute concentration Halophiles: prefer high concentration of salt - Obligate halophiles: Halobacterium and Halococcus grow optimally at solutions of 25% NaCl but require at least 9% NaCl. - Facultative halophiles: remarkably resistant to salt, even though they do not normally reside in high salt environments - Staphylococcus aureus can grow on NaCl media ranging from 0.1% to 20%. Growth Requirements (14 of 17) Physical Requirements Physical effects of water Hydrostatic pressure Water exerts pressure in proportion to its depth. Barophiles live under extreme pressure. (for example, bottom of the ocean) Their membranes and enzymes depend on pressure to maintain their three-dimensional, functional shape. Associations Between Organisms Methods of Microbial Control Table 9.1 Terminology of Microbial Control (1 of 2) Term Definition Examples Comments Antisepsis Reduction in the number of Use of iodine or alcohol to Antiseptics are frequently disinfectants microorganisms and viruses, prepare skin for an injection whose strength has been reduced to particularly potential pathogens, on make them safe for living tissues. living tissue Aseptic Refers to an environment or procedure Preparation of surgical field; Scientists, laboratory technicians, and free of pathogenic contaminants hand washing; flame health care workers routinely follow sterilization of laboratory standardized aseptic techniques. equipment -cide Suffixes indicating destruction of a type Bactericide; fungicide; Germicides include ethylene oxide, -cidal of microbe germicide; virucide propylene oxide, and aldehydes. Degerming Removal of microbes by mechanical Hand washing; alcohol swabbing Chemicals play a secondary role to the means at site of injection mechanical removal of microbes. Disinfection Destruction of most microorganisms Use of phenolics, alcohols, The term is used primarily in relation to and viruses on nonliving tissue aldehydes, or soaps on pathogens. equipment or surfaces Pasteurization Use of heat to destroy pathogens and Pasteurized milk and fruit juices Heat treatment is brief to minimize reduce the number of spoilage alteration of taste and nutrients; microorganisms in foods and microbes remain and eventually cause beverages spoilage. Table 9.1 Terminology of Microbial Control (2 of 2) Term Definition Examples Comments Sanitization Removal of pathogens from objects to Washing tableware in scalding Standards of sanitization vary among meet public health standards water in restaurants governmental jurisdictions. -stasis Suffixes indicating inhibition but not Bacteriostatic; fungistatic; Germistatic agents include some -static complete destruction of a type of virustatic chemicals, refrigeration, and freezing. microbe Sterilization Destruction of all microorganisms and Preparation of microbiological Typically achieved by steam under viruses in or on an object culture media and canned food pressure, by incineration, or by ethylene oxide gas. Sterility – absence of microbes Antiseptic, degermation, and decontamination – can be used on human tissue Physical Methods of Microbial Control (4 of 14) Heat-Related Methods Moist heat Autoclaving Pressure applied to boiling water prevents steam from escaping Boiling temperature increases as pressure increases Autoclave conditions: 121°C, 15 psi, 15 minutes Figure 9.7 An Autoclave Figure 9.10 Filtration Equipment Used for Microbial Control Used in drug production when high temperature or pressure is damaging to the chemicals Table 9.3 Membrane Filters Pore Size (μm) Smallest Microbes That Are Trapped 5 Multicellular algae, animals, and fungi 3 Yeasts and larger unicellular algae 1.2 Protozoa and small unicellular algae 0.45 Largest bacteria 0.22 Largest viruses and most bacteria 0.025 Larger viruses and pliable bacteria (mycoplasmas, rickettsias, chlamydias, and some spirochetes) 0.01 Smallest viruses Chemical Methods of Microbial Control (6 of 17) Surfactants “Surface active” chemicals Reduce surface tension of solvents Soaps and detergents Soaps have hydrophilic and hydrophobic ends Good degerming agents but not antimicrobial Detergents are positively charged organic surfactants Quatenary ammonium compounds (quats) Low-level disinfectants Disrupt cellular membranes Ideal for many medical and industrial applications Kirby-Bauer test: agar diffusion test Results of a Sample Kirby-Bauer Test Zone Size (mm) Zone Size (mm) Example Results for Required for Required for Staphylococcus Drug Susceptibility (S) Resistance (R) aureus Evaluation Erythromycin >18 13 17 29 15 12