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• Impacts of Microbial Metabolism

  • Disease and food spoilage
  • Nitrogen cycle
  • Beverages and food
  • Sewage treatment
  • Drugs
• Carbohydrate catabolism

  1. Respiration - Glycolysis is followed by Krebs cycle, and electron transport chain which generates the most ATP

  2. Fermentation - doesn't require Krebs cycle or ETC, and produces end products such as lactic acid or ethanol
• Lipid Catabolism

  1. Lipids are first broken down into component fatty acids and glycerols by lipases

  2. Each component can then enter the Krebs cycle
• Protein catabolism

  1. Proteases and peptidases break down into proteins into component amino acids

  2. Amino acids must undergo enzymatic conversion into substances that can enter the Kreb cycle
• Phototrophs


  • Light as energy source
• Chemotrophs


  • Redox of in/organic compounds
• Autotrophs


  • Self-feeders
• Heterotrophs


  • Feed on others
• Chemoheterotrophic


  An organism which derives its energy from chemicals, and needs to consume other organisms in order to live
• Psychrophiles


  • Cold-loving
• Mesophiles


  • Moderate temperature

  
• Thermophiles

  • Heat-loving
• Most bacteria grow within a limited range of temperatures, with min and max growth temps only 30° C apart
• Optimum temperature is the temperature at which the species can best grow
• Most bacteria grow best between pH6.5-7.5, and few bacteria grow below pH 4
• When bacteria are cultured in the lab, they often produce acids which interfere with their growth, so chemical buffers are included
• Facultative halophiles


  • Do not require high salt concentrations but can grow at concentrations up to 2%
• Chemical Requirements

  • Carbon
  • Nitrogen
  • Sulfur
  • Phosphorus
  • Trace Elements
  • Organic growth factors
  • Oxygen
• Facultative anaerobes


  Can use anaerobic respiration or fermentation when oxygen is absent, e.g. E. coli and yeasts
• Obligate anaerobes

  Cannot use molecular oxygen for energy-yielding reactions, e.g. Clostridium
• Aerotolerant anaerobes


  e.g. lactobacilli; they can survive convert harmful forms of oxygen to O2
• Microaerophiles


  Can only tolerate oxygen concentrations lower than air
• Nutrient material prepared for the growth of microorganisms

  Culture media
• Pellicle


  A mass of organisms is floating on top of the broth
• Turbidity


  The organisms appear as a general cloudiness throughout the broth
• Sediment


  A mass of organisms appears as a deposit at the bottom of the tube
• Obtaining Pure Cultures

  The streak plate method is the most commonly used method
• Preservation Methods

  • Refrigeration for short-term storage
  • Deep-freezing
  • Lyophilization(freeze-drying)
• Five "I"s of Culturing Microbes

  • Inoculation
  • Isolation
  • Incubation
  • Inspection
  • Identification
• Microbial Growth


  Produces more cells thus increases microbial count and consequently microbial growth
• Binary fission


  The most common mode of reproduction
• Budding


  Another mode of reproduction
• Sterilization


  Removal or destruction of all living microorganisms
• Disinfection


  Control of harmful organisms
• Antisepsis (antiseptic)


  If disinfection is directed at living tissue
• Sanitization


  Lower microbial counts to save public health and minimize the chances of disease transmission
• Aseptic Technique

  1. Preventing contamination of a culture with environmental microbes

  2. Preventing contamination of yourself or the environment with the organism in the culture
• Moist Heat Sterilization

  1. Autoclave for media and other items that can withstand pressure

  2. Kills vegetative bacterial and fungal pathogens and almost all viruses within 10 min; less effective on endospores
• Pasteurization


  Heat treatment that kills all pathogens and most nonpathogens, best for food
• Dry Heat Sterilization

  1. Direct - e.g. in inoculating loops

  2. Incineration - e.g. for paper cups, dressings

  3. Hot-air sterilization - empty glassware, etc.