micropara

• Outline


  • Microbial Physiology
  • Impacts of Microbial Metabolism
  • Important Processes
  • Metabolic Diversity
  • Microbial Nutrition
  • Physical Requirements
  • Chemical Requirements
  • Viruses
  • Host-Microbe Interaction
• Carbohydrate catabolism


  1. Glycolysis

  2. Krebs cycle

  3. Electron transport chain
• 38 ATPs can be generated from 1 glucose molecule
• Fermentation


  1. Doesn't require Krebs cycle or ETC

  2. Produces end products such as lactic acid or ethanol
• 2 ATPs are produced from 1 glucose molecule
• 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 proteins into component amino acids

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


  • Phototrophs - light as energy source
  • Chemotrophs - redox of in/organic compounds
  • Autotrophs - self-feeders
  • Heterotrophs - feed on others
• Most medically important organisms are chemoheterotrophic, because typically, infectious organisms catabolize substances obtained from the host
• Chemoheterotrophic


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


  • Temperature
  • pH
  • Osmotic pressure
  • Adaptations
• Temperature


  • Psychrophiles - cold-loving
  • Mesophiles - moderate temperature
  • Thermophiles - heat-loving
  • Most bacteria grow within a limited range of temperatures
  • Min and max growth temps are only 30° C apart
  • Optimum temperature - temperature at which the species can best grow
• pH


  • Most bacteria grow best between pH6.5-7.5
  • Few bacteria grow below pH 4
  • Chemical buffers such as phosphate salts and peptones are included
• Osmotic pressure


  • Microbes obtain nutrients in solution from water
• Adaptations


  • Extreme halophiles
  • Obligate halophiles
  • 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
• Obligate aerobes


  Cannot use anaerobic respiration or fermentation
• 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
• Culture media


  Nutrient material prepared for the growth of microorganisms
• Inoculum


  Microbes that are introduced into a culture medium to initiate growth
• Culture


  Microbes that grow and multiply in a culture medium
• Culture media must be initially sterile
• Agar


  A solidifying agent, few microbes can degrade it, liquefies at 100°C, remains liquid until temperature drops to 40°C, NOT a nutrient
• Forms of culture media

  • Broth (liquid)
  • Slants
  • Stab tubes/ deeps
  • Plates
• Broth (liquid)


  • 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
• Mannitol salt agar


  • Differential (distinguishes mannitol fermenters and non-fermenters) and selective (high salt con'c prevents most bacteria except Staphylococcus spp.)
• MacConkey agar


  • Differentiates from lactose fermenters (left) and non-fermenters
• Streak plate method


  Most commonly used method for obtaining pure cultures
• Preservation


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

  • Inoculation: Producing a pure culture
  • Isolation: Colony on media, one kind of microbe, pure culture
  • Incubation: growing microbes under proper conditions
  • Inspection: Observation of characteristics (data)
  • Identification: use of data, correlation, to ID organism to exact species
• Binary fission is the most common mode of microbial reproduction
• Budding is another mode of microbial reproduction
• Sterilization, disinfection, and sanitization

  • Sterilization - removal or destruction of all living microorganisms
  • Disinfection - control of harmful organisms
  • Sanitization - lower microbial counts to save public health and minimize the chances of disease transmission
• Aseptic technique


  To protect yourself from contact with biohazards, to protect your sample from contamination, and to protect others in the lab
• Methods of control of microbial growth

  • Moist heat
  • Pasteurization
  • Dry heat
  • Filtration
  • Refrigeration
  • Deep-freezing and freeze-drying
  • High pressure
  • Desiccation
  • Osmotic pressure
  • Radiation
• Moist heat


  • Best for dishes, various equipment; autoclave for media and other items that can withstand pressure
  • Kills vegetative bacterial and fungal pathogens and almost all viruses within 10 min; less effective on endospores
  • Autoclaving - at about 15 psi of pressure (121°C), all vegetative cells and their endospores are killed in about 15 min
• Pasteurization


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