Microbiology

Microbiology

1. BACTERIA

   • Prokaryotes with peptidoglycan which composes Gram-positive cell walls
   • Anaerobic or aerobic
   • 1 to 10um
   • Chromosomes pulled apart by attachments to inner membrane
   • External cell wall
   • RNA and protein synthesized in the single compartment
   • No organelles
   • No endo or exo cytosis
   • Rods or cocci
   • BACTERIAL SPORE FORMATION
     • Gram-positive bateria in rod shape can produce spores
     • Spores are highly resistant to chemicals, desiccation and nutrient depletion
     • Heat resistant so can survive pasteurisation/cooking
     • Dormant but germinate when the environment is optimal
   • BACTERIA ASSOCIATED WITH FOOD
     • Pathogenic bacteria: food poisoning
       • Gram negative rods (Enterobacteriaceae non-spore forming rods) E.G. E coli.
       • Gram negative rods (Pseudomonads)
       • Gram positive rods (Clostridia)
     • Cultured bacteria
       • Gram positive rods (Lactobactilli - found in yoghurt)
   • BACTERIAL STRUCTURE AND THE GRAM STAIN
     • Three types of cell wall layers; Gram positive, Gram negative and Acid fast
     • GRAM STAIN
       • 1. Add bacteria to microscope slide
       • 2. Set and stain with Crystal Violet (only retained in Gram positive cell walls
       • 3. Wash and stain Iodine
       • 4. Wash and destain with Ethanol
       • 5. Counterstain with Safranin
   • BINARY FISSION
     • Asexual
     • Genomic DNA replicates
     • Cell doubles its mass
     • In ideal growth conditions E. coli is capable of undergoing one cell cycle every 20 minutes
   • CONTROLLING PATHOGENIC BACTERIA
     • Sterilisation
       • Complete destruction/elimination of all viable organisms
       • E.G. spores, sterile objects, heat, radiation, chemicals and physical removal of cells
     • Disinfection
       • Kills, inhibits or removes organisms that may cause disease
       • Vegetative microorganisms but not spores
       • Inanimate objects (not safe for living tissues)
     • Decontamination with biocides
       • Kills, inhibits or removes organisms that may cause disease
       • Vegetative microorganisms and potentially spores
       • Very strong
       • Used for inanimate objects, healthcare

2. EUKARYA

   • 10 to 100um
   • Anaerobic or aerobic
   • Internal cytoskeleton
   • Long linear DNA
   • RNA synthesized and processed in nucleus; proteins synthesized in cytoplasm
   • Endo and exo cytosis
   • Chromosomes pulled apart by attachments to cytoskeletal components
   • FUNGI
     • Three groups: Moulds, Yeasts and Mushrooms
     • Cell walls made of chitin
     • Fungal cell walls made of hyphae
     • Together these make a mycelium
     • Form branches
     • Can reproduce sexually or asexually- fungal spores
     • Yeast 'bud'

3. ARCHAEA

   • Prokaryotes without peptidoglycan

4. VIRUSES

   • Contains either RNA or DNA and replicates in cells
   • Has an extracellular state

5. PRIONS

   • Entirely protein
   • No nucleic acids
   • Infectious
   • Causes disease in animals
   • Currently not found in plants

6. MICROBIAL NUTRITION

   • AUTOTROPHS
     • Capable of synthesising complex organic molecules from a simple non-organic molecules
   • HETEROTROPHS
     • Use organic molecules such as carbon

7. GROWING MICROBES IN THE LAB

   • OPTIMAL CONDITIONS
     • Nutrient source
     • Optimal temperature
     • Water availability
     • pH
     • Gaseous atmosphere
     • No antimicrobials (agent that kills microorganisms or stops their growth)
   • CULTURE
     • 1. Nutrient source
       • Carbohydrate - sugars
       • Proteins/amino acids - meat/yeast extracts
       • Minerals/Vitamins
     • 2. Broth culture
       • Test tubes/bottles
     • 3. Solid media
       • Test tubes/bottles
     • Culture media can be formulated to:
       • Meet nutritional requirements of certain bacteria
       • Selectively grow bacteria, inhibit others
       • Be diagnostic

8. MICROBES

   • MICROBIAL GROWTH IN LIQUID (broth)
     • When bacteria grow in a liquid broth the normally follow a standard pattern of growth
   • MICROBES AND TEMPERATURE
     • High temperatures cause:
       • Membrane disruption
       • Protein denaturation
       • For every 10C increase in temperature the metabolic rate and growth rates approximately double
     • Low temperatures cause:
       • Adaptations to maintain membrane fluidity
       • Slow metabolic processes
       • Slow growth rates

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