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  • Created by: Ciara
  • Created on: 29-08-14 16:29


  • No membrane bound organelles
  • No membrane bound nuceleus
  • Smaller ribosomes than eukaryotes
  • Cell wall made up of peptidoglycan
  • 0.5-5 micrometers
  • Reproduce by binary fission

Gram Positive Bacteria

  • Thick layer of peptidoglycan
  • Stains purple when crystal violet is added
  • Penicillin is effective against them

Gram Negative Bacteria

  • Thin layer of peptidoglycan and a thick layer of lipopolysaccharide 
  • Stains red because of the counter stain Safrinin
  • Penicillin is not effective against them

Nutrients needed for Microbes

  • Carbon - Usually organic e.g. glucose energy source
  • Nitrogen - Inorganic (nitrate) or organic (amino acids)
  • Inorganic ions - Growth factors
  • Vitamins - Growth factors

Types of Antibiotics

  • Bacteriostatic - Agents/chemicals that stop the growth and division of the bacteria by inhibiting protein synthesis or by inhibiting replication of DNA.
  • Bacteriocidal - Chemicals/drugs that kill bacteria by breaking down the cell membrane or by stopping the formation of the cell wall.

Counting Bacteria

  • Viable cell count - counting living cells only by serial dilution
  • Total cell count - counting living and dead cells by using a haemocytometer or turbidity using a colorimeter


  • The industrial use of living organisms to produce food, drugs or other commercial products
  • Drugs synthesised by microbes include antibiotics and insulin
  • Microbes are also used to synthesise biofuels and the enzymes added to biological washing powders

Growth of microbes in a closed culture

  • Bacteria divide by binary fission
  • The time taken for the population to double is the generation time

Types of culture

  • Batch culture
  • Continuous culture

Population Growth

Population: a group of organisms if a single species, interbreeding and occupying a paticular area

Species: a group of organisms which share a large number of common characteristics and which can interbreed to produce fertile offspring

Population numbers


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