Microbiology

• Microbiology

  The study of microorganisms.
• example of beneficial microorganisms

  yeast -for bread
• harmful microorganism

  salmonella - can cause food poisoning

  mould - can cause food spoilage
• examples of fungi

  moulds

  yeast

  large fungi -mushrooms
• examples of bacteria

  E-coli

  listeraia

  salmonella
• What conditions neccessory for the growth of microorganisms

  Food

  oxegen

  temperature

  moisture

  PH
• Food

  Saprophytic microorganisms - feed on non-living matter e.gdecaying plants

  Parasitic microorganisms-feed on living matter e.g animals
• oxygen

  Aerobic micro-require oxegen for growth

  
  

  Anaerobic micro-do not require oxegen for growth

  
  

  Facultative micro-can grow with or without oxegen
• Temperature

  Psychrophilic micro-grow best at low temperatures of -5oC to 20oC

  
  

  Mesophilic micro-grow best at medium-warm temperature of 20-45oC. most micro prefer this temperatures

  
  

  Thermophilic micro-groe best at hot temperatures of 45-80oC

  
  

  Hyperthermophilic micro-grow best at 65-105oC
• Moisture

  All micro require moisture for growth.

  Most micro grow best in foods with an aw level of 0.80 or higher
• PH level

  acidic envirment-PH of 1-6

  
  

  neutral environment-ph of 7

  
  

  basic (alkaline) envirment -ph of 8-14
• fungi

  simple plants dont create there own food

  
  

  feed on non-living matter (saprophytic) e.gmushrooms

  
  

  feeding on living matters (parasitic) e.g athletes foot
• fungi classifications

  moulds

  large fungi (mushrooms)

  yeast
• Moulds

  multicellular fungi

  e.g penicillin
• Conditions necessory for the growth of moulds

  food-most mould are saprophytic

  
  

  Oxegen-moulds are aerobic

  
  

  Temperature-most moulds are mesophilic (20-45oC) above 75oC destroys moulds

  
  

  Moisture-grow best in humid conditions on food with high water activity ,above 0.8aw

  
  

  ph level-grow best in slightly acidic envirments (ph4-6)

  
  

  Time-mould require between 24 and 48 hours to grow and multiply
• structure of moulds

  spore-is a single cell

  
  

  hypha-grows down into food to absorb nutrients for growth.

  
  

  hyphae-intertwined and form a branched mass called a mycelium.

  
  

  mycelium-is well established on the food source,some hyphae will grow upwards and produce sporangium or conidia
• phycomycetes

  reproduce asexually and sexually

  
  

  examples-

  mucor e.gmeat

  Rhizopus - bread

  
  

  characterisitic - Saprophytic reproduce sexually and asexually

  has white hyphae with grey sporangia
• Ascomycetes

  reproduce asexually

  
  

  e.g penicillium - bread and Aspergilus - dried fruit

  
  

  characteristics- saprophytic reproduces asexually has a green/blue/black powdery mould
• large fungi

  basidiomycetes

  e.gfield mushrooms/truffles
• yeast

  unicellur fungi that can only be clearly seen using a microscope but become visible to the naked eye.

  used to make vinegar

  
• contions nessery for yeast

  food-yeast cells are saprophytic,feeding on high -carbohydrate foods

  
  

  oxegen-yeast are facultative organisms

  
  

  temperature-yeast cells are mesophilic.optium temp 25-30oC temp below 15oC slows down growth

  
  

  moisture-above 0.85 aw

  
  

  ph level- ph4-6
• yeast cell

  must know!

  
• reproduction of yeast cells

  yeast cells reproduce asexually

  1.when conditions are favaerable apart cell developes a bud.a budis an outward bulge from the side of the parent cell.

  2.nuclous of the yeast cell moves towards the bud

  3.nuuclous divides in two resulting in two nuclei.one nucleus enters the bud and the other remains in the parent cell.

  4.as the bud developes a wall forms that separates the bud from the parent cell.

  5.when the finds suitable conditions the asexual reproduction cycle begins again
• advantages and disadvantages3


  advantage

  1.many fungi are edible e.gtruffild

  2.some molds are used in the production of antibiotics e.g penicillin

  3.yeast can be used to make bread products and brewing alcohol e.gbeer

  
  

  disadvantages

  1.can cause food spoilage e.g mucor on bread

  2.can be poisonous e.g Fly agaric

  3.can cause human disease e.g athletes foot
• bacteria

  are microscpoic unicellur microorganisms. found almost everywere

  
  

  bacteria can be

  pathogenic

  non-pathogenic
• conditons need for growth

  food

  oxegen

  temperature

  moisture

  ph level

  time
• saprophytic

  feed on non-living matter such as food causing spoilege(non-pathogenic)
• parasitic

  feeds on living matter such as animals
• bacteria can be

  aerobic

  anaerobic

  facultative

  name e.g

  mycobacterium tuberculosis

  clostridium botulinum

  E.coli
• bacteria can be

  psychrophilic

  mesophilic

  thermophilic

  hyperthermophilic


  listeria

  E.coli

  thermus aquaticus

  thermotoga
• moisture bacteria

  0.90aw
• ph level bacteria

  ph6-7
• time


  20min
• stucture of bacteria

  
• reproduction of bacteria

  bacteria asexually reproduces

  
  

  1. when conditions are favorable ,a bacteria cell elongates and its DNA duplicates

  2.a cell wall and cell membrane developes to seperate the bacteria cell into two halves

  to form two cells
• growth stages of bacteria

  
• bateria toxins

  during the periods of rapid growth ,pathogenic bacteria produce waste toxins.toxins are posinous and cause food poising
• the shapes of bacteria

  coccus (spherical)

  bacillus(rod shaped)

  or curved
• coccus (spherical)

  pneumonia
• bacillus(rod shaped)

  E.coli