Microbes

• Eukaryotic organism


  - organism where cells have a nucleus
• Prokaryotic organism


  - organism where cells do not have a nucleus
• Pathogen


  - Microorganism that can cause disease
• Microorganisms


  - need a microscope to see them
• Eukaryotes examples


  - Fungi

  - Protoctists
• Fungi


  - eukaryote (with nucleus)

  - Have a cell wall made of chitin

  - do not contain chloroplasts

  - can't photosynthesise but feed by saprotrophic nutrition

  - excreting enzymes onto the food and absorbing the products of digestion (external digestion)
• Two main groups of fungi


  - yeast

  -mould
• Yeast


  - single-celled organisms

  - used to make bread and beer

  - they reproduce by a process called budding (mitosis)

  
• Moulds


  - frequently found growing on rotting food (external, saprotrophic nutrition)

  - used in food preparation e.g. blue cheese and making drugs like penicillin

  - grown as thread like structures called hyphae which form a mycelium (network)

  - as the hyphae grown individual cells fuse together forming large structures containing several nuclei (they are multinucleated)

  - reproduce by forming spores (containing DNA)

  - micro is the example often found in mouldy bread or vegetables

  
• Protoctists


  - diverse group

  - some species are quite similar to animal cells e.g. amoeba

  - others look more like plants e.g. chlorella

  - malaria is caused by Protoctists called plasmodium

  - some Protoctists such as chlamydomonas have a combination of features found in plant and animal cells

  
• Bacteria


  - many different forms and are vital to sustaining life on earth

  - only a small number cause disease in humans

  - do not have nuclei (prokaryotes), mitochondria or chloroplasts

  - have cell walls that are not made of cellulose or chitin

  - do not have ribosomes

  - they have small circles of DNA in the cytoplasm called plasmids (genetic engineering)

  
• Viruses


  - not living as they do not carry out MRS C GREN

  - very simple structure consisting of a molecule of genetic material (DNA or RNA) surrounded by a protein coat

  
• Nm in mm


  1 Nm= 1/1000 mm
• Nm into nm


  1 nm= 1/1000Nm
• Bacteria summary


  - prokaryotes

  - single celled

  - no nucleus

  - cell was is not cellulose or chitin

  - circular chromosome

  - plasmids
• Examples of Bacteria


  - Lactobacillus is rod shaped and used to make yogurt

  - Pneumococcus is spherical and is the pathogen that causes pneumonia
• Virus summary


  - not living

  - parasites

  - nucleic acid (DNA or RNA) inside a protein coat
• Virus examples


  - tobacco mosaic virus causes discolouring of the leaves by preventing the formation of chloroplasts

  - influenza virus causes flu

  - HIV causes AIDS
• Useful microorganisms


  - grow bacteria in fermenters to make useful products such as insulin

  - use bacteria to grow food
• Using Bacteria to make yoghurt industrial process


  - Milk is heated to 85 degrees

  - Milk is then cooled to incubation temperature of 40 degrees

  - a bacteria called lactobacillus is added

  - it respires anaerobically producing lactic acid

  - acid causes pH to drop, denaturing the proteins in the milk, causing the yogurt to thicken

  - the lactic acid also gives natural yoghurt a distinctive taste
• Making yoghurt using bacteria in the lab


  - Measure milk in a beaker

  - heat until near boiling (do not burn or boil)

  - let the milk cool to about 30 degrees

  - add half a teaspoon of sugar to the milk and stir well

  - add one teaspoon of live yoghurt (bacteria) and stir well

  - cover the top and incubate for 1 week
• Why is the milk boiled?


  - kill off any bacteria in the milk that may reproduce and be harmful to
• Why can live yoghurt be used as a starter culture?


  - live yoghurt contains lactobacillus bacteria

  - this respires anaerobically and produces lactic acid

  - the acid thickens the milk
• Why is the yoghurt left in a warm place to set?

  Respiration enzymes work at their optimum temp
• What chemical reaction do the bacteria carry out that produces set yoghurt?

  - Anaerobic respiration

  And

  - Glucose —> lactic acid + energy
• Using yeast to make bread


  - done using yeast (single celled fungus)

  - mixture of sugar (glucose for respiration) is added to the flour and water

  - this is left at a warm (opt temp for respiration enzymes) temperature and the yeast respires anaerobically

  - the CO2 (and ethanol which is burn off during baking) produced forms bubble in the dough, causing the bread to rise
• Other useful microorganisms


  - alcoholic drinks such as beer and wine are made using yeast

  - cheese is made using bacteria

  - vegetarian meat Quorn is a fungus

  - the antibiotic penicillin (kills off bacteria) is also made by a fungus
• Precautions to take when working with bacteria


  - bacteria can be pathogenic

  - use bacteria which are known not to be pathogens

  - incubate at 25C, below body temperature and so less likely to promote the growth of pathogens

  - do not make airtight seal over the bacteria. many pathogenic bacteria grown better in anaerobic conditions

  - protect yourself using lab coats and goggles

  - Ensure that you work in sterile conditions e.g. using ethanol sterilise equipment
• Air supply and filter function


  - provides a source of O2 for aerobic respiration
• Fermenters


  - containers used to grow microorganisms are called fermenters

  
• Cooling jacket function


  - prevents respiration enzymes getting too hot and denaturing
• Stirring motor and paddles function


  - ensures the microbes mix with the O2 and glucose for respiration
• Tap function


  - allows the product to be removed
• Temp recorder function


  - monitor the temperature

  - low temp. Means not enough KE, fewer collisions, less product —> less money

  - high temp. Denature respiration enzymes
• Pressure release valve function


  - respiration produces CO2

  - this increases the pressure and could damage the equipment
• Abiotic factors to control


  - pH caused by CO2 which is an acidic gas which would lower the pH and could denature the resp enzymes
• "Sparger" on the end of the air pipe causes air to be released in the form of bubbles, why good?

  - source of O2

  - mixes the microbes and oxygen/glucose more thoroughly

  - more resp —> more product—> better yield
• Between use ferment has to be sterilised with...


  - steam

  - cannot use strong products like bleach and cleaning products because could contaminate the products

  - Steam causes any other microbes to be killed from high temp
• Products made in aerobic fermenters


  - penicillin

  - insulin
• Products made in anaerobic fermenters


  - beer

  - wine