bacterial growth

• bacteria multiply by a process called

  binary fission

  
• binary fission is a type of

  asexual reproduction

  
• asexual production means that bacteria

  don't need male or female individuals

  
• bacteria make identical copies of themselves called

  clones

  
• bacteria must have what inorder to multiply

  the right conditions

  
• an example of a right condition is

  warmth

  
• to develop ,bacteria cells need an adequate supply of 


  nutrients

  
• when conditions are ideal a bacteria can multiply as often as

  every 20 minutes

  
• if there is one bacteria after 20 minute there will be

  two bacteria, after 40 minutes there will be four bacteria and after 60 minutes there will be eight bacteria

  
• so after 6 hours one bacteria on a cloth could multiply into

  a colony of 262144

  
• the growth where bacterial multiplies most rapidly is called

  exponential growth

  
• colonies of bacteria can only get larger when they have a

  continuous supply of nutrients

  
• if the nutrients on a kitchen cloth eventually run out

  the bacteria colony decreases

  
• after the exponential growth phase,

  resources start to run out.

  multiplication decreases

  
• eventually the bacteria will run out of resources and space at the same time there is a build up of waste products

  
• the waste products produced by the bacteria are

  toxic to the bacteria

  
• due to its waste products the bacteria colony

  DIES

  
• the number of bacteria will 


  double every 20 minutes

  
• different types of bacteria may multiply best in different temperatures and need different nutrients.

  
• a bacteria needs

  moisture

  
• where do we study the growth of bacteria

  in the lab

  
• we can grow bacteria in a

  liquid nutrient broth

  
• in a liquid nutrient broth we can

  see bacterial growth as a cloudy solution

  
• we can observe bacterial growth on an

  agar plate

  
• on an agar plate we can see

  bacterial growth as colonies

  
• we make sure we don't have contaminated cultures by using

  aseptic technique

  
• we use the aseptic technique to

  analyse the conditions needed for bacteria to grow.

  study the effects of disinfectants on antibiotics.

  
• petri dishes must be sterilised

  to remove any microorganisms

  
• glass petri dishes are sterilised by 


  heating

  
• plastic petri dishes are usually

  pre-sterilised and packaged before use

  
• An inoculating loop

  can be used to transfer bacteria

  
• An inoculating loop is sterilised by

  passing through a flame

  
• the lead of the petri dish must be secure with

  tape before being stored upside down

  
• petri dishes are stored upside down to

  reduce contamination with the air

  
• at school we culture bacteria at 25 degrees Celsius because 


  some bacteria that are harmful to humans are likely to grow at higher temperatures

  
• bacteria hat cause diseases to humans,

  grow well at body temperature

  
• harmful bacteria grows well at how many degrees Celsius

  thirty seven

  
• microorganisms that cause disease are called

  pathogens

  
• after the cultures have been incubated 


  bacterial growth is seen as colonies on the agar plate

  
• we can compare the colonies by

  calculating the area of each.

  as colonies are circular

  we use the equation A = π r2