Required Practical activity

• Some diseases can be treated with antibiotics.
• Vaccinations allow protection against specific diseases, but the level of protection depends on the amount of people vaccinated.
• Infection and response is a part of Biology (Single Science).
• The effectiveness of antibiotics can be tested experimentally using uncontaminated agar plates.
• Agar plates are used to culture (grow) bacteria and fungi in the lab.
• Aseptic technique is vital when the effectiveness of antibacterial substances is being tested.
• Agar gel is a jelly-like substance that is derived from a type of seaweed and used in the lab as a medium on which to grow bacteria and fungi.
• Glass Petri dishes and agar gel must be sterilised before use in an autoclave.
• Pre-sterilised plastic Petri dishes can be bought.
• Bacteria are single-celled microorganisms, some of which are pathogenic in humans, animals and plants.
• The singular of bacteria is bacterium.
• Bacteria that are present in the solution or on the Petri dishes must be killed before use.
• Pouring the sterile agar plates and allowing them to set fully provides the selected bacterium with all the nutrients needed to grow.
• Inoculating loop: a small wire loop used to transfer microorganisms from one growth medium to another, by heating it in the Bunsen burner flame.
• Replace the lid as soon as possible, secure with tape.
• Pour the sterile agar plates and allow to set fully: the effectiveness of the solutions at killing the bacteria can be tested.
• Incubate at a maximum temperature of 25°C in schools and colleges: reduces the chance of growing harmful pathogens.
• A clear area (zone of inhibition) indicates that the bacteria have been killed by the solution or have not been able to reproduce.
• Reason for sterilising: kills any bacteria that are present on the loop.
• Soak filter paper disks in a variety of solutions, use either different concentrations of the same solution, or a variety of different solutions.
• Sterilise: to kill any living organisms, usually microbes that might cause disease, on an object or in a substance.
• The size of the zone indicates the effect of the substance tested on the growth of the specific bacterium.
• Do not fully seal the lid, as this will stop oxygen reaching the bacterium, and this may encourage harmful anaerobic bacteria to grow.
• Hospital laboratories would incubate plates at 37°C (body temperature) to allow quick growth and identification.
• Reason for storing the plate upside down: stops additional unwanted bacteria in the air contaminating the plate.
• Reason for soaking filter paper disks in a variety of solutions: kills any bacteria that are present in the solution or on the petri dishes.
• Labels are important, as this identifies the growing bacterium.
• By adding filter paper soaked in a variety of anti-microbial solutions to the pre-prepared agar plate (method A), the effective of the solutions can be tested experimentally.
• Reason for dipping the inoculation loop into the microorganism solution: allows the bacteria to spread out and to grow in individual colonies on the agar plate.
• Dip the inoculation loop into the microorganism solution and make streaks on the surface of the agar plate.
• Method B: Adding antibiotic or antiseptic soaked patches to pre-prepared agar plates.
• Label and invert the plate, and store upside down.
• A lawn of bacteria can be produced by using a sterile spreader to evenly spread the bacteria across the whole of the plate.
• Measure the clear area around the soaked filter paper disks: a control disk must be also included.