Topic 8: Micro-organisms and disease Flashcards
What is a microorganism?
A living organism which is so small that it can only be seen with a microscope.
What are the 4 types of microorganism?
Viruses
Bacteria
Fungi
Protists
Which type of microorganism is not always a microorganism?
Fungi
What is a protist?
An organism belonging to the Kingdom Protista. Many consist of just one cell, which is eukaryotic.
What does eukaryotic mean?
Containing a nucleus.
What is a pathogen?
A disease causing microorganism.
What is a virus?
A microorganism (pathogen) capable of infecting every type of living organism.
Why are microorganisms grown by scientists?
In large numbers, they are easier to study and work with.
What is put in a petri dish to grow microorganisms?
Agar jelly and the microorganisms themselves.
What is a colony?
A (circular) group of bacteria visible to the naked eye.
What are the optimum growth rates for bacteria?
between 30-37 degrees. For a petri dish, keep it at 25 to make sure bacteria isn’t harmful to humans (in school).
What is aseptic technique used for?
The procedure of growing microorganisms in a way that minimises the risk of contamination.
What are the 5 steps to aseptic technique?
- Loop placed in Bunsen flame to stop contamination.
- Lid/stopper taken off of bacterial tube and top of tube placed in flame.
- Loop is dipped into bacteria, tube flamed again.
- 4 striking patterns on agar jelly, lightly. Petri dish lid partially lifted.
- Loop flamed again. Petri dish sealed across dish, NOT around (don’t want optimum environment.
How often does bacteria reproduce?
Approximately every 20 minutes.
What is binary fission?
Asexual reproduction of bacteria in which they copy their DNA and divide into two.
What is a culture of bacteria?
Bacteria grown deliberately by humans.
What are 4 safety precautions to take when culturing microorganisms?
Wear protective equipment - goggles
Wash hands before and after
Clean all work surfaces
Keep eyes and face away from culture
What is an antibiotic?
A chemical used in medicine to destroy bacteria.
What do antibiotics not effect?
Viriuses.
What type of microorganism is penicillium?
A fungus.
What are the 3 optimal conditions for fermentation?
Temperature - 23-28°c
pH - 6.5
Oxygen level - oxygen needed for respiration and growth
Nutrient levels and contamination must be monitored too
Label a fermentation diagram.
DO IT
How can the amount of original bacteria be estimated from the number of colonies present?
Each bacterium will divide many times to produce a colony, so the number of colonies is usually how many bacterium there were to begin with.
Why is counting colonies an inaccurate way of finding the number of original bacteria?
Colonies may clump together
Difficult to count with so many
What happens to the rate of bacterial growth if the temperature is increased?
The growth rate increases but if the temp is too high the proteins denature and the bacteria will die.
What happens to the rate of bacterial growth if the temperature is decreased?
It will decrease but when the temperature is too low bacteria will stop growing altogether.
Why are refrigeration and freezing useful in food storage?
Food will last longer as microorganism growth is limited/stopped.
What is a fermenter used for?
To produce large cultures of microorganisms.
What does the air intake do?
Allows sterile (for no contamination) air to get in as penicillium is aerobic and requires oxygen.
What does the stirrer do?
Mixes the nutrients throughout the fermenter (otherwise they would collect at the bottom).
What does the cooling jacket do?
Cools the culture because respiration of the penicillium produces heat.
What does the pH probe do?
Monitors pH levels so it can be corrected.
What does the pressure relief valve do?
To avoid dangerous levels of pressure, air is allowed out via this valve.
What is agar?
A jelly that has nutrients in it to help grow cultures of bacteria.
