Microbial Techniques
Culturing microorganisms
Area and mass of fungi
Culturing microorganisms
- They are only visible in large quantities
- Things to be careful of
- The microorganism could always mutate and become pathogenic
- Risk of contamination (from air to sample)
- Nutrient medium; agar or broth
- Agar sets at 50 degrees and melts at 90 degrees
- Selective medium
- A medium in which only a select group of microorganisms with those particular requirements will grow
- Inoculation
- Placing the bacteria on the nutrient medium
- Stopper the flask
- Prevents airborne bacteria entering the sample
- Hold the inoculating loop in the flame
- This kills all bacteria on the loop
- If the desired organism doesn’t need oxygen for respiration then growing the culture under anaerobic conditions will ensure that only anaerobic bacteria will survive
- The most effective way of producing a pure culture from a mixture is to manipulate the medium.
- Produce a medium that will favour the growth of the organism and inhibit the growth
- Indicator media that cause certain types of bacteria to change colour
- You can directly count the bacteria using a microscope and a haemocytometer
- The haemocytometer is like a quadrat, each corner is 16 squares
- The north and west lines are counted
- The number of bacterial cells increases correlates to how cloudy the liquid is
- The cloudiness can be quantified using a colorimeter which measures how much light travels through a cuvette
- It is based on the fact that if you tried counting the colonies some may overlap so it would be too many too count
- To make sure this is not an issue they can dilute the sample so they can see fewer in each sample
Area and mass of fungi
- You can measure the diameter of the colonies of mycelium. This can be used to compare the growth rates in different conditions