There are many ways to measure bacterial growth, and one way is more complicated than the other. Although sometimes the consistency of measurement has to be ignored, the easiest way is enough to measure bacterial growth accurately so it is often used. The most commonly used methods are monitoring and counting bacteria, measuring dry or wet mass, and measuring turbidity/turbidity levels. Your school's lab should have the tools and equipment needed to perform at least one of these experiments.
Step
Method 1 of 3: Monitoring Bacteria Live
Step 1. Prepare the ingredients
There are many special tools that need to be prepared and may not be available in a biology laboratory. Prepare all the equipment and containers before running the experiment so there is no hassle during the process. You'll need to know each ingredient that's used right away, and the basic terms of this experiment.
- Prepare the counting chamber. It has a built-in chamber, microscope glass and microscope so it's easy to set up and use. You can buy it from a lab or school supply store. This tool should have instructions that guide you through the whole process.
- Prepare a pouring cup or spread cup. Both of these containers allow you to monitor the bacteria inside.
- Culture is a term used to describe the growth of organisms in an experiment.
- Broth is a liquid medium in which the culture grows.
Step 2. Use the pour plate or spread plate method
You can also place the bacteria directly on the dish for viewing using a microscope. Pour the culture on a saucer and place it under the microscope. Monitor the number of bacterial cells present.
Step 3. Make sure the concentration dose is right
If there are too many, the bacteria will pile up on each other and you may miscalculate. Dilute the culture by mixing in more broth. If there are too few, the results of the calculation will not be accurate. Strain the broth using a filtration system.
Step 4. Count bacteria
The last step is to count the bacteria one by one. Look through the magnifying lens in the counting chamber and write down the number of bacteria you see. Compare the results with the results of other tests.
Method 2 of 3: Measuring Dry and Wet Mass
Step 1. Make sure you have the right equipment
This method uses expensive equipment and a lot of time. If your laboratory doesn't have the necessary equipment, it's a good idea to use another method. However, if your laboratory is well-equipped, we recommend this method as it provides more consistent results. In this method, you will need:
- Hydraulic gravity convection oven
- Weighing container made of aluminum
- A set of flasks (laboratory bottles)
- Centrifugal machine (centrifuge) or laboratory filtration system
Step 2. Make sure the culture is in the flask
Add the culture to the pumpkin. At this stage, the culture should be a broth, although it will be separated later.
Step 3. Dry the aluminum weighing container in the lab oven
Instead, you can use a cellulose acetate filter membrane with a diameter of 47 mm and a pore size of 0.45µm. Whatever weighing container you use, weigh it as it will need to be deducted later when weighing bacterial cells.
Step 4. Stir the culture in the flask until it is evenly mixed
The cell will sink naturally due to gravity and will need to be stirred to spread evenly in the flask. That way, you can have more samples.
Step 5. Use a centrifuge to separate the bacterial cells from the broth
This tool rotates the flask and equilibrates rapidly so that it drains the broth and leaves the culture in the flask.
Step 6. Scrape off the paste on the pumpkin and put it in a weighing container
Throw out the broth because you don't need it anymore. However, don't get rid of the pumpkin just yet because it will still be used.
Step 7. Rinse the centrifugal machine and pour the rinse water into the container
Drop the rinse water in the flask onto the bacterial cells to obtain the wet weight.
Step 8. Find the dry weight
To measure dry weight, place the container in the oven and dry at 100ºC for 6-24 hours according to the instructions from the oven and/or weighing container used. Make sure the temperature is not too high so that the bacteria do not burn. Weigh the bacteria when finished, and don't forget to reduce the result by the weight of the weighing container.
Method 3 of 3: Measuring Turbidity
Step 1. Prepare the necessary equipment
You will need a light source and a spectrophotometer. Both can be obtained at laboratory supply stores. The spectrophotometer should have instructions that will guide you in using the instrument according to the model you have. The price of the spectrophotometer is quite affordable and easy to use so that it may become one of the most commonly used methods for measuring bacterial growth.
Step 2. Light the sample
According to Layman's term, turbidity is the level of turbidity of a sample. You need to get the turbidity measurement number, which is measured in NTU (Nephelometric Turbidity Unit). This tool needs to be calibrated before it can measure the sample accurately.
Step 3. Record the results
Turbidity is affected by the number of bacteria in the sample. The spectrophotometer will also tell you the percentage of transmission (%T). This figure will increase if the turbidity decreases. Compare the results with the results of other tests to measure bacterial growth.
Warning
- Since you are dealing with a bacterial colony, take precautions by wearing safety equipment such as safety glasses and gloves. It's also a good idea to wear a mask, especially if you don't know the type of bacteria being studied.
- Take precautions before handling any type of bacteria, even the harmless type. Make sure all open wounds on your body are completely covered before starting.
