Yogurt has been made and consumed for thousands of years, and is today recommended for effective regulation of the digestive system. Although milk from a number of animals (sheep, goat and water buffalo) can be used, it’s more popularly produced by using milk from cows. This process also involves the use of bacteria, which thickens the milk, giving it a tangy taste.
Yogurt is produced through a simple process referred to as fermentation. Here, the lactose in milk is fermented by rod-shaped bacteria to produce lactic acid. It is this acid that gives yogurt its characteristics.
Without Using Stain
Note** Yogurt bacteria are not bad, and are therefore safe to use.
The two types of bacteria observed are:
The student will be able to see rod-like organisms, which may be in clusters.
With a stained slide, students will be able to observe light bluish rod-like organisms (individual bacillus or in clusters) moreover, the student may observe organisms that are round in shape (cocci). These may be in clusters, isolated or in pairs.
While staining may appear a little more complicated than the former, it would prove to be an easy procedure if the steps are followed appropriately. This would also be an important process, which would allow the student to compare stained and unstained yogurt slides.
With unstained slides, students are more likely to see and identify the bacteria if they are in clusters rather than single, individual cells.
On the other hand, in bright-field, closing the condenser iris diaphragm will also make the bacteria appear darker, allowing for easier identification.
is a fun and interesting experiment that will allow the student to learn more
about yogurt. It is an opportunity to learn the different between stained and
unstained slides as well as the different types of bacteria that are used to
make the yogurt they drink.
Although yogurt bacteria are safe to handle in the laboratory, safety is still emphasized given that students will still come in contact with glass slides and stains. Gloves should therefore be used at all times while avoiding clutter in the working space.
See Also: More advanced - Bacteria under the Microscope
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