What are the three main types (in terms of their physical forms) of microbiological culture media?
b) semi-solid (gel like)
Define defined or synthetic medium.
composed of complex materials that are rich in vitamins and nutrients
Why is culture medium cooled to about 48 to 50 degrees Celsius before it is poured into petri plates?
to minimize the amount of condensation
What is the source of carbon in the chemically defined medium in table 13.1?
The source of nitrogen?
When is a negative stain used?
when the bacteria doesn't stain well or when it is desirable to confirm observations made on the shape and size of bacteria, also good for viewing capsules.
Why do the bacteria remain unstained in the negative staining procedure?
due to repulsion between the negative charge of the stains and the negatively charged bacterial wall. Instead , these stains either produce a deposit around the bacteria or produce a dark background so that the bacteria appear as unstained cells with a clear area around them. ex. chaulk outline
Why is negative staining also called either direct or background staining?
because the stain goes around the organism like a chalk outline
When streaking with the second slide, why must it be held at a 45 degree angle?
So the bacteria-nigrosin solution spreads over the bacteria
What are the two purposes of heat fixation?
a) to adhere the organism to the slide
b) to kill the organism without serious distortion of the cell structure
What is the purpose of simple staining?
when information about cell shape, size, and arrangement is desired.
Why are basic dyes more successful in staining bacteria than acidic dyes?
they bind to bacterial cells by ionic interactions.
Why is time an important factor in simple staining?
because it can produce a false reaction also you don't want to over/under stain
How would you define a properly prepared bacterial stain?
Is a dried preparation of bacterial cells on a glass slide.
1) The bacteria is evenly spread out on the slide in such a concentration that they are adequately seporated from from each other.
2) The bacteria is not washed off the slide during staining.
3) Bacterial form is not distorted.