Why is it recommended that you use the broth regardless of m

Why is it recommended that you use the broth (regardless of medium) with the most growth to serve as the \"standard\" for scoring a \"3\"? (3 for adundant growth)

Why is it important to use the uninoculated controls for each medium to serve as the \"standard\" for scorinh a \"0\" in yheir respective tubes? (0 for no growth)

Suppose afte performing this experiment, you examine the growth of two different organisms in Medium X. Both show growth and Organism 1 has produced less turnidity than organism 2. Explain how it could be possible that Organism 1\'s needs are actually better supplied by the medium than organism 2\', yet there is less turbidity?

What is the biochemical basis for the spectrum of fastidousness seen in the mircobiol world? That is, why are some organism fastidious and others are nonfastidious?

What are some consequences of leabing a stain on a bacterial smear too long? (over staining)

What are some conswquences of not leabing a stain on a smear long enough? (under-staining)

Consider a coccus and a rod of equal volume.

Which is more likely to survive in a dry enviroment? Why?

Which would be better adapeted to a moist enviroment? why?

Solution

1. Broth with the maximum growth is used as a standard for measuring growth because broth helps in maintaining optimal concentration of bacteria. Broth results in uniform growth on solid media. Additionally growth can be measured with respect to turbidity either with the help of spectrophotometer or through visual examination of the broth.

2. Uninoculated medium serves as a negative control. It is used as an indicator for testing the sterility of the medium. In case any growth is present on uninoculated medium, it is an indicator of contanimation.

3. There might be various reasons for less turbidity shown by organism 1. Optimum temperature might not be maintained for Organism 1, which leads to slower growth. The growth rate of organism 1 may be less than organism 2. It might also be possible that there is production of inhibitory substances by organism 2 which are interfering with the growth of organism 1.

4. Some microorganisms are fastidious as they lack the metabolic pathways required to syntheisze certain nutrients. Therefore they rely on particular media for fulfilling their complex nutritional reqirements.

5. Overstaining a bacterial smear will cause cell wall disruption as a result of which the cell looses its true morphological characteristics.

6. Understaining will cause false Gram negative results. In case of simple staining understaining will cause difficulty in observing the cells.

7. Cocci are more likely to survive in a dry environment because they have a lower surface area to volume ratio which causes them to dehydrate slowly.

8. Rods are more likely to survive in a moist environment because they have a larfer surface area to volume ratio due to which they can easily exchange materials with their surroundings.