The EMB (Eosin Methylene Blue) agar is a selective and differential agar medium. It contains sucrose and lactose as fermentable substrates together with Eosin Y and methylene blue dyes which in combination gives the agar its characteristic color when prepared and serves as a pH indicator as well as an inhibitor of growth of Gram-positive bacteria. Hence, it is primarily used to isolate Gram-negative fecal coliforms while some positive fecal coliforms such as Staphylococci are also able to grow.
These coliforms are of two types:
- Lactose or sucrose fermenting coliforms form metallic sheens on the agar as a result of acid production and the response of the indicator to the increased acidity.
- Non-lactose/sucrose fermenters are only able to produce acid by protein deamination. Hence they either form colorless or pinkish colonies on the agar
On the other hand, Mannitol salt agar is a selective and differential agar medium that is primarily used to isolate Staphylococcal bacteria. The presence of sodium chloride in the medium makes it a partial or complete inhibitor of other bacteria.
Hence, an unknown bacterium that forms colorless colonies on EMB will either be a non-lactose fermenting, Gram-negative coliform that will hardly grow on Mannitol salt agar, or a Gram-positive fecal Staphylococcus.
Staphylococci bacteria are of two types:
- Coagulase-positive will form yellow colonies on the Mannitol salt agar.
- Coagulase-negative will form red colonies on the Mannitol salt agar.
More about isolating media can be found here: https://brainly.in/question/7238948
common descent means the evolutionary in biology and how they have something linked with their common ancestors.
Carl Linnaeus
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1. Answer: C
Explanation: Species that are inclined to clumping means they are more likely to cooperate in tasking such as gathering food. However, evenly distributed population means there is competition between individuals hence the need to their own space and territory from the other individual.
2. Answer: B
Explanation: While the clumped up populations may be inclined to cooperate in tasks such as food gathering, such distribution results to increases intraspecies competition especially during scarcity. This is because the individuals are close together – which is also advantageous during mating season.
3. Answer: A
Explanation: Type 3 survivorship curve is characterized by a high mortality rate early in the life of the species which gradually progresses to a low mortality rate for the individuals that survive the early stages of life. These species, therefore, bear a lot of offspring most of which will not make to adulthood.
4. Answer: B
Explanation: If the death rate of a population is higher than the birth+ immigration rate, then the population must be decreasing. This can be demonstrated by a growth curve of a population such as that of bacteria. The population starts decreasing due to increased competition for reduced resources after reaching carrying capacity - depicted by the stationary phase.
The primary function of decomposers...Decompose
