True or false: Most bacterial colonies are visible by the naked eye. Select one:

Question

True or false: Most bacterial colonies are visible by the naked eye.

Select one:

a. True

b. False

If the human body temp is approximately 37°C, why do we incubate microbes in the lab at 35°C +/-2? (think of protein denaturization, also discussed in the textbook Microbial Growth chapter.)

Select one:

a. It is based on electrical efficiency of the incubator

b. It is a couple degrees lower because organism can handle cold better than hot temperatures

c. Exactly 35 degrees is the optimum growth temperature

d. It really wouldn't matter, just need any temperature as long as it is constant

In the Osmotic Pressure lab, the results are based upon turbidity measurements. A relatively low turbidity suggests:

Select one:

a. More bacterial growth

b. The culture will be relatively cloudy

c. A color chang occured

d. Less bacterial growth

If the Staphylococcus aureus grew more in a 5% NaCl environment than it did in 2% or 11% NaCl, you would conclude that it is probably a:

Select one:

a. Extreme halophile

b. Osmotolerant

c. Intestinal bacteria

d. Halophile

False negatives are likely in a test with low:

Select one:

a. Sensitivity

b. Specificity

c. Experimental variables

d. 10% bleach solution

e. Sharps container

An experimental result that is positive when the microbe of interest was present is a:

Select one:

a. A false negative

b. A false positive

c. A true negative

d. A true positive

e. Low sensitivity

Explanation / Answer

Yes, most of bacterial colonies are visible from naked eye, as its size is more than 1 mm, which is well within range of naked eye.

In fact, all most all human pathogenic Bactria are mesophilic in nature they exhibit their optimal growth at 35oC, also due to human handling of pathogen, it would be risky to handle. Thus the BEST possible answer will be option (c).

Turbidity is measured through the photoelectric cells and as numbers of bacterial colony grow, it will increase the turbidity due hindrance in passing light. Therefore, it can be said that the turbidity is directly proportional to growth of culture. Thus, the answer would be (d).

The diverse range of salinity (2-11%) given is quite high, and therefore if microorganisms can grow in this range, then it will be Osmotolerant. Thus, the option would be (b).

a. Sensitivity

b. Specificity

c. Experimental variables

d. 10% bleach solution

In such cases, where the specificity of instruments applied is low then even, tests results become less authentic and may be delivered false results. Thus, the option would be (b).

An experimental result that is positive when the microbe of interest was present is a: Select one:

a. A false negative

b. A false positive

c. A true negative

d. A true positive

e. Low sensitivity

There is no need of any explanation, as the true positive test is only when the microbes of interest would be truly diagnose.

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