Question

"Three organisms were innoculated on a culture media. Results showed Escherichia coli as red colonies, no growth of Staphylococcus epidermidis, and colorless colonies of Salmonella enterica. The medium is:"

	a	selective and differential
	b	differential
	c	selective
	d	minimal
	e	heterotrophic

"A bacterium was incubated with aeration in a nutrient medium containing two carbon sources. After logarithmic growth, a lag phase was observed for 25 minutes. Then logarithmic growth at a slower rate was observed. Which substate was preferred by the bacteria?"

a		The first substrate used up is preferred.
b		The second substrate used up is preferred.
c		Neither substate is preferred.
d		Both substrates are preferred equally.
e		not enough information is given to determine the correct answer

"A culture of 10 bacteria of Escherichia coli has a generation time of 30 minutes at 35 degrees Celsius. After 5 hours at this temperature, how many bacteria would you expect to see?"

	a	"10,240"
	b	50
	c	"1,000"
	d	320
	e	"10,000,000,000"

Pasteurization of 63 degress Celsius for 30 minutes or 72 degrees Celsius for 15 seconds best illustrate

a		equivalent treatments
b		methods of sterlization
c		methods of filtration
d		how thermoduric bacteria survive
e		decimal reduction time

Why is Mycobacterium often resistant to disinfectants?

a		acid-resistant cell wall
b		endospore formation
c		metabolism
d		anaerobic behavior
e		genetic recombination

Microwave radiation was examined in wet and dry conditions. What is the most likely method of lethal action of microwave radiation?

a		heat
b		ionizing radiation
c		pressure
d		moisture
e		all of the choices are correct

Which causes protein denaturation and is effective against enveloped viruses?

a		alcohols
b		halogens
c		organic acids
d		biguanides
e		silvera

Answer 1

Ans-1- selective because kills E Coli and differential because help to differentiate between Staphylococcus epidermidis and Salmonella enterica

So the option A is correct

Ans-2- Since the rate of growth in second phase is slow the first carbon source is preferred by bacteria.

So the option A is correct

Ans-3- N0 =10 G.T. = 30 min Total time = 5 hrs = 300 min.

So the number of generation (n) = 300 / 30 =10

from the formula

N = N0 * 2n = 10 * 210 = 10240 cells

So the option A is correct

Ans-4- Both the treatment are equivalent

So the option A is correct

Ans-5- mycobacterium contains an acid-resistant cell wall, that contains a waxy layer and prevents disinfectant to enter into the cell

So the option A is correct

Ans-6- Microwave heat the bacteria that cause loss of water and due dehydration bacteria dies.

So the option A is correct

Ans-7- Alcohol is most commonly used disinfactant that kills pathogen by denauring their proteins

So the option A is correct