You prepare an agar plate by spread plating & place an antibiotic disk in the middle of the plate. After incubating for a day at 37 degrees C, there are no bacteria on the plate. Which of the following is NOT a reasonable interpretation of what might have happened?

O The bacteria in the culture tube were already dead when you made the plate

O The medium used was defective and provided no nutrition for the bacteria

O The bacteria grew all over the plate but were then killed by the antibiotic

O The spreading tool was too hot when spreading the bacteria

A. The bacteria in the culture tube were already dead when you made the plate

Explanation:

Antibiotics are the chemical substance used to kill or stop the growth of bacteria and some other microorganism.

Antibiotics are added to agar plate during experiment for the selection of only those bacteria with resistance to that antibiotic.

There can be several interpretation for the absence of bacteria such as:

The bacteria grows on the nutrients in the medium but due to defective medium they were unable to grow and die. It may also happen bacteria might have grown in all over the plate but due to the action of antibiotic, all the bacteria got killed. Tool used for spreading might kill bacteria as it was hot and bacteria may not be able to tolerate the excessive heat and die.

Hence, the only not reasonable interpretation is bacteria in the culture tube were already dead when you made the plate.

So, the correct option is A.