Ascientist studied the effect of several new drugs (antibiotics x, y and z) to kill anthrax bacteria growing on petri plates with proper nutrients. the treatments in this study, applied to the bacterial media to compare with the currently used antibiotic are as follows: antibiotic x antibiotic y antibiotic z water currently used antibiotic which treatments are considered as negative and positive controls?

Negative control is the experimental setup in which no response is expected or the control in which the result is bound to be negative.

Positive control is the experimental setup in which a response is expected or the control in which the result may be positive.

So our,

Positive controls are: Currently used antibiotic

Negative control is: Water

Currently used antibiotic affects the bacteria whereas the water does not. Antibiotic X,Y,Z treatments are being checked for their activity and effect on the bacteria.