Kanamycin and Ampicillin against bacteria.

In order to graphically display the biochemical mechanism of action against E.coli bacteria of  a) Ampicillin and b) Kanamycin ( which of these is mainly bactericidal and which is mainly bacteriostatic?), sketch a typical batch culture growth curve as it would appear on semi-log paper and indicate a time of addition of each of these antibiotics and their effect on growth relative to the normal growth curve.

Ampicillin belongs to the penicillin class of antibiotics, which you may know have a very specific mechanism of action, in which they attack the peptidoglycan cell wall characteristic of ALL bacteria, including the E. coli mentioned here. Essentially, this B-lactam antibiotic doesn't necessarily cause bacteriolysis *cell bursting* but actually gets the cell ready for death.Thus it is technically considered bacteriostatic.

On the other hand, Kanamycin is an aminoglycoside (as opposed to a B-lactam). These drugs bind to the 30s subunit of bacteria ribosomes (which is responsible for producing the proteins required for function and life. Kanamycin ultimately stalls or alters protein production so that proteins are not produced at all, or made with a lot of mutations. Each of these indicate that the E. coli would not live, since these proteins are required for survival, thus it is a bacteriocidal event.

Therefore, ampicillin is respective to the first image posted, demonstrating a bacterostatic agent, where the viable cell count is static (cells are still living, but not growing, i.e. undergoing separation and growth), indicated by the plateau and the second is the graphical representation of kanamycin, a bacteriocidal agent, where the viable cell count plummets.