RESPOND THOUGHTFULLY TO THIS DISCUSSION POST The Question:

How would the use of bacteriocidal, bacteriostatic or bacteriolytic antimicrobial agents differ in their resulting cell counts (total and viable). How would the effects differ regarding the growth curve of the cells? Use examples to support your answer.

The Person's

There are 3 different ways antimicrobial agents can affect microorganisms. One way is bactericidal, where the antibiotic can kill all the cells, but the total cell count is still present since the dead cells were not destroyed. That means we can still count the cells on a Petri dish, but the cells are no longer living. The viable cell count goes down, but the total number stays the same after the antimicrobial agent is added. An example of such an agent is penicillin since it binds to biosynthetic proteins involved in peptidoglycan synthesis and thus prevents cell wall formation.
Another way is bacteriostatic when the antibiotic stops bacterial growth. However, if the bacteria aren't all dead before the agent was removed, the bacteria can continue growing as they did previously. That means the cell count and viable cell count are the same. Both lines will follow the same pattern. An example in the text was Triclosan. At high concentrations, it is bactericidal, but at low concentrations, it only inhibits the fatty acid synthesis and thus only bacteriostatic. This doesn't necessarily kill the bacteria; it just inhibits it from growing temporarily until it is removed.
Lastly, there's bacteriolytic, which kills the cell as well as lowers the total cell count. This means the viable and total count both go down when the agent is added. Cell lysis decreases viable and total cell count. Since some bactericidal agents can also be bacteriolytic, penicillin can be used again as an example since it ruptures the cytoplasmic membrane.