If you expose a bacterium to the antibiotic, how will the antibiotic kill it?

Answer 1

Different antibiotics have different modes of action. Some interfere with the formation of the bacterial cell wall like penicillin, or some interfere with the bacterias ability to synthesize proteins, and others I cannot think of off hand. Each of the modes are lethal to the bacterial cell.

Answer 2

Although all the above are correct, the last one being the most detailed, they miss a fundalmental point. Many antibiotics, especially those that interfer with the bacterial cell wall and DNA synthases don't kill the bacterium. They just stop them from dividing. Most analytical methods used to see if a bacterium is alive are only looking to see if the bacterium is dividing. But just because the bacteria can't devide doesn't mean its dead!

But getting back to the question: Penicillins (anything that ends "-illin") acts to prevent cross linking of the peptidoglycan in the cell wall. Streptogramins bind to part of the ribosome, stopping the cell from making proteins (still doesn't kill the cell), Vancomycin binds Lipid II in the cell wall synthesis process....i believe that chloramphenicol acts on RNA polymerase.

Answer 3

Antibiotics are a VERY wide array of drugs that can do several things to bacteria.
Some inhibit the synthesis of the cell wall of bacteria and these are your classic beta-lactams and glycopeptides like Penicillin and Vancomycin. There are dozens of antibiotics in this class, some FDA approved, some not. Second, we have drugs that inhibit protein synthesis in the bacteria. Some examples of these are Tetracyclines and Chloramphenicol, to name a few. Next there are inhibitors of nucleic acid synthesis and replication, and these are mainly Quinolones. The most prominent example of this class is the antibiotic Ciprofloxacin (Cipro). Then there's those than inhibit cytoplasmic membrane function. These are more effective on anaerobic bacteria, yeasts and pathogenic protozoa like Giardia. The last group I can think of is those that inhibit metabolic functions of bacteria.

It should be noted that the reason we have so many classes of antibiotics is because each strain of bacteria responds differently to different antibiotics. Some strains of bacteria are totally resistant to a certain drug whether it be naturally because of its nature or because of acquired resistance. So it's important to have a wide array of drug types to combat infections because certain strains of bacteria are becoming resistant to widely used drugs they were once susceptible to.

Answer 4

Depends. Some antibiotics kill by disturbing the cell wall, others by inhibiting growth, some just outright kill bacteria.