Bacteria are fascinating prokaryotic organisms, but not all bacteria are created equally. For the most part, bacteria are divided into two categories, gram negative and gram positive bacteria. Gram positive bacteria are distinguishable by their thick peptidoglycan cell wall made of sugars. However, a gram negative bacterium has a thin outer peptidoglycan wall and a thin inner layer separated by a periplasmic space. This fundamental difference between gram negative and gram positive bacteria drastically influence which drugs are more effective at killing which type of bacteria.
Penicillin is one drug that is more effective at killing a gram positive bacterium by targeting its peptidoglycan cell wall. However, there are other things besides drugs like Penicillin that can kill bacteria. Fluctuations in temperature, salinity, and pH are effective in killing bacteria as well. The effects of temperature, salinity, and acidity or alkalinity are found freely in nature. While it is true that Penicillin is useful, byproducts created by one organism that have the ability to kill another organism is a common phenomenon in nature be it known or unknown.