Below is a chart of some common microbe-induced illnesses and their causes. $$ \begin{array}{|l|l|} \hline \text { IIlness } & \text { Cause } \\ \hline \text { Common Cold } & \text { Rhinovirus } \\ \hline \text { Strep Throat } & \text { Streptococcal bacterium } \\ \hline \text { Athlete's Foot } & \text { Candida yeast } \\ \hline \text { Malaria } & \text { Malaria protist } \\ \hline \end{array} $$ Which of the following is most likely treatable with penicillin? A. common cold B. strep throat C. athlete's foot D. malaria

Penicillin is a groundbreaking antibiotic that marked the beginning of a new era in combating bacterial infections. Discovered by Alexander Fleming in 1928, penicillin works by interfering with the synthesis of the cell walls of bacteria, ultimately leading to their destruction. What makes it truly revolutionary is the selective toxicity it has towards bacteria, meaning it targets the bacteria without harming human cells.

Certain strains of bacteria have, however, developed resistance to penicillin, which has led to the development of a variety of penicillin derivatives and other antibiotics aiming to overcome this challenge. While penicillin is not a cure-all, it's most effective against Gram-positive bacteria such as Streptococcus and Staphylococcus species, which cause conditions like strep throat, pneumonia, and skin infections.

Bacterial infections occur when harmful bacteria enter the body and begin to multiply, challenging the immune system's ability to fight them off. Symptoms vary widely depending on the area affected – from coughing and sneezing in respiratory infections to inflammation and pus in skin infections.

Importantly, not all antibiotics are suitable for every type of bacterial infection. Factors such as the location of the infection, the type of bacteria causing it, and the patient's medical history are considered before prescription. As seen in the original exercise, strep throat, caused by Streptococcal bacterium, is an example of a bacterial infection where penicillin is often the first line of treatment due to its effectiveness.

Microbes encompass a vast diversity of microscopic organisms, including bacteria, viruses, fungi, and protists. Bacteria are single-celled organisms with a simple internal structure. In contrast, viruses are much smaller and cannot reproduce without infecting a host cell. Fungi, which include yeasts and molds, are eukaryotic, like plants and animals, and get their energy from degrading organic matter. Protists are a group of mostly single-celled eukaryotes that are neither plants, animals, nor fungi.

Understanding the type of microbe responsible for an illness is crucial for determining the correct treatment. Viral infections, for example, do not respond to antibiotics like penicillin. This fact highlights the importance of accurate diagnosis in treating infections effectively and avoiding the misuse of antibiotics.