Which of the following is classified as a gram-positive microbe?

The classification of Streptococcus as a gram-positive microbe is based on its cell wall structure, which is rich in peptidoglycan. The primary characteristic of gram-positive bacteria is their ability to retain the crystal violet stain used in the Gram staining procedure, resulting in a purple color under the microscope. Streptococcus species are known for causing various human infections, including strep throat and other respiratory infections, due to their presence in the upper respiratory tract.

In contrast, the other organisms listed have different characteristics: H. influenza and Pseudomonas are gram-negative bacteria, which do not retain the crystal violet stain due to their thinner peptidoglycan layer and additional outer membrane. Proteus also belongs to the gram-negative category and is associated with urinary tract infections. This distinction between gram-positive and gram-negative organisms is crucial in microbiology and pharmacology for determining appropriate antibiotic treatments, as gram-positive bacteria often respond differently to various types of antibiotics compared to gram-negative bacteria.