Selman Waksman and streptomycin

Although Mycobacterium tuberculosis has a thick layer of peptidoglycan like the Gram-positive bacteria the mycobacteria are usually considered separately because they have a thick waxy layer surrounding their cell wall. So, unusually, they are classified as Gram-positive because they lack the outer membrane of the gram-negatives but they don't actually retain the Gram stain like the other Gram-positives.

This is actually of considerable significance because they are also not susceptible to beta-lactam antibiotics like penicillin. The first antibiotic to be effective against tuberculosis, streptomycin, was discovered in 1943 by Selman Waksman a Ukrainian-American biochemist and microbiologist. A professor of biochemistry and microbiology at Rutgers University for four decades, he discovered over twenty antibiotics and, in fact, coined the word antiobiotic. He was awarded the Nobel Prize in Physiology or Medicine in in 1952.