Laboratory of Bacterial Pathogenesis and Immunology

The Streptococcus

Gram-positive bacteria:
Bacteria may be differentiated using the Gram stain procedure. The cell wall of gram-positive bacteria, such as B. subtilus, S. pyogenes and S. aureus, retain gentian violet. In contrast, gram-negative bacteria, such as E. coli and V. cholerae, which do not have a comparable cell wall, do not retain gentian violet.