Gram-Positive and Gram-Negative
Gram staining is the application of a crystal violet dye to a culture of bacteria. Bacteria that retain the color of the dye are called Gram positive; bacteria that don't are Gram negative. The diagram to the right shows Gram-positive Staph aureus at the top and Gram-negative Pseudomonas aeruginosa at the bottom. The Gram stain attaches to peptidoglycan (also called murein) in the bacterial cell wall. In Gram-negative bacteria, the peptidoglycan layer is protected by an outer membrane. In most bacteria, the Peptidoglycan biosynthesis 2 subsystem creates peptidoglycan and the Murein hydrolase subsystem breaks it down. These two processes are essential to the reproductive process of the bacteria, and in fact the antibiotic action of penicillin is derived from the fact it binds to the enzyme that catalyzes the peptidoglycan subsystem's final Functional Role, preventing the bacterium from reproducing. Mapping this subsystem for antibiotic-resistant pathogens is an important step toward developing next-generation drug therapies.
To see a gram-positive organism, select it from the list below and click the button. To see a gram-negative organism, select it from the list below and click the button.
Topic revision: r8 - 16 Jan 2009 - 15:08:13 - Bruce Parrello
Notice to NMPDR Users - The NMPDR BRC contract has ended and bacterial data from NMPDR has been transferred to PATRIC (http://www.patricbrc.org), a new consolidated BRC for all NIAID category A-C priority pathogenic bacteria. NMPDR was a collaboration among researchers from the Computation Institute of the University of Chicago, the Fellowship for Interpretation of Genomes (FIG), Argonne National Laboratory, and the National Center for Supercomputing Applications (NCSA) at the University of Illinois. NMPDR is funded by the National Institute of Allergy and Infectious Diseases, National Institutes of Health, Department of Health and Human Services, under Contract HHSN266200400042C. Banner images are copyright © Dennis Kunkel.