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Name: Sunitha 
Status: Student
Age: 20s
Location: N/A
Country: N/A
Date: N/A 


Question:
Although Nesseriae are gram negative they are sensitive to penicillin (which is usually used against gram positive bacteria). Why is this so?



Replies:
The bacterial cell wall is made primarily of a substance known as peptidoglycan. It is protein based (peptido-) and sugar based (-glycan). The sugar parts are actually two sugars called n-acetyl-muramic acid and n-acetyl-glucosamine. They alternate in long rows. They are joined by tetrapeptides that hook them together kind of like a chain link fence. This makes for a very strong cell wall. Penicillin acts by preventing the tetrapeptides from cross-linking and the cell wall loses its strength. The organisms then become sensitive to changes in osmotic pressure and burst. Gram positive organisms have a very thick peptidoglycan layer and therefore are most sensitive to penicillin based antibiotics. But gram negative bacteria also have peptidoglycan in their wall, even though it is only about 20%. So penicillin so far has been able to kill gonorrhea organisms. However, many are becoming resistant to this antibiotic.

vanhoeck



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