Question

Antibiotic A: 0.5 kDa protein, targets peptidoglycan Antibiotic B: 20 kDa protein, targets peptidoglycan Antibiotic C: Cationic Antimicrobial Peptide (CAMP) Antibiotic D: Targets lipopolysaccharide With some more searching, you found the following results in your notebook. Percent Survival Percent Survival Antibiotic Antibiotic Control Control protoplast C. difficile protoplast Bacteria S. aureus E. coli V. cholera C. difficile S. aureus E. coli V. cholera Bacteria Percent Survival Percent Survival Antibiotic Antibiotic Control Control E.coli S. aureus Bacteria S. aureus E. colis V. cholera C. difficile protoplast V. cholera C. difficile Papp protoplast Bacteria

Answer 1

2) Graph1

Indicates an antibiotic which is effective against both the gram-positive and gram-negative bacteria and also is effective against protoplasts. Hence it is a broad spectrum antibiotic.

Graph 2

Represents a combination of antibiotics which that are effective against both gram-positive as well as gram-negative bacteria but do not have any effect on protoplast

Graph 3

Represents an antibiotic that is only effective against gram negative bacteria which means it targets that lipopolysaccharide layer of the cell wall of bacteria.

Graph 4

Indicates an antibiotic effective only against gram-positive bacteria which means it targets the peptidoglycan layer of the bacteria. Moreover it has no effect against protoplast.

Part II

1)

a) Experiment #1 is represents antibiotic c which is Cationic Antimicrobial Peptide as it is a broad spectrum antibiotic that is effective against both gram-positive and gram-negative bacteria since it interacts with the negatively charged residues on the cell wall and incorporates into it leading to the disruption and it also is capable of targetting the intracellular components including the DNA binding ability which makes it effective against protoplasts.

b) Experiment #2 represents combination of either (Antibiotic A and Antibiotic D), or (Antibiotic B and D) that is effective against both gram-positive and gram-negative bacteria but has no effect on protoplasts.

c) Experiment #3 indicates the use of only Antibiotic D that targets the lipopolysaccharide layer of gram-negative bacteria.

d) Experiment #4 represents use of either Antibiotic A or Antibiotic B since both of them target peptidoglycans and are not effective against protoplasts.

2) If we consider the Antibiotic D that targets the lipopolysaccharide layer of the bacteria by inhibiting the transpeptidase enzyme (required for the biosynthesis of peptidoglycan layer) in gram-positive bacteria. In general the antibiotic d would contain a Beta-lactam ring that is significant for interacting with transpeptidase enzyme leading to its inhibition. Some bacteria that are resistant to antibiotic D would have been producing enzymes called Beta-lactamases that degrade the Beta-lactam ring structure of antibiotic D rendering it to be inactive.