A researcher has applied penicillin to a new strain of Gram-positive bacteria. Surprisingly, she observes no adverse effects on these bacteria. Which statement would best explain her observation?

These bacteria have a new cell wall component that can replace peptidoglycan

Explanation:

Penicillin is an antibiotic derived from penicillium molds.

They are effective against infections caused by most Gram positive.

Its' mode of action is, it prevents the synthesis of bacterial cell wall by preventing the proper cross-linking of peptidoglycan.

Therefore, if penicillin had no adverse effect on the new strain of bacteria, the bacteria must have a new cell wall component that can replace peptidoglycan.