Final answer:
Penicillin G is ineffective against gram-negative bacteria because their outer membrane prevents the antibiotic from reaching the cell wall, and many produce ß-lactamases that break down the antibiotic.
Step-by-step explanation:
Penicillin G, a cell wall synthesis inhibitor, is not effective against gram-negative bacteria due to the unique structure of gram-negative bacterial cell walls. These bacteria have an outer membrane that is impermeable to many antibiotics including penicillin G, preventing the antibiotic from reaching the inner cell wall where it could exert its effect. Moreover, gram-negative bacteria often produce ß-lactamases like Extended-Spectrum ß-Lactamases (ESBLs), which confer resistance by breaking down the antibiotic before it can act on the bacteria. Consequently, penicillin G and other ß-lactam antibiotics cannot perform their function of disrupting cell wall synthesis, which is critical to bacterial survival. Some gram-negative bacteria, such as Escherichia coli, may occasionally be susceptible, but many others possess intrinsic or acquired resistance mechanisms.
CORRECT QUESTION:
Why is penicillin g NOT effective against gram (-) bacteria ?