Which types of pathogenic bacteria are susceptible to MACs and why?

• A. Gram-positive bacteria because MACs easily pass through the thick cell wall to reach the plasma membrane.
• B. Gram-negative bacteria because the MACs attack their outer membrane which is not protected by the cell wall.
• C. Both gram-negative and gram-positive bacteria are susceptible to MACs.

Answer: (B)

Verified step by step guidance

1. Understand the structure of Gram-positive and Gram-negative bacteria. Gram-positive bacteria have a thick peptidoglycan layer, while Gram-negative bacteria have a thin peptidoglycan layer and an outer membrane.
2. Learn about the Membrane Attack Complex (MAC), which is part of the immune system's complement pathway. MACs form pores in the membranes of target cells, leading to cell lysis.
3. Recognize that the outer membrane of Gram-negative bacteria is a key target for MACs. This outer membrane is not present in Gram-positive bacteria, which have a thick peptidoglycan layer instead.
4. Analyze why Gram-negative bacteria are more susceptible to MACs. The MACs can insert into the outer membrane of Gram-negative bacteria, leading to cell lysis, whereas the thick peptidoglycan layer of Gram-positive bacteria provides a protective barrier.
5. Conclude that Gram-negative bacteria are susceptible to MACs due to their outer membrane, which is vulnerable to attack, unlike the protective thick cell wall of Gram-positive bacteria.