What type of microorganism is primarily affected by lysozyme?

Lysozyme is an enzyme that plays a crucial role in the immune system by targeting and breaking down the cell walls of bacteria. It does this by hydrolyzing the glycosidic bonds in peptidoglycan, which is a vital component of the bacterial cell wall. This action renders the bacteria vulnerable and can lead to their destruction, making lysozyme an effective antibacterial agent.

Although viruses, fungi, and protozoa are important groups of microorganisms, they do not have peptidoglycan cell walls. Viruses are composed of nucleic acid enclosed in a protein coat and do not possess a cellular structure that can be affected by lysozyme. Fungi have cell walls made primarily of chitin, and protozoa generally have more complex structural components that are not targeted by lysozyme. Therefore, the primary target of lysozyme's antibacterial properties is bacteria, making this the correct answer.