The structure of flagella in gram-negative bacteria is distinct due to the presence of an additional outer membrane, which necessitates a more complex basal body structure compared to gram-positive bacteria. In gram-negative cells, the basal body consists of four protein rings, unlike the two found in gram-positive cells. These rings include the MS ring and the C ring, which are similar to those in gram-positive cells, along with two additional rings: the L ring and the P ring.

The L ring is embedded in the outer membrane, a feature unique to gram-negative bacteria, as gram-positive bacteria lack this outer membrane. The P ring, on the other hand, is situated within the thin peptidoglycan layer and partially extends into the periplasmic space. This arrangement allows the P ring to fit snugly within the limited peptidoglycan layer characteristic of gram-negative cells.

Understanding the structural differences in the basal bodies of gram-negative and gram-positive bacteria is crucial for comprehending how these organisms move and interact with their environments. The additional rings in gram-negative cells play a vital role in anchoring the flagella securely to the cell, facilitating motility and adaptability in various conditions.