Chapter 3, Problem 1CHI

Propose a model for the assembly of a flagellum in a typical Gram-positive cell envelope.

Summary Introduction

A thin, long, whip-like appendage that attached to a bacterial cell is called as flagella. It is involved in the locomotion of bacteria. Flagella have several specialized roles. The reproduction rate is increased in some eukaryotic cells by flagella. The bacterial and eukaryotic flagella are also used to sense alteration in environments such as pH disturbances and temperature.

Explanation of Solution

In a gram-positive bacterium, an assembly of flagellum needs the basal body, which is inserted into the plasma membrane. The basal body and hook are relatively different from the filament and it is little wider when compared to the filament. The basal body is the most complex portion of flagellum. The hook proteins and flagellin subunits must also have a way for breaking the plasma membrane and the peptidoglycan layers that enclosed it.

First, the basal body is introduced into the plasma membrane. Then, the hook proteins can utilize the channel through the basal body and assemble outer surface of the plasma membrane. The subunits of flagellin are followed through the hook proteins and the basal body. The subunits of flagellin travelled through the tube of filament and added to the tip. They are spontaneously aggregated under the direction of protein, when the subunits reaches the tip, filament grows at the base. There also must be lytic enzymes, which degrade the peptidoglycan and allow the flagella to break through the layers.

In gram-negative bacterium, the biogenesis of flagella is complex by the addition lipid bilayer called outer membrane. The basal body of gram-negative bacteria flagella are anchored in the inner plasma membrane and passes through the entire. The basal body is used to transport the filament protein and hook outside of the cytoplasm.