From the Guidelines
Many intestinal bacteria possess flagella, including Escherichia coli, Salmonella species, Proteus mirabilis, Vibrio cholerae, Helicobacter pylori, and Campylobacter jejuni, as evidenced by recent studies 1. These whip-like structures allow these bacteria to move through the intestinal environment, which gives them advantages in colonization, nutrient acquisition, and evading host immune responses.
Key Points
- Flagella are composed of the protein flagellin and extend from the bacterial cell surface, rotating like propellers to generate movement.
- Not all gut bacteria have flagella; many beneficial intestinal bacteria like most Lactobacillus and Bifidobacterium species lack them.
- The presence of flagella is significant because flagellin can trigger immune responses through Toll-like receptor 5, contributing to both protective immunity and inflammatory conditions in the gut.
- The ability to move via flagella helps pathogenic bacteria penetrate the mucus layer protecting the intestinal epithelium, which can be important in their virulence and colonization strategies. Some of the bacteria mentioned, such as Campylobacter spp. and Yersinia spp., are also discussed in the context of gastrointestinal infections in cancer patients 1, highlighting their potential to cause disease. However, the primary focus here is on the presence of flagella in intestinal bacteria, which is a critical aspect of their biology and interaction with the host environment, as noted in the most recent guidelines 1.
From the Research
Intestinal Bacteria with Flagella
- Salmonella enterica serovar Typhimurium has flagella, which are supramolecular assemblies consisting of at least three distinct functional parts: a basal body, a filament, and a hook 2.
- Escherichia coli has flagella, which propel the cell by rotating, and this rotation is regulated in response to information transmitted by chemoreceptors on the surface of the cell 3.
- Campylobacter species have polar flagella, which are required for colonization of the mucus lining of the gastrointestinal tract 4.
- Shigella species do not have a detailed description of their flagella in the provided studies, but they are mentioned as common causes of infectious diarrhea 5.
Flagella Structure and Function
- The flagellum of Salmonella enterica serovar Typhimurium has a basal body that acts as a bidirectional rotary motor, a filament that functions as a helical propeller, and a hook that works as a universal joint 2.
- The flagellar system of Escherichia coli is complex and includes many elements in addition to those found in the intact flagellar structures purified from the cell membrane, such as proteins required for energy and sensory transduction 3.
- Campylobacter flagellins are heavily glycosylated, and changes in glycan composition affect autoagglutination and microcolony formation on intestinal epithelial cells 4.
Motility Behaviors
- Bacteria use a wide variety of flagellar architectures to navigate their environment, and recent work has revealed a variety of new motility behaviors that can be achieved with different flagellar architectures 6.