Which of the following is involved in gliding motility in bacteria?
1. Specialized cell- surface proteins.
2. Slimy polysaccharides.
3. Flagella.
4. Specialized cell – surface proteins and slimy polysaccharides.
5.Capsules
The correct answer and explanation is:
Correct Answer: 4. Specialized cell-surface proteins and slimy polysaccharides
Explanation:
Gliding motility is a form of surface translocation used by certain bacteria to move across solid surfaces without the aid of flagella or pili. Unlike swimming (which relies on flagella) or twitching motility (which uses pili), gliding motility is smooth, slow, and often involves direct contact with the surface.
Two key components are involved in gliding motility:
1. Specialized Cell-Surface Proteins:
These proteins are located on the outer surface of gliding bacteria and play a vital role in movement. In species like Myxococcus xanthus, motor proteins located within the inner membrane are linked to protein complexes that traverse the cell envelope. These proteins essentially “walk” along the internal cytoskeleton and interact with the outer membrane, creating movement across surfaces. This system is called the A-motility (adventurous motility) mechanism.
2. Slimy Polysaccharides:
These are secreted by the bacterial cells and act like a lubricant or track for the bacteria to glide on. The polysaccharide slime creates a physical medium that reduces friction and assists with propulsion. This component is prominent in B-motility (biofilm-related motility) seen in some gliding bacteria. The slime may also play a role in adhesion to surfaces.
Why Not the Other Options?
- 3. Flagella: Gliding motility occurs without flagella.
- 5. Capsules: While capsules are composed of polysaccharides, they are generally associated with protection, not motility.
- 4 is correct because it includes both key components: proteins and polysaccharides.
Conclusion:
Gliding motility is a unique bacterial locomotion involving specialized cell-surface proteins and slimy polysaccharides working together to move the cell across surfaces. Thus, option 4 is the correct and most comprehensive answer.