Bacterial Structures and Motility

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Questions and Answers

Which statement accurately describes the movement of spirochetes due to their axial filaments?

They move exclusively in a straight line.

They can only move in a backward motion.

They exhibit a spiral or corkscrew-like movement. (correct)

They move by undulating like cilia.

What type of bacteria possess flagella distributed over their entire surface?

Amphitrichous bacteria

Peritrichous bacteria (correct)

Lophotrichous bacteria

Monotrichous bacteria

Which type of motility involves the use of pili?

Ciliary movement

Amoeboid movement

Gliding motility (correct)

Flagellar propulsion

What is the primary function of fimbriae in bacteria?

Attachment to surfaces Signup and view all the answers

Bacteria that lack flagella are classified as what type?

Atrichous Signup and view all the answers

What is a key function of the bacterial capsule?

Protecting bacteria from being phagocytized Signup and view all the answers

What distinguishes a slime layer from a capsule?

A slime layer is loose and water-soluble. Signup and view all the answers

What structural component primarily makes up bacterial flagella?

Protein called flagellin Signup and view all the answers

How does energy generation affect bacterial motility through flagella?

Flagellar rotation relies on the continuous generation of energy. Signup and view all the answers

Which type of movement do spirochetes exhibit due to their unique flagellar structure?

Spiral or helical movement Signup and view all the answers

What is the term for the movement of bacteria toward or away from a chemical stimulus?

Chemotaxis Signup and view all the answers

What pattern of movement do bacteria exhibit when they approach an attractant?

Long runs and few tumbles Signup and view all the answers

What does a flagellum NOT contain?

Microtubules Signup and view all the answers

What is the primary feature of the glycocalyx that distinguishes it from other cell structures?

It is a viscous, gelatinous material. Signup and view all the answers

Which type of cell division is characteristic of prokaryotic cells?

Binary fission Signup and view all the answers

What is the main function of a slime layer in bacteria?

To facilitate motility and adherence to surfaces. Signup and view all the answers

Which of the following best describes the structure of flagella in prokaryotic cells?

They consist of a hook, a filament, and a basal body. Signup and view all the answers

What are bacilli commonly characterized by?

They can be short, long, thick, or thin. Signup and view all the answers

Which type of bacteria are described as being monomorphic?

Those that maintain a single shape. Signup and view all the answers

How do spirilla bacteria primarily move?

Using flagella in a corkscrew motion. Signup and view all the answers

What is a common occurrence in the arrangement of diplo- and streptococci?

They occur in pairs or chains. Signup and view all the answers

Study Notes

Glycocalyx

A viscous, gummy material composed of sugars and proteins
Produced by the cell membrane and secreted outside the cell.
Classified as a slime layer or a capsule

Slime Layer

Unorganized
Only loosely attached to the cell wall
Enables bacteria to glide or slide along solid surfaces

Capsule

Organized and firmly attached to the cell wall
Composed of polysaccharides, with possible combinations with lipids and proteins
Protects bacteria from being engulfed by white blood cells (phagocytosis).

Flagella

Threadlike protein appendages that enable bacteria to move.
The presence of flagella indicates a motile bacterium
Flagellated bacteria are about 10 to 20 nanometers (nm) thick
Composed of protein fibers called flagellin, twisted together like a rope.
Prokaryotic flagella do not have microtubules and are not membrane-bound.

Axial Filament

Two flagella-like fibrils
Wrap around the organism
Enable spirochetes to move in a spiral or helical fashion

Flagellum Structure

Arises from a basal body in the cell membrane
Projects outward through the cell wall and capsule.
A semirigid, helical structure that rotates from the basal body
Rotation is clockwise or counterclockwise
Flagellar rotation relies on continuous energy production by the cell

Bacterial Movement

Bacteria can alter the speed and direction of flagellar rotation
The movement of bacteria towards or away from a stimulus is called taxis

Chemotaxis

Movement toward or away from chemical stimuli
Oxygen, ribose, and galactose are examples of chemical stimuli

Phototaxis

Movement toward or away from light stimuli
Motile bacteria contain receptors to detect stimuli

Pili and Fimbriae

Observed on Gram-negative bacteria
Polymerized protein molecules called pilin, arranged in a helix
Extend from the cytoplasm through the plasma membrane, cell wall, and capsule.

Fimbriae (Adhesin)

Located at the bacterial cell poles or evenly distributed on the surface
Important for bacterial attachment to surfaces

Pili

Usually longer than fimbriae
Typically only one or two per cell
Involved in bacterial motility and DNA transfer
Enable gliding motility.

Bacterial Shape

Monomorphic: maintains a single shape
Pleomorphic: can have multiple shapes

Prokaryotic Cell Structure

All bacteria are prokaryotes
Significantly smaller than eukaryotic cells
Reproduction occurs through binary fission
The cytoplasm contains a chromosome, ribosomes, and other particles
Surrounded by a cell wall, sometimes with a capsule or slime layer

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Description

This quiz explores the various structures of bacteria, including glycocalyx, slime layers, capsules, flagella, and axial filaments. Understand the functions and characteristics of these structures and their role in bacterial motility and protection. Test your knowledge on prokaryotic cell structures!