Bacterial Anatomy

Question 1

Relevant diagrams:
[Diagram 1] [Diagram 2] [Diagram 3] [Diagram 4] [Diagram 5]

Answer 1

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Question 2

Lists the key components of bacterial anatomy.

Answer 2

cell wall, cell membrane, cytoplasm, nucleoid, flagella, pili (fimbriae), capsule

Question 3

Briefly describe the characteristics and functions of the bacterial capsule.

Answer 3

Characteristics:
It is a gelatinous, sticky layer that surrounds the cell wall and is primarily composed of polysaccharides.

Functions:
◾ It protects bacteria from phagocytosis.
◾ It helps prevent desiccation.
◾ The capsule aids in the adherence of bacteria to surfaces and host tissues.
◾ It plays a role in the formation of biofilms, which are communities of bacteria that adhere to surfaces and are embedded in a protective extracellular matrix.

Question 4

List the important features/characteristics of the cell wall of gram-positive bacteria.

Answer 4

(1) Thick peptidoglycan layer (murein)
(2) Teichoic acids
(3) Lipoteichoic acids
(4) Polysaccharides and proteins
(4) Absence of outer membrane
(5) It stains purple under a microscope

Question 5

List the important features/characteristics of the cell wall of gram-negative bacteria.

Answer 5

(1) Thin peptidoglycan layer
(2) Have an additional outer membrane
(3) Have a periplasmic space
(4) Porin protein
(5) Lipoprotein
(6) Lipopolysaccharide

Question 6

State the function of teichoic acids in the cell wall of gram positive-bacteria.

Answer 6

◾ They contribute to cellular adhesion.
◾ Teichoic acids help maintain the structure and integrity of the cell wall by providing rigidity and stability.
◾ They play a role in regulating the movement of cations (such as magnesium and sodium) across the cell wall, which is essential for various cellular processes.
◾ They can trigger an immune response in the host.

Question 7

State the function of lipoteichoic acid in gram-positive bacteria.

Answer 7

◾ LTAs anchor the peptidoglycan layer to the cell membrane.
◾ LTAs play a role in the adhesion of bacteria to host tissues and surfaces, facilitating colonization and infection.
◾ They help regulate the movement of cations across the cell wall.

Question 8

State the function of porin proteins in the cell walls of gram-negative bacteria.

Answer 8

It forms channels in the outer membrane that allow the passage of small molecules and ions.

Question 9

State the significance of lipid A in the lipopolysaccharide layer of the outer membrane of gram-negative bacteria.

Answer 9

◾ Lipid A is responsible for the toxic effects of LPS. It can trigger strong immune responses in the host, leading to inflammation, fever, and in severe cases, septic shock.
◾ It helps to maintain the structural integrity of the outer membrane.

Question 10

State the significance of the cell wall in bacteria.

Answer 10

(1) It maintains cell shape
(2) It protects bacteria from osmotic lysis
(3) It determines reactivity to Gram stain
(4) It is the site of action of certain antimicrobial agents
(5) It enhances pathogenicity

Question 11

State the functions of bacterial cell membrane.

Answer 11

◾ Provides structural support
◾ Selective permeability
◾ Active transport of molecules into the cell
◾ Synthesis of precursors of the cell wall
◾ Secretion of enzymes and toxins
Energy production

Question 12

Pili are composed of a protein called ________.

Answer 12

pilin

Question 13

State the function of pili in bacteria.

Answer 13

(1) They enable adhesion to surfaces, host tissues and other cells.
(2) Some pili, known as sex pili, are involved in the transfer of genetic material between bacterial cells during a process called conjugation. This allows for the exchange of plasmids and can contribute to the spread of antibiotic resistance.
(3) Certain types of pili are involved in bacterial motility.

Question 14

Flagella are composed of a protein called ________.

Answer 14

flagellin

Question 15

What is the function of flagella in bacteria?

Answer 15

Motility

Question 16

Bacterial ribosomes are smaller than eukaryotic ribosomes, with a sedimentation coefficient of ____(a)____S (Svedberg units). They consist of two subunits: the ____(b)____S large subunit and the ____(c)____S small subunit.

Answer 16

(a) 70
(b) 50
(c) 30

Question 17

What is the bacterial nucleoid?

Answer 17

This is a region within the bacterial cell where the genetic material is located.

Question 18

What are plasmids?

Answer 18

◾ These are extrachromosomal DNA molecules. They replicate autonomously within the bacterial cell.
◾ They can be easily passed from one bacterium to another through a process called conjugation.
◾ They may exist freely in the cytoplasm or become integrated into the bacterial chromosome. When integrated, they are referred to as episomes.

Question 19

What are mesosomes?

Answer 19

These are convoluted indentations (invaginations) in the cytoplasmic membrane.

Functions:
◾ Are sites of respiratory enzyme activity
◾ Coordinate nuclear & cytoplasmic division during binary fission

Question 20

What is an endospore?

Answer 20

This is a highly resistant, dormant structure formed by certain bacteria as a survival mechanism under unfavorable environmental conditions. They exhibit no metabolic activity and are resistant to heat, radiation and drying and can remain dormant for hundreds of years.

Question 21

Endospores are typically formed by bacteria in the genera ________ and ________.

Answer 21

Clostridium, Bacillus