Structure & Functions of Bacterial Components

Question 1

Label the structure

Answer 1

A. Lipid A: embedded within the membrane and is released after cell death

B. Core oligosaccharide: similar among species and is essential for LPS structure and bacteria viability

C. O antigen: can bind to antibody or antigen (antigenic) and is variable among species or strains

Question 2

Define Primary Pathogen

Answer 2

can cause disease in a host regardless of host’s resident microbiota or immune system

Question 3

What are structures found inside the cell wall of the bacteria?

Answer 3

• plasma membrane
• nuclear region & plasmids
• ribosomes
• endospores

Question 4

What is the role of teichoic and mycolic acid and where are they found?

Answer 4

• teichoic acid: repeating subunits of sugar-phosphate molecules that act as important surface antigens
• mycolic acid: produced by Mycobacterium and is a waxy layer surrounding the cell that resists environmental stress and provides a barrier against many antibiotics

Question 5

What is the function of the bacterial cell wall?

Answer 5

protects against osmotic pressure changes and other environmental stresses

Question 6

What is the primary structure of the cell wall and how can it be degraded?

Answer 6

• peptidoglycan
• degraded by lysozymes (can be found in human tears / mucous)

Question 7

Characteristics of the capsule in bacteria

Answer 7

• very sticky (made of polysaccharides and/or polypeptides)
• tightly attached
• highly organised
• major virulence
• antiphagocytic

Question 8

Characteristics of the slime layer

Answer 8

• very sticky (made of polysaccharides and/or polypeptides)
• loosely attached to cell wall
• involved in dental decay (Streptococcus mutans)
• biofilm

Question 9

Function of the flagella

Answer 9

• induces movcement of the bacteria via rotary (spinning) of the flagella

: anti-clockwise (run)

: clockwise (random- tumble)

• movement is directional (towards chemoattractant / away from chemorepellent)

Question 10

4 types of flagella

Answer 10

1. monotrichous: 1 flagella
2. amphitrichous: 2 flagella (1 on each side)
3. lophotrichous: 2+ flagella on the same end
4. peritrichous: entire cell surrounded

Question 11

Label the image

Answer 11

Question 12

Endotoxins are a characteristic of what type of bacteria and why?

Answer 12

• characteristic of Gram-negative bacteria
• endotoxins are lipopolysaccharides (LPS) and these are found only within the outer cell membrane (which only Gram-negative bacteria have)

Question 13

What are structures found outside the bacterial cell wall?

Answer 13

• flagella
• fimbriae & pilli
• glycocalyx (capsule & slime layer)

Question 14

Function of the slime layer in bacteria?

Answer 14

• prevents dessication

Question 15

What are fimbriae & pilli made of?

Answer 15

• pillin proteins

Question 16

Explain how penicillin is expected to work against some bacteria?

Answer 16

Penicillin is a beta-lactam drug containing PBPs and a beta-lactam ring. This beta-lactam ring is expected to cleave to sites on the NAG-NAM chain to dissallow pentapeptide chains to link other NAG-NAM chains together. If the drug succeeds in doing this, the peptidoglycan layers will be unable to form

Question 17

Define Pathogen

Answer 17

microorganism capable of causing disease in a susceptible host

Question 18

What are endospores and what are their functions?

How are they formed and where are they mostly found?

Answer 18

• endospores are a defense mechanism formed in response to environmental stress and lack of nutrients
• it protects against dessication, heat, toxic chemicals, antibiotics, UV light, etc.
• formed via sporulation
• mostly found in Gram-positive bacteria

Question 19

4 types of pathogens

Answer 19

1. bacteria 2. virus 3. fungi 4. parasite

Question 20

What are plasmids in bacteria and what are their functions?

Answer 20

• extrachromosomal pieces of DNA
• carry genes for toxins, antibiotic resistance, etc. that are able to be transferred between cells via pilli during conjugation

Question 21

What is the peptidoglycan layer made up of?

Answer 21

• NAM (N-acetyl muramic acid)
• NAG (N-acetyl glucosamine)
• peptide chain links

Question 22

How does beta-lactamse work against beta-lactam drugs?

Answer 22

Beta-lactamase enzymes cleave to the beta-lactam ring found within the beta-lactam drug and break the ring open via hydrolysis so that the ring will not be able to stop the peptidoglycan layer from forming

Question 23

Function of the capsule on bacteria?

Answer 23

• prevents dessication (drying)

Question 24

Example of Opportunistic Pathogen

Answer 24

Streptococci normally found in the URT, but if in the blood can cause endocarditis

Question 25

Label the image

Answer 25

Question 26

Define Secondary Pathogen

Answer 26

normally harmless but can cause disease when introduced to a foreign location or in immunocompromised hosts

Question 27

Which bacteria has an outer cell membrane and what is the use of this structure?

Answer 27

• Gram-negative
• outer cell membrane has porins for transport and contains lipopolysaccharides which are an endotoxin

Question 28

How can the Gram-positive cell wall be distinguished?

Answer 28

• thick peptidoglycan layer with only an inner cell membrane
• presence of teichoic and mycolic acid
• the cell wall stains purple with Gram-stain (excl. Myobacterium which does not retain crystal violet but is considered Gram-positive due to the lack of an outer cell membrane)

Question 29

Which bacteria are fimbriae & pilli found on?

Answer 29

• fimbriae are found on some Gram-positive and Gram-negative bacteria
• pilli are found only on some Gram-negative bacteria

Question 30

What are the additional components found within Gram-positive bacteria?

Answer 30

• teichoic acid: repeating subunits of sugar-phosphate molecules
• myocolic acid: produced by Mycobacterium and is a waxy lipid around the cell used as protection from environmental stress and against manny antibiotics

Question 31

What is vancomycin?

Answer 31

Vancomycin is prescribed to patients that have resistance to pencillin. It’s a drug that interferes with the peptidoglycan cell wall synthesis by disrupting the bonds between the NAM and NAG

Question 32

What are the major targets of antibacterial drugs and why?

Answer 32

• proteins and RNA of ribosomes in prokaryotes, as the the ribosomes are different in comparison to eukaryotes

Question 33

Which bacteria has a periplasmic space and what is the use of this structure?

Answer 33

• Gram-negetive bacteria
• contains beta-lactamase enzymes which cleave beta-lactam drugs (i.e. penicillin, cephalosporins)
• contain protein translocation systems for transportation of substances out of the cell

Question 34

Function of fimbriae & pilli

Answer 34

• adherence
• transfer of genetic material

Question 35

Function of plasma membrane

Answer 35

• electron transport, energy production
• transport of nutrients, waste
• shape, cell division

Question 36

How can the Gram-negative cell wall be distinguished?

Answer 36

• thin layer of peptidoglycan surrounded by an inner and outer cell membrane
• presence of a periplasmic space
• stains pink/red with a Gram-stain

Question 37

Label the image

Answer 37

Question 38

How does the peptidoglycan layer appear within Gram-positive and Gram-negative bacteria?

Answer 38

• Gram-positive: thick peptidoglycan layer
• Gram-negative: thin peptidoglycan layer

Question 39

What is the glycocalyx composed of?

Answer 39

• capsule
• slime layer

Question 40

Additional components found within Gram-negative bacteria?

Answer 40

• outer cell membrane: porins & LPS
• periplasmic space: beta-lactam enzymes & protein translocation systems

Question 41

Chromosomes of bacteria are found where?

Answer 41

nucleioid (as they have no nucleus)