The Bacterial Cell

Question 1

What are the characteristics of staphylococci?

Answer 1

Bacteria that look like clusters of grapes, normally found on the skin and are usually transfereed from other humans to newborns after birth (ex. s. aureus)

Question 2

What are the characteristics diplococci?

Answer 2

Spherical bacteria that always comes in pairs.

Ex: s. pneumoniae

Question 3

What are the characteristics of Streptococci?

Answer 3

A chain of speherical bacteria

Ex: s. pyogenes (causes sore throat)

Question 4

What are the characteristics of bacilli or rods?

Answer 4

Elongated, sightly spherical bacteria

Ex: E.coli & Lactobacillus

Question 5

What are the characteristics of vibrio or bent rods?

Answer 5

Boomerang-shapted bacteria

Ex: Vibrio Cholerae

Question 6

What are the characteristics of spirilium bacteria?

Answer 6

Worm shaped bacteria that can cause STIs

Question 7

What are the characteristics of spirochete bacteria?

Answer 7

Shaped like a strand of curly (3c-4c) hair, rope like, flexible

Ex: Trepanema Pallidum (Syphillis)

Question 8

Whare are pleomorphic bacteria?

Answer 8

Bacterial cells of the same type that vary in shape and size

Question 9

Whare are the characteristics of coccobacillus?

Answer 9

These are vcells that are the intermediate shape between cocci and bacilli/ Used when it is difficult to determine if the cell is an elonbgated coccus or a short bacillus

Question 10

What is Opsonisation?

Answer 10

A. The build up of antibodies
B. The coating of pathogens by proteins called ‘opsonin’ making them more vulnerable to phagocytes.
i.) Opsonins (like antibodies) tag foreign pathogens for elimination by phagocytes. Without them the pathogen and phagocyte cell walls repel each other.

Question 11

What are the characteristics of Bacterial Capsules?

Answer 11

> GLYCOCALYX - formal name for the bacterial capsule
Gelatenous, sticky substance that surrounds the outside of the cell
Protects cells from drying (desiccation)
Chemicals in capsules can be similar to those found in the body
Water-soluble glycocalyx (slime layer) help bacteria attach to surfaces as BIOFILMS
Can be negatively stained - look like halos
Contains GLUCARONIC ACID

Question 12

How do bacterial capsules protect bacteria?

Answer 12

(1) Prevents detection by phagocytes by masking, (2) protect cell walls (which drugs like penicillin target), (3) prevents opsonisation due to lack of detection

Question 13

What is Chemotaxis?

Answer 13

The motion of cells TOWARDS nutrients, AWAY FROM toxic conditions

Question 14

What are the characteristics of peritrichous flagella?

Answer 14

These are flagella that cover the entire surface of the cell
Used for tumbling motion and ‘rush’ motion [all flagella bundle oin one end creating a fast linear movement]

Question 15

What are the characteristics of polar lophotrichous flagella?

Answer 15

These are flagella at both ends of the bacteria (can be tufts)
Used for turning motion

Question 16

What are the characteristics of polar monotrichous flagella?

Answer 16

These are flagellum at one end of the bacterium (can be tufts)
Used for linear motion

Question 17

What are FIMBRIAE?

Answer 17

Sticky, proteinaceous extenstions of some bacterial cells that finction to adhere cells to one another and to environmental surfaces.

Helps bacteria to attach to surfaces and move up the body.

Bristle-like (straight, not-like a broom)

Usually SHORTER than flagella

Question 18

What are FLAGELLA?

Answer 18

Long structures that extend beyond the surface of a cell (and its capsule) and move the cell through its environment.

Question 19

What are PILUS/PILI?

Answer 19

> A tubule involved in bacterial conjugation
Brings cells closer together in order for genetic exchange of plasmids to ccur
Shorter than fimbrae, MUCH FEWER IN NUMBER

Question 20

What are the characteristics of the bacterial cell wall?

Answer 20

• Provides structure and shape to cell
• Protects it from osmotic forces
• Assists soem cells in attaching to other cells or in resisting antimicrobial drugs
• PENICILLIN ATTACKS BACTERIAL CELL WALL

Question 21

What is ‘peptidoglycan’?

Answer 21

• Main component of bacterial cell walls
• Large, interconnected polysaccharide composed of chains of two alternating sugars and crossbridging of amino acids

Question 22

What are the characteristics of a ‘Gram-Positive Cell Wall’?

Answer 22

> Strong cell wall - no gaps
STAPHYLOCOCCI tend to be gram-positive
Single-layer celll wall
Crystal violet stain will not be removed with acetone because cell wall is tight
Counter-stain doesn’t work – shows as ‘PURPLE’
Contains teichoic acids which anchor peptidoglycan to cystoplasmic membrane

Question 23

What are the characteristics of a ‘Gram-Negative Cell Wall’?

Answer 23

> Two layer cell wall [thin peptiodoglycan layer (inner), outer bilayer membrane (inner = phospholipids, proteins, outer = lipopolysaccharide)
Looser wall due to gap between layers
Crystal violet stain can be removed – counter-stain (copper) stains bacteria PINK
Ex: E.coli

Question 24

What are ‘lipopolysaccharides’?

Answer 24

• A union of lipid with sugar
• Lipid portion is called ‘Lipid A’
• Outer most layer in a gram negative bacteria cell wall

Question 25

Why is Lipid A important in disease?

Answer 25

• A dead cell releases Lipid A when outer membrane disintegrates
• Can trigger: fever, inflammation, shock, blood clotting, constriction of blood vessels , vasodilation
• Internal gram negative infections are dangerous becsuse more dead cells = more lipid A
• Virulence factor in gram negative bacteria

Question 26

What is a gene?

Answer 26

Tightly clustered, on both strands, and organised in operonic structures for coregulation.

Question 27

What are the steps of the lytic cycle?

Answer 27

1. Phage binds to bacteria
2. Phage DNA enters host cell
3. Host DNA is digested
4. New phage DNA forms
5. Host transcribes and translates phage DNA
6. Assembly complete; encoded enzyme causes lysis
7. New phages are released

Question 28

What are the steps of the lysogenic cycle?

Answer 28

1. Phage DNA enters cell
2. Phage DNA integrates and becomes prophage
3. Integrated prophage replicates
4. Prophage may separate and enters lytic cycle
5. Mutliplies with the cell until it is triggered and then goes into lytic cycle

Question 29

How long does it take for bacteria to multiply?

Answer 29

20 minutes — 200 phages produced.

Question 30

How can prophages be involved in disease?

Answer 30

Non-toxic organisms can produce toxins with the help of the prophage

Question 31

What are examples of toxins produced by prophages in pathogenic bacteria?

Answer 31

A. Diptheria toxin in cornyebacterium diptheria
B. Botulin is Clostridium Boltinium
C. Choleratoxin in Vibrio Cholerae – only S. pyogenes carrying a prophage are able to produce the toxin causing ‘scarlet fever’

Question 32

What are Polyhydroxybutyrate (PHB) Granules?

Answer 32

Granules that form in bacteria and are used for storing energy. They are sometimes used to produce SPORES

Question 33

What are examples of endospore-forming bacteria?

Answer 33

Clostridia (can cause gas gangrene) and Bacillus (anthrax)