Lecture 5

Question 1

Glycocalyx

Answer 1

also known as extracellular polymeric substance or the slime layer.
It is often described as gel-like, viscous, mucilaginous and slimy. Can be up to 10 micrometers in diameter. It is made internally and excreted by the cell.

Question 2

capsule

Answer 2

Glycocalyx when well organized and firmly attached it is called a capsule

Question 3

Glycocalyx Possible functions

Answer 3

Protective-against drying; against phagocytosis
May act as a food reservoir
May be a sloppy method of waste disposal
May be a combination of the above

Question 4

Protective-against drying; against phagocytosis

Answer 4

Phagocytic immune cells such as monocytes and neutrophils cannot engulf a bacterial cell that has become too enlarged due to a capsule layer. Therefore, the capsule can contribute to causing virulence.

Question 5

Is the capsule essential to life

Answer 5

The capsule is not essential to life. A cell can lose a capsule without an effect on growth or reproduction. However, loss of capsules may cause loss of virulence.

Question 6

Colonies of capsule positive bacteria

Answer 6

are often mucoid and shiny (smooth)

Question 7

Capsules are associated with immunologic specificity

Answer 7

This means that specific antibodies can
attach to capsular material. (Capsular material can be antigenic)
The Quellung reaction is utilized to identify one of the bacterial etiologic agents of pneumonia (Streptococcus
pneumoniae). Specific antibodies are used to target this organism’s capsule. This will cause swelling and make these bacteria highly recognizable under the microscope for purposes of
identification

Question 8

Chemically, most capsules are

Answer 8

polysaccharides

Question 9

Klebsiella pneumoniae

Answer 9

a Gram negative rod that can cause pneumonia and Bacillus anthracis a Gram positive rod that causes anthrax, are examples of bacteria that produce capsules

Question 10

Flagella

Answer 10

(singular flagellum)-Whip-like appendages that provide a mechanism for motility. They are thin (below the resolution of the light microscope-approximately 0.02 micrometers
wide)

Question 11

A mordant

Answer 11

(any additive that intensifies a staining reaction) will precipitate upon the flagella to enlarge this structure. A stain is then used for visualization under the light microscope.

Question 12

Flagella in prokaryotes

Answer 12

are simple in structure. They are made up of repeating units of a single type of protein. Flagella can be used to help classify bacteria.

Question 13

Atrichous flagellation

Answer 13

organisms without flagella

Question 14

Unitrichous flagellation

Answer 14

organisms with one (usually polar) flagellum

Question 15

Amphitrichous (bipolar) flagellation

Answer 15

organisms with flagella at both ends of the cell

Question 16

Lophotrichous flagellation

Answer 16

organisms that have tufts (two or more) of flagella

Question 17

Peritrichous flagellation

Answer 17

organisms that have flagella distributed over the entire cell. Members of the genus Proteus display this. When grown on a plate, they sometimes become “swarmers” where they can spread out across the entire plate.

Question 18

Axial filaments

Answer 18

structure for motility found in Spirochetes. They are positioned from one pole to the other within the cell. They are flexible and can contract and then spring forward. They are simple in structure like flagella

Question 19

Fimbriae (singular fimbria), Pili (singular pilus)

Answer 19

• hairlike appendages that are shorter and thinner than flagella. They are used for attachment and transfer of DNA. There can be hundreds on a cell.

Question 20

Neisseria gonorrhoeae has

Answer 20

has fimbriae (pili) which it uses to attach to the urethral lining and therefore stay anchored during urination.

Question 21

Pili may cause and may serve as

Answer 21

bacterial cells to stick to each other.
The appearance of membranes (thin films on broth surfaces), pellicles (thick, tough films on broth surfaces) and floc’s (rafts of cells in broth media) can be explained by the presence of pili.
A sex pilus may attach two bacteria together (conjugation) for purposes of conveying genetic (DNA) material. Pili may serve as receptor sites for viruses.

Question 22

Cell wall-provides bacteria with

Answer 22

shape and protection from lysis during osmotic imbalances

Question 23

Prokaryotic cell walls are

Answer 23

more complex than the cell walls found in eukaryote cells that have cell walls (plant cell walls for example are made up of cellulose)

Question 24

Gram positive cell walls

Answer 24

are thicker yet less complex than Gram negative cell walls.

Question 25

Gram positive cell wall is almost

Answer 25

entirely made up of peptidoglycan (small amount of peptidoglycan in Gram negative cell walls). Peptidoglycan provides for a rigid and yet permeable framework. It is a heteropolymer

Question 26

It is a heteropolymer

Answer 26

(the subunits consist of different materials). It consists of amino sugars (NAG and NAM) and amino acids (DAP or diaminopimelic acid is a strange amino acid found in peptidoglycan). Small amount of teichoic acid is found in Gram positive cell walls.

Question 27

Gram negative cell walls

Answer 27

are thinner yet more complex in structure. They consist of a small amount of peptidoglycan and an additional layer of LPS (lipopolysaccharide) and LP (lipoprotein)

Question 28

The LPS component is associated with

Answer 28

endotoxin (more later)

Question 29

Gram positive bacteria are

Answer 29

sensitive to penicillin, are inhibited by crystal violet stain and are susceptible to lysozyme digestion. This is due to the large amount of peptidoglycan.

Question 30

Members of the genus Mycoplasma

Answer 30

``` lack cell walls. They are pleomorphic and must exist in hyperosmotic conditions (rich lung exudates). They are free living forms of life. ```

Question 31

L-forms

Answer 31

(named after the Lister Institute) are cells that have lost their cell walls as a result of antibiotic exposure

Question 32

Protoplasts

Answer 32

are Gram positive bacteria that have been stripped of their cell walls

Question 33

Spheroplasts

Answer 33

are Gram negative bacteria that have been partially stripped of cell wall material