Introduction to Bacteria

Question 1

What are the main structures of a typical bacterial cell?

Answer 1

Chromosome,
Cytoplasm
Cell wall
Ribosome
Penicillin binding proteins Peptidoglycan,
Lipopolysaccharide
Capsule
Flagella
Fimbriae
Plasmid
Bacteriophage
Spores

Question 2

Discuss the chromosome

Answer 2

A single chromosome in bacteria but no nucleus.

Question 3

Discuss the cytoplasm

Answer 3

Very thin, elastic and semi- permeable membrane around the bacterial cell content.

Made of phospholipids.

Allows passage of water and uncharged small molecules but otherwise forms a barrier.

There are proteins in the membrane.

Question 4

Discuss the cell wall

Answer 4

Rigid structure, gives cell strength and shape but it is permeable.

Made from peptidoglycan

Question 5

Discuss the ribosome

Answer 5

Consist of RNA and associated with proteins, their function is to synthesise proteins.

Divided into subunits

Bacteria have 70S ribosomes with large (50S) and small (30S) subunits

Subunit in small subunit called 16S

Question 6

Discuss penicillin binding proteins

Answer 6

Enzymes which synthesise peptidoglycans.

Question 7

Discuss peptidoglycans

Answer 7

Gives the cell strength and shape, these are made of carbohydrates that are cross linked with amino acids.

Question 8

Discuss lipopolysaccharides (LPS)

Answer 8

A component of gram negative cell wall.

They protect peptidoglycans from bile salts, lysosomes and also blocks antibiotics from getting into the cell.

Question 9

Discuss the capsule

Answer 9

Polysaccharide layer outside the cell wall.

Question 10

Discuss the flagella

Answer 10

Hairlike structure used for motility

Question 11

Discuss the fimbriae

Answer 11

Shorter and thinner than flagella and are important in mediating adhesion between bacteria cell and host cell.

Question 12

Discuss the plasmid

Answer 12

Often, the genes carried in plasmidsprovide bacteria with genetic advantages, such as antibiotic resistance.

Question 13

Discuss bacteriophage

Answer 13

A bacteriophage is a type of virus that infects bacteria.

Question 14

Discuss bacteria spores

Answer 14

To protect bacteria against ecological degrading agents.

Question 15

How are gram positive bacteria seen under the microscope?

Answer 15

Purple

Question 16

How are gram negative bacteria seen under the microscope?

Answer 16

Red

Question 17

What are the different shapes a bacteria can be?

Answer 17

Cocci - spherical
Bacilli - rod shaped
Spiral - corkscrew

Question 18

What are spores?

Answer 18

Highly resistant dominant structures.

A unit of asexual reproduction

Used in unfavourable conditions

The most dormant form of bacteria since they exhibit minimal metabolism and respiration, as well as reduced enzyme production.

Question 19

What is an example of a spore?

Answer 19

Bacillus subtilis

A Gram-positive, catalase-positive bacterium, found in soil and the gastrointestinal tract of ruminants, humans

Question 20

How can individual bacteria be seen?

Answer 20

Only with a microscope

Question 21

How can colonies of individual bacteria be seen?

Answer 21

Cultured on agar - can be seen by wyw

Question 22

What are the key differences between gram positive and gram negative bacteria?

Answer 22

+ve

Retain stain
No outer membrane
Smooth cell wall w/ 70-80% peptigoglycan
No porins

-ve

Does not retain stain
Outer membrane (lipopolysaccharide and protein)
Wavy wall that comes in contact with the plasma membrane - contains 10-20 percent peptidoglycan.

Question 23

What can you find on the cell surface of bacteria?

Answer 23

Plasma membrane

Penicillin binding sites

Peptidogylcan

Lipopolysaccharides (in gram negative bacteria)

Question 24

How do bacteria replicate?

Answer 24

Binary fission - identical progeny

Question 25

How is genetic variation increased in bacteria?

Answer 25

Spontaneous mutation

Transfer of DNA

Question 26

A bacteria name is the combination of the genus and the species. What is the difference?

Answer 26

The genus name forms the first part of the name for each species within the genus.

Question 27

What is the difference in the cell wall between gram positive and gram negative bacteria?

Answer 27

Gram positive cell wall is thick as it has layers and layers of peptidoglycan and then the plasma membrane contain proteins.

Gram negative cell wall is thinner as even though it has an outer membrane layer and a inner membrane layer, it only has one layer of peptidoglycans.