Lecture 23 - Bacteria: Prokaryotic Pathogens

Question 1

Do bacteria maintain structural integrity during replication? What about viruses?

Answer 1

Bacteria do, viruses do not.

Question 2

Why are bacteria generally not obligate parasites?

Answer 2

Because they make ATP and protein themselves.

Question 3

Which bacteria ARE obligate parasites?

Answer 3

Chlamydia and infectious blindness (trachoma).

Question 4

What is the cell size of a bacterium?

Answer 4

0.5-3µm by 0.5µm

Question 5

How many genes does the average bacterium have? Give an example of a bacterium and its number of genes.

Answer 5

Normally a bacterium will have 4000 genes.

For example Salmonella has 4500 genes.

Question 6

Do bacteria have organelles?

Answer 6

No

Question 7

Do bacteria have cell membranes?

Answer 7

Yes

Question 8

What is the cytoskeleton of a bacterium like?

Answer 8

Rudimentary

Question 9

Do bacteria have cell walls and what are they like?

Answer 9

Yes, they are complex.

Question 10

How do bacteria move?

Answer 10

Vi a flagella polymer that rotates (helical propellers)

Question 11

How do bacteria divide?

Answer 11

Binary fission.

Question 12

How do bacteria sexually reproduce?

Answer 12

There is no meiosis, but there is DNA transfer.

Question 13

What is the genome of a bacterium like?

Answer 13

Haploid, usually single and circular.

Other components are plasmids and bacteriophages.

Question 14

What is the mRNA of bacteria like?

Answer 14

Polycistronic (co-linear genes), unstable (length of survival measured in minutes).

Question 15

What is the regulation of proteins like in bacteria?

Answer 15

Mostly transcription initiation.

Question 16

What is the difference between the terms ‘pathogenic’ and ‘virulent’?

Answer 16

Being pathogenic is the intrinsic nature of a bacteria, whereas bacteria can be more or less virulent - it is a term that can be compared.

Question 17

What is MreB? What does MreB do in a bacteria? What does the deletion of MreB lead to?

Answer 17

MreB is a homologue of actin, which controls the cell shape of bacteria. Deletion of MreB leads to the coccus shape that bacteria can have.

Question 18

Which shapes do pathogenic bacteria usually have?

Answer 18

Coccus, curved rods or spiral.

Question 19

Which pathogenic bacteria adopt the coccus shape?

Answer 19

Staphylococcus, Streptococcus, Enterococcus.

Question 20

Which pathogenic bacterium adopts the ‘curved rod’ shape?

Answer 20

Vibrio cholerae.

Question 21

Which pathogenic bacteria are spirally shaped?

Answer 21

Treponema (syphillis) and Helicobacter (gastric ulcers).

Question 22

Which bacteria produce dormant endospores to survive in the environment?

Answer 22

Clostridium tetani (tetanus), C. perfringens (gas gangrene, food poisoning), C. botulinum (‘botulism’ food poisoning) and Bacillus anthrax (anthrax).

Question 23

Which bacteria was discovered first and why?

Answer 23

Anthrax because it is the largest.

Question 24

What is the difference between Gram-negative and gram-positive bacteria?

Answer 24

Gram positive bacteria have a thicker peptidoglycan wall whereas gram negative bacteria have an extra (outer) membrane.

Question 25

Which bacteria are gram positive?

Answer 25

Staphylococci, streptococci, enterococci.

Question 26

Which medically important bacteria do not gram stain? Give the reason why each of these do not gram stain, and if there is an alternative stain that can be used.

Answer 26

Mycobacteria because they are acid-fast as they are difficult to stain/destain because of their waxy lipid coat. Can use the Ziehl-neelsen stain.

Chlamydia and mycoplasma (causes non-gonococcal urethritis), because they lack a cell wall. They are difficult to culture and insensitive to many antibiotics.

Question 27

What is the bacteria cell wall made of?

Answer 27

Peptidoglycan, a huge macromolecule of alternating sugars N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM), cross-linked by short oligopeptides.

Question 28

How thick is gram positive peptidoglycan?

Answer 28

150-500 angstroms thick.