Topic 2-L2 - Prokaryotic Cell Morphology

Question 1

6 types of morphological

Answer 1

• coccus (cocci)
• Rod (rods)
• spirillum (spirilla)
• spirochete
• budding and appendaged
• filamentous

Question 2

Cocci: spheres

Clusters = Staphylococci – Staphylococcus aureus

Answer 2

Common component of human microbiota (often nasal), opportunistic pathogen (often via wounds/cuts). Can enter bloodstream and cause life-threatening infections.

• Many S. aureus infections are by antibiotic-resistant strains (e.g.MRSA, VRSA) and are very difficult to treat clinically.

Question 3

Cocci: spheres Pairs = diplococci – Neisseria gonorrhoeae

Answer 3

• Gram negative coccus

- Etiological agent of the common STD gonorrhea

Question 4

Cocci: spheres Chains = streptococci – Streptococcuspyogenes

Answer 4

-The predominant “group A strep”

• Can cause a range of diseases, including “strep throat”. Can also
  be carried by healthy individuals.

Question 5

Bacilli: rods Salmonella enterica

Answer 5

• Common cause of “food poisoning” worldwide. Also cause of Typhoid Fever.
• Different S. enterica serovars – some rarely infect humans, some only infect humans.

Question 6

Vibrio: comma shaped or bent rod Vibrio cholerae

Answer 6

• Important human pathogen, especially in developing world, that causes profuse diarrhea and dehydration.

Question 7

Helical Helicobacter pylori

Answer 7

• Commonly found in human stomach, often innocuous

- Cause of vast majority of stomach ulcers, stomach cancers

Question 8

Spirochetes Borrelia burgdorferi

Answer 8

• Pathogen that causes Lyme disease, transmitted by ticks

Question 9

Appendaged/Budding Caulobactercrescentus

Answer 9

• Used as a model system to study bacterial cell cycle, asymmetric cell division
• Cell cycle can be synchronized, facilitating its characterization

Question 10

Filamentous Chloroflexusaurantiacus

Answer 10

• Photosynthetic bacterium that does not produce O2

- Studied to understand the evolutionary origins of photosynthesis

Question 11

Cell Shape can affect many aspects of day to day life

Answer 11

• Nutrient access/uptake (surface:volume ratio)
• Motility
• Attachment to surfaces
• Formation of biofilms
• Interactions with other microbes and/or eukaryotic host cells

Question 12

Monomorphic:

Answer 12

one shape; observed in most pure cultures of bacteria

Question 13

Pleomorphic:

Answer 13

multiple different morphologies for same bacterium

Question 14

What causes different morphologies/changes of morphology?

Answer 14

• Differentiation into different cell types or spore formation
• Altered morphology in response to environmental cues
• Altered morphology due to mutation

Question 15

Normally a bacillus (rod), becomes filamentous in a growth medium that induces

Answer 15

Mg2+ starvation