1.4: Cells of Bacteria and Archaea

Question 1

What are the 3 most common cell shapes of bacteria (in order most common to least common)

Answer 1

• Bacillus (rod shaped)
• Coccus (roughly spherical)
• Spirillum (spiral shaped)

Question 2

What are the 3 unusual shapes of bacteria

Answer 2

• spirochete
• budding and appendaged bacteria
• filamentous bacteria

Question 3

what does filamentous bacteria look like

Answer 3

It’s continuous long branching.

Question 4

how do characteristic arrangments occur?

Answer 4

• When cells of some prokaryotes remain together after cell division, forming characteristic arrangments.

Question 5

where does bacteria Staphlyococcus get its name?

Answer 5

• staph means grape-like bc they form grape-like clusters.

Question 6

what does cell morpholgoy not do? But what can it be used for?

Answer 6

• morphology typically does not predict physiology, ecology, phylogeny (doesn’t tell us how it will behave or disease it causes)
• but it can be used diagnostically (to identify the bacteria)

Question 7

what selective forces may be involved in setting the morphology

Answer 7

If they need:
*optimization for nutrient uptake (then small cells and those with high surface-to-volume ratio)
* swimming motility (then helical or spiral-shaped cells)
* gliding motility (then filamentous bacteria)

Question 8

even if bacteria have the shape helical or spiral shaped it doesn’t mean they’re _, but this shape usually is.

Answer 8

doesn’t mean they’re motile

Question 9

what is the size range for prokaryotes?

Answer 9

0.2 um to >700 um in diameter

Question 10

size range for eukaryotes

Answer 10

• 10 to >200 um in diameter

Question 11

what can be generally said about prokaryotes vs eukaryotes size, despite the overlap in size?

Answer 11

• the vast majority of prokaryotes are very small compared with eukaryotes.

Question 12

what is the average prokaryote size

Answer 12

1 um

Question 13

what is the size of e. coli

Answer 13

1.0 x 3.0 um

Question 14

what’s an example of a rare case where a prokaryote is large

Answer 14

• epulopiscium fishelsonii

Question 15

small cells have a higher S/V ratio, what are the advantages to this?

Answer 15

• supports greater nutrient exchange per unit cell volume
• Allows faster growth
• which allows them to achieve high population numbers
• leading to increased rate of evolutionary change

Question 16

what is the lower limit of cell size, what conditions cause small bacteria

Answer 16

• cellular organisms cannot be <0.15 um in diameter
  -conditions:
• open oceans tend to contain small cells (0.2-0.4 um in diameter)
• many pathogenic bacteria are also small, and have small genomes
  -this is possible bc they are missing many genes whose functions are supplied to them by host

Question 17

how is it possible that pathogenic bacteria are so small

Answer 17

They have smaller genomes, as they don’t need genes whose functions are supplied to them by host.