Chapter 22

Question 1

Relationships between microbes

Answer 1

Symbiosis—rela:onships between microbes
•  Parasite—microorganism benefits at the expense of the host
•  Pathogenic—microorganism causes disease in the host
•  Commensal—microorganism does not affect host
•  Mutualis:c—the microbe benefits the host

Question 2

Symbioses between microbes: Liche

Answer 2

Fungus and alga or cyanobacteria living in symbiosis with one another
•  Phototroph produces organic material for fungus
•  Fungus

Question 3

Fungus and alga or cyanobacteria living in symbiosis with one another
•  Phototroph produces organic material for fungus
•  Fungus

Answer 3

  Anchors phototroph–  Produces lichen acids to

dissolve inorganic nutrients –  Water uptake

Question 4

Consortia

Answer 4

Microbial mutualisms

•  Example: 13-‐‐69 Non-‐‐mo:le phototrophic green sulfur bacteria (epibionts) and one mo:le non-‐‐phototrophic bacteria

Question 5

Consortia

Answer 5

Epibiont in genus Chlorobium
•  Scotophobotaxis•  Chemotaxis towards sulfide •  Fusion of periplasms•  Epibiont supplies α-‐‐ketoglutarate to central
microbe

Question 6

Legume-‐‐root nodule symbiosi

Answer 6

•   Legumes—clover, alfalfa, beans, peas, soybeans
•   Rhizobia—nitrogen-‐‐fixing symbionts of plants
•   Root nodules—rhizobial infec:on of legume roots

Question 7

Root nodules

Answer 7

  Leghemoglobin—binds oxygen to protect nitrogenases, produced by rhizobia
•  10,000:1—bound oxygen:free oxygen in nodules

Question 8

Bacteroid

Answer 8

differen:ated rhizobial cell

Question 9

Stem nodules on Sesbania are formed

by Azorhizobium

Answer 9

Tropical aqua:c legumes

•  Some contain Bradyrhizobium -‐‐ photosynthe:c

Question 10

Non-‐‐legume nitrogen-‐‐fixing symbiosis

Answer 10

Azolla-‐‐Anabaena
– Rice paddies
– Red arrow -‐‐ heterocyst

•  Alnus-‐‐Frankia
– Vesicles for N2 fixa:on

Question 11

Agrobacterium and crown gall disease

Answer 11

Uncontrolled growth of :ssue
•  A. tumefaciens
•  Ti (tumor inducing) plasmid must be presen

Question 12

Agrobacterium T-‐‐DNA is transferred to the plant

Answer 12

Genes for tumor forma:on and opines
•  Opines—modified amino acids that serve as source of carbon and nitrogen for bacteria
– Octopine– Nopaline

Question 13

Symbioses between microbes: Mycorrhizae

Answer 13

•  “fungus root” •  Partners coevolved •  Photosynthe:c partner
provides carbon compounds
•  Fungal partner allows for
absorp:on and nutrient availability

Question 14

Symbioses between microbes: Endomycorrhizae

Answer 14

•  Fungal mycelium embeds in root :ssue •  Most common—arbuscular mycorrhizae -‐‐
Glomeromycota
•  Hyphopodium (HP)—aeachment structure •  Spore (SP)

I