L6

Question 1

What is the energy source for giant hot vent worms?

Answer 1

Have large trophosome with sulphide-oxidizing bacteria. Energy released from oxidation powers Calvin-Benson cycle

Question 2

What do the red branchial filaments have?

Answer 2

Hemoglobin

Question 3

How was bacterial metabolism in hot vent worms demonstrated?

Answer 3

1. Elemental sulfur in trophosome
2. TEM: trophosomal cells were packed with
   bacteria
3. Assays for sulfide oxidation
   (benzyl viologen as alternative electron acceptor)
4. Assays for RuBisCO
   (Calvin-Benson cycle)
5. Sulfide stimulation of 14C02 fixation

Question 4

How does bacterial metabolism in the gutless bivalves soleyma spp. work?

Answer 4

Have sulphide-oxidizing bacteria living within cells of the ctenidia

Question 5

What shape are the bacteria?

Answer 5

Rod-shaped

Question 6

What is a bivalve that uses sulfide oxidizing bacteria to live in the deep ocean? Why does it have lots of hemoglobin?

Answer 6

• The giant vent clam, has bacteria in cells of its body

- lots of hemoglobin to pull O2 out of surrounding sea water

Question 7

How does the lepetodrilus gastropod acquire food?

Answer 7

• suspension feeds

- farms bacterial endosymbionts and directly eats those sulfur-oxidizing bacteria

Question 8

How does the scaly foot gastropod acquire food? What is the scaly foot made of?

Answer 8

• has INTRACELLULAR sulfur oxidizing bacteria in esophageal gland
• shell and sclerites of food covered in iron sulfide

Question 9

Why are high sulfide levels toxic to aerobic organisms?

Answer 9

• binds to cytochrome oxidase in electron transport chain of mitochondria
• sulfide detoxified by oxidation

Question 10

How can organisms defend against sulfide toxicity?

Answer 10

• temporary switch to anaerobiosis (glycolysis)
• external coating of sulfide-oxidizing bacteria
• sulfide-binding hemoglobin
• sulfide-binding proteins
• partial oxidation of sulfide in mitochondria

Question 11

How does the gutless oligochaete survive coastal oligotrophic and anoxic sediments?

Answer 11

• sulfide oxidizing bacteria cultured between cuticle and epidermal epithelium
• bacteria phagocytized by epidermal cells
• vertical transmission of bacterial symbionts

Question 12

How do gutless oligochaetes obtain nutrition?

Answer 12

from their symbionts

Question 13

What is the significance of the yeti crab?

Answer 13

• Have chelipeds w long setae that are coated by sulfide oxidizing bacteria
• 3rd pair maxillipeds can harvest bacteria to eat from setae or from environment

Question 14

What is special about hemoglobin in siboglinid hot vent worms? What does this do

Answer 14

has binding sites for BOTH O2 and H2S

-this helps prevent toxicity and delivers H2S to the symbionts in the trophosome

Question 15

How does partial oxidation of sulfide in mitochondria work? How does it help? What happens when S concentration get high?

Answer 15

1. S can be taken up by mito if not too concentrated, mito have systems to oxidize sulfide and energy that is released is harvested as ATP
2. this helps animals living in mudflats detoxify by producing non-toxic thiosulfate
3. It doesn’t work at high H2S [] and is toxic to the mitochondria

Question 16

What are the energy/carbon source of thiotrophic bacteria?

Answer 16

energy source: H2S

C source: CO2

Question 17

What are the energy/carbon source of methanotrophic bacteria?

Answer 17

energy: methane
C: methane

Question 18

Is dual symbiosis of methanotropic/thiotropic bacteria possible? What is an example

Answer 18

Yes

Gill bacteriocytes in bathymodiolus contain both types

Question 19

What is unique about methane ice worms?

Answer 19

They are colonized on surface by methanotrophic bacteria.

Question 20

What do annelid worms specialists feed on?

Answer 20

Methanotropic bacteria, but they don’t have them as symbionts