Hydrothermal Vent Biology-Lecture 21

Question 1

What are hydrothermal vents

Answer 1

1. Cold water seeps into the crust-> becomes heated
2. Minerals leach from rock into hot water
3. Dissolved Metal such as Fe, Cu, Zn
4. Hot water under pressure spews out vents-> air is pressurized
5. vent fluid toxic to most life

Question 2

Black Smokers vs. White smokers

Answer 2

Black smokers- Hottest of all vents
-spews out Fe and sulfide
these react and precipitate giving the smoker its color and forming a black chimney

White smokers- Silica and CaSO4 gives white smoke
fluid rich in barium, calcium and silicon

Observed as fast spreading ridges characterized by high temperature and volcanic activity

Question 3

Temperature and Chemical gradients

Answer 3

-Highest temp at which microbial growth has been observed is 122C=> deep sea hydrothermal vent archaea

• Hydrothermal geochemistry strongly influences the composition and metabolism of microbial communities along mixing gradients
• adaptations to dynamic conditions (gradients) include motility and metabolic versatility, which provide adbilityt to find preferred environments
• some organisms maintain their position in the thermochemical gradient by attaching to surfaces as biofilms

Question 4

temperature and chemistry of hydrothermal vents

Answer 4

Ocean water and vent fluids provide extremes
Ocean water is rich in O2 and NO3

Vent fluid is very hot, has an acidic pH, is anaerobic, rich in dissolved metals and has H2S and CH3

Question 5

What role do chemolithoautotrophs play in these systems?

Answer 5

They gain energy from oxidizing reduced compounds released from vents
—> Hydrogen oxidizers, Fe oxidizers, sulfide oxidizers

All oxidize inorganic compounds for energy using O2 as a terminal electron accapetor (or nitrate) AND they fix carbon

—> All life in vents is depended on these microbes

Question 6

Biggiatoa

Answer 6

A mat forming sulfur oxidizer-> Store elemental sulfur, form white shaggy mats
White because sulfur granules from sulfur oxidation

With cells up to 200 microns, largest prokaryotes

Question 7

How does autotrophy play a role in fixing CO2?

Answer 7

Via the Calvin-Benson cycle and enzymes: ribulose diphosphate carboxylaseand phosphoribulokinase

Question 8

CO2 fixing pathways also distributed along thermal gradients

Answer 8

<20C: Calvin cycle-energetically costly O2 tolerant=> main way of fixing CO2

20-90C: reductive TCA cycle-energy efficient and O2 sensitive

> 90C: decarboxylate-4-hydroxybutyrate pathway used by hyperthermophilic archaea

Question 9

What Kind of phototrophs have been found at these vents?

Answer 9

Obligate phototroph bacterium, chlorobacceae (green sulfur anoxygenic phototroph) that uses faint glow of black smoker for photosynthesis

FIRST ORGANISM TO USE A LIGHT OTHER THAN SUNLIGHT FOR PHOTOSYNTHESIS

Question 10

Symbiosis-Tube worms

Answer 10

Have a chitin sheath
Gill-Like red plumes absorb hydrogen sulfide from the hot water and oxygen from the cold water
- they get their red color from sulfur oxidizing bacteria

Gills extract oxygen and hydrogen sulfide from water and it gets delivered via Hb-> H2S is taken to the trophosome-> capillary beds in trophosome distribute hydrogen sulfide to symbiotic bacteria which oxidize H2S, fix carbon and grow and are phagocytosized by trophosome tissue

Question 11

Vent clams and Vent shrimp

Answer 11

clams: utilize symbiotic bacteria in large thick gills that use hemoglobin to deliver nutrients
shrimp: Predator that eat mussels and chimney microbes, use bioluminescent bacteria to survive

Question 12

What types of metabolic bacteria are present?

Answer 12

In sea water, we have aerobic respiratory bacteria that are psychrophiles, such as beggiatoria

In vent fluid, we have hyperthermophiles that are methanogens

Question 13

What kind of metabolism is present in vent plumes? What are vent plumes?

Answer 13

Plumes are where sea water and vent fluid mix
vent fluid contains reduced metals such as Fe2+, Mn2+, H2S and H2
Sea water contains O2 and nitrate

Metabolism times: aerobic, sulfide oxidation, H2 oxidation, Fe oxidation, Mn oxidation

Question 14

How does chemolithoautotrophy work?

Answer 14

They oxidize inorganic compounds for energy and use the ETC to generate PMF
Mainly use O2 or NO3 as electron acceptors
They fix C-Primary producers of this ecosystem

Question 15

2000 New vent

Answer 15

Highly alkaline vent fluid (pH 9-11) at lower temperatures, chimneys formed by ca present in vent fluid precipitating with carbonate in sea water

Question 16

What is Serpentization?

Answer 16

ABiotic formation of hydrogen, lies in the ultramafic rocks

Rich vent fluids here with H2 and CH4

Processed abiotically via serpentization

Microbiology at these sites are dominated by methanotrophs and hydrogen oxidizing bacteria