1. Hydrothermal Vents I: Chemoautotrophs
Chris Choe

2. Hydrothermal Vents I
Vents on bottom of ocean from which superheated water flows
Form near areas with tectonic and volcanic activity.
BBC
NOAA

3. Hydrothermal Vents II

4. Hydrothermal Vents III
Water picks up and ejects minerals
Notably, dissolved sulfates in water are converted to hydrogen sulfide through superheating
Autotrophs can use hydrogen sulfides for chemosynthesis
Note: Not all hydrothermal vents vent the same minerals. “Black smokers” tend to vent iron sulfides, “white smokers” silicon, calcium, and barium compounds. Some just vent methane and hydrogen, etc.
Indiana State University, 2013

5. Chemoautotrophs
Hyper (or super) thermophilic chemo-autotropic bacteria are effectively the sole autotrophs for hydrothermal vents.
Provides the foundation for hydrothermal vent communities.
However, bacteria are generally not free-ranging; tend exist in symbiotic relationships with invertebrates near the vent.
Major Symbionts
Tube worms
Molluscs
Beggiatoa mats

6. Sulfur Bacteria
Bacteria that oxidize sulfides are the most common autotrophs in hydrothermal vent communities.
However, most can also undergo heterotrophic growth.
~37% of species can undergo fermentation, ~88% can do denitrification.
Sulfur reduction is also used
In general, bacteria have multiple methods for generating energy and carbon compounds.
State College of Florida, 2013

7. Methylotropes/Methanogens
Methanogens are bacteria that produce methane from carbone dioxide to generate energy.
Includes substrates like carbon dioxide, methanol, acetic acid
General reaction is CO2 + 4 H2 → CH4 + 2 H2O
Coenzyme M reductase is inhibited by sulfite (necessary for methanogenesis)
Sulfides react with oxygen to make anaerobic conditions (favors methanogenesis)
Fortunately, evolution allows hydrothermal vent methanogens to function regardless.
Methylotropes use one-carbon sources to generate energy
Substrates include cyanide, carbon monoxide, and methylamines
Teske et al 2003
ScienceDaily 2008

8. Iron, Manganese, Ammonium, Hydrogen
Autotrophs using these elements are generally less important than the ones using sulfur or one-carbon compounds
However, they still can play a substantial role in some hydrothermal vent communities, depending on the exact minerals/elements spewed out by the vents in the area.
Not much information on these bacteria and their role in hydrothermal vent communities as of yet.
ScienceDaily 2011

9. Photosynthesis?! In a word: yes.
Robert Blankenship found green sulfur bacteria in a black smoker vent field in 2003
Bacteria was capturing geothermal radiation using pigments and chlorosome, a photosynthetic antennae complex.
“An obligately photosynthetic bacterial anaerobe from a deep-sea hydrothermal vent” (Beatty, 2005)
ASU 2005

10. Tube Worms (Giant Tube Worm)
Related to tube worms closer to the surface
Red plume exchanges compounds with environment, white tube attached to vent surroundings
Has no mouth or digestive tract: has specialized organ (troposome) for chemo-autotrophic bacteria.
Bacteria provide tube worm with carbon compounds, tube worm provides bacteria with shelter, oxygen, and nitrates.
Bacteria constitute over 50% of total body mass. Hemoglobin is active in the presence of sulfides and reversibly binds to it.
Stephen Low Productions

11. Bivalve Molluscs Grow in crevices around vents
Lack guts, completely reliant on chemosynthetic bacteria for organic compounds
Bacteria grow in gills; clams provide carbon dioxide through gills, as well as shelter and proximity to vent minerals.
Bacterial colonies passed on during fertilization.
Bacterial colonies are not necessarily sulfur-based; colonies can be of different species, and can include methanogens.
Damm, 2002
Monterey Bay Aquarium Research Institute
Bathymodiolus
Calyptogena

12. Bibliography
1: ”Deep sea vents: Exploring a strange world.” BBC, 20 Feb 2013 < 2: ”Global compilation of confirmed and inferred vent sites.” NOAA Vents Program < 3: “Deep Hot Springs Discovered.” Marum Center for Marine Environmental Sciences < 4:”Deep Sea Vent Communities: Did Life Originate in the Abyss?” Indiana State University, 2013 < 5: “MARINE ENVIRONMENT AND PRIMARY PRODUCTIVITY”, State College of Florida, 2013 < 6: “Deep Sea Vent Mussels” Monterey Bay Aquarium Research Institute. Dec 17, 2009 < 7: Damm, Karen Von. “Crew Log of Karen Von.” University of New Hampshire 2002 < 8: Tseke, Andreas. “Gulf of Mexico Cruise Log” November 2010 < 9: “Quakes Under Pacific Floor Reveal Unexpected Circulatory System” The Earth Columbia Research Institute (picture from National Science Foundation) January < 10: Beatty, Thomas “An obligately photosynthetic bacterial anaerobe
from a deep-sea hydrothermal vent” PNAS March
11: “Giant Tube Worm, Riftia pachyptila” RedOrbit
12: “Hydrogen-Powered Symbiotic Bacteria Found in Deep-Sea Hydrothermal Vent Mussels” ScienceDaily Aug
13: “Researchers find photosynthesis deep within ocean” Arizone State University. June 15,
14: "East Pacific Vent at 9degN, 2,600meters on Tube Worm Pillar. Giant tubeworms form a large bush. “ Stephen Low Productions
15:”Lost City Pumps Life-Essential Chemicals At Rates Unseen At Typical Deep Ocean Hydrothermal Vents” ScienceDaily Feb
16: Teske et al. “Genomic Markers of Ancient Anaerobic Microbial Pathways: Sulfate Reduction, Methanogenesis, and Methane Oxidation “ The Biological Bulletin