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Hydrothermal Vents I: Chemoautotrophs Chris Choe.

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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. BBCNOAA

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 CO H 2 → CH H 2 O – 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. BathymodiolusCalyptogena Monterey Bay Aquarium Research Institute Damm, 2002

12 Bibliography 1: ”Deep sea vents: Exploring a strange world.” BBC, 20 Feb : ”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, : “MARINE ENVIRONMENT AND PRIMARY PRODUCTIVITY”, State College of Florida, : “Deep Sea Vent Mussels” Monterey Bay Aquarium Research Institute. Dec 17, : Damm, Karen Von. “Crew Log of Karen Von.” University of New Hampshire : Tseke, Andreas. “Gulf of Mexico Cruise Log” November : “Quakes Under Pacific Floor Reveal Unexpected Circulatory System” The Earth Columbia Research Institute (picture from National Science Foundation) January : Beatty, Thomas “An obligately photosynthetic bacterial anaerobe from a deep-sea hydrothermal vent” PNAS March : “Giant Tube Worm, Riftia pachyptila” RedOrbit : “Hydrogen-Powered Symbiotic Bacteria Found in Deep-Sea Hydrothermal Vent Mussels” ScienceDaily Aug : “Researchers find photosynthesis deep within ocean” Arizone State University. June 15, : "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 : Teske et al. “Genomic Markers of Ancient Anaerobic Microbial Pathways: Sulfate Reduction, Methanogenesis, and Methane Oxidation “ The Biological Bulletin 2003


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