Deep sea vent
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Description of Niche
Where located?
Physical Conditions?
What are the conditions in your niche? Temperature, pressure, pH, moisture, etc.
Influence by Adjacent Communities (if any)
Is your niche close to another niche or influenced by another community of organisms?
Conditions under which the environment changes
Do any of the physical conditions change? Are there chemicals, other organisms, nutrients, etc. that might change the community of your niche.
Who lives there?
Microbes Present
Many different kinds of archaea and chemolithotrophic bacteria live here. Studies have classified entire archaeal communities in deep-sea hydrothermal vent chimney structures. (http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pubmed&pubmedid=11472939) Scientists discovered deep-sea hydrothermal vents in 1979 and many microorganisms have been isolated from these deep-sea samples.
The majority of the microbes that live in this niche include hyperthermophiles and thermophiles from both the bacterial and archaeal domains. Recent studies have shown and increasing number of unclassified and uncultivated thermophiles. This leads scientists to believe that these communities are very phylogenetically diverse. Major types of bacteria that live near these vents are mesophilic sulfur bacteria. These bacteria are able to achieve high biomass densities due to their unique physiological adaptations. For example, Beggiatoa spp. is able to carry an internal store of nitrate as an electron acceptor that helps with the harvesting of free sulfide in the upper sediment region of the vents. Page 70
Some bacterial samples contained bacterial specific to the genera Thermotoga and Thermosipho. An analysis of a specific morphotype revealed that it was an anaerobic autotrophic sulfur and thiosulfate-reducing strain of bacteria but did not belong to any known phyla. It belongs to a branch between the orders Aquificales and Thermotogales. The new bacterium was named Desulfurobacterium thermolithotrophicum.
Recent studies have shown that large populations of extremely halophilic archaea inhabit the inside structures of black smoker chimneys. These bacteria belong to the genera Halomonas and Marinobacter. The existence of these halophilic archaea is probably due to the brines/salt deposits found in deep-sea hydrothermal systems. http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pubmed&pubmedid=11472939
Based on microbiological, geochemical, and geophysical observations, some scientists believe that a whole new biosphere exists beneath active hydrothermal vents. This idea is supported by the detection of microbial rDNA in the black smoker vent water. However it is difficult to conclude if there is a true microbial population living under black smoker vents because deep ocean water is continuously being filtered underneath sea floor basalts and pumped out of black smoker vents. http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pubmed&pubmedid=11472939
Are there any other non-microbes present?
Plants? Animals? Fungi? etc.
Microbe interaction with each other or other organisms
The hydrothermal vent tubeworm Riftia pachyptila is well-known for its symbiotic relationship with sulfide oxidizing chemoautotrophic bacteria found in the cells of its trophosome tissue. The tube worms have no gut so the bacteria live inside them. Tubeworms have red plumes which contain hemoglobin. The hemoglobin combines hydrogen sulfide and then gives this product to the bacteria. The bacteria, in return, give back carbon compounds to the worm. This interaction requires specific communications mechanism in both the bacteria and the worms. Scientists have found two classes of genes from Riftia symbionts that encode for environmental sensors, response regulators, and components of bacterial chemotaxis systems.
In detail, scientists have found functional genes encoding the following: members of the two-competent regulatory family, the methyl-accepting chemotaxis protein, and the flagellar C protein of the eubacterial flagellum. These functional genes strongly support the idea that these bacteria have a motile, free stage and are then acquired by Riftia each new generation. (page 71)
Do the microbes change their environment?
Do they alter pH, attach to surfaces, secrete anything, etc. etc.
Microbe metabolism affecting the environment
The primary source of metabolism for providing food is through animal-bacteria symbiosis. These bacteria are typically chemolithotrophic bacteria. In many worms, they have a layer of tissue called trophosome that fills the body cavity and allows these chemolithotrophic bacteria to live symbiotically in these trophosomes where they can oxidize sulfide. Enzymes in the trophosome also have the capacity to oxidize hydrogen sulfide. The energy produced can be used to drive net fixation of CO2 and to reduce nitrate to ammonia. A mechanism to avoid poisoning aerobic respiration by hydrogen sulfide is protected by sulfide binding proteins in the blood. The idea is to prevent as little free floating sulfide as possible.
Many invertebrates also show a range of O2 consumption that is similar to species that live closer to the surface. Besides a difference in thermal effects, there is no decline of O2 consumption, strongly indicating the importance of endosymbionts. Other organisms, such as deep sea pelagic animals will show a lower O2 consumption due to its inability to swim. If they lose the ability to swim, they can save that energy and lower their O2 consumption.
Current Research
1. Current research is being done to learn more about photosynthesis evolution. Some scientists believe that photosynthesis evolved from geothermal vents and then sunlight. This idea raises the possibility that photosynthesis originated from deep-ocean hydrothermal vents and then dispersed upwards to shallow-waters and more sunlight. The first photosynthetic bacteria to be found living at deep sea vents were discovered in 1998. The overall question was: what were the morphological and physiological properties of this new bacterium.
They addressed this question by extracting samples from non-buoyant regions of plumes emitted from the hydrothermal vents. The scientists then brought the samples on board the ship and stored them in sterile bottles at 4 degrees Celsius. The scientists plated the bacteria and incubated them aerobically at room temperature in the dark for 5 days. After the colonies were identified, the bacteria were incubated at 30 degrees Celsius for another 5 days. The bacteria’s capability for anaerobic photosynthetic growth was tested in screw-cap test tubes and in agar by using media for purple sulfur and non-sulfur bacteria. However, none of the strains tested were able to grow anaerobically in light.
This particular species had bacterial chlorophyll alpha and carotenoids. It is a member of the aerobic anoxygenic photosynthetic bacteria due to its following characteristics: the inability to grow anaerobically in the light, the small number of photosynthetic units it has, and its abundance of carotenoids. Aerobic anoxygenic photosynthetic bacteria belong under the subclass of Proteobacteria.
Aerobic anoxygenic photosynthetic bacteria are different in comparison to purple sulfur or non-sulfur bacteria, because they can utilize light as a source of energy for anaerobic growth. Photosynthetic activity in these bacteria is shown by the following three characteristics: the reversible photo-oxidation of cytochromes and the reversible photo-bleaching of bacterial chlorophyll, photo-inhibition of respiration, and light-stimulated increase in ATP pools which lead to an increase in growth rate and biomass production. The scientists concluded that light is a secondary source of energy for these bacteria.
References
Edited by [Vicky Chen , Vicky Kuo , Ban Lam , Pan Lu , Tam Pham , Cassie Tom], students of Rachel Larsen
