Hydrothermal Vent and Barophile MCBA P3 T

Hydrothermal vents

Source: 1. Madigan MT, Martinko JM and Parker J. (2014). Brock Biology of Microorganisms. 14th edition. Pearson/ Benjamin Cummings 2. Willey JM, Sherwood LM, and Woolverton CJ. (2013). Prescott’s Microbiology. 9th edition. McGraw Hill Higher Education. 3. Maier RM, Pepper IL and Gerba CP. (2009). Environmental Microbiology. 2nd edition, Academic Press Formation of Hydrothermal vents

• Hydrothermal vents are the result of seawater percolating down through fissures in the ocean crust in the vicinity of spreading centers or subduction zones (places on Earth where two tectonic plates move away or towards one another). The cold seawater is super-heated by hot magma, dissolving metals and minerals and reemerges to form the vents • A venting black smoker emits jets of particle-laden fluids. The particles are predominantly very fine-grained sulfide minerals formed when the hot hydrothermal fluids mix with near-freezing seawater. These minerals solidify as they cool, forming chimney-like structures. “Black smokers” are chimneys formed from deposits of iron sulfide, which is black. “White smokers” are chimneys formed from deposits of barium, calcium, and silicon, which are white • Seawater in hydrothermal vents may reach temperatures of over 700° Fahrenheit (300°C). Hot seawater in hydrothermal vents does not boil because of the extreme pressure at the depths where the vents are formed Hydrothermal Vent Ecosystem Bacteria in hydrothermal vent

• The bacteria are autotrophs that oxidize hydrogen sulfide in vent water to obtain energy, which is used to produce organic material. Chemosynthetic bacteria are the primary producers and form the base of vent food webs. All vent animals ultimately depend on the bacteria for food. • 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 hemoglobin in the worms combines hydrogen sulfide and then gives this product to the bacteria Barophiles/ piezophile

• A barophile is an organism that needs a high-pressure environment in order to grow. Barophiles are a type of an extremophile. • The term Barophil Barophil is coined by Zobell and Johnson in 1949 • Barotolerant: Those that can live at high pressures (100-500 atm) as well as in less extreme environment. • Obligate barophiles: Barophiles that cannot survive outside their high- pressure habitats (400-500 atm). • Extreme Barophile: Grows at pressures pressures higher than 500 atm • Halomonas salaria, a Gram-negative proteobacterium, is an example of an obligate barophile. It needs a pressure of 1000 atm. Shewanella, Moritella etc. • An example of a high-pressure habitat is the deep-sea environment (~62% of ocean biosphere), such as ocean floors, hydrothermal vents. Another is the subsurface rocks with high lithostatic pressures.

Characteristic of barophiles

• Increased binding capacity of enzymes with substrate • Poly unsaturated fatty acids in membranes • Pressure controlled gene expression • Many barophiles are sensitive to ultraviolet rays and are susceptible to UV radiation. They lack the essential mechanisms of DNA repair to counter the effects of UV radiation. Thus, many of them grow in darkness. • Because of this, they also tend to be psychrophilic. That means they live under cold temperatures, e.g. about 2-3 °C below 100 m.