Geomicrobiology is the scientific field at the intersection of geology and microbiology and is a major subfield of geobiology. It concerns the role of microbes on geological and geochemical processes and effects of minerals and metals to microbial growth, activity and survival. Such interactions occur in the geosphere, the atmosphere and the hydrosphere. Geomicrobiology studies microorganisms that are driving the Earth's biogeochemical cycles, mediating mineral precipitation and dissolution, and sorbing and concentrating metals. The applications include for example bioremediation, mining, climate change mitigation and public drinking water supplies.
Hydrothermal vents are fissures on the seabed from which geothermally heated water discharges. They are commonly found near volcanically active places, areas where tectonic plates are moving apart at mid-ocean ridges, ocean basins, and hotspots. Hydrothermal deposits are rocks and mineral ore deposits formed by the action of hydrothermal vents.
Kamaʻehuakanaloa Seamount is an active submarine volcano about 22 mi (35 km) off the southeast coast of the island of Hawaii. The top of the seamount is about 3,200 ft (975 m) below sea level. This seamount is on the flank of Mauna Loa, the largest active subaerial shield volcano on Earth. Kamaʻehuakanaloa is the newest volcano in the Hawaiian–Emperor seamount chain, a string of volcanoes that stretches about 3,900 mi (6,200 km) northwest of Kamaʻehuakanaloa. Unlike most active volcanoes in the Pacific Ocean that make up the active plate margins on the Pacific Ring of Fire, Kamaʻehuakanaloa and the other volcanoes of the Hawaiian–Emperor seamount chain are hotspot volcanoes and formed well away from the nearest plate boundary. Volcanoes in the Hawaiian Islands arise from the Hawaii hotspot, and as the youngest volcano in the chain, Kamaʻehuakanaloa is the only Hawaiian volcano in the deep submarine preshield stage of development.
Sulfate-reducing microorganisms (SRM) or sulfate-reducing prokaryotes (SRP) are a group composed of sulfate-reducing bacteria (SRB) and sulfate-reducing archaea (SRA), both of which can perform anaerobic respiration utilizing sulfate (SO2−
4) as terminal electron acceptor, reducing it to hydrogen sulfide (H2S). Therefore, these sulfidogenic microorganisms "breathe" sulfate rather than molecular oxygen (O2), which is the terminal electron acceptor reduced to water (H2O) in aerobic respiration.
The iron cycle (Fe) is the biogeochemical cycle of iron through the atmosphere, hydrosphere, biosphere and lithosphere. While Fe is highly abundant in the Earth's crust, it is less common in oxygenated surface waters. Iron is a key micronutrient in primary productivity, and a limiting nutrient in the Southern ocean, eastern equatorial Pacific, and the subarctic Pacific referred to as High-Nutrient, Low-Chlorophyll (HNLC) regions of the ocean.
Geobiology is a field of scientific research that explores the interactions between the physical Earth and the biosphere. It is a relatively young field, and its borders are fluid. There is considerable overlap with the fields of ecology, evolutionary biology, microbiology, paleontology, and particularly soil science and biogeochemistry. Geobiology applies the principles and methods of biology, geology, and soil science to the study of the ancient history of the co-evolution of life and Earth as well as the role of life in the modern world. Geobiologic studies tend to be focused on microorganisms, and on the role that life plays in altering the chemical and physical environment of the pedosphere, which exists at the intersection of the lithosphere, atmosphere, hydrosphere and/or cryosphere. It differs from biogeochemistry in that the focus is on processes and organisms over space and time rather than on global chemical cycles.
The important sulfur cycle is a biogeochemical cycle in which the sulfur moves between rocks, waterways and living systems. It is important in geology as it affects many minerals and in life because sulfur is an essential element (CHNOPS), being a constituent of many proteins and cofactors, and sulfur compounds can be used as oxidants or reductants in microbial respiration. The global sulfur cycle involves the transformations of sulfur species through different oxidation states, which play an important role in both geological and biological processes. Steps of the sulfur cycle are:
Iron-oxidizing bacteria are chemotrophic bacteria that derive energy by oxidizing dissolved iron. They are known to grow and proliferate in waters containing iron concentrations as low as 0.1 mg/L. However, at least 0.3 ppm of dissolved oxygen is needed to carry out the oxidation.
Lithotrophs are a diverse group of organisms using an inorganic substrate to obtain reducing equivalents for use in biosynthesis or energy conservation via aerobic or anaerobic respiration. While lithotrophs in the broader sense include photolithotrophs like plants, chemolithotrophs are exclusively microorganisms; no known macrofauna possesses the ability to use inorganic compounds as electron sources. Macrofauna and lithotrophs can form symbiotic relationships, in which case the lithotrophs are called "prokaryotic symbionts". An example of this is chemolithotrophic bacteria in giant tube worms or plastids, which are organelles within plant cells that may have evolved from photolithotrophic cyanobacteria-like organisms. Chemolithotrophs belong to the domains Bacteria and Archaea. The term "lithotroph" was created from the Greek terms 'lithos' (rock) and 'troph' (consumer), meaning "eaters of rock". Many but not all lithoautotrophs are extremophiles.
The Endeavour Hydrothermal Vents are a group of hydrothermal vents in the north-eastern Pacific Ocean, located 260 kilometres (160 mi) southwest of Vancouver Island, British Columbia, Canada. The vent field lies 2,250 metres (7,380 ft) below sea level on the northern Endeavour segment of the Juan de Fuca Ridge. In 1982, dredged sulfide samples were recovered from the area covered in small tube worms and prompted a return to the vent field in August 1984, where the active vent field was confirmed by HOV Alvin on leg 10 of cruise AII-112.
The class Zetaproteobacteria is the sixth and most recently described class of the Pseudomonadota. Zetaproteobacteria can also refer to the group of organisms assigned to this class. The Zetaproteobacteria were originally represented by a single described species, Mariprofundus ferrooxydans, which is an iron-oxidizing neutrophilic chemolithoautotroph originally isolated from Kamaʻehuakanaloa Seamount in 1996 (post-eruption). Molecular cloning techniques focusing on the small subunit ribosomal RNA gene have also been used to identify a more diverse majority of the Zetaproteobacteria that have as yet been unculturable.
The Beebe Hydrothermal Vent Field is located just south of Grand Cayman in the Caribbean, on the north side of the Mid-Cayman Spreading Centre in the Cayman Trough. Approximately 24 kilometres (15 mi) south of Beebe is the Von Damm Vent Field.
Beth N. Orcutt is an American oceanographer whose research focuses on the microbial life of the ocean floor. As of 2012, she is a senior research scientist at the Bigelow Laboratory for Ocean Sciences. She is also a senior scientist of the Center for Dark Energy Biosphere Investigations, a Science and Technology Center funded by the National Science Foundation and headquartered at the University of Southern California and part of the Deep Carbon Observatory Deep Life Community. Orcutt has made fundamental contributions to the study of life below the seafloor, particularly in oceanic crust and has worked with the International Scientific Ocean Drilling Program.
Marine biogeochemical cycles are biogeochemical cycles that occur within marine environments, that is, in the saltwater of seas or oceans or the brackish water of coastal estuaries. These biogeochemical cycles are the pathways chemical substances and elements move through within the marine environment. In addition, substances and elements can be imported into or exported from the marine environment. These imports and exports can occur as exchanges with the atmosphere above, the ocean floor below, or as runoff from the land.
Matthew Schrenk is an associate professor in geomicrobiology at Michigan State University. His research focuses on the diversity, distribution, and activities of microorganisms in the deep subsurface biosphere. His work couples molecular biological approaches and geochemical analyses to investigate microbial ecosystems. Schrenk investigates high pH environments fueled by underground serpentinization reactions between water and certain rock types and hydrothermal vent systems along the ocean floor that are driven by volcanic activity.
Frederick (Rick) Colwell is a microbial ecologist specializing in subsurface microbiology and geomicrobiology. He is a professor of ocean ecology and biogeochemistry at Oregon State University, and an adjunct and affiliate faculty member at Idaho State University.
The hydrothermal vent microbial community includes all unicellular organisms that live and reproduce in a chemically distinct area around hydrothermal vents. These include organisms in the microbial mat, free floating cells, or bacteria in an endosymbiotic relationship with animals. Chemolithoautotrophic bacteria derive nutrients and energy from the geological activity at Hydrothermal vents to fix carbon into organic forms. Viruses are also a part of the hydrothermal vent microbial community and their influence on the microbial ecology in these ecosystems is a burgeoning field of research.
Vailuluʻu is a volcanic seamount discovered in 1975. It rises from the sea floor to a depth of 593 m (1,946 ft) and is located between Taʻu and Rose islands at the eastern end of the Samoa hotspot chain. The basaltic seamount is considered to mark the current location of the Samoa hotspot. The summit of Vailuluʻu contains a 2 km wide, 400 m deep oval-shaped caldera. Two principal rift zones extend east and west from the summit, parallel to the trend of the Samoan hotspot. A third less prominent rift extends southeast of the summit.
The deep biosphere is the part of the biosphere that resides below the first few meters of the surface. It extends down at least 5 kilometers below the continental surface and 10.5 kilometers below the sea surface, at temperatures that may reach beyond 120 °C (248 °F) which is comparable to the maximum temperature where a metabolically active organism has been found. It includes all three domains of life and the genetic diversity rivals that on the surface.
Annette Summers Engel is an American earth scientist who is Donald and Florence Jones Professor of Aqueous Geochemistry at the University of Tennessee. Her research considers how microbes interact with rocks and minerals. She was elected Fellow of the American Association for the Advancement of Science in 2019.
