Mark Alexander Lever is a microbial ecologist and biogeochemist who studies the role of microorganisms in the global carbon cycle. He is a professor of biogeochemistry and geobiology at the Marine Science Institute of the University of Texas at Austin.
Mark A. Lever earned his MA in Marine Biology at the Boston University Marine Program at Woods Hole in 2002 and his PhD in Marine Sciences at the University of North Carolina, Chapel Hill in 2008. He worked as a postdoctoral scientist at Aarhus University from 2009 to 2014, and was a faculty member at ETH Zurich from 2014 to 2022, before joining the University of Texas at Austin. Lever was a member of the Deep Life Scientific Steering Committee and Synthesis Group 2019 for the Deep Carbon Observatory, [1] and vice-chair of the European Cooperation of Science and Technology network "COST", and is an associate editor for Frontiers in Microbiology. [2]
In his research, Mark A. Lever investigates the factors that determine the production, fate, and storage of organic carbon in aquatic sediments and in the Earth's crust. [3] [4] [5] In 2013 he discovered that microbes survive deep in the oceanic crust by living off of chemical energy released by water-rock reactions. [6] In addition, his research group is investigating the impact of macrofaunal bioturbation on microbial community structure and the sedimentary carbon cycle, [7] the ecological and physiological strategies of microbial life inhabiting long-term energy-limited environments, [8] [9] and the potential for sediments to serve as genetic archives of past environmental change. [10]
Thiomargarita is a genus which includes the vacuolate sulfur bacteria species Thiomargarita namibiensis, Candidatus Thiomargarita nelsonii, and Ca. Thiomargarita joergensii. In 2022, scientists working in a Caribbean mangrove discovered an extremely large member of the genus, provisionally named T. magnifica, whose cells are easily visible to the naked eye at up to 2 centimetres (0.79 in) long.
A biogeochemical cycle, or more generally a cycle of matter, is the movement and transformation of chemical elements and compounds between living organisms, the atmosphere, and the Earth's crust. Major biogeochemical cycles include the carbon cycle, the nitrogen cycle and the water cycle. In each cycle, the chemical element or molecule is transformed and cycled by living organisms and through various geological forms and reservoirs, including the atmosphere, the soil and the oceans. It can be thought of as the pathway by which a chemical substance cycles the biotic compartment and the abiotic compartments of Earth. The biotic compartment is the biosphere and the abiotic compartments are the atmosphere, lithosphere and hydrosphere.
Methanogenesis or biomethanation is the formation of methane coupled to energy conservation by microbes known as methanogens. Organisms capable of producing methane for energy conservation have been identified only from the domain Archaea, a group phylogenetically distinct from both eukaryotes and bacteria, although many live in close association with anaerobic bacteria. The production of methane is an important and widespread form of microbial metabolism. In anoxic environments, it is the final step in the decomposition of biomass. Methanogenesis is responsible for significant amounts of natural gas accumulations, the remainder being thermogenic.
Microbial ecology is the ecology of microorganisms: their relationship with one another and with their environment. It concerns the three major domains of life—Eukaryota, Archaea, and Bacteria—as well as viruses.
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.
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.
Campylobacterota are a phylum of bacteria. All species of this phylum are Gram-negative.
Gammaproteobacteria is a class of bacteria in the phylum Pseudomonadota. It contains about 250 genera, which makes it the most genus-rich taxon of the Prokaryotes. Several medically, ecologically, and scientifically important groups of bacteria belong to this class. It is composed by all Gram-negative microbes and is the most phylogenetically and physiologically diverse class of Proteobacteria.
Thioploca is a genus of filamentous sulphur-oxidizing bacteria which occurs along 3,000 kilometres (1,900 mi) of coast off the west of South America. Was discovered in 1907 by R. Lauterborn classified as belonging to the order Thiotrichales, part of the Gammaproteobacteria. They inhabit as well marine as freshwater environments, with vast communities present off the Pacific coast of South America and other areas with a high organic matter sedimentation and bottom waters rich in nitrate and poor in oxygen. A large vacuole occupies more than 80% of their cellular volume and is used as a storage for nitrate. This nitrate is used for the sulphur oxidation, an important characteristic of the genus. Due to their unique size in diameters, ranging from 15-40 µm, they are considered part of the largest bacteria known. Because they use both sulfur and nitrogen compounds they may provide an important link between the nitrogen and sulphur cycles. They secrete a sheath of mucus which they use as a tunnel to travel between the sulfide containing sediment and the nitrate containing sea water.
The Guaymas Basin is the largest marginal rift basin located in the Gulf of California. It made up of the northern and southern trough and is linked to the Guaymas Fault to the north and the Carmen Fault to the south. The mid-ocean ridge system is responsible for the creation of the Guaymas Basin and giving it many features such as hydrothermal circulation and hydrocarbon seeps. Hydrothermal circulation is a significant process in the Guaymas Basin because it recycles energy and nutrients which are instrumental in sustaining the basin's rich ecosystem. Additionally, hydrocarbons and other organic matter are needed to feed a variety of organisms, many of which have adapted to tolerate the basin's high temperatures.
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.
Dissimilatory nitrate reduction to ammonium (DNRA), also known as nitrate/nitrite ammonification, is the result of anaerobic respiration by chemoorganoheterotrophic microbes using nitrate (NO3−) as an electron acceptor for respiration. In anaerobic conditions microbes which undertake DNRA oxidise organic matter and use nitrate (rather than oxygen) as an electron acceptor, reducing it to nitrite, then ammonium (NO3−→NO2−→NH4+).
Fumio Inagaki is a geomicrobiologist whose research focuses on the deep subseafloor biosphere. He is the deputy director of the Research and Development Center for Ocean Drilling Science and the Kochi Institute for Core Sample Research, both at the Japan Agency for Marine-Earth Science and Technology (JAMSTEC).
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.
Microbial oxidation of sulfur is the oxidation of sulfur by microorganisms to build their structural components. The oxidation of inorganic compounds is the strategy primarily used by chemolithotrophic microorganisms to obtain energy to survive, grow and reproduce. Some inorganic forms of reduced sulfur, mainly sulfide (H2S/HS−) and elemental sulfur (S0), can be oxidized by chemolithotrophic sulfur-oxidizing prokaryotes, usually coupled to the reduction of oxygen (O2) or nitrate (NO3−). Anaerobic sulfur oxidizers include photolithoautotrophs that obtain their energy from sunlight, hydrogen from sulfide, and carbon from carbon dioxide (CO2).
The sulfate-methane transition zone (SMTZ) is a zone in oceans, lakes, and rivers typically found below the sediment surface in which sulfate and methane coexist. The formation of a SMTZ is driven by the diffusion of sulfate down the sediment column and the diffusion of methane up the sediments. At the SMTZ, their diffusion profiles meet and sulfate and methane react with one another, which allows the SMTZ to harbor a unique microbial community whose main form of metabolism is anaerobic oxidation of methane (AOM). The presence of AOM marks the transition from dissimilatory sulfate reduction to methanogenesis as the main metabolism utilized by organisms.
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.
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.
Hydrogen sulfide chemosynthesis is a form of chemosynthesis which uses hydrogen sulfide. It is common in hydrothermal vent microbial communities Due to the lack of light in these environments this is predominant over photosynthesis
Helle Ploug is marine scientist known for her work on particles in seawater. She is a professor at the University of Gothenburg, and was named a fellow of the Association for the Sciences of Limnology and Oceanography in 2017.
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