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Anaerobic respiration is respiration using electron acceptors other than molecular oxygen (O2). Although oxygen is not the final electron acceptor, the process still uses a respiratory electron transport chain.
Geobacter is a genus of Proteobacteria. Geobacter species are anaerobic respiration bacterial species which have capabilities that make them useful in bioremediation. Geobacter was found to be the first organism with the ability to oxidize organic compounds and metals, including iron, radioactive metals, and petroleum compounds into environmentally benign carbon dioxide while using iron oxide or other available metals as electron acceptors. Geobacter species are also found to be able to respire upon a graphite electrode. They have been found in anaerobic conditions in soils and aquatic sediment.
Sulfur-reducing bacteria are microorganisms able to reduce elemental sulfur (S0) to hydrogen sulfide (H2S). These microbes use inorganic sulfur compounds as electron acceptors to sustain several activities such as respiration, conserving energy and growth, in absence of oxygen. The final product or these processes, sulfide, has a considerable influence on the chemistry of the environment and, in addition, is used as electron donor for a large variety of microbial metabolisms. Several types of bacteria and many non-methanogenic archaea can reduce sulfur. Microbial sulfur reduction was already shown in early studies, which highlighted the first proof of S0 reduction in a vibrioid bacterium from mud, with sulfur as electron acceptor and H2 as electron donor. The first pure cultured species of sulfur-reducing bacteria, Desulfuromonas acetoxidans, was discovered in 1976 and described by Pfennig Norbert and Biebel Hanno as an anaerobic sulfur-reducing and acetate-oxidizing bacterium, not able to reduce sulfate. Only few taxa are true sulfur-reducing bacteria, using sulfur reduction as the only or main catabolic reaction. Normally, they couple this reaction with the oxidation of acetate, succinate or other organic compounds. In general, sulfate-reducing bacteria are able to use both sulfate and elemental sulfur as electron acceptors. Thanks to its abundancy and thermodynamic stability, sulfate is the most studied electron acceptor for anaerobic respiration that involves sulfur compounds. Elemental sulfur, however, is very abundant and important, especially in deep-sea hydrothermal vents, hot springs and other extreme environments, making its isolation more difficult. Some bacteria – such as Proteus, Campylobacter, Pseudomonas and Salmonella – have the ability to reduce sulfur, but can also use oxygen and other terminal electron acceptors.
Microbial metabolism is the means by which a microbe obtains the energy and nutrients it needs to live and reproduce. Microbes use many different types of metabolic strategies and species can often be differentiated from each other based on metabolic characteristics. The specific metabolic properties of a microbe are the major factors in determining that microbe's ecological niche, and often allow for that microbe to be useful in industrial processes or responsible for biogeochemical cycles.
Microbial fuel cell (MFC) is a type of bioelectrochemical fuel cell system that generates electric current by diverting electrons produced from the microbial oxidation of reduced compounds on the anode to high-energy oxidized compounds such as oxygen on the cathode through an external electrical circuit. MFCs can be grouped into two general categories: mediated and unmediated. The first MFCs, demonstrated in the early 20th century, used a mediator: a chemical that transfers electrons from the bacteria in the cell to the anode. Unmediated MFCs emerged in the 1970s; in this type of MFC the bacteria typically have electrochemically active redox proteins such as cytochromes on their outer membrane that can transfer electrons directly to the anode. In the 21st century MFCs have started to find commercial use in wastewater treatment.
Shewanella is the sole genus included in the marine bacteria family Shewanellaceae. Some species within it were formerly classed as Alteromonas. Shewanella consists of facultatively anaerobic Gram-negative rods, most of which are found in extreme aquatic habitats where the temperature is very low and the pressure is very high. Shewanella bacteria are a normal component of the surface flora of fish and are implicated in fish spoilage. Shewanella chilikensis, a species of the genus Shewanella commonly found in the marine sponges of Saint Martin's Island of the Bay of Bengal, Bangladesh.
In taxonomy, Methanospirillum is a genus of microbes within the family Methanospirillaceae. All its species are methanogenic archaea. The cells are bar-shaped and form filaments. Most produce energy via the reduction of carbon dioxide with hydrogen, but some species can also use formate as a substrate. They are Gram-negative and move using archaella on the sides of the cells. They are strictly anaerobic, and they are found in wetland soil and anaerobic water treatment systems.
Bacterial nanowires are electrically conductive appendages produced by a number of bacteria most notably from the Geobacter and Shewanella genera. Conductive nanowires have also been confirmed in the oxygenic cyanobacterium Synechocystis PCC6803 and a thermophilic, methanogenic coculture consisting of Pelotomaculum thermopropionicum and Methanothermobacter thermoautotrophicus. From physiological and functional perspectives, bacterial nanowires are diverse. The precise role microbial nanowires play in their biological systems has not been fully realized, but several proposed functions exist. Outside of a naturally occurring environment, bacterial nanowires have shown potential to be useful in several fields, notably the bioenergy and bioremediation industries.
Rhodopseudomonas palustris is a rod-shaped, Gram-negative purple nonsulfur bacterium, notable for its ability to switch between four different modes of metabolism.
A Bioelectrochemical reactor is a type of bioreactor where bioelectrochemical processes are used to degrade/produce organic materials using microorganisms. This bioreactor is divided in two parts: The anode, where the oxidation reaction takes place; And the cathode, where the reduction occurs. At these sites, electrons are passed to and from microbes to power reduction of protons, breakdown of organic waste, or other desired processes. They are used in microbial electrosynthesis, environmental remediation, and electrochemical energy conversion. Examples of bioelectrochemical reactors include microbial electrolysis cells, microbial fuel cells, enzymatic biofuel cells, electrolysis cells, microbial electrosynthesis cells, and biobatteries.
Microbial electrosynthesis (MES) is a form of microbial electrocatalysis in which electrons are supplied to living microorganisms via a cathode in an electrochemical cell by applying an electric current. The electrons are then used by the microorganisms to reduce carbon dioxide to yield industrially relevant products. The electric current would ideally be produced by a renewable source of power. This process is the opposite to that employed in a microbial fuel cell, in which microorganisms transfer electrons from the oxidation of compounds to an anode to generate an electric current.
Electrofuels or e-fuels are an emerging class of drop-in replacement fuels that are made by storing energy from renewable sources in the chemical bonds of liquid or gas fuels, aiming to be a carbon-neutral fuel. They are an alternative to aviation biofuel. The primary targets are butanol, biodiesel, and hydrogen, but include other alcohols and carbon-containing gases such as methane and butane.
Power-to-gas is a technology that uses electrical power to produce a gaseous fuel. When using surplus power from wind generation, the concept is sometimes called windgas.
Geobacter sulfurreducens is a gram-negative metal and sulphur-reducing proteobacterium. It is rod-shaped, obligately anaerobic, non-fermentative, has flagellum and type four pili, and is closely related to Geobacter metallireducens. Geobacter sulfurreducens is an anaerobic species of bacteria that comes from the family of bacteria called Geobacteraceae. Under the genus of Geobacter, G. sulfurreducens is one out of twenty different species. The Geobacter genus was discovered by Dr. Derek R. Lovley in 1987. G. sulfurreducens was first isolated in Norman, Oklahoma, USA from materials found around the surface of a contaminated ditch.
Desulfobulbus propionicus is a Gram-negative, anaerobic chemoorganotroph. Three separate strains have been identified: 1pr3T, 2pr4, and 3pr10. It is also the first pure culture example of successful disproportionation of elemental sulfur to sulfate and sulfide. Desulfobulbus propionicus has the potential to produce free energy and chemical products.
Geopsychrobacter electrodiphilus is a species of bacteria, the type species of its genus. It is a psychrotolerant member of its family, capable of attaching to the anodes of sediment fuel cells and harvesting electricity by oxidation of organic compounds to carbon dioxide and transferring the electrons to the anode.
Rhodoferax is a genus of Betaproteobacteria belonging to the purple nonsulfur bacteriarophic. Originally, Rhodoferax species were included in the genus Rhodocyclus as the Rhodocyclus gelatinous-like group. The genus Rhodoferax was first proposed in 1991 to accommodate the taxonomic and phylogenetic discrepancies arising from its inclusion in the genus Rhodocyclus. Rhodoferax currently comprises four described species: R. fermentans, R. antarcticus, R. ferrireducens, and R. saidenbachensis. R. ferrireducens, lacks the typical phototrophic character common to two other Rhodoferax species. This difference has led researchers to propose the creation of a new genus, Albidoferax, to accommodate this divergent species. The genus name was later corrected to Albidiferax. Based on geno- and phenotypical characteristics, A. ferrireducens was reclassified in the genus Rhodoferax in 2014. R. saidenbachensis, a second non-phototrophic species of the genus Rhodoferax was described by Kaden et al. in 2014.
Syntrophococcus sucromutans is a Gram-negative strictly anaerobic chemoorganotrophic Firmicutes. These bacteria can be found forming small chains in the habitat where it was first isolated, the rumen of cows. It is the type strain of genus Syntrophococcus and it has an uncommon one-carbon metabolic pathway, forming acetate from formate as a product of sugar oxidation.
Microbial electrolysis carbon capture (MECC) is a carbon capture technique using microbial electrolysis cells during wastewater treatment. MECC results in net negative carbon emission wastewater treatment by removal of carbon dioxide (CO2) during the treatment process in the form of calcite (CaCO3), and production of profitable H2 gas.
The Bionic Leaf is a biomimetic system that gathers solar energy via photovoltaic cells that can be stored or used in a number of different functions. Bionic leaves can be composed of both synthetic and organic materials (bacteria), or solely made of synthetic materials. The Bionic Leaf has the potential to be implemented in communities, such as urbanized areas to provide clean air as well as providing needed clean energy.
References
- ↑ Möller, Bernhard (1984). "Sporomusa, a new genus of gram-negative anaerobic bacteria including Sporomusa sphaeroides spec. nov. and Sporomusa ovata spec. nov". Archives of Microbiology. 139 (4): 388. doi:10.1007/BF00408385. S2CID 31011370.
- ↑ Nevin, Kelly (2010). "Microbial electrosynthesis: feeding microbes electricity to convert carbon dioxide and water to multicarbon extracellular organic compounds". mBio. 1 (2): e00103-10. doi:10.1128/mBio.00103-10. PMC 2921159 . PMID 20714445.
- ↑ Lovley, Derek (2013). "Electrobiocommodities: powering microbial production of fuels and commodity chemicals from carbon dioxide with electricity". Current Opinion in Biotechnology. 24 (3): 385–90. doi:10.1016/j.copbio.2013.02.012. PMID 23465755.
- ↑ Netburn, Deborah (September 29, 2015). "MacArthur 'genius' grant winner creates artificial leaves that photosynthesize". Los Angeles Times.
