Magnetite is a mineral and one of the main iron ores, with the chemical formula Fe2+Fe3+2O4. It is one of the oxides of iron, and is ferrimagnetic; it is attracted to a magnet and can be magnetized to become a permanent magnet itself. With the exception of extremely rare native iron deposits, it is the most magnetic of all the naturally occurring minerals on Earth. Naturally magnetized pieces of magnetite, called lodestone, will attract small pieces of iron, which is how ancient peoples first discovered the property of magnetism.
The Thermomicrobia is a group of thermophilic green non-sulfur bacteria. Based on species Thermomicrobium roseum and Sphaerobacter thermophilus, this bacteria class has the following description:
A microaerophile is a microorganism that requires environments containing lower levels of dioxygen than that are present in the atmosphere (i.e. < 21% O2; typically 2–10% O2) for optimal growth. A more restrictive interpretation requires the microorganism to be obligate in this requirement. Many microaerophiles are also capnophiles, requiring an elevated concentration of carbon dioxide (e.g. 10% CO2 in the case of Campylobacter species).
Magnetosomes are membranous structures present in magnetotactic bacteria (MTB). They contain iron-rich magnetic particles that are enclosed within a lipid bilayer membrane. Each magnetosome can often contain 15 to 20 magnetite crystals that form a chain which acts like a compass needle to orient magnetotactic bacteria in geomagnetic fields, thereby simplifying their search for their preferred microaerophilic environments. Recent research has shown that magnetosomes are invaginations of the inner membrane and not freestanding vesicles. Magnetite-bearing magnetosomes have also been found in eukaryotic magnetotactic algae, with each cell containing several thousand crystals.
Nitrosomonas is a genus of Gram-negative bacteria, belonging to the Betaproteobacteria. It is one of the five genera of ammonia-oxidizing bacteria and, as an obligate chemolithoautotroph, uses ammonia as an energy source and carbon dioxide as a carbon source in presence of oxygen. Nitrosomonas are important in the global biogeochemical nitrogen cycle, since they increase the bioavailability of nitrogen to plants and in the denitrification, which is important for the release of nitrous oxide, a powerful greenhouse gas. This microbe is photophobic, and usually generate a biofilm matrix, or form clumps with other microbes, to avoid light. Nitrosomonas can be divided into six lineages: the first one includes the species Nitrosomonas europea, Nitrosomonas eutropha, Nitrosomonas halophila, and Nitrosomonas mobilis. The second lineage presents the species Nitrosomonas communis, N. sp. I and N. sp. II, meanwhile the third lineage includes only Nitrosomonas nitrosa. The fourth lineage includes the species Nitrosomonas ureae and Nitrosomonas oligotropha and the fifth and sixth lineages include the species Nitrosomonas marina, N. sp. III, Nitrosomonas estuarii and Nitrosomonas cryotolerans.
Magnetotaxis is a process implemented by a diverse group of Gram-negative bacteria that involves orienting and coordinating movement in response to Earth's magnetic field. This process is mainly carried out by microaerophilic and anaerobic bacteria found in aquatic environments such as salt marshes, seawater, and freshwater lakes. By sensing the magnetic field, the bacteria are able to orient themselves towards environments with more favorable oxygen concentrations. This orientation towards more favorable oxygen concentrations allows the bacteria to reach these environments faster as opposed to random movement through Brownian motion.
Magnetotactic bacteria are a polyphyletic group of bacteria that orient themselves along the magnetic field lines of Earth's magnetic field. Discovered in 1963 by Salvatore Bellini and rediscovered in 1975 by Richard Blakemore, this alignment is believed to aid these organisms in reaching regions of optimal oxygen concentration. To perform this task, these bacteria have organelles called magnetosomes that contain magnetic crystals. The biological phenomenon of microorganisms tending to move in response to the environment's magnetic characteristics is known as magnetotaxis. However, this term is misleading in that every other application of the term taxis involves a stimulus-response mechanism. In contrast to the magnetoreception of animals, the bacteria contain fixed magnets that force the bacteria into alignment—even dead cells are dragged into alignment, just like a compass needle.
The bacterium, despite its simplicity, contains a well-developed cell structure which is responsible for some of its unique biological structures and pathogenicity. Many structural features are unique to bacteria and are not found among archaea or eukaryotes. Because of the simplicity of bacteria relative to larger organisms and the ease with which they can be manipulated experimentally, the cell structure of bacteria has been well studied, revealing many biochemical principles that have been subsequently applied to other organisms.
The class Flavobacteriia is composed of a single class of environmental bacteria. It contains the family Flavobacteriaceae, which is the largest family in the phylum Bacteroidota. This class is widely distributed in soil, fresh, and seawater habitats. The name is often spelt Flavobacteria, but was officially named Flavobacteriia in 2012.
Marinobacter is a genus of bacteria found in sea water. They are also found in a variety of salt lakes. A number of strains and species can degrade hydrocarbons. The species involved in hydrocarbon degradation include M. alkaliphilus, M. arcticus, M. hydrocarbonoclasticus, M. maritimus, and M. squalenivorans.
Magnetofossils are the fossil remains of magnetic particles produced by magnetotactic bacteria (magnetobacteria) and preserved in the geologic record. The oldest definitive magnetofossils formed of the mineral magnetite come from the Cretaceous chalk beds of southern England, while magnetofossil reports, not considered to be robust, extend on Earth to the 1.9-billion-year-old Gunflint Chert; they may include the four-billion-year-old Martian meteorite ALH84001.
Richard B. Frankel is an Emeritus Professor of Physics at the California State Polytechnic University, San Luis Obispo. He is noted for his research on magnetotaxis and biomineralization of magnetic iron minerals in general and magnetotactic bacteria in particular. His expertise in the latter was prominently discussed in Stephen Jay Gould's The Panda's Thumb. He is a graduate of the University of Missouri (1961) and took a PhD from Berkeley (1965). Much of his career was spent at the Francis Bitter National Magnet Laboratory, Massachusetts Institute of Technology before joining Cal Poly in 1988.
Desulfomonile limimaris is a bacterium. It is an anaerobic dehalogenating bacterium first isolated from marine sediments. Its cells are large, Gram-negative rods with a collar girdling each cell, like Desulfomonile tiedjei. The type strain is DCB-MT.
Desulfovibrio magneticus is a bacterium. It is sulfate-reducing and is notable for producing intracellular single-domain-sized magnetite particles, making it magnetotactic. Its type strain is RS-1T.
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.
Desulfacinum hydrothermale is a thermophilic sulfate-reducing bacterium. Its cells are oval-shaped, 0.8–1 μm in width and 1.5–2.5 μm in length, motile and Gram-negative. The type strain is MT-96T.
Magnetococcus marinus is a species of Alphaproteobacteria that has the peculiar ability to form a structure called a magnetosome, a membrane-encased, single-magnetic-domain mineral crystal formed by biomineralisation, which allows the cells to orient along the Earth’s geomagnetic field. The Magnetococcus marinus grows chemolithoautotrophically with thiosulfate and chemoorganoheterotrophically on acetate.
Cyclobacterium is a mesophilic, neutrophilic, chemoorganotrophic and aerobic bacterial genus from the family of Cyclobacteriaceae. Cyclobacterium bacteria occur in marine habitats
Magnetobacterium bavaricum is a species of bacterium.
The flagellated alga Dinema platysomum, synonym Anisonema platysomum, is the first eukaryote in which magnetotactic structures have been discovered. Monje & Baran (2004) describe how this euglenoid alga stores magnetite in a similar way that already discovered magnetotactic bacteria do. It has been shown that the cells contain magnetite particles aligned with the longitudinal axis of the alga, and each magnetite chain is a permanent dipole. The observed magnetic momentum of the cell has been estimated to be 1000 times stronger than those of typical magnetotactic bacteria.
