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An endosymbiont or endobiont is an organism that lives within the body or cells of another organism. Typically the two organisms are in a mutualistic relationship. Examples are nitrogen-fixing bacteria, which live in the root nodules of legumes, single-cell algae inside reef-building corals and bacterial endosymbionts that provide essential nutrients to insects.
Nitrogen fixation is a chemical process by which molecular dinitrogen is converted into ammonia. It occurs both biologically and abiologically in chemical industries. Biological nitrogen fixation or diazotrophy is catalyzed by enzymes called nitrogenases. These enzyme complexes are encoded by the Nif genes and contain iron, often with a second metal.
Pseudomonadota is a major phylum of Gram-negative bacteria. Currently, they are considered the predominant phylum within the realm of bacteria. They are naturally found as pathogenic and free-living (non-parasitic) genera. The phylum comprises six classes Acidithiobacilia, Alphaproteobacteria, Betaproteobacteria, Gammaproteobacteria, Hydrogenophilia, and Zetaproteobacteria. The Pseudomonadota are widely diverse, with differences in morphology, metabolic processes, relevance to humans, and ecological influence.
Symbiosis is any type of a close and long-term biological interaction between two biological organisms of different species, termed symbionts, be it mutualistic, commensalistic, or parasitic. In 1879, Heinrich Anton de Bary defined it as "the living together of unlike organisms". The term is sometimes used in the more restricted sense of a mutually beneficial interaction in which both symbionts contribute to each other's support.
Cyanobacteria, also called Cyanobacteriota or Cyanophyta, are a phylum of autotrophic gram-negative bacteria that can obtain biological energy via oxygenic photosynthesis. The name "cyanobacteria" refers to their bluish green (cyan) color, which forms the basis of cyanobacteria's informal common name, blue-green algae, although as prokaryotes they are not scientifically classified as algae.
The green sulfur bacteria are a phylum, Chlorobiota, of obligately anaerobic photoautotrophic bacteria that metabolize sulfur.
Rhizobia are diazotrophic bacteria that fix nitrogen after becoming established inside the root nodules of legumes (Fabaceae). To express genes for nitrogen fixation, rhizobia require a plant host; they cannot independently fix nitrogen. In general, they are gram negative, motile, non-sporulating rods.
Diazotrophs are bacteria and archaea that fix atmospheric nitrogen(N2) in the atmosphere into bioavailable forms such as ammonia.
Root nodules are found on the roots of plants, primarily legumes, that form a symbiosis with nitrogen-fixing bacteria. Under nitrogen-limiting conditions, capable plants form a symbiotic relationship with a host-specific strain of bacteria known as rhizobia. This process has evolved multiple times within the legumes, as well as in other species found within the Rosid clade. Legume crops include beans, peas, and soybeans.
Frankia is a genus of nitrogen-fixing bacteria that live in symbiosis with actinorhizal plants, similar to the Rhizobium bacteria found in the root nodules of legumes in the family Fabaceae. Frankia also initiate the forming of root nodules.
Azotobacter is a genus of usually motile, oval or spherical bacteria that form thick-walled cysts and may produce large quantities of capsular slime. They are aerobic, free-living soil microbes that play an important role in the nitrogen cycle in nature, binding atmospheric nitrogen, which is inaccessible to plants, and releasing it in the form of ammonium ions into the soil. In addition to being a model organism for studying diazotrophs, it is used by humans for the production of biofertilizers, food additives, and some biopolymers. The first representative of the genus, Azotobacter chroococcum, was discovered and described in 1901 by Dutch microbiologist and botanist Martinus Beijerinck. Azotobacter species are Gram-negative bacteria found in neutral and alkaline soils, in water, and in association with some plants.
Biological soil crusts are communities of living organisms on the soil surface in arid and semi-arid ecosystems. They are found throughout the world with varying species composition and cover depending on topography, soil characteristics, climate, plant community, microhabitats, and disturbance regimes. Biological soil crusts perform important ecological roles including carbon fixation, nitrogen fixation and soil stabilization; they alter soil albedo and water relations and affect germination and nutrient levels in vascular plants. They can be damaged by fire, recreational activity, grazing and other disturbances and can require long time periods to recover composition and function. Biological soil crusts are also known as biocrusts or as cryptogamic, microbiotic, microphytic, or cryptobiotic soils.
Bradyrhizobium is a genus of Gram-negative soil bacteria, many of which fix nitrogen. Nitrogen fixation is an important part of the nitrogen cycle. Plants cannot use atmospheric nitrogen (N2); they must use nitrogen compounds such as nitrates.
Archaea is a domain of single-celled organisms. These microorganisms lack cell nuclei and are therefore prokaryotic. Archaea were initially classified as bacteria, receiving the name archaebacteria, but this term has fallen out of use.
Cyanobionts are cyanobacteria that live in symbiosis with a wide range of organisms such as terrestrial or aquatic plants; as well as, algal and fungal species. They can reside within extracellular or intracellular structures of the host. In order for a cyanobacterium to successfully form a symbiotic relationship, it must be able to exchange signals with the host, overcome defense mounted by the host, be capable of hormogonia formation, chemotaxis, heterocyst formation, as well as possess adequate resilience to reside in host tissue which may present extreme conditions, such as low oxygen levels, and/or acidic mucilage. The most well-known plant-associated cyanobionts belong to the genus Nostoc. With the ability to differentiate into several cell types that have various functions, members of the genus Nostoc have the morphological plasticity, flexibility and adaptability to adjust to a wide range of environmental conditions, contributing to its high capacity to form symbiotic relationships with other organisms. Several cyanobionts involved with fungi and marine organisms also belong to the genera Richelia, Calothrix, Synechocystis, Aphanocapsa and Anabaena, as well as the species Oscillatoria spongeliae. Although there are many documented symbioses between cyanobacteria and marine organisms, little is known about the nature of many of these symbioses. The possibility of discovering more novel symbiotic relationships is apparent from preliminary microscopic observations.
Bacterioplankton refers to the bacterial component of the plankton that drifts in the water column. The name comes from the Ancient Greek word πλανκτος, meaning "wanderer" or "drifter", and bacterium, a Latin term coined in the 19th century by Christian Gottfried Ehrenberg. They are found in both seawater and freshwater.
CandidatusAtelocyanobacterium thalassa, also referred to as UCYN-A, is a diazotrophic species of cyanobacteria commonly found in measurable quantities throughout the world's oceans and some seas. Members of A. thalassa are spheroid in shape and are 1-2 μm in diameter, and provide nitrogen to ocean regions by fixing non biologically available atmospheric nitrogen into biologically available ammonium that other marine microorganisms can use.
The root microbiome is the dynamic community of microorganisms associated with plant roots. Because they are rich in a variety of carbon compounds, plant roots provide unique environments for a diverse assemblage of soil microorganisms, including bacteria, fungi, and archaea. The microbial communities inside the root and in the rhizosphere are distinct from each other, and from the microbial communities of bulk soil, although there is some overlap in species composition.
Some types of lichen are able to fix nitrogen from the atmosphere. This process relies on the presence of cyanobacteria as a partner species within the lichen. The ability to fix nitrogen enables lichen to live in nutrient-poor environments. Lichen can also extract nitrogen from the rocks on which they grow.
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.
References
- 1 2 Hodkinson BP, Lutzoni F (2009). "A microbiotic survey of lichen-associated bacteria reveals a new lineage from the Rhizobiales" (PDF). Symbiosis. 49 (3): 163–180. Bibcode:2009Symbi..49..163H. doi:10.1007/s13199-009-0049-3. S2CID 4129219. Archived from the original (PDF) on 2012-10-17. Retrieved 2009-12-09.
- ↑ De la Torre JR, Goebel BM, Friedmann EI, Pace, NR (2003). "Microbial Diversity of Cryptoendolithic Communities from the McMurdo Dry Valleys, Antarctica". Applied and Environmental Microbiology. 69 (7): 3858–3867. Bibcode:2003ApEnM..69.3858D. doi:10.1128/AEM.69.7.3858-3867.2003. PMC 165166 . PMID 12839754.
{{cite journal}}: CS1 maint: multiple names: authors list (link) - ↑ Cabello P, Roldán MD, Moreno-Vivián C (November 2004). "Nitrate reduction and the nitrogen cycle in archaea". Microbiology. 150 (Pt 11): 3527–46. doi: 10.1099/mic.0.27303-0 . PMID 15528644.
- ↑ Brodo, IM (1973). "Substrate ecology". In: The Lichens. Ahmadjihan V, Hale ME, Eds. Academic Press, New York and London: 401–441.
- ↑ Henckel, P. A.; T. T. Plotnikova (1973). "[Nitrogen-fixing bacteria in lichens]". Izvestiya Akademii Nauk SSSR. Seriya Biologicheskaya (in Russian). 6: 807–813.
- ↑ Krasil’nikov NA (1949). "Is Azotobacter present in lichens?". Mikrobiologiia. 18: 3.
- ↑ Lambright, DD Kapustka, LA (1981). "The association of N2-fixing bacteria with Dermatocarpon miniatum and Lepraria sp". Botanical Society of America: Miscellaneous Serial Publication. 160: 5.
{{cite journal}}: CS1 maint: multiple names: authors list (link) - ↑ Liba CM, Ferrara FI, Manfio GP, Fantinatti-Garboggini F, Albuquerque RC, Pavan C, Ramos PL, Moreira CA, Barbosa HR (2006). "Nitrogen-fixing chemo-organotrophic bacteria isolated from cyanobacteria-deprived lichens and their ability to solubilize phosphate and to release amino acids and phytohormones". Journal of Applied Microbiology. 101 (5): 1076–1086. doi: 10.1111/j.1365-2672.2006.03010.x . PMID 17040231.
- ↑ Grube M, Cardinale M, Vieira de Castro J, Müller H, Berg G (2009). "Species-specific structural and functional diversity of bacterial communities in lichen symbiosis". The ISME Journal . 3 (9): 1105–1115. Bibcode:2009ISMEJ...3.1105G. doi: 10.1038/ismej.2009.63 . PMID 19554038.