As per the definition of 'symbiosis', it is a long-term interaction between two organisms which live in each other's vicinity. Basically, there are three types of symbiotic relationships: (i) mutualistic, (ii) commensal, and (iii) parasitic. These biological interactions have a crucial role to play in the smooth functioning of any given ecosystem.
The number of these microorganisms is usually higher in man-made ecosystems providing perfect conditions for their growth (Guyard and Low 2011) than in natural ecosystems, where their number is usually low (Steinert et al. 2002). The growth and survival rate of Legionella in the environment depend mainly on their ability to develop symbiotic relationships with protists. Legionella have been identified inside several ciliates including Tetrahymena and Cyclidium species as well as inside amoeba species belonging to Acanthamoeba, Hartmanella, Valkampfia, and Naegleria genera (Lee and West 1991; Paszko-Kolva et al. 1993; States et al. 1989; Kramer and Ford 1994; Henke and Seidel 1986; Fields 1996; Vandenesch et al. 1990), referred to as free-living amoebae (FLA), ubiquitous and opportunistic protists, which can induce human and animal diseases (Dendana et al. 2008).
Australian Outback Symbiotic Relationships
Truffles exist in symbiotic relationships with their host trees, called mycorrhizal relationships. The ecology of mycorrhizal fungi such as truffles is somewhat mysterious, owing to the fact that their life cycle and growth occurs below ground. Most species require a temperate climate, making Southern Europe and some parts of North America hotspots for growth. Certain species also grow in the unlikely parts of the world such as the Kalahari Desert of Africa and the Australian Outback. Given the rising temperatures, these regions may not be suitable for truffles in the future.
The "Wood Wide Web" hides underneath our feet, barely noticed but very important. The wood wide web (also known as mycorrhizal networks) is a network of mutually beneficial symbiotic relationships between fungi, plants, and bacteria. In these networks, fungi wind tendrils of thin, almost invisible, thread-like "hyphae" through the soil, connecting fungi to the roots of plants. These hyphae allow for communication and nutrient exchange between plants and fungi underneath the forest floor.
Species in the Gobiidae sometimes form symbiotic relationships with other species,[23] such as with burrowing shrimps. The shrimp maintains a burrow in the sand in which both the shrimp and the fish live. The shrimp has poor eyesight compared to the gobiid, but if it sees or feels the fish suddenly swim into the burrow, it will follow. The fish and shrimp keep in contact with each other, the shrimp using its antennae, and the fish flicking the shrimp with its tail when alarmed. These gobiids are thus sometimes known as "watchmen gobies" or "prawn gobies". Each party gains from this relationship: the shrimp gets a warning of approaching danger, and the fish gets a safe home and a place to lay its eggs. Only the alpha male and female reproduce, other fish in the colony eat sparingly to resist being eaten by the alpha male or female. This way, only the largest and fittest are able to reproduce.[citation needed]
To increase the resolution of the evolutionary relationships between the 6 strains belonging to the new Ensifer species, phylogenies were also performed using these 103 alpha-rhizobia conserved concatenated gene sequences which were in great majority (100/103) located in contigs showing synteny with E. meliloti chromosome. Furthermore, to compare evolutionary relationships according to replicon type synteny with E meliloti genome, a selection of E. aridi core genes which were all located in contigs ordered according to E. meliloti 1021 symbiotic plasmid pSymA (86 genes) or the chromid pSymB (55 genes selected according to their distribution along the contigs in synteny with E. meliloti 1021 chromid) were retrieved for all 6 strains. The Additional file 1 (Table S4) reports E. aridi PEG lists corresponding to the 103 alpha-rhizobia most conserved gene set (Table S4a), the 86 pSymA conserved orthologous gene set (Table S4b) and the selected 55 pSymB conserved orthologous gene set (Table S4c). These PEGs were retrieved, aligned and phylogenies were inferred as described above. 2ff7e9595c
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