Nature. Nov 3;() Algae acquire vitamin B12 through a symbiotic relationship with bacteria. Croft MT(1), Lawrence AD, Raux-Deery E, Warren. Symbiotic bacteria are bacteria living in symbiosis with another organism or each other. Certain plants establish a symbiotic relationship with bacteria, enabling them to dinoflagellate and certain cyanobacteria, endosymbiotic algae and the coral contain enzymes enabling them to both undergo ammonium assimilation. Algae-bacteria interactions cover all possible forms of symbiotic relationships, though, many types of interactions in the planktonic zone have.
The relevance of microalgae-bacteria interactions in improving the microalgal role in aquaculture is also reviewed. Relevance and Types The plankton communities, in which many microalgae and bacteria are included, influence the global carbon cycle and therefore the climate. It was demonstrated that heterotrophic bacteria not only decompose organic matter but also promote plant growth by certain complex communication mechanisms and nutrient exchange [ 7 ].
In last few years, the same phenomenon has also been observed for algae in the context of coevolution [ 3589 ].
Algae acquire vitamin B12 through a symbiotic relationship with bacteria.
Therefore, any innovation in algal biotechnology should always take into account the existing relationship between algae and bacteria. They influence the ecosystem together in a natural way, and therefore could potentially be implied in future biotechnology industry [ 1011 ]. Algae-bacteria interactions cover all possible forms of symbiotic relationships, though, many types of interactions in the planktonic zone have not yet been completely explored, mainly due to the onerous task of separating the partners, which are naturally bound to each other [ 12 ].
For example, the interaction between Emiliania huxleyi—a single cell marine microalga—and Roseobacter has most widely been studied. These mutual interactions are extremely species specific as the microenvironment of each alga is different. In the examples of microalgae-bacteria interactions studied thus far, nutrient exchange seems to play a major role. Micronutrients like vitamins [ 1314 ] and macronutrients like nitrogen and carbon [ 3141516 ] are usually exchanged between algae and bacteria.
In addition, plant hormones excreted from bacteria also promote algal growth [ 14 ]. Some studies suggest that such inter-regulation plays a major role in these interactions, as in the case of the Roseobacter [ 14 ].
Mutualism Mutualism is a biologic interaction in which two or more partners of different species benefit each other [ 6812 ]. A typical example of mutualism is that a bacterial species supplies vitamin B12 to an algal partner in exchange for fixed carbon [ 1317 ]. However, mutualism is not only limited to micronutrient supply from bacteria [ 18 ], as there are studies highlighting the role of Azospirillum, Mesorhizobium and Rhizobium sp.
Symbiotic bacteria - Wikipedia
Such exchanges between biotic communities in aquatic ecosystems have a huge role in cycling of nitrogen, sulphur, carbon and phosphorus [ 22232425262728 ]. Commensalism Commensalism is a relationship in which only one partner benefits. Commensals could be considered as non-interacting partners [ 29 ]. Microorganisms that belong to the phycosphere represent a bacterial diversity dwelling on the algal surface [ 21 ]."Frontonia atra," with symbiotic algae
However, there is a very faint line that separates mutualism and commensalism, and even parasitism, and environmental factors may shift an interaction from one type to another. In this sense, there are studies that partially demonstrate the role of nutrient availability, N: P ratio and light intensity in the shift from mutualism to parasitism and vice versa via commensalism, although the mechanisms behind such shifts still remain unclear [ 1230 ].
The interaction between Chlamydomonas reinhardtii and heterotrophic bacteria is another example of commensalism. Parasitism Parasitism is a well-studied interaction in which one species benefits at the expense of the other and exerts negative effects on it.
Normally, the parasite is smaller in size and needs the host to be alive. Many bacteria are known to negatively affect algae, and, therefore, they have been proposed as microalgae and cyanobacterial bloom controlling microorganisms [ 313233 ]. In the case of bacterial parasitism on algae, the algal cell is lysed by the action of glucosidases, chitinases, cellulases and other enzymes [ 3336 ]. Once the algal cell is lysed, the bacteria can use intracellular algal compounds as nutrients. However, there is one more form of parasitism, where a competition for existing nutrients occurs that results in slower growth rates of algae [ 12 ].
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They usually have a mutual relationship with other bacteria. Some live in tube worms. Characteristics[ edit ] Corals have been found to form characteristic associations with symbiotic nitrogen-fixing bacteria. Corals must therefore form a mutualistic relationship with nitrogen fixing organism, in this case the subject of this study, namely Symbiodinium.
In addition to this dinoflagellate, coral also form relationships with bacteria, archae and fungi. In addition, cyanobacteria have been found to possess genes that enable them to undergo nitrogen fixation.
Due to the small size of the genome of most endosymbionts, they are unable to exist for any length of time outside of the host cell, thereby preventing a long-term symbiotic relationship.
However, in the case of the endonuclear symbiotic bacterium Holospora, it has been discovered  that Holospora species can maintain their infectivity for a limited time and form a symbiotic relationship with Paramecium species. It is well accepted and understood that there is a mutualistic relationship between plants and rhizobial bacteria and mycorrhizal fungi enabling the plants to survive in an otherwise nitrogen-poor soil environment.
Co-evolution is described as a situation where two organisms evolve in response to one another. In a study reported in Functional Ecology,  these scientists investigated whether such a mutualistic relationship conferred an evolutionary advantage to either plant or symbiont. They did not find that the rhizobial bacteria studied had any evolutionary advantage with their host but did find great genetic variation among the populations of rhizobial bacteria studied.