Cyanobacteria symbiosis

Villareal, T. A. (1994). Widespread occurrence of the Hernwn/ns-cyanobacteria symbiosis in the southwest North Atlantic Ocean. Bull. Mar. Sci. 54, 1—7. 

In wetlands N2 fixation can occur in the water colnmn, in the aerobic water-soil interface, in the anaerobic soil bulk, in the rhizosphere, and on the leaves and stems of plants. Phototrophic bacteria in the water and at the water-soil interface are generally more important than non-photosynthetic, heterotrophic bacteria in the soil and on plant roots (Buresh et al, 1980 Roger 1996). The phototrophs comprise bacteria that are epiphytic on plants and cyanobacteria that are both free-living and epiphytic. A particularly favourable site for cyanobacteria is below the leaf surface of the water fern Azolla, which forms a very efficient symbiosis with the cyanobacterinm Anabaena azollae. This symbiosis and those in various leguminous plants have been exploited in traditional rice prodnction systems to sustain yields of 2 to 4 t ha of grain withont fertilizer for hnndreds of years. 

Symbiosis with algae and bacteria (including Cyanobacteria) is widespread in ascidians and is responsible for coloration as well as defensive metabolites, which may themselves be colorful. Symbiotic bacteria are also responsible for the (probably defensive) bioluminescence of their pelagic relatives, the Thaliacea.96 Brooding of the young tadpole larva may facilitate the transfer of symbionts from one generation to the next. Many of the metabolites in ascidians are quite similar to those known to be produced by bacteria, and the taxonomic distribution of the metabolites in the animals tends to confirm this.97 Others, however, are evidently produced by the tunicates themselves. 

According to this hypothesis (Margulis, 1993), the eukaryotic cell is a result of symbiosis of different prokaryotic cells, where mitochondria originated from eubacteria, and chloroplasts - from cyanobacteria, and vacuoles - from archae. 

Ascidians are marine filter feeders with a rich natural products chemistry that five commonly associated with symbiotic bacteria (88, 89, 109). A well-studied symbiosis consists of photosynthetic Prochloron spp. cyanobacteria that occur in ascidians of the family Didemnidae (110). Prochloron spp. also can be found in bacterial mat structures of stromatoliths (111) but so far have not been detected outside of such structured environments. From didemnid ascidians, numerous cytotoxic cyclic peptides of the patellamide group (Fig. 5) were isolated (109, 112, 113). Mechanical separation of the Prochloron sp. symbiont from its host Lissoclinum patella and subsequent genome sequencing revealed a set of biosynthetic genes that after transfer into E. coli enabled this bacterium to produce two different patellamides (114). The genes also were identified in an independent study by screening a library of Prochloron sp. DNA... 

The most likely setting of symbiosis is a microbial mat community, in which a complex community of cells is clustered across a redox boundary, cycling and recycling redox power (Nisbet and Fowler, 1999 Nisbet, 2002). The aerobic top of the mat would include photosynthetic cyanobacteria, above photosynthesizing purple bacteria. There would be a very sharply focused redox boundary. Below would be the green photosynthetic bacteria, and at the base the methanogens and the hydrogen producers. 

Leppanen, J. M., Niemi, A., Rinne, L, 1988. Nitrogen fixation of Cyanobacteria (blue-green algae) and the nitrogen cycle of the Baltic Sea. Symbiosis, 6, 181-194. 

The meat of some marine fish, shellfish and many other animals can be toxic. In most cases, the toxic substance is present throughout the organism, as it is usually caused by the consumption of phytoplankton, microscopic algae (Dinoflagellates), blue-green algae (Cyanobacteria) and diatoms (Diatomeae), which contain various hepatotoxins, neurotoxins, dermatotoxins or intestinal toxins. The primary sources of toxins are bacteria that live with these algae in symbiosis or as epiphytes. A number of toxins are also produced by... 

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