User:Mabelz97/sandbox

Original - "Heterocyst"

The mechanism of controlling heterocysts is thought to involve the diffusion of an inhibitor of differentiation called patS. Heterocyst formation is inhibited in the presence of a fixed nitrogen source, such as ammonium or nitrate. Heterocyst maintenance is dependent on an enzyme called hetN. The bacteria may also enter a symbiotic relationship with certain plants. In such a relationship, the bacteria do not respond to the availability of nitrogen, but to signals produced by the plant. Up to 60% of the cells can become heterocysts, providing fixed nitrogen to the plant in return for fixed carbon.

Edits - "Heterocyst"

Anabaena-Azolla
A notable symbiotic relationship is that of Anabaena cyanobacteria with Azolla plants. Anabaena reside on the stems and within leaves of Azolla plants. The Azolla plant undergoes photosynthesis and provides fixed carbon for the Anabaena to use as an energy source for dinitrogenases in the heterocyst cells. . In return, the heterocysts are able to provide the vegetative cells and the Azolla plant with fixed nitrogen in the form of ammonia which supports growth of both organisms.

This symbiotic relationship is exploited by humans in agriculture. In Asia, Azolla plants containing Anabaena species are used as biofertilizer where nitrogen is limiting as well as in animal feed. Different strains of Azolla-Anabaena are suited for different environments and may lead to differences in crop production. Rice crops grown with Azolla-Anabaena as biofertilizer have been shown to result in a much greater quantity and quality of produce compared to crops without the cyanobacteria. Azolla-Anabaena plants are grown before and after rice crops are planted. As the Azolla-Anabaena plants grow, they accumulate fixed nitrogen due to the actions of the nitrogenase enzymes and organic carbon from photosynthesis by the Azolla plants and Anabaena vegetative cells. When the Azolla-Anabaena plants die and decompose, they release high amounts of fixed nitrogen, phosphorus, organic carbon, and many other nutrients into the soil, providing a rich environment ideal for the growth of rice crops.

The Anabaena-Azolla relationship has also been explored as a possible method of removing pollutants from the environment, a process known as phytoremediation. Anabaena sp. together with Azolla caroliniana has been shown to be successful in removing uranium, a toxic pollutant caused by mining, as well as the heavy metals mercury (II), chromium(III), and chromium(VI) from contaminated waste water.