New nitrogen fixator at sea

2001/08/09 Astobiza, Amaia

• Mikrobiologia
• Ozeanografia

Nitrogen is a necessary element for all living beings. The most common form of nitrogen is atmospheric gas N2, which can be used by very few organisms. Most organisms need fixed nitrogen (N). Therefore, the availability of fixed nitrogen limits the growth of most terrestrial and marine organisms.

The only ones that can use nitrogen gas are microorganisms with nitrogase enzyme. So far, the best-known marine nitrogen fixers have been photosynthetic cyanobacteria of the genus Trichodesmium. These cyanobacteria form plankton and can have a length of up to 0.5 mm. However, according to studies, it does not seem that all the fixed nitrogen of the sea is fixed by these microorganisms. Therefore, scientists are constantly looking for organisms responsible for fixing the rest of the nitrogen.

In this week's journal Nature you can read an article in which another microorganism that fixes nitrogen is reported. The authors of the article are researchers from American universities, including Jonathan P, from the University of California. Zehr and Patricia J. Turner.

To carry out the research, scientists analyze the marine nanoplankton of the Hawaii area. As they have seen, also a unicellular cyanobacteria between 3 and 10 _m in diameter contains the gene of the enzyme nitrogase essential to fix nitrogen. In addition, this cyanobacteria is very abundant in the sea, so it can have great importance in the marine nitrogen cycle.

Therefore, it seems that the way has begun to resolve doubts about nitrogen fixation. In fact, scientists found it impossible to believe that all marine nitrogen was fixed by the cyanobacteria of the genus Trichodesmium.