Glutamine synthetase and nitrogen cycling in colonies of the marine diazotrophic cyanobacteria Trichodesmium spp

Article Abstract:

The pathway for fixed nitrogen assimilation in the cyanobacterium Trichodesmium thiebautii was elucidated. The pools and uptake rates of glutamine and glutamate as well as the possible enzymes involved in primary ammonium assimilation were determined. The analyses showed high levels of glutamine and glutamate, which reached peak levels at midday. Enzyme assays showed that these amino acids were synthesized by glutamine synthetase (GS), which was associated with the nitrogen-fixing cells. These results indicate that GS is the primary enzyme responsible for ammonium incorporation in T. thiebautii.

Cyanobacteria, Glutamate, Ammonium, Nitrogen, Glutamine metabolism, Nitrogen metabolism

N2 fixation by unicellular bacterioplankton from the Atlantic and Pacific Oceans: Phylogeny in situ rates

Article Abstract:

The tropical North Atlantic and Pacific oceans show an abundance of N2 fixing alpha as well as gamma proteobacteria and unicellular cyanobacteria with the growth rates of plankton in such waters often limited by the availability of reduced form of N. The magnitude of fixation by bacterioplankton can be as high as those of fixation by the colonial N2-fixing marine cyanobacteria.

Science & research, Methods, Phylogeny, Unicellular organisms

Bacterial activity in south pole snow

Article Abstract:

Occurrence of bacterial cell populations in the surface snow and firn from the south pole is presented. Analysis of the isolated DNA show similarities to psychrophilic bacteria related to genus Deinococcus. The bacteria are metabolically active at subzero temperatures as indicated by low rates of DNA and protein synthesis.

United States, Environmental aspects, Discovery and exploration, Bacterial growth, Bacteria, Snow, South Pole