Article Abstract:
A study was undertaken that cloned and sequenced the nitrogenase structural nifU and nifHDK genes of the Trichodesmium sp. IMS101 for the purpose of comparing the nitrogenase proteins and nif regulatory region of Trichodesmium to other cyanobacterial diazotrophs. Nif genes are transcribed by a RNA polymerase that employs a sigma factor known as RpoN or sigma54. Results indicated that the multiple nif transcripts presented potential stem-loop structures that terminated at the transcription downstream of nifH and nifD. NifHDK transcription was unaffected by changes in light intensity.
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Article Abstract:
The nifH gene encodes the two identical subunits of the Fe protein of nitrogenase. Sequences of a portion of nifH gene from diverse cyanobacteria were compared to provide additional insight into the evolution of cyanobacteria and to determine the evolutionary relationship of nitrogenase within the cyanobacteria as a group. In addition, phylogenetic analysis of nitrogenase genes provide a basis for the identification of uncultivated nitrogen-fixing cyanobacterial strains in the environment which in turn will provide molecular markers for the cultivation of desirable strains.
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Article Abstract:
Research was conducted to examine novel nitrogen-fixing microbial populations and diverse habitats that can support nitrogen fixation in the open ocean other than those previously reported. Nitrogenase genes were amplified from oligotrophic surface water picoplankton from the tropical Pacific and Atlantic oceans and from the Caribbean and Sargasso seas. Results demonstrate that there are diverse nitrogen-fixing phylotypes in the oceanic environment in the plankton.
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