Cyanobacteria, especially the nitrogen fixation, are considered as one of the most important bacteria in all aquatic and terrestrial environments and have vital roles in the arid and semi-arid ecosystems. Therefore, in the present study, cyanobacteria obtained from a harsh terrestrial ecosystem were selected and the nitrogen fixation activities were assayed by acetylene reduction and Real-Time Polymerase Chain Reaction (RT-PCR). First, the soil cyanobacteria were isolated by using the BG11 medium. Then, all the isolates were transferred into the nitrogen-free medium of BG11 (BG0). In addition, the rate of nitrogen fixation was assayed by gas chromatography mass based on acetylene reduction assay. Next, the nifH gene was expressed in the nitrogen fixation isolates utilizing the RT-PCR. Based on the results, the highest level of ethylene production was observed in Nodularia sp. with 86.3% yielding. Further, the RT-PCR data indicated that all the selected isolates could express the nifH gene. Furthermore, the nifH gene expression of Nodularia sp. and Trichocleus sp. was considerable compared to the other genera. Additionally, the activity of nitrogenase and its increase in the gene expression of nitrogen fixation were much higher than those of the filamentous and heterocystous cyanobacteria compared to the other genera. Therefore, cyanobacteria play a crucial role in the nitrogen fixation of the soil.
Key words: cyanobacteria, nifH gene, nitrogen fixation, Real-Time Polymerase Chain Reaction
Topic: BIOLOGY