Inhibition of biosynthesis and activity of nitrogenase in Azospirillum brasilense Sp7 under salinity stress.
Azospirillum brasilense is a microaerophilic, plant growth-promoting bacterium, whose nitrogenase activity has been shown to be sensitive to salinity stress. Growth of A. brasilense in semi-solid medium showed that diazotrophic growth in N-free medium was relatively less sensitive to high NaCl concentrations (200-400 mM) than that in presence of NH4+. Increase in salinity stress to diazotrophic A. brasilense in the semi-solid medium led to the migration of the pellicle to deeper anaerobic zones. Assays of acetylene reduction and nifH- lacZ and nifA- lacZ fusions indicated that salinity stress inhibited nitrogenase biosynthesis more strongly than nitrogenase activity. Under salt stress, the amount of dinitrogenase reductase inactivated by ADP-ribosylation was strongly reduced, indicating that the dinitrogenase reductase ADP ribosyl transferase (DRAT) activity was also inhibited by increased NaCl concentrations. Movement of the pellicle to the anaerobic zone and inhibition of DRAT might be adaptive responses of A. brasilense to salinity stress under diazotrophic conditions. Supplementation of glycine betaine, which alleviates salt stress, partially reversed both responses.
Tripathi
Anil Kumar
AK
Laboratory of Bacterial Genetics, School of Biotechnology, Faculty of Science, Banaras Hindu University, Varanasi - 221005, India. tripathianil@hotmail.com
Nagarajan
Thirunavukkarasu
T
Verma
Subhash Chandra
SC
Rudulier
Daniel Le
DL
D000693:Anaerobiosis; D015806:Azospirillum brasilense / Q000187:drug effects* / Q000201:enzymology*; D001426:Bacterial Proteins / Q000378:metabolism; D017037:Dinitrogenase Reductase / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D009591:Nitrogenase / Q000096:biosynthesis* / Q000378:metabolism*; D010088:Oxidoreductases / Q000378:metabolism; D012965:Sodium Chloride / Q000378:metabolism / Q000494:pharmacology*; D014157:Transcription Factors / Q000378:metabolism
D001426:Bacterial Proteins; D017037:Dinitrogenase Reductase; C061338:NifA protein, Bacteria; D014157:Transcription Factors; D012965:Sodium Chloride; D010088:Oxidoreductases; D009591:Nitrogenase; C029130:nitrogenase reductase