Guihua Hu and Min Lin*
Nitrogenase activity is a very distinct property of Pseudomonas stutzeri A1501. It is carried out in the presence of a microaerophilic environment that is in oxygenlimited condition. The biofilm formation is at its best in minimal media at nitrogen depletion state. Anr, a global transcription regulator that promotes biofilm formation. Anr absence plays a negative role in nitrogen fixation by regulating nifA, nifH and ntrC. The nitrogenase activity in anr insertion mutant was significantly down-regulated. At a different concentration of oxygen, the nitrogenase activity was substantially differentiated. The qRT-PCR showed down-regulation of nif island genes at nitrogen fixation condition under the absence of anr. The finding suggested that different oxygen concentration in the environment play a differential role against the nitrogenase activity and biofilm formation. The qRTPCR results for narL during biofilm formation was up-regulated showing that low level of oxygen has a signaling effect causing anr to express which in turns controls not only rsmXYZ but also regulate the biofilm formation. Effect of oxidative stress using H2O2 showed no significant effect on the survival of Pseudomonas stutzeri A1501 that suggested no role in the survival of the organism under high oxygen concentration.
