T7 protein expression system is one of the most commonly used protein expression systems in the world. Although it provided quick protein expression, there is still a lot of deficient in the system. Therefore, we suggest a novel T7 polymerase-dependent ammonia inducible protein expression system using Azotobacter vinelandii. By putting nifH promoter upstream of the T7 polymerase, proteins are predicted to be able to express downstream of T7 promoter. To the best of our knowledge, this system is the first protein expression system in the world that provides an anaerobic intracellular environment within aerobic extracellular environment. We suggest that the system provides a way for genetic engineering oxygen sensitive protein like nitrogenase and oxygen sensitive organelle like magnetosome aerobically. Moreover, by stable genome integration, the system provides a way for transforming cluster gene up to Mbps, which are ten folds higher than the systems that are commonly used.

Methane is a multifunctional gas that is used as fuel and an important carbon source. It is also used to make bio-degradable plastic. We aim at converting carbon dioxide and carbonate, which are excessive to the ecosystem, into methane. An engineered nitrogenase (α-70Ala, α-195Gln) in Azotobacter vinelandii has been shown to have the ability of reducing carbon dioxide and carbonate into methane and other carbon compound. However, the carbon fixation process consumes a large numbers of protons and thus decreases the reaction rate. We propose to co-express hydrogenase III from Aquifex aeolicus to speed up the carbon fixation step in A. vinelandii.