In many organisms the energy required for growth is furnished by respiration. Escherichia coli and other organisms do not have an efficient way of delivering oxygen to the terminal oxidase for respiration - a factor that limits their growth and ability to produce useful products like proteins and chemical reagents.
Vitreoscilla stercoria is a gram negative aerobe that is usually found in fresh water sediments or other environments where the oxygen concentration is low. V. stercoria survives in hypoxic conditions by switching on the expression of a hemoglobin (VHb) – a soluble dimeric molecule that binds one protophorphrin IX per subunit, as do other Hbs.
We have evolved the VHb to allow better growth of E.coli. – as shown in figure. Experiments to monitor the enhanced production of useful materials are ongoing.