Expression of Vitreoscilla hemoglobin is superior to horse heart myoglobin or yeast flavohemoglobin expression for enhancing Escherichia coli growth in a microaerobic bioreactor.

The research shows that expressing a gene for a particular type of hemoglobin, derived from an oxygen-loving bacterium, in E. coli bacteria, enhances their growth under low-oxygen conditions. Other types of hemoglobin derived from horse heart and yeast did not have the same effect.

Methodology

• Scientists utilized the genes encoding three types of hemoglobins – Vitreoscilla hemoglobin (VHb), horse heart myoglobin (HMb), and yeast flavohemoglobin (YFb).
• These genes were inserted behind a tac promoter on a medium-copy-number vector – a method used to induce controlled expression of the genes.
• The altered vectors containing the hemoglobin genes were then transformed into two strains of E. coli bacteria, MG1655 and DH5 alpha, essentially creating genetically modified bacteria expressing the different types of hemoglobin.
• Validity of the transformation was checked by ensuring these hemoglobins could bind carbon monoxide, mimicking one of their usual biological activities.

Results & Observations

• Observations from the study revealed different outcomes based on the type of hemoglobin used.
• The horse heart myoglobin increased E. coli growth initially but ultimately didn’t augment the final cell density, suggesting that its influence was only temporary.
• Vitreoscilla hemoglobin had the most beneficial effect, enhancing final cell density by 70% in comparison to unmodified E. coli.
• The yeast-derived flavohemoglobin, surprisingly, decreased the final cell density by 30% relative to unmodified E. coli, contrary to what was expected.

Implications of the Study

• This research demonstrates that not all hemoglobins can improve the growth of microaerobic E. coli.
• The study provides valuable insights into the influences of different globins on the growth trajectory of E. coli, and by implication, other bacteria.
• This work could be influential in the field of genetically altered bacteria tailored for specific roles within the biotech industry to yield high productivity under low oxygen conditions.