Thesis Title

Overexpression of the Hmp Gene in Esherichia Coli and Its Effect on Growth Rate

Date of Graduation

Spring 1998


Master of Science in Biology



Committee Chair

John Steiert

Subject Categories



A globin-like protein, HMP, was recently found to be produced in Escherichia coli. The hmp gene encodes for a protein that has extensive amino acid sequence homology with the N-terminal sequence of the Vitreoscilla sp. hemoglobin-like protein (Vhb), and the C-terminal has extensive sequence homology to the ferredoxin NADP⁺ reductase family. The hmp gene was shown to be regulated by oxygen concentration, similar to the regulation of the vhb gene in Vitreoscilla. Additionally the hmp gene is expressed under anaerobic conditions when nitrate is present as the terminal electron acceptor. A recent report showed the vhb gene, when inserted into E. coli, improved the overall growth rate of E. coli under oxygen limiting conditions. Regulatory mutants were isolated to study the regulation of the hmp gene. All mutants constitutively express the hmp gene and the mutation mapped at the same location on the chromosome. One of these mutants, MB-11, was selected to study the effect of overproduction of the HMP protein on the growth rate of E. coli. Initial studies showed a significant improved growth rate of MB-11 under low oxygen concentrations when compared to the growth rate of a concurrently grown wild-type strain under similar conditions. MB-21, an hmp mutant strain of MB-11, was constructed by insertional inactivation of the hmp gene. The growth rate of strain MB-21 was similar to the wild type strain under low oxygen conditions. This suggests the increased growth rate of MB-11 was due to the overexpression of the hmp gene.


© Jon-David S Sears