Development of GFP fusions for examination of the effects of the space environment on gene expression in Escherichia coli
Abstract
The goal of the In situ Space Gene Expression on Nano-satillites (ISGEN) program is to be ready to fly technology that can support a fully automated experiment to quantify changes in model organisms in situ in low earth orbit in a free flyer platform in less than two years. A straightforward gene expression assay that meets the ISGEN flight objective for testing flight hardware as well as return data regarding the effects of microgravity on gene expression has been developed. Escherichia coli K-12, a bacterium that exhibits changes in its growth pattern when flown in micro-gravity on the Space Shuttle, was used. The scientific objective of this work is to determine if there is a discernable change in metabolic and stress pathway gene expression due to growth in the space environment. To that end, we have linked the green fluorescent protein (GFP) reporter gfp to phoP, a gene that responds to extracellular Mg2+ levels, and pykF, a gene involved in the glycolytic pathway that responds to changes in intracellular pyruvate. These genes respond to the metabolic needs of the cell and may be altered in the micro-gravity environment. E. coli cells containing a plasmid encoding the phoP-gfp-mut3 reporter construct were grown with or without MgSO_4. The effect of the added MgSO_4 is the repression of the expression of GFP. This is the expected result if GFP expression were under the control of a magnesium-regulated promoter such as phoP. Consistent with the negative feedback loop, we observe repression of GFP production in cells containing our pykF-gfp plasmid construct, when grown in the presence of excess glucose. Thus, the pykF-gfp fusion functions as a glucose sensor.
- Publication:
-
35th COSPAR Scientific Assembly
- Pub Date:
- 2004
- Bibcode:
- 2004cosp...35.1767M