HA5 Genomics and Proteomics
Room 17A/B, Level 4
8:00 AM - 12:00 PM, Thursday, 13 November 2003
Chair: Ferguson, Lee ,
(523) Gene expression study of Escherichia coli MG1655 in response to a standard toxic compound, para-nitrophenol.
Brown, A1, Snape, J2, Harwood, C1, Curtis, T1, Head, I1, 1 University of Newcastle, Newcastle-upon-Tyne, UK2 AstraZeneca, Brixham, Devon, UK
ABSTRACT- Ecotoxicology testing ensures new and existing chemicals do not pose a threat to any environmental compartment upon their release. To meet requirements of EU directives chemicals are subjected to internationally standardised tests. These tests involve an effect assessment, which determines the fate of a chemical, and exposure assessment, which determines the biodegradability of a chemical, within the environment. Of these tests, there are biological tests that determine the effects of a chemical on mixed populations or pure cultures of microorganisms, such as Escherichia coli, Pseudomonas putida or Photobacterium phosphoreum. One such test is the microbial multiplication inhibition test, which measures the degree of inhibition of growth of a population of microorganisms when exposed to a chemical. Whilst these tests indicate inhibitory effects of the chemical on the cells, they offer no insight as to why the cells are inhibited. Genomic array technology was used to investigate the mode of action of para-nitrophenol (PNP, a standard test compound) on E. coli cells. E. coli gene expression in response to PNP exposure at a range of concentrations (0, 10, 32 & 56 mg/l) was investigated over time. The E. coli general stress response is observed when cells are exposed to stressors e.g. starvation, low pH, high osmolarity, temperature shifts. Physiological effects include stress resistance, accumulation of storage compounds, changes in cell envelope composition and cell morphology. At the molecular level, the general stress response is dependent on two sigma subunits of RNA polymerase, 
S and 70. Genes associated with and regulated by the E. coli general stress response genes (rpoS encoding S, rpoD encoding 70) were identified associated with PNP exposure. Effects on genes related to the general stress response and other gene expression patterns are reported.
Key words: Escherichia coli, Ecotoxicology, Gene expression, Para-nitrophenol