Submitted to: Meeting Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: February 3, 2004
Publication Date: April 8, 2004
Citation: Fraser, K., Tuite, N., Bhagwat, A.A., O'Bryne, C. 2004. Investigating the basis of homocysteine toxicity in escherichia coli. In: Proceedings of Bionet Conference, November 2003, Galway, Ireland.
In Escherichia coli accumulation of the sulphur-containing amino acid homocysteine has been shown to result in growth inhibition. Interestingly, homocysteine is also toxic in humans, elevated serum homocysteine being associated with increased risk of cardiovascular disease and neural tube defects during pregnancy. Therefore, it is hoped that defining homocysteine toxicity in E. coli might lead to a better understanding of the toxic effects of this compound in humans. Initial growth experiments suggested that growth in the presence of homocysteine led to an auxotrophy for the amino acid isoleucine. In order to further understand the inhibitory effects of homocysteine, we used DNA macroarrays to investigate changes in gene expression that occur when E. coli is treated with homocysteine. We will present and discuss the findings of this analysis, which are summarised as follows: (i) 158 genes demonstrated reproducible changes in expression (> 1.5 fold); (ii) a large number of the genes that were upregulated were involved in translation; (iii) there were large changes in amino acid biosynthetic gene expression, with (a) up-regulation of genes involved in arginine and isoleucine biosynthesis, and (b) down-regulation of genes involved in cysteine, glutamate and methionine biosynthesis and transport; (iv) genes involved in stress responses also showed altered expression, with (a) repression of genes involved with protection against oxidative stress, (b) down-regulation of the periplasmic chaperone HdeA, and (c) up-regulation of the cold-shock protein CspA. We will use the results of this analysis to propose a model of homocysteine toxicity in E. coli.