The influence of CsgD on the expression of genes of folate metabolism and hmp in Escherichia coli K-12.

The csgD gene codes for the regulatory protein CsgD. CsgD upregulates the synthesis of the adhesive fimbriae, curli, that are important for biofilm formation and downregulates flagellar synthesis. We compared the expression of genes involved in folate metabolism and a gene (hmp) in strains with an intact csgD gene and with a deletion in csgD. The hmp gene codes a flavohemoglobin that inactivates nitric oxide. Expression was monitored by measuring light production from single copy lux operon fusions. At late times of growth, expression of genes responsible for methylene tetrahydrofolate synthesis (glyA and gcvTHP) and formyltetrahydrofolate recycling (purU) was higher in cells with CsgD than those without. In contrast, expression of hmp was lower in the presence of CsgD throughout the period monitored. We used a novel defined medium which should assist in defining nutritional factors that contribute to curli formation.

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