Abstract: The invention provides methods of increasing the production of aromatic carboxylic acids from a host cell via manipulation of the yhcRQP operon encoding a family of efflux proteins. Up-regulation of all or a sub-set of the genes in the yhcRQP were additionally found to enhance tolerance to aromatic carboxylic acids toxicity.

Abstract: A method for the facile and inexpensive inducible expression of heterologous genes has been discovered. The yhcS regulator gene has been found to be inducible by aromatic carboxylic acids and to alter the expression of operons in the LysR gene family, including the yhcRQP operon, common in enteric bacteria. Heterologous nucleic acid molecules placed under the control of yhcS responsive promoters may be overexpressed in response to the presence of inexpensive aromatic carboxylic acids.