This invention relates to the isolation of a novel tonB operon from Pseudomonas putida. These genes are useful to render the cells more sensitive to antibiotics, toluene, pHBA, aromatic compounds, parabenes, and aromatic amino acids after inactivation with specific mutant allels or more tolerant to these compounds after overexpression with appropriate expression vector. These findings are important in the field of medicine and biotechnology and biocatalysis. In addition a screen to identify pHBA tolerant genes is provided and strains with significant tolerance to pHBA were identified. These strains are important for pHBA production.