Time courses of l-cysteine uptake (A) and export (B) by cells of strain JM39ΔtnaA with pUC118 (○), pUCydeD carrying ydeD (▵), pUCbcr carrying bcr (□), pUCemrAB carrying emrAB (▿), pUCacrEF carrying acrEF (▪), pUCybjYZ carrying ybjYZ (▾), or pUCyojIH carrying yojIH (⧫). Values indicate means and standard deviations of results from three independent experiments.