Purpose: To determine whether vitamins influence the expression of stress response genes in Escherichia coli O157:H7.
Methods: E. coli O157:H7 EDL933 carrying rpoS-lux or osmC-lux constructs were treated with optimized concentrations of biotin, folate, cobalamin, pantothenate, riboflavin, menaquinone ascorbate and α-tocopherol. Cells were screened for bioluminescence during 5.5 h exposure, and compared to controls. Additionally, three E. coli O157:H7 EDL933 were treated with the maximal concentrations of respective vitamins and plated on Luria Bertani agar to assess growth.
Results: Following vitamin addition, repression in relative bioluminescence was observed with cobalamin (1 mg/ml, >8-fold, rpoS; >13-fold, osmC) and 2-fold induction with α-tocopherol (1 mg/ml, rpoS) and menaquinone (0.005, 0.05 mg/ml, osmC), while after 1 h treatment, >2-fold repression resulted with pantothenate (50 mg/ml, rpoS and osmC) and ascorbate (10 mg/ml, osmC), and >3-fold repression with ascorbate (10 mg/ml, rpoS). After 5.5 h, previous inductions of α-tocopherol (rpoS) and menaquinone (osmC) were ameliorated to <2-fold, strong repression by ascorbate (18-fold, rpoS and >83-fold, osmC), pantothenate (>224-fold, rpoS and >216-fold, osmC), and cobalamin (>14-fold, rpoS and >6-fold, osmC) occurred, and 2-fold repression for pantothenate (5 mg/ml, osmC) resulted. Following vitamin exposure, significantly fewer bacteria were observed in pantothenate (50 mg/ml, 1.5 and 3 h; P < 0.001) and ascorbate [10 mg/ml, 1.5 h (P < 0.05) and 3 h (P < 0.001)] treatments, while significantly more E. coli O157:H7 were observed in biotin (0.1 mg/ml, 1.5 h; P < 0.05) and cobalamin (1 mg/ml, 3 h; P < 0.05) treatments when compared to controls.
Significance: Our results show vitamins present in food or those produced by enteric bacteria influence rpoS and osmC gene expression of E. coli O157:H7.