Autoinduction of Vitreoscilla Hemoglobin Enhanced the Production of Syringomycin from Pseudomonas syringae HS191
Guiyao Li 1, Taoran Zhou 1, Yuqi Wang 2, Yang Wang 2*, Zichun Hua 1*
1 School of Life Science, Nanjing University, 210023, Nanjing, Jiangsu Province, China
2 School of Environmental and Biological Engineering, Nanjing University of Science and Technology, 210094, Nanjing, Jiangsu Province, China
Syringomycin is a cyclic lipodepsipeptide produced by strains of Pseudomonas syringae. The potent herbicidal and fungicidal activities of syringomycin make it a promising compound for fungiostasis and weed control. However, the production of syringomycin from the wild-type strains is low. The discoveries that Pseudomonas syringae is aerobic, and the syringomycin synthetase SyrB2 is an O2-dependent halogenase, led us to establish an autoinducible Vitreoscilla hemoglobin expression system for oxygen supply during fermentation, thereby increasing the yield of syringomycin. By employing the quorum sensing system for the expression of Vitreoscilla hemoglobin gene (vgb), we found that Pseudomonas syringae HS191 that expressed vgb, facilitated the cell growth and the general biomass. Furthermore, syringomycin bioassay showed that the fungal inhibition zones increased from 2.5 mm to 3.2 mm, and HPLC analysis confirmed that the expression of vgb resulted in a 71.1% increase in syringomycin production compared to the wild-type strain. The Vitreoscilla hemoglobin has been widely applied to fermentation optimization; however, in the case of Pseudomonas, increased oxygen supply is only beneficial during the stationary phase, while a high concentration of oxygen inhibited the cell propagation during the logarithmic phase. Here we report the autoinduction of Vitreoscilla hemoglobin by engineering the quorum-sensing system. This synthetic circuit significantly improved the syringomycin production. The Vitreoscilla hemoglobin-autoinduction system not only caters to the dynamic oxygen demand but also avoids inducer supplementation.