假单胞菌Rs-198的IAA合成途径分析

Analysis of indole acetic acid (IAA) synthesis pathway inPseudomonas putida Rs-198

为探索假单胞菌Pseudomonas putida Rs-198的吲哚-3-乙酸(IAA)合成途径,本研究考察色氨酸及中间物对Rs-198菌株生长和IAA产量的影响。结果表明:在培养基中,只有少量色氨酸并不影响P.putida Rs-198菌株的生长,Rs-198菌株的IAA产量却可以显著增加2~5倍。添加50 mg/L的色氨酸培养Rs-198菌株96 h后,其IAA产量可以达到55.52 mg/L,是纯营养培养基(NA)发酵液的3.58倍。另外,经高效液相色谱(HPLC)分析中间代谢产物的消长后发现,随IAA浓度的增加,发酵液中色胺、吲哚丙酮酸浓度逐渐降低,而吲哚乙酰胺和吲哚乙腈浓度未见显著变化,由此可以推断色胺(TAM)、吲哚丙酮酸(IPyA)途径为Rs-198合成IAA的主要途径。盆栽实验也表明,培养基中添加色氨酸培养P.putida Rs-198菌株对辣椒种子成苗及生长有较大的促进作用。

The indole acetic acid(IAA)synthesis pathway in Pseudomonas putida Rs-198 was thoroughly investigated through the experiments with various additives to the nutrient medium(NA).Upon the addition of tryptophan and its metabolic intermediates to the nutrient medium,the growth of P.putida Rs-198 and ultimate IAA production were evaluated.As a result,the tryptophan additions at different concentrations could significantly improve the IAA production by 2 to 5 times although the Rs-198 cell concentrations were barely changed.Notably,Rs-198 cells grew well under 50 mg/L tryptophan condition and the maximum IAA production in this case reached 55.52 mg/L at 96 h,which was 3.58 times of the control.Further analysis of the fermentation broth with high performance liquid chromatography(HPLC)showed the contents of tryptamine and indole pyruvic acid gradually decreased during the IAA production,while indole acetamide and indole acetonitrile remained at similar levels,suggesting that tryptamine(TAM)and indole pyruvate(IPyA)were involved in the main pathway for the synthesis of IAA in P.putida Rs-198.Additionally,the production of IAA by P.putida Rs-198 was confirmed by a pot experiment,in which significant improvement was observed not only for the seeding rate of pepper but also for the continuous pepper growth.