Ganusova Elena E, Banerjee Ishita, Seats Trey, Alexandre Gladys
Biochemistry and Cellular and Molecular Biology Department, University of Tennessee, Knoxville, Tennessee, USA.
Appl Environ Microbiol. 2025 Apr 23;91(4):e0238424. doi: 10.1128/aem.02384-24. Epub 2025 Mar 25.
is plant-growth promoting rhizobacteria that produces the phytohormone indole-3-acetic acid (IAA) to induce changes in plant root architecture. The major pathway for IAA biosynthesis in converts tryptophan into indole-3-pyruvic acid (I3P) and then, through the rate-limiting enzyme, indole-3-pyruvate decarboxylase (IpdC), into IAA. Here, we characterize the potential role for IAA biosynthesis in the physiology of these bacteria by characterizing the expression pattern of the promoter, analyzing an mutant using multiple physiological assays and characterizing the effect of I3P, which likely accumulates in the absence of and affects bacterial physiology. We found that the mutant derivative has a reduced growth rate and an altered physiology, including reduced translation activity as well as a more depolarized membrane potential compared to the parent strain. Similar effects could be recapitulated in the parent strain by exposing these cells to increasing concentrations of I3P, as well as other indole intermediates of IAA biosynthesis. Our results also indicate a protective role for IAA against the harmful effects of indole derivatives, with exogenous IAA restoring the membrane potential of cells exposed to indole derivatives for prolonged periods. These protective effects appeared to restore cell physiology, including in the wheat rhizosphere. Together, our data suggest that the IAA biosynthesis pathway plays a major role in physiology by maintaining membrane potential homeostasis and regulating translation, likely to mitigate the potential membrane-damaging effects of indoles that accumulate during growth under stressful conditions.IMPORTANCEIAA is widely synthesized in bacteria, particularly in soil and rhizosphere bacteria, where it functions as a phytohormone to modulate plant root architecture. IAA as a secondary metabolite has been shown to serve as a signaling molecule in several bacterial species, but the role of IAA biosynthesis in the physiology of the producing bacterium remains seldom explored. Results obtained here suggest that IAA serves to protect from the toxic effect of indoles, including metabolite biosynthetic precursors of IAA, on membrane potential homeostasis. Given the widespread production of IAA in soil bacteria, this protective effect of IAA may be conserved in diverse soil bacteria.
是一种促进植物生长的根际细菌，它能产生植物激素吲哚 - 3 - 乙酸（IAA）以诱导植物根系结构发生变化。在 中，IAA 生物合成的主要途径是将色氨酸转化为吲哚 - 3 - 丙酮酸（I3P），然后通过限速酶吲哚 - 3 - 丙酮酸脱羧酶（IpdC）转化为 IAA。在此，我们通过表征 启动子的表达模式、使用多种生理测定法分析 突变体以及表征 I3P 的作用来确定 IAA 生物合成在这些细菌生理过程中的潜在作用，I3P 可能在缺乏 的情况下积累并影响细菌生理。我们发现 突变体衍生物的生长速率降低且生理状态改变，包括与亲本菌株相比翻译活性降低以及膜电位更去极化。通过将这些细胞暴露于浓度不断增加的 I3P 以及 IAA 生物合成的其他吲哚中间体中，在亲本菌株中也能重现类似的效果。我们的结果还表明 IAA 对吲哚衍生物的有害影响具有保护作用，外源性 IAA 可恢复长时间暴露于吲哚衍生物的细胞的膜电位。这些保护作用似乎恢复了细胞生理，包括在小麦根际。总之，我们的数据表明 IAA 生物合成途径通过维持膜电位稳态和调节翻译在 生理过程中起主要作用，这可能是为了减轻在压力条件下生长期间积累的吲哚对膜的潜在破坏作用。重要性IAA 在细菌中广泛合成，特别是在土壤和根际细菌中，它作为一种植物激素调节植物根系结构。IAA 作为一种次生代谢产物已被证明在几种细菌物种中作为信号分子起作用，但 IAA 生物合成在产生细菌的生理过程中的作用仍很少被探索。此处获得的结果表明 IAA 有助于保护 免受吲哚对膜电位稳态的毒性作用，包括 IAA 的代谢生物合成前体。鉴于 IAA 在土壤细菌中广泛产生，IAA 的这种保护作用可能在多种土壤细菌中是保守的。
