Drehe Ignacio, Simonetti Ester, Ruiz Jimena A
Instituto de Investigaciones en Biociencias Agrícolas y Ambientales, Universidad de Buenos Aires, CONICET, Facultad de Agronomía, Avenida San Martín 4453, C1417DSE, Buenos Aires, Argentina.
Curr Microbiol. 2018 Dec;75(12):1560-1565. doi: 10.1007/s00284-018-1560-7. Epub 2018 Aug 28.
Pseudomonas protegens synthesizes two major iron-chelating metabolites (siderophores): pyoverdine (Pvd) and enantio-pyochelin (E-Pch). Although iron sequestration and uptake seem to be the main biological role of these siderophores, other functions including metal homeostasis and antibiotic activity have been proposed. The aim of this study was to evaluate the contribution of Pvd and E-Pch to the survival of P. protegens in soil using wild type and isogenic mutant strains unable to produce Pvd, E-Pch or both siderophores. Survival of these strains in sterile soil microcosms, in soil microcosms containing the native microflora and in sterile soil microcosms containing fusaric acid (a mycotoxin able to chelate iron and other metals), was compared by determination of colony forming units (CFU) per gram dry soil over time. In sterile soil, cell densities of Pvd-producing strains were significantly higher than that of non-producers after 21 days of permanence in the microcosms. In non-sterile soil, viability of all strains declined faster than in sterile soil and Pvd producers showed higher CFU × (g dry weight soil) values than non-producers. The presence of fusaric acid negatively affected viability of strains unable to produce Pvd, while had no effect on the viability of strains able to produce Pvd. Altogether, these results show that the ability to produce Pvd increases survival of P. protegens in soil, while the ability to synthesize E-Pch does not, indicating that under the conditions which prevail in soil, iron scavenging via Pvd is more beneficial than via E-Pch.
嗜麦芽窄食单胞菌合成两种主要的铁螯合代谢产物（铁载体）：绿脓菌素（Pvd）和对映体绿脓菌素（E-Pch）。尽管铁的螯合和摄取似乎是这些铁载体的主要生物学功能，但也有人提出了包括金属稳态和抗生素活性在内的其他功能。本研究的目的是使用无法产生Pvd、E-Pch或两种铁载体的野生型和同基因突变菌株，评估Pvd和E-Pch对嗜麦芽窄食单胞菌在土壤中存活的贡献。通过测定每克干土中随时间变化的菌落形成单位（CFU），比较这些菌株在无菌土壤微宇宙、含有天然微生物群落的土壤微宇宙以及含有镰刀菌酸（一种能够螯合铁和其他金属的霉菌毒素）的无菌土壤微宇宙中的存活率。在无菌土壤中，在微宇宙中放置21天后，产生Pvd的菌株的细胞密度显著高于不产生Pvd的菌株。在非无菌土壤中，所有菌株的活力下降速度均快于无菌土壤，且产生Pvd的菌株的CFU×（每克干重土壤）值高于不产生Pvd的菌株。镰刀菌酸的存在对无法产生Pvd的菌株的活力有负面影响，而对能够产生Pvd的菌株的活力没有影响。总之，这些结果表明，产生Pvd的能力增加了嗜麦芽窄食单胞菌在土壤中的存活率，而合成E-Pch的能力则没有，这表明在土壤中普遍存在的条件下，通过Pvd清除铁比通过E-Pch更有益。
