Abstract

In previous studies it was found that the antimicrobial properties of pulcherrimin-producing Metschnikowia species are related to the formation of a red pigment—pulcherrimin and sequestration of free iron from their growth medium. For strains of Metschnikowia pulcherrima, M. sinensis, M. shaxiensis, and M. fructicola, at a high, ≈80 mg/kg, elemental Fe concentration in agar growth media we observed the essentially different (metal luster, non-glossy rust like, and colored) yeast biomass coatings. For the studied strains the optical and scanning electron microscopies showed the increased formation of chlamydospores that accumulate a red pigment—insoluble pulcherrimin rich in iron. The chlamydospore formation and decay depended on the iron concentration. In this study pulcherrimin in biomass of the selected Metschnikowia strains was detected by Mössbauer spectroscopy. At ≈80 mg/kg elemental Fe concentration the Mössbauer spectra of biomass of the studied strains were almost identical to these of purified pulcherrimin. Iron in pulcherrimin reached ≈1% of biomass by weight which is very high in comparison with elemental Fe percentage in growth medium and is not necessary for yeast growth. The pulcherrimin in biomass was also observed by Mössbauer spectroscopy at lower, ≈5 mg/kg, elemental Fe concentration. Through chemical binding of iron pulcherrimin sequestrates the soluble Fe in the growth media. However, at high Fe concentrations, the chemical and biochemical processes lead to the pulcherrimin accumulation in biomass chlamydospores. When soluble iron is sequestrated or removed from the growth media in this way, it becomes inaccessible for other microorganisms.

Graphic abstract

中文翻译：

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生产 pulcherrimin 的 Metschnikowia 酵母生物质中高浓度铁积累的特征

摘要

在之前的研究中发现，产生 pulcherrimin 的Metschnikowia物种的抗菌特性与红色色素 pulcherrimin 的形成和从其生长培养基中螯合游离铁有关。对于Metschnikowia pulcherrima、M. sinensis、M. shaxiensis和M. fructicola 的菌株，在琼脂培养基中约 80 mg/kg 的高元素 Fe 浓度下，我们观察到了本质上不同的（金属光泽、无光泽的锈状和有色）酵母生物质涂层。对于所研究的菌株，光学和扫描电子显微镜显示厚壁孢子的形成增加，这些厚壁孢子积累了红色色素——富含铁的不溶性 pulcherrimin。厚壁孢子的形成和衰变取决于铁浓度。在本研究中，所选Metschnikowia生物量中的 pulcherrimin穆斯堡尔光谱法检测菌株。在 ≈80 mg/kg 元素 Fe 浓度下，所研究菌株的生物量穆斯堡尔谱几乎与纯化的 pulcherrimin 相同。pulcherrimin 中的铁达到 ≈1% 的生物质重量，与生长培养基中的元素 Fe 百分比相比非常高，并且对于酵母生长不是必需的。穆斯堡尔光谱还观察到生物质中的 pulcherrimin 在较低的 ≈5 mg/kg 元素 Fe 浓度下。通过化学结合铁 pulcherrimin 螯合生长培养基中的可溶性 Fe。然而，在高 Fe 浓度下，化学和生化过程导致生物质厚壁孢子中 pulcherrimin 的积累。当可溶性铁以这种方式从生长培养基中隔离或去除时，其他微生物就无法获得它。

图形摘要