This study describes Chromobacterium violaceum's use of extracellular membrane vesicles (MVs) to both solubilize and transport violacein to other microorganisms. Violacein is a hydrophobic bisindole with known antibiotic activities against other microorganisms. Characterization of the MVs found they carried more violacein than protein (1.37 ± 0.19-fold), suggesting they may act as a reservoir for this compound. However, MVs are not produced in response to violacein - a ΔvioA isogenic mutant, which is incapable of making violacein, actually produced significantly more MVs (3.2-fold) than the wild-type strain. Although violacein is insoluble in water (Log Poctanol:water = 3.34), 79.5% remained in the aqueous phase when it was present within the C. violaceum MVs, an increase in solubility of 1740-fold. Moreover, tests with a strain of Staphylococcus aureus showed MV-associated violacein is bactericidal, with 3.1 mg/l killing 90% of S. aureus in 6 h. Tests with the ΔvioA MVs found no loss in the S. aureus viability, even when its MVs were added at much higher concentrations, demonstrating violacein is the active component within the wild-type MVs. In conclusion, our study clearly demonstrates C. violaceum produces MVs and uses them as vehicles to solubilize violacein and transport this hydrophobic antibiotic to other microbes.

中文翻译：

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紫罗兰杆菌将紫罗兰素（一种疏水性抗生素）传递给膜小泡中的其他微生物。

这项研究描述了紫胶杆菌利用胞外膜小泡（MVs）来溶解和转运紫胶菌素到其他微生物。紫罗兰素是一种疏水性双吲哚，对其他微生物具有已知的抗生素活性。MV的特征发现它们比蛋白携带更多的紫胶素（1.37±0.19倍），表明它们可能充当该化合物的贮藏库。但是，MV并不是响应于紫胶素而产生的，紫胶素是一种不能制造紫胶素的ΔvioA等基因突变体，实际上比野生型菌株产生了更多的MV（3.2倍）。尽管紫胶素不溶于水（Log Poctanol：水= 3.34），但当紫胶藻MVs中存在紫胶素时，其在水相中的残留量为79.5％，溶解度增加了1740倍。而且，用金黄色葡萄球菌菌株进行的试验显示，MV相关的紫胶菌素具有杀菌作用，在6小时内以3.1 mg / l的剂量杀死了90％的金黄色葡萄球菌。用ΔvioAMV进行的测试未发现金黄色葡萄球菌的生存能力下降，即使以更高的浓度添加了MV，也表明紫胶素是野生型MV中的活性成分。总而言之，我们的研究清楚地表明，紫色假丝酵母产生了MV，并将其用作增溶紫色素并将这种疏水性抗生素转运至其他微生物的媒介。