Department of Biotechnology and Biomedicine, Technical University of Denmarkgrid.5170.3, Lyngby, Denmark.
Microbiol Spectr. 2021 Oct 31;9(2):e0117121. doi: 10.1128/Spectrum.01171-21. Epub 2021 Sep 29.
Pseudoalteromonas rubra S4059 produces the red pigment prodigiosin, which has pharmaceutical and industrial potential. Here, we targeted a putative prodigiosin-synthesizing transferase PigC, and a in-frame deletion mutant did not produce prodigiosin. However, extractions of the mutant cultures retained antibacterial activity, and bioassay-guided fractionation found antibacterial activity in two fractions of blue color. A precursor of prodigiosin, 4-methoxy-2,2'-bipyrrole-5-carbaldehyde (MBC), was the dominant compound in both the fractions and likely caused the antibacterial activity. Also, a stable blue pigment, di-pyrrolyl-dipyrromethene prodigiosin, was identified from the two fractions. We also discovered antibacterial activity in the sterile filtered (nonextracted) culture supernatant of both wild type and mutant, and both contained a heat-sensitive compound between 30 and 100 kDa. Deletion of prodigiosin production did not affect growth rate or biofilm formation of P. rubra and did not change its fitness, as the mutant and wild type coexisted in equal levels in mixed cultures. In conclusion, a prodigiosin biosynthetic gene cluster (BGC) was identified and verified genetically and chemically in S4059 and a stable blue pigment was isolated from the mutant of S4059, suggesting that this strain may produce several prodigiosin-derived compounds of pharmaceutical and/or industrial potential. Pigmented strains are renowned for their production of secondary metabolites, and genome mining has revealed a high number of biosynthetic gene clusters (BGCs) for which the chemistry is unknown. Identification of those BGCs is a prerequisite for linking products to gene clusters and for further exploitation through heterologous expression. In this study, we identified the BGCs for the red, bioactive pigment prodigiosin using genomic, genetic, and metabolomic approaches. We also report here for the first time the production of a stable blue pigment, di-pyrrolyl-dipyrromethene prodigiosin (Dip-PDG), being produced by the mutant of Pseudoalteromonas rubra S4059.
红色素普罗色林的产生菌希瓦氏菌 S4059 具有医药和工业应用潜力。本文针对推测的普罗色林合成转移酶 PigC 进行了研究，结果表明缺失突变体不能产生普罗色林。然而，该突变体培养物的提取物仍具有抗菌活性，并且基于生物测定的分步提取发现两种蓝色组分具有抗菌活性。普罗色林的前体 4-甲氧基-2,2′-联吡啶-5-甲醛（MBC）是这两种组分中的主要化合物，可能是导致抗菌活性的原因。此外，从这两种组分中还鉴定出了一种稳定的蓝色色素二吡咯并二吡咯并甲烷普罗色林。我们还发现野生型和突变型的无菌过滤（未提取）培养上清液都具有抗菌活性，并且都含有一种 30-100 kDa 之间的热敏化合物。普罗色林生物合成基因簇（BGC）的缺失并不影响希瓦氏菌 S4059 的生长速度或生物膜形成，也不会改变其适应性，因为突变体和野生型在混合培养中以相同水平共存。总之，我们在 S4059 中鉴定并通过遗传和化学方法验证了普罗色林生物合成基因簇，并从 S4059 的突变体中分离出了一种稳定的蓝色色素，表明该菌株可能产生几种具有医药和/或工业应用潜力的普罗色林衍生化合物。色素产生菌以其产生次生代谢产物而闻名，基因组挖掘显示出大量化学性质未知的生物合成基因簇（BGC）。鉴定这些 BGC 是将产物与基因簇联系起来并通过异源表达进行进一步开发的前提。在本研究中，我们使用基因组学、遗传学和代谢组学方法鉴定了红色生物活性色素普罗色林的 BGC。我们还首次报道了由希瓦氏菌 S4059 的突变体产生的稳定蓝色色素二吡咯并二吡咯并甲烷普罗色林（Dip-PDG）的产生。
