Graduate Program in Genomic Sciences and Biotechnology, Universidade Católica de Brasília, SGAN 916, Brasília, DF, 70790-160, Brazil.
Braz J Microbiol. 2021 Dec;52(4):1825-1833. doi: 10.1007/s42770-021-00597-x. Epub 2021 Aug 26.
Paenibacillus elgii AC13 produces antimicrobial lipopeptides of agricultural and pharmaceutical importance. It secretes four cyclic lipopeptides named pelgipeptins, previously characterized in P. elgii B69. These lipopeptides result from the expression of a nonribosomal peptide gene cluster. P. elgii AC13 also produced two linear lipopeptides with ratios of [M + H] + 1105 and 1119 m/z. These compounds were previously observed in Paenibacillus sp. strain OSY-N, but due to purification difficulties, their characterization was executed using synthetically produced linear pelgipeptins. In the present study, purification was achieved from the supernatants of cultures from three complex media by high-performance liquid chromatography. The partial characterization of linear pelgipeptins revealed the similar antimicrobial activity and cytotoxicity of their synthetically produced counterparts, known as paenipeptins. Cyclic forms were highly stable to changes in pH, temperature, and organic extraction with n-butanol as shown by mass spectrometry (MALDI-TOF); therefore, these steps did not cause the hydrolysis of pelgipeptins. A low-activity thioesterase could also generate the linear isoforms observed; this enzyme catalyzes the cyclization process and is coded in the same gene cluster. Alternatively, the cyclic forms were hydrolyzed by an unknown protease produced during growth in the complex medium used in the present study. Although culture conditions are known to produce pelgipeptins with different yields and amino acid compositions, the occurrence of linear and cyclic forms simultaneously has not yet been reported. A mixture of cyclic and linear pelgipeptins presents a potential advantage of the higher antimicrobial activity of cyclic forms combined with the lower cytotoxicity of linear isoforms.
短小芽孢杆菌 AC13 产生具有农业和医药重要性的抗菌脂肽。它分泌四种环状脂肽，命名为 pelgipeptins，以前在短小芽孢杆菌 B69 中被表征。这些脂肽是由非核糖体肽基因簇表达产生的。短小芽孢杆菌 AC13 还产生了两种具有 [M+H]+1105 和 1119 m/z 比值的线性脂肽。这些化合物以前在芽孢杆菌属 OSY-N 中观察到，但由于纯化困难，它们的特性是使用合成的线性 pelgipeptins 来执行的。在本研究中，通过高效液相色谱从三种复杂培养基的培养物上清液中进行了纯化。线性 pelgipeptins 的部分表征揭示了其合成对应物 paenipeptins 的相似抗菌活性和细胞毒性。环状形式对 pH 值、温度和正丁醇等有机溶剂萃取的变化非常稳定，如质谱（MALDI-TOF）所示；因此，这些步骤不会导致 pelgipeptins 水解。低活性硫酯酶也可以产生观察到的线性异构体；该酶催化环化过程，并且编码在相同的基因簇中。或者，未知的蛋白酶在本研究中使用的复杂培养基中生长时也可以水解环状形式。尽管已知培养条件会产生具有不同产率和氨基酸组成的 pelgipeptins，但同时出现线性和环状形式尚未报道。环状和线性 pelgipeptins 的混合物具有环状形式更高抗菌活性与线性异构体更低细胞毒性相结合的潜在优势。
