Biosynthesis of Ditropolonyl Sulfide, an Antibacterial Compound Produced by Burkholderia cepacia Complex Strain R-12632
Biosynthesis of Ditropolonyl Sulfide, an Antibacterial Compound Produced by Burkholderia cepacia Complex Strain R-12632
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DOI：
10.1128/aem.01169-21
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发表时间：
2021-11-01
影响因子：
4.4
通讯作者：
Vandamme, Peter
中科院分区：
文献类型：
--
作者：
Depoorter, Eliza;Coenye, Tom;Vandamme, Peter
洋葱伯克霍尔德氏菌复合菌株R-12632通过一种未知的生物合成途径产生一种不寻常的含硫托品酮--二托品壬基硫醚。从菌株R-12632的培养物中纯化的二硝基戊二酰硫抑制各种革兰氏阳性和革兰氏阴性抗性细菌的生长，MIC值低至16 μ g/ml。在本研究中，我们使用转座子诱变方法结合代谢物分析，以确定菌株R-12632对革兰氏阴性细菌病原体的抗菌活性的遗传基础。研究的8304个转座子突变体中有15个完全丧失了对肺炎克雷伯菌LMG 2095的抗菌活性。在这些丧失活性的突变体中，9个基因被中断。这些基因中有四个参与同化硫酸盐还原，两个参与苯乙酸（PAA）催化，一个参与谷胱甘肽代谢。通过半制备分馏和代谢产物鉴定，证实PAA降解途径或谷胱甘肽代谢的失活导致ditropolonyl sulfide生产的损失。基于对托酚酮化合物生物合成的早期研究，菌株R-12632中抗菌活性对功能性PAA分解代谢途径的需求表明，该途径可能为二托酚酰硫提供托酚酮骨架。在同化硫酸盐还原和谷胱甘肽生物合成缺陷的突变体中观察到的活性损失表明，半胱氨酸和谷胱甘肽是连接两个托酚酮部分的硫原子的潜在来源。不寻常的抗菌化合物ditropolonyl sulfide的抗菌活性证明了其生物合成和生物学作用的进一步研究。重要Burkholderia细菌在历史上以其生物控制特性而闻名，并已被提出作为一个有前途的和未开发的生物活性专门代谢物的来源。洋葱伯克霍尔德氏菌复合菌株R-12632抑制多种革兰氏阳性和革兰氏阴性耐药病原体，并产生许多专门的代谢产物，其中包括二托泊壬基硫。这种不寻常的抗菌剂的研究很少，其生物合成途径仍然未知。在本研究中，我们进行转座子诱变菌株R-12632和进行基因组和代谢产物分析的活性丧失突变体，研究抗菌活性的遗传基础。我们的研究结果表明，苯乙酸催化剂，同化硫酸盐还原，谷胱甘肽代谢是必要的ditropolonyl硫生产。这些发现有助于了解这种不寻常的抗菌剂的生物合成和生物学作用。
Burkholderia cepacia complex strain R-12632 produces ditropolonyl sulfide, an unusual sulfur-containing tropone, via a yet-unknown biosynthetic pathway. Ditropolonyl sulfide purified from a culture of strain R-12632 inhibits the growth of various Gram-positive and Gram-negative resistant bacteria, with MIC values as low as 16 mu g/ml. In the present study, we used a transposon mutagenesis approach combined with metabolite analyses to identify the genetic basis for antibacterial activity of strain R-12632 against Gram-negative bacterial pathogens. Fifteen of the 8304 transposon mutants investigated completely lost antibacterial activity against Klebsiella pneumoniae LMG 2095. In these loss-of-activity mutants, nine genes were interrupted. Four of those genes were involved in assimilatory sulfate reduction, two were involved in phenylacetic acid (PAA) catabolism, and one was involved in glutathione metabolism. Via semipreparative fractionation and metabolite identification, it was confirmed that inactivation of the PAA degradation pathway or glutathione metabolism led to loss of ditropolonyl sulfide production. Based on earlier studies on the biosynthesis of tropolone compounds, the requirement for a functional PAA catabolic pathway for antibacterial activity in strain R-12632 indicated that this pathway likely provides the tropolone backbone for ditropolonyl sulfide. Loss of activity observed in mutants defective in assimilatory sulfate reduction and glutathione biosynthesis suggested that cysteine and glutathione are potential sources of the sulfur atom linking the two tropolone moieties. The demonstrated antibacterial activity of the unusual antibacterial compound ditropolonyl sulfide warrants further studies into its biosynthesis and biological role.IMPORTANCE Burkholderia bacteria are historically known for their biocontrol properties and have been proposed as a promising and underexplored source of bioactive specialized metabolites. Burkholderia cepacia complex strain R-12632 inhibits various Gram-positive and Gram-negative resistant pathogens and produces numerous specialized metabolites, among which is ditropolonyl sulfide. This unusual antimicrobial has been poorly studied and its biosynthetic pathway remains unknown. In the present study, we performed transposon mutagenesis of strain R-12632 and performed genome and metabolite analyses of loss-of-activity mutants to study the genetic basis for antibacterial activity. Our results indicate that phenylacetic acid catabolism, assimilatory sulfate reduction, and glutathione metabolism are necessary for ditropolonyl sulfide production. These findings contribute to understanding of the biosynthesis and biological role of this unusual antimicrobial.