Abstract：
Xenorhabdus nematophila is a symbiotic Gammaproteobacterium that produces diverse natural products that facilitate mutualistic and pathogenic interactions in their nematode and insect hosts, respectively. The interplay between X. nematophila secondary metabolism and symbiosis stage is tuned by various global regulators. An example of such a regulator is the LysR-type protein transcription factor LrhA, which regulates amino acid metabolism and is necessary for virulence in insects and normal nematode progeny production. Here, we utilized comparative metabolomics and molecular networking to identify small molecule factors regulated by LrhA and characterized a rare γ-ketoacid (GKA) and two new N-acyl amides, GKA-Arg (1) and GKA-Pro (2) which harbor a γ-keto acyl appendage. A lrhA null mutant produced elevated levels of compound 1 and reduced levels of compound 2 relative to wild type. N-acyl amides 1 and 2 were shown to be selective agonists for the human G-protein-coupled receptors (GPCRs) C3AR1 and CHRM2, respectively. The CHRM2 agonist 2 deleteriously affected the hatch rate and length of Steinernema nematodes. This work further highlights the utility of exploiting regulators of host-bacteria interactions for the identification of the bioactive small molecule signals that they control.
OBJECTIVE: Xenorhabdus bacteria are of interest due to their symbiotic relationship with Steinernema nematodes and their ability to produce a variety of natural bioactive compounds. Despite their importance, the regulatory hierarchy connecting specific natural products and their regulators is poorly understood. In this study, comparative metabolomic profiling was utilized to identify the secondary metabolites modulated by the X. nematophila global regulator LrhA. This analysis led to the discovery of three metabolites, including an N-acyl amide that inhibited the egg hatching rate and length of Steinernema carpocapsae nematodes. These findings support the notion that X. nematophila LrhA influences the symbiosis between X. nematophila and S. carpocapsae through N-acyl amide signaling. A deeper understanding of the regulatory hierarchy of these natural products could contribute to a better comprehension of the symbiotic relationship between X. nematophila and S. carpocapsae.
OBJECTIVE: Xenorhabdus bacteria are of interest due to their symbiotic relationship with Steinernema nematodes and their ability to produce a variety of natural bioactive compounds. Despite their importance, the regulatory hierarchy connecting specific natural products and their regulators is poorly understood. In this study, comparative metabolomic profiling was utilized to identify the secondary metabolites modulated by the X. nematophila global regulator LrhA. This analysis led to the discovery of three metabolites, including an N-acyl amide that inhibited the egg hatching rate and length of Steinernema carpocapsae nematodes. These findings support the notion that X. nematophila LrhA influences the symbiosis between X. nematophila and S. carpocapsae through N-acyl amide signaling. A deeper understanding of the regulatory hierarchy of these natural products could contribute to a better comprehension of the symbiotic relationship between X. nematophila and S. carpocapsae.
摘要：
Xenorhabdusnematophila是一种共生的γ变形杆菌，可产生多种天然产物，促进其线虫和昆虫宿主之间的相互作用和致病相互作用，分别。X.线虫次级代谢和共生阶段之间的相互作用由各种全球监管机构调整。这种调节因子的一个例子是LysR型蛋白转录因子LrhA,它调节氨基酸代谢，是昆虫和正常线虫后代产生的毒力所必需的。这里,我们利用比较代谢组学和分子网络来鉴定由LrhA调节的小分子因子，并表征了一种罕见的γ-酮酸（GKA）和两种新的N-酰基酰胺，含有γ-酮酰基附属物的GKA-Arg(1)和GKA-Pro(2)。相对于野生型,lrhA无效突变体产生升高水平的化合物1和降低水平的化合物2。显示N-酰基酰胺1和2分别是人G蛋白偶联受体（GPCRs）C3AR1和CHRM2的选择性激动剂。CHRM2激动剂2有害地影响了Steinernema线虫的孵化率和长度。这项工作进一步强调了利用宿主细菌相互作用的调节剂来鉴定它们控制的生物活性小分子信号的实用性。
目的：由于与Steinernema线虫的共生关系以及它们产生多种天然生物活性化合物的能力，因此引起了人们的兴趣。尽管它们很重要,人们对连接特定天然产品及其监管机构的监管体系知之甚少。在这项研究中,比较代谢组学分析用于鉴定由X.线虫全局调节因子LrhA调节的次级代谢产物。这项分析导致发现了三种代谢物，包括N-酰基酰胺，可抑制卵孵化率和SteinernemaCarpocapsae线虫的长度。这些发现支持以下观点：X.nematophilaLrhA通过N-酰基酰胺信号传导影响X.nematophila和S.carpocapsae之间的共生关系。对这些天然产物的调控层次的更深入了解可能有助于更好地理解X.线虫和S.carpocapsae之间的共生关系。
目的：由于与Steinernema线虫的共生关系以及它们产生多种天然生物活性化合物的能力，因此引起了人们的兴趣。尽管它们很重要,人们对连接特定天然产品及其监管机构的监管体系知之甚少。在这项研究中,比较代谢组学分析用于鉴定由X.线虫全局调节因子LrhA调节的次级代谢产物。这项分析导致发现了三种代谢物，包括N-酰基酰胺，可抑制卵孵化率和SteinernemaCarpocapsae线虫的长度。这些发现支持以下观点：X.nematophilaLrhA通过N-酰基酰胺信号传导影响X.nematophila和S.carpocapsae之间的共生关系。对这些天然产物的调控层次的更深入了解可能有助于更好地理解X.线虫和S.carpocapsae之间的共生关系。
