Faculty of Science and Technology, Department of Biosciences and Informatics, Keio University, Yokohama, 223-8522, Japan.
Department of Biotechnology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo, 113-8657, Japan.
J Antibiot (Tokyo). 2020 Apr;73(4):203-210. doi: 10.1038/s41429-020-0279-4. Epub 2020 Feb 3.
In actinomycetes, many secondary metabolite biosynthetic genes are not expressed under typical laboratory culture conditions and various efforts have been made to activate these dormant genes. In this study, we focused on high-temperature culture. First, we examined the thermotolerance of 3160 actinomycete strains from our laboratory culture collection and selected 57 thermotolerant actinomycetes that grew well at 45 °C. These 57 thermotolerant actinomycetes were cultured for 5 days in liquid medium at both 30 °C and 45 °C. Culture broths were extracted with 1-butanol, and each extract was subjected to LC/MS analysis. The metabolic profiles of each strain were compared between the 30 °C and 45 °C cultures. We found that almost half of these thermotolerant actinomycetes produced secondary metabolites that were detected only in the 45 °C culture. This result suggests that high-temperature culture induces the production of dormant secondary metabolites. These compounds were named "heat shock metabolites (HSMs)." To examine HSM production in more detail, 18 strains were selected at random from the initial 57 strains and cultivated in six different media at 30 °C and 45 °C; as before, metabolic profiles of each strain in each medium were compared between the 30 °C and 45 °C cultures. From this analysis, we found a total of 131 HSMs. We identified several angucycline-related compounds as HSMs from two thermotolerant Streptomyces species. Furthermore, we discovered a new compound, murecholamide, as an HSM from thermotolerant Streptomyces sp. AY2. We propose that high-temperature culture of actinomycetes is a convenient method for activating dormant secondary metabolite biosynthetic genes.
在放线菌中，许多次级代谢产物生物合成基因在典型的实验室培养条件下不表达，因此人们做出了各种努力来激活这些休眠基因。在本研究中，我们专注于高温培养。首先，我们检查了来自我们实验室培养物收集的 3160 株放线菌菌株的耐热性，并选择了 57 株在 45°C 下生长良好的耐热放线菌。这 57 株耐热放线菌在 30°C 和 45°C 的液体培养基中培养 5 天。用 1-丁醇提取培养物，然后将每个提取物进行 LC/MS 分析。比较了每个菌株在 30°C 和 45°C 培养物中的代谢谱。我们发现，这些耐热放线菌中的近一半产生了仅在 45°C 培养物中检测到的次级代谢产物。这一结果表明高温培养诱导了休眠次级代谢产物的产生。这些化合物被命名为“热激代谢物（HSMs）”。为了更详细地检查 HSM 的产生，我们从最初的 57 株中随机选择了 18 株，并在 30°C 和 45°C 下在六种不同的培养基中进行培养；与之前一样，比较了每种培养基中每个菌株在 30°C 和 45°C 培养物之间的代谢谱。通过这项分析，我们共发现了 131 种 HSMs。我们从两种耐热链霉菌中鉴定出几种与 angucycline 相关的化合物作为 HSMs。此外，我们从耐热链霉菌 sp. AY2 中发现了一种新化合物，murecholamide，作为 HSM。我们提出，放线菌的高温培养是一种激活休眠次级代谢产物生物合成基因的便捷方法。
