Usami Keisuke, Tezuka Takeaki, Ohnishi Yasuo, Shigeto Shinsuke
Department of Chemistry, Graduate School of Science and Technology, Kwansei Gakuin University, Sanda 669-1330, Japan.
Department of Biotechnology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Bunkyo-ku, Tokyo 113-8657, Japan.
ACS Omega. 2024 Sep 9;9(38):39956-39964. doi: 10.1021/acsomega.4c05706. eCollection 2024 Sep 24.
The bacterium belongs to the genus , a prolific source of useful natural products. This microbe forms globular structures called sporangia, which contain many dormant spores. Recent studies using transmission electron microscopy have shown that the sporangium membrane has an unprecedented three-layer structure, but its molecular components remain unclear. Here, we present multimodal (spontaneous Raman scattering, coherent anti-Stokes Raman scattering, second harmonic generation, sum frequency generation, and third-order sum frequency generation) label-free molecular imaging of intact sporangia. Spontaneous Raman imaging assisted with multivariate curve resolution-alternating least-squares analysis revealed a novel component in the sporangium membrane that exhibits unique Raman bands at 1550 and 1615 cm in addition to those characteristic of lipids. A plausible candidate for this component is an unsaturated carbonyl compound with an aliphatic moiety derived from fatty acid. Furthermore, second harmonic generation imaging revealed that a layer(s) of the sporangium membrane containing this unknown component has an ordered, noncentrosymmetric structure like fibrillar proteins and amylopectin. Our results suggest that the sporangium membrane is a new type of biological membrane, not only in terms of architecture but also in terms of components. We demonstrate that multimodal molecular imaging with Raman scattering as the core technology will provide a promising platform for interrogating the chemical components, whether known or unknown, of diverse biological structures produced by microbes.
该细菌属于一个能大量产生有用天然产物的属。这种微生物形成称为孢子囊的球状结构，其中包含许多休眠孢子。最近使用透射电子显微镜的研究表明，该孢子囊膜具有前所未有的三层结构，但其分子成分仍不清楚。在此，我们展示了完整孢子囊的多模态（自发拉曼散射、相干反斯托克斯拉曼散射、二次谐波产生、和频产生以及三阶和频产生）无标记分子成像。借助多元曲线分辨-交替最小二乘法的自发拉曼成像揭示了孢子囊膜中的一种新成分，除了具有脂质特征的拉曼带外，该成分在1550和1615厘米处还表现出独特的拉曼带。该成分的一个合理候选物是一种具有源自脂肪酸的脂肪族部分的不饱和羰基化合物。此外，二次谐波产生成像显示，含有这种未知成分的孢子囊膜层具有像纤维状蛋白质和支链淀粉那样的有序、非中心对称结构。我们的结果表明，孢子囊膜不仅在结构方面，而且在成分方面都是一种新型的生物膜。我们证明，以拉曼散射为核心技术的多模态分子成像将为探究微生物产生的各种生物结构的化学成分（无论已知还是未知）提供一个有前景的平台。
