Elucidating Mechanisms of Metal Sulfide-Enabled Growth of Anoxygenic Photosynthetic Bacteria Using Transcriptomic, Aqueous/Surface Chemical, and Electron Microscopic Tools

紫色细菌通过无氧光合作用将光能转化为化学能。紫色硫磺细菌(PSB)是紫色细菌的一个亚类，它将还原硫物种的氧化作用耦合到光营养生长中。虽然PSB被认为是各种生态系统(例如，分生湖泊、内陆海和海洋盆地)中硫循环的关键驱动因素，但对它们的代谢能力和灵活性还没有完全了解。研究小组最近的工作表明，使用固相过渡金属硫化物(TMS)作为硫磺和电子供体，PSB菌株可以强劲地自养生长。值得注意的是，这一发现揭示了PSB在直接从固相衬底中清除电子以及与TMS的密切联系方面的显著潜力，TMS自然地出现在它们的壁龛中，值得进一步研究。因此，该小组将系统地研究PSB-TMS的相互作用和相关机制。这项工作通过为古代和现代金属-硫生物地球化学循环提供新的约束，建立新的细菌胞外电子转移研究模型，以及展示纳米粒子光化学与微生物能量需求之间的潜在协同作用，可能对地球化学和生物电化学具有重要意义。本研究要解决的主要研究问题是：(I)是否所有的TMS相都可以使PSB作为唯一的硫和电子供体进行自养生长；以及(Ii)PSB-TMS相互作用的分子机制是什么。研究小组将结合转录测序、结合先进光谱和冷冻技术的透射电子显微镜以及各种水/表面化学分析工具来解决这些问题。为了最大限度地发挥其工作对社会的影响，他们将纳入协同的外展和辅导活动。例如，他们将制作一系列动画短片(将在YouTube上托管)来传播这项工作的主要成果。他们还将开发一个开放获取的环境纳米科学教程。这些外展活动的长期目标是为跨学科的STEM研究创造一个强大的渠道，并将不同的学生群体培养成一支称职的STEM工作队伍。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Purple bacteria convert light energy into chemical energy through anoxygenic photosynthesis. Purple sulfur bacteria (PSB) are a sub-group of purple bacteria, coupling the oxidation of reduced sulfur species to phototrophic growth. While PSB are recognized as key drivers of the sulfur cycle in various ecosystems (e.g., meromictic lakes, inland seas, and marine basins), their metabolic capability and flexibility are not fully understood. The research team's recent work demonstrated robust autotrophic growth of PSB strains using solid-phase transition metal sulfide (TMS) as sulfur and electron donors. Significantly, this finding reveals PSB’s remarkable potential in scavenging electrons directly from solid-phase substrate and close ties with TMS, which naturally occur in their niches, meriting further investigations. As such, the team will examine the PSB-TMS interactions and relevant mechanisms systematically. This work may have key implications for geochemistry and bioelectrochemistry, through providing new constraints for ancient and modern metal-sulfur biogeochemical cycles, establishing new models for bacterial extracellular electron transfer research, and demonstrating the potential synergy between nanoparticle photochemistry and microbial energy demand. The main research questions to be addressed in this study are: (i) if all TMS phases may enable the autotrophic growth of PSB as sole sulfur and electron donors; and (ii) what molecular mechanisms are involved in the PSB-TMS interactions. The research team will use a combination of transcriptomic sequencing, transmission electron microscopy coupled with advanced spectroscopy and cryo-techniques, and various aqueous/surface chemical analytical tools to resolve these questions. To maximize the impact of their work on society, they will incorporate synergistic outreach and mentoring activities. For example, they will create a series of short animation videos (to be hosted on YouTube) to disseminate the main results of this work. They will also develop an open-access Environmental Nanoscience tutorial. The long-term goal for these outreach activities is to create a robust pipeline for cross-disciplinary STEM research and to train a diverse group of students into a competent STEM workforce.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.