Ng Simon, Williamson Cayden, van Zee Mark, Di Carlo Dino, Santa Maria Sergio R
Department of Bioengineering, University of California-Los Angeles, Los Angeles, CA 90095, USA.
Space Life Sciences Training Program, NASA Ames Research Center, Mountain View, CA 94035, USA.
Life (Basel). 2022 Jul 31;12(8):1168. doi: 10.3390/life12081168.
Studying microbes at the single-cell level in space can accelerate human space exploration both via the development of novel biotechnologies and via the understanding of cellular responses to space stressors and countermeasures. High-throughput technologies for screening natural and engineered cell populations can reveal cellular heterogeneity and identify high-performance cells. Here, we present a method to desiccate and preserve microbes in nanoliter-scale compartments, termed PicoShells, which are microparticles with a hollow inner cavity. In PicoShells, single cells are confined in an inner aqueous core by a porous hydrogel shell, allowing the diffusion of nutrients, wastes, and assay reagents for uninhibited cell growth and flexible assay protocols. Desiccated PicoShells offer analysis capabilities for single-cell derived colonies with a simple, low resource workflow, requiring only the addition of water to rehydrate hundreds of thousands of PicoShells and the single microbes encapsulated inside. Our desiccation method results in the recovery of desiccated microparticle morphology and porosity after a multi-week storage period and rehydration, with particle diameter and porosity metrics changing by less than 18% and 7%, respectively, compared to fresh microparticles. We also recorded the high viability of yeast desiccated and rehydrated inside PicoShells, with only a 14% decrease in viability compared to non-desiccated yeast over 8.5 weeks, although we observed an 85% decrease in initial growth potential over the same duration. We show a proof-of-concept for a growth rate-based analysis of single-cell derived colonies in rehydrated PicoShells, where we identified 11% of the population that grows at an accelerated rate. Desiccated PicoShells thus provide a robust method for cell preservation before and during launch, promising a simple single-cell analysis method for studying heterogeneity in microbial populations in space.
在太空中对微生物进行单细胞水平的研究，通过开发新型生物技术以及了解细胞对空间应激源和应对措施的反应，能够加速人类太空探索。用于筛选天然和工程化细胞群体的高通量技术可以揭示细胞异质性并识别高性能细胞。在此，我们提出了一种在纳升规模的隔室（称为皮可壳，即具有中空内腔的微粒）中干燥和保存微生物的方法。在皮可壳中，单个细胞被多孔水凝胶壳限制在内部水核中，允许营养物质、废物和检测试剂扩散，以实现不受抑制的细胞生长和灵活的检测方案。干燥的皮可壳通过简单、低资源的工作流程为单细胞衍生菌落提供分析能力，只需要加水使数十万皮可壳及其内部封装的单个微生物重新水化即可。我们的干燥方法在数周的储存期和重新水化后，干燥微粒的形态和孔隙率得以恢复，与新鲜微粒相比，粒径和孔隙率指标分别变化不到18%和7%。我们还记录了在皮可壳内干燥并重新水化的酵母具有较高的活力，在8.5周内与未干燥的酵母相比活力仅下降了14%，尽管在相同时间段内我们观察到初始生长潜力下降了85%。我们展示了对重新水化的皮可壳中单细胞衍生菌落进行基于生长速率分析的概念验证，其中我们识别出11%的群体生长速率加快。因此，干燥的皮可壳为发射前和发射期间的细胞保存提供了一种可靠的方法，有望成为一种简单的单细胞分析方法，用于研究太空中微生物群体的异质性。
