School of Chemistry, University of Bristol, Bristol, United Kingdom.
Defence Science Technology Laboratory (DSTL), Porton Down, Salisbury, United Kingdom.
Appl Environ Microbiol. 2020 Nov 10;86(23). doi: 10.1128/AEM.01543-20.
Emerging outbreaks of airborne pathogenic infections worldwide, such as the current severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic, have raised the need to understand parameters affecting the airborne survival of microbes in order to develop measures for effective infection control. We report a novel experimental strategy, TAMBAS (tandem approach for microphysical and biological assessment of airborne microorganism survival), to explore the synergistic interactions between the physicochemical and biological processes that impact airborne microbe survival in aerosol droplets. This innovative approach provides a unique and detailed understanding of the processes taking place from aerosol droplet generation through to equilibration and viability decay in the local environment, elucidating decay mechanisms not previously described. The impact of evaporation kinetics, solute hygroscopicity and concentration, particle morphology, and equilibrium particle size on airborne survival are reported, using MRE162 as a benchmark system. For this system, we report that (i) particle crystallization does not directly impact microbe longevity, (ii) bacteria act as crystallization nuclei during droplet drying and equilibration, and (iii) the kinetics of size and compositional change appear to have a larger effect on microbe longevity than the equilibrium solute concentration. A transformative approach to identify the physicochemical processes that impact the biological decay rates of bacteria in aerosol droplets is described. It is shown that the evaporation process and changes in the phase and morphology of the aerosol particle during evaporation impact microorganism viability. The equilibrium droplet size was found to affect airborne bacterial viability. Furthermore, the presence of MRE162 in a droplet does not affect aerosol growth/evaporation but influences the dynamic behavior of the aerosol by processing the culture medium prior to aerosolization, affecting the hygroscopicity of the culture medium; this highlights the importance of the inorganic and organic chemical composition within the aerosolized droplets that impact hygroscopicity. Bacteria also act as crystallization nuclei. The novel approach and data have implications for increased mechanistic understanding of aerosol survival and infectivity in bioaerosol studies spanning the medical, veterinary, farming, and agricultural fields, including the role of microorganisms in atmospheric processing and cloud formation.
全球范围内新出现的空气传播致病性感染，如当前的严重急性呼吸系统综合征冠状病毒 2（SARS-CoV-2）大流行，提高了人们对了解影响微生物空气传播存活的参数的需求，以便制定有效的感染控制措施。我们报告了一种新的实验策略 TAMBAS（空气传播微生物存活的微物理和生物学综合评估的串联方法），以探索影响气溶胶液滴中空气传播微生物存活的物理化学和生物学过程的协同相互作用。这种创新方法提供了对从气溶胶液滴生成到局部环境平衡和生存能力衰减过程的独特而详细的了解，阐明了以前未描述的衰减机制。使用 MRE162 作为基准系统，报告了蒸发动力学、溶质吸湿性和浓度、颗粒形态和平衡颗粒大小对空气传播存活的影响。对于该系统，我们报告：（i）颗粒结晶不会直接影响微生物的寿命；（ii）在液滴干燥和平衡过程中，细菌充当结晶核；（iii）大小和组成变化的动力学似乎对微生物的寿命有更大的影响，而不是平衡溶质浓度。描述了一种变革性方法，用于确定影响细菌在气溶胶液滴中生物衰减率的物理化学过程。结果表明，蒸发过程和蒸发过程中气溶胶颗粒的相和形态变化会影响微生物的生存能力。发现平衡液滴尺寸会影响空气传播细菌的生存能力。此外，MRE162 在液滴中的存在不会影响气溶胶的生长/蒸发，但会通过在气溶胶化之前处理培养基来影响气溶胶的动态行为，从而影响培养基的吸湿性；这突出了气溶胶化液滴中影响吸湿性的无机和有机化学成分的重要性。细菌也充当结晶核。这种新方法和数据对增加对生物气溶胶研究中气溶胶存活和传染性的机制理解具有重要意义，涵盖了医学、兽医、农业和农业领域，包括微生物在大气处理和云形成中的作用。
