Fernander Mizpha C, Parsons Paris K, Khaled Billal, Bradley Amina, Graves Joseph L, Thomas Misty D
Department of Biology North Carolina Agricultural and Technical State University, Greensboro, NC, USA.
NPJ Microgravity. 2022 Jun 2;8(1):17. doi: 10.1038/s41526-022-00205-8.
Long-term space missions have shown an increased incidence of oral disease in astronauts' and as a result, are one of the top conditions predicted to impact future missions. Here we set out to evaluate the adaptive response of Streptococcus mutans (etiological agent of dental caries) to simulated microgravity. This organism has been well studied on earth and treatment strategies are more predictable. Despite this, we are unsure how the bacterium will respond to the environmental stressors in space. We used experimental evolution for 100-days in high aspect ratio vessels followed by whole genome resequencing to evaluate this adaptive response. Our data shows that planktonic S. mutans did evolve variants in three genes (pknB, SMU_399 and SMU_1307c) that can be uniquely attributed to simulated microgravity populations. In addition, collection of data at multiple time points showed mutations in three additional genes (SMU_399, ptsH and rex) that were detected earlier in simulated microgravity populations than in the normal gravity controls, many of which are consistent with other studies. Comparison of virulence-related phenotypes between biological replicates from simulated microgravity and control orientation cultures generally showed few changes in antibiotic susceptibility, while acid tolerance and adhesion varied significantly between biological replicates and decreased as compared to the ancestral populations. Most importantly, our data shows the importance of a parallel normal gravity control, sequencing at multiple time points and the use of biological replicates for appropriate analysis of adaptation in simulated microgravity.
长期太空任务显示宇航员口腔疾病的发病率有所上升，因此，口腔疾病是预计会影响未来任务的主要健康问题之一。在此，我们着手评估变形链球菌（龋齿的病原体）对模拟微重力的适应性反应。这种微生物在地球上已得到充分研究，治疗策略也更具可预测性。尽管如此，我们并不确定该细菌在太空中会如何应对环境压力源。我们在高长宽比容器中进行了100天的实验进化，随后进行全基因组重测序以评估这种适应性反应。我们的数据表明，浮游的变形链球菌确实在三个基因（pknB、SMU_399和SMU_1307c）中进化出了变体，这些变体可唯一归因于模拟微重力环境中的菌群。此外，在多个时间点收集的数据显示，另外三个基因（SMU_399、ptsH和rex）发生了突变，在模拟微重力环境中的菌群中比在正常重力对照组中更早被检测到，其中许多与其他研究结果一致。模拟微重力环境和对照方向培养的生物重复之间与毒力相关的表型比较通常显示抗生素敏感性变化不大，而酸耐受性和黏附性在生物重复之间有显著差异，并且与原始菌群相比有所下降。最重要的是，我们的数据表明了平行正常重力对照、多个时间点测序以及使用生物重复对于在模拟微重力环境中进行适当的适应性分析的重要性。
