PDF(Pubmed)
Abstract：
In microgravity, bacteria undergo intriguing physiological adaptations. There have been few attempts to assess global bacterial physiological responses to microgravity, with most studies only focusing on a handful of individual systems. This study assessed the fitness of each gene in the genome of the aromatic compound-degrading Alphaproteobacterium Novosphingobium aromaticavorans during growth in spaceflight. This was accomplished using Comparative TnSeq, which involves culturing the same saturating transposon mutagenized library under two different conditions. To assess gene fitness, a novel comparative TnSeq analytical tool was developed, named TnDivA, that is particularly useful in leveraging biological replicates. In this approach, transposon diversity is represented numerically using a modified Shannon diversity index, which was then converted into effective transposon density. This transformation accounts for variability in read distribution between samples, such as cases where reads were dominated by only a few transposon inserts. Effective density values were analyzed using multiple statistical methods, including log2-fold change, least-squares regression analysis, and Welch\'s t-test. The results obtained across applied statistical methods show a difference in the number of significant genes identified. However, the functional categories of genes important to growth in microgravity showed similar patterns. Lipid metabolism and transport, energy production, transcription, translation, and secondary metabolite biosynthesis and transport were shown to have high fitness during spaceflight. This suggests that core metabolic processes, including lipid and secondary metabolism, play an important role adapting to stress and promoting growth in microgravity.
摘要：
在微重力中,细菌经历有趣的生理适应。很少有人尝试评估全球细菌对微重力的生理反应，大多数研究只关注少数个体系统。这项研究评估了在太空飞行中生长过程中，降解芳香族化合物的变形杆菌Novosphingoumaromaticavorans基因组中每个基因的适应性。这是使用比较TnSeq完成的，这涉及在两种不同条件下培养相同的饱和转座子诱变文库。为了评估基因适合度，开发了一种新的比较TnSeq分析工具，名叫TnDivA,这对利用生物复制特别有用。在这种方法中，转座子多样性使用修改的香农多样性指数进行数字表示，然后转化为有效的转座子密度。这种转换解释了样本之间读数分布的可变性，例如读段仅由几个转座子插入物主导的情况。使用多种统计方法分析有效密度值，包括log2倍的变化，最小二乘回归分析，和韦尔奇的t检验。在应用的统计方法中获得的结果显示了鉴定的显著基因的数量的差异。然而,在微重力下对生长重要的基因的功能类别显示出相似的模式。脂质代谢和运输，能源生产，转录,翻译,和次生代谢产物的生物合成和运输在航天飞行中具有很高的适应性。这表明核心代谢过程，包括脂质和次级代谢，在微重力条件下适应胁迫和促进生长中起着重要作用。
