Division of Biology, Kansas State University, 116 Ackert Hall, Manhattan, KS, 66506, USA.
Department of Environmental Science and Ecology, University of Texas at San Antonio, San Antonio, TX, USA.
Microb Ecol. 2020 Apr;79(3):662-674. doi: 10.1007/s00248-019-01432-5. Epub 2019 Sep 3.
A history of drought exposure promoted by variable precipitation regimes can select for drought-tolerant soil microbial taxa, but the mechanisms of survival and death of microbial populations through the selective stresses of soil drying and re-wet are not well understood. We subjected soils collected from a 15-year field drought experiment ("Altered" precipitation history with extended dry periods, versus the "Ambient" field control) to a laboratory drying/re-wetting experiment, to learn whether selective population survival, death, or maintenance of protein synthesis potential and microbial respiration through variable soil water conditions was affected by field drought legacy. Microbial community composition, as measured by Illumina MiSeq sequencing of the 16S rRNA and 16S rRNA gene, shifted with laboratory drying/re-wet and field drought treatments. In Ambient soils, there was a higher proportion of reduced OTU abundance (indicative of mortality) during re-wet, whereas Altered soils had a greater proportion of stable OTU populations that did not change in abundance (indicative of survival) through drying/re-wet. Altered soils also had a lower proportion of rRNA:rRNA genes (lower protein synthesis potential) during dry-down, a greater weighted mean rRNA operon number (potential growth rate and r-selection) which was associated with higher abundance of Firmicutes (order Bacillales), and lower average microbial respiration rates. These data demonstrate that soils with a weaker historical drought legacy exhibit a higher prevalence of microbial water-stress mortality and differential survival and death at OTU levels following short-term dryingand re-wetting, concurrent with higher carbon loss potential. This work provides novel insight into the mechanisms and consequences of soil microbial changes resulting from extended drought conditions.
历史上可变的降水模式导致的干旱暴露可以选择耐旱的土壤微生物类群，但土壤干燥和再湿润的选择压力下微生物种群的生存和死亡机制尚不清楚。我们对从一个为期 15 年的田间干旱实验中收集的土壤（“改变”降水历史，延长干旱期，与“环境”田间对照）进行了实验室干燥/再湿润实验，以了解选择性种群生存、死亡或维持蛋白质合成潜力和微生物呼吸是否通过可变土壤水分条件受到田间干旱历史的影响。通过 Illumina MiSeq 测序的 16S rRNA 和 16S rRNA 基因，微生物群落组成随实验室干燥/再湿润和田间干旱处理而变化。在环境土壤中，再湿润时减少的 OTU 丰度（指示死亡率）比例较高，而改变的土壤中稳定的 OTU 种群比例较高，在干燥/再湿润过程中丰度没有变化（指示生存）。改变的土壤在干燥过程中 rRNA:rRNA 基因的比例也较低（蛋白质合成潜力较低），加权平均 rRNA 操纵子数量较高（潜在生长速度和 r 选择），与厚壁菌门（目芽孢杆菌目）的丰度较高相关，平均微生物呼吸速率较低。这些数据表明，历史干旱遗留问题较弱的土壤在经历短期干燥和再湿润后，在 OTU 水平上表现出更高的微生物水分胁迫死亡率和差异生存与死亡的趋势，同时伴随着更高的碳损失潜力。这项工作为扩展干旱条件下土壤微生物变化的机制和后果提供了新的见解。
