Akinwole Philips, Kaplan Louis, Findlay Robert
Department of Biology, DePauw University, Greencastle, IN, USA.
Department of Biological Sciences, University of Alabama, Tuscaloosa, AL, USA.
World J Microbiol Biotechnol. 2021 Jan 19;37(2):32. doi: 10.1007/s11274-021-02997-5.
Terrestrial dissolved organic matter (tDOM) is susceptible to microbiological and photolytic oxidations and contributes significantly to the energy flow in aquatic ecosystems. However, bacterial species actively utilizing this tDOM are still not determined. We here elucidated the microbial groups actively utilizing tDOM. We characterized sediment microbial biomass and community structure using phospholipid phosphate and phospholipid fatty acids (PLFAs) analysis, respectively, and identified metabolically active members using PLFA stable-isotope-probing. Prokaryotes comprised 61% of the streambed microbial community consisting of aerobic, facultative anaerobic and anaerobic bacteria while microeukaryotes comprised the remaining 39%. Sediments were incubated in re-circulating mesocosm chambers amended with leachate from composted C-labelled tulip poplar (Liriodendron tulipifera L.) tree-tissues and examined for C incorporation into microbial PLFAs. The structure of stream sediment microbial communities prior to and after mesocosm incubation, in both the presence and absence of C-labeled DOM, showed no significant differences and indicated our mesocosm-based experimental design as sufficiently robust to investigate the utilization of C-DOM by sediment microbial communities. After 48 h of incubation, bacterial fatty acids i15:0, a15:0, 16:0, 16:1ω9, 18:1ω9c, 18:1ω7c, 10me16 and cy19:0 showed increased abundance of C. This identified the aerobic, facultative anaerobic and anaerobic bacteria as actively utilizing the C-labeled DOM. A single dark 48 h incubation showed incorporation into both bacterial and microeukaryotic fatty acids (20:4ω6, 20:5ω3) suggesting that microeukaryotic predators consumed bacteria that utilized C-labeled DOM. Hence, our data support the hypothesis that streamwater tDOM is utilized by stream bacteria, and substantially contributes to the energy flow in aquatic ecosystems.
陆地溶解有机物（tDOM）易受微生物和光解氧化作用影响，对水生生态系统的能量流动有重要贡献。然而，积极利用这种tDOM的细菌种类仍未确定。我们在此阐明了积极利用tDOM的微生物群体。我们分别使用磷脂磷酸盐和磷脂脂肪酸（PLFA）分析来表征沉积物微生物生物量和群落结构，并使用PLFA稳定同位素探测来鉴定代谢活跃成员。原核生物占河床微生物群落的61%，包括需氧菌、兼性厌氧菌和厌氧菌，而微型真核生物占其余的39%。沉积物在循环中宇宙室中孵育，用堆肥的C标记郁金香杨树（Liriodendron tulipifera L.）树组织的渗滤液进行修正，并检测C掺入微生物PLFA的情况。在有和没有C标记DOM的情况下，中宇宙孵育前后溪流沉积物微生物群落的结构没有显著差异，这表明我们基于中宇宙的实验设计足够稳健，能够研究沉积物微生物群落对C-DOM的利用。孵育48小时后，细菌脂肪酸i15:0、a15:0、16:0、16:1ω9、18:1ω9c、18:1ω7c、10me16和cy19:0显示出C丰度增加。这确定了需氧菌、兼性厌氧菌和厌氧菌为积极利用C标记DOM的细菌。单次48小时黑暗孵育显示C掺入细菌和微型真核生物脂肪酸（20:4ω6、20:5ω3）中，这表明微型真核生物捕食者消耗了利用C标记DOM的细菌。因此，我们的数据支持了溪流水tDOM被溪流细菌利用并对水生生态系统的能量流动有重大贡献这一假设。
