Department of Biology, Virginia Commonwealth University, 1000 W Cary Street, Richmond, VA 23284, USA.
FEMS Microbiol Ecol. 2022 Mar 16;98(3). doi: 10.1093/femsec/fiac019.
In freshwater wetlands, competitive and cooperative interactions between respiratory, fermentative and methanogenic microbes mediate the decomposition of organic matter. These interactions may be disrupted by saltwater intrusion disturbances that enhance the activity of sulfate-reducing bacteria (SRB), intensifying their competition with syntrophic bacteria and methanogens for electron donors. We simulated saltwater intrusion into wetland soil microcosms and examined biogeochemical and microbial responses, employing metabolic inhibitors to isolate the activity of various microbial functional groups. Sulfate additions increased total carbon dioxide production but decreased methane production. Butyrate degradation assays showed continued (but lower) levels of syntrophic metabolism despite strong demand by SRB for this key intermediate decomposition product and a shift in the methanogen community toward acetoclastic members. One month after removing SRB competition, total methane production recovered by only ∼50%. Similarly, butyrate assays showed an altered accumulation of products (including less methane), although overall rates of syntrophic butyrate breakdown largely recovered. These effects illustrate that changes in carbon mineralization following saltwater intrusion are driven by more than the oft-cited competition between SRB and methanogens for shared electron donors. Thus, the impacts of disturbances on wetland biogeochemistry are likely to persist until cooperative and competitive microbial metabolic interactions can recover fully.
在淡水湿地中，呼吸作用、发酵作用和产甲烷微生物之间的竞争和合作相互作用调节着有机物的分解。这些相互作用可能会被盐水入侵干扰破坏，盐水入侵会增强硫酸盐还原菌（SRB）的活性，加剧其与产甲烷菌和产氢菌对电子供体的竞争。我们模拟了盐水入侵湿地土壤微宇宙，并通过使用代谢抑制剂来分离各种微生物功能群的活性，研究了生物地球化学和微生物的响应。硫酸盐的添加增加了总二氧化碳的产生，但减少了甲烷的产生。丁酸降解试验表明，尽管硫酸盐还原菌对这种关键的中间分解产物有强烈的需求，而且产甲烷菌群落向乙酰化成员转移，但协同代谢仍在继续（但水平较低）。在去除硫酸盐还原菌竞争一个月后，总甲烷产量仅恢复了约 50%。同样，丁酸试验显示出产物的积累发生了变化（包括甲烷减少），尽管协同丁酸分解的总体速率已基本恢复。这些影响表明，盐水入侵后碳矿化的变化不仅仅是由于硫酸盐还原菌和产甲烷菌争夺共享电子供体而引起的。因此，湿地生物地球化学的干扰影响可能会持续存在，直到合作和竞争的微生物代谢相互作用能够完全恢复。
