Department of Molecular Ecology, Max Planck Institute for Marine Microbiology, Bremen, Germany.
Department of Marine Sciences, University of North Carolina-Chapel Hill, Chapel Hill, NC, USA.
Environ Microbiol. 2022 May;24(5):2333-2347. doi: 10.1111/1462-2920.15997. Epub 2022 Apr 17.
Marine heterotrophic bacteria contribute considerably to global carbon cycling, in part by utilizing phytoplankton-derived polysaccharides. The patterns and rates of two different polysaccharide utilization modes - extracellular hydrolysis and selfish uptake - have previously been found to change during spring phytoplankton bloom events. Here we investigated seasonal changes in bacterial utilization of three polysaccharides, laminarin, xylan and chondroitin sulfate. Strong seasonal differences were apparent in mode and speed of polysaccharide utilization, as well as in bacterial community compositions. Compared to the winter month of February, during the spring bloom in May, polysaccharide utilization was detected earlier in the incubations and a higher portion of all bacteria took up laminarin selfishly. Highest polysaccharide utilization was measured in June and September, mediated by bacterial communities that were significantly different from spring assemblages. Extensive selfish laminarin uptake, for example, was detectible within a few hours in June, while extracellular hydrolysis of chondroitin was dominant in September. In addition to the well-known Bacteroidota and Gammaproteobacteria clades, the numerically minor verrucomicrobial clade Pedosphaeraceae could be identified as a rapid laminarin utilizer. In summary, polysaccharide utilization proved highly variable over the seasons, both in mode and speed, and also by the bacterial clades involved.
海洋异养细菌在全球碳循环中起着重要作用，部分原因是它们利用了浮游植物衍生的多糖。先前已经发现，在春季浮游植物爆发事件中，两种不同多糖利用模式（细胞外水解和自私摄取）的模式和速率会发生变化。在这里，我们研究了三种多糖（褐藻淀粉、木聚糖和硫酸软骨素）的细菌利用的季节性变化。多糖利用的模式和速度以及细菌群落组成都存在明显的季节性差异。与 2 月的冬季相比，在 5 月的春季浮游植物爆发期间，培养物中更早地检测到多糖的利用，并且更多的细菌自私地摄取褐藻淀粉。6 月和 9 月的多糖利用率最高，这是由与春季组合明显不同的细菌群落介导的。例如，在 6 月，细菌可以在几个小时内大量吸收自私的褐藻淀粉，而在 9 月，硫酸软骨素的细胞外水解则占主导地位。除了众所周知的拟杆菌门和γ变形菌门外，数量较少的疣微菌门 Pedosphaeraceae 也可以被鉴定为快速褐藻淀粉利用者。总之，多糖的利用在模式和速度上都具有高度的季节性变化，而且涉及的细菌类群也不同。
