School of Marine Science and Policy, University of Delaware, Lewes, Delaware, USA.
Appl Environ Microbiol. 2012 Apr;78(7):2402-9. doi: 10.1128/AEM.07130-11. Epub 2012 Jan 27.
Environmental conditions in the western Arctic Ocean range from constant light and nutrient depletion in summer to complete darkness and sea ice cover in winter. This seasonal environmental variation is likely to have an effect on the use of dissolved organic matter (DOM) by heterotrophic bacteria in surface water. However, this effect is not well studied and we know little about the activity of specific bacterial clades in the surface oceans. The use of DOM by three bacterial subgroups in both winter and summer was examined by microautoradiography combined with fluorescence in situ hybridization. We found selective use of substrates by these groups, although the abundances of Ant4D3 (Antarctic Gammaproteobacteria), Polaribacter (Bacteroidetes), and SAR11 (Alphaproteobacteria) were not different between summer and winter in the Beaufort and Chukchi Seas. The number of cells taking up glucose within all three bacterial groups decreased significantly from summer to winter, while the percentage of cells using leucine did not show a clear pattern between seasons. The uptake of the amino acid mix increased substantially from summer to winter by the Ant4D3 group, although such a large increase in uptake was not seen for the other two groups. Use of glucose by bacteria, but not use of leucine or the amino acid mix, related strongly to inorganic nutrients, chlorophyll a, and other environmental factors. Our results suggest a switch in use of dissolved organic substrates from summer to winter and that the three phylogenetic subgroups examined fill different niches in DOM use in the two seasons.
北极西部的环境条件从夏季的持续光照和营养物质枯竭到冬季的完全黑暗和海冰覆盖变化多样。这种季节性的环境变化很可能对异养细菌在地表水层中利用溶解有机物质（DOM）产生影响。然而，这种影响尚未得到充分研究，我们对特定海洋表层细菌类群的活性知之甚少。通过微放射性自显影技术结合荧光原位杂交技术，研究了冬季和夏季三种细菌亚群对 DOM 的利用情况。我们发现这些群体对底物有选择性的利用，尽管在波弗特海和楚科奇海，Ant4D3（南极γ变形菌）、Polaribacter（拟杆菌门）和 SAR11（α变形菌门）在夏季和冬季的丰度没有差异。所有三种细菌群体内摄取葡萄糖的细胞数量从夏季到冬季显著减少，而利用亮氨酸的细胞比例在季节之间没有明显的模式。尽管其他两组没有出现这种大量的增加，但是 Ant4D3 组对氨基酸混合物的摄取量从夏季到冬季显著增加。细菌对葡萄糖的利用，但不是对亮氨酸或氨基酸混合物的利用，与无机养分、叶绿素 a 和其他环境因素密切相关。我们的研究结果表明，从夏季到冬季，溶解有机底物的利用发生了转变，并且所研究的三个系统发育亚群在两个季节中对 DOM 的利用填补了不同的生态位。
