Anesio AM, Theil-Nielsen J, Granéli W
Department of Ecology/Limnology, Lund University, S-223 62 Lund, Sweden
Microb Ecol. 2000 Aug;40(3):200-208. doi: 10.1007/s002480000045.
We measured bacterial growth on phototransformed dissolved organic matter (DOM) leached from eight different primary producers. Leachates (10 mg C liter(-1)) were exposed to artificial UVA + UVB radiation, or kept in darkness, for 20 h. DOM solutions were subsequently inoculated with lake water bacteria. Photoproduction of dissolved inorganic carbon (DIC), ranging from 3 to 16 µg C liter(-1) h(-1), and changes in the absorptive characteristics of the DOM were observed for all leachates upon UV irradiation. The effects of irradiation exposure on DOM bioavailability varied greatly, depending on leachate and type of bacterial growth criterion. Bacterial carbon utilization (biomass production plus respiration) over the entire incubation period (120 h) was enhanced by UV radiation of leachate from the terrestrial leaves, relative to carbon utilization in non-irradiated leachates. Conversely, carbon utilization was reduced by radiation of the leachates from aquatic macrophytes. In a separate experiment, the stable C and N isotope composition of bacteria grown on irradiated and non-irradiated DOM was estimated. Bacterial growth on UV-irradiated DOM was enriched in (13)C relative to the bacteria in the non-irradiated treatments; this result may be explained by selective assimilation of photochemically produced, isotopically enriched labile compounds.
我们测量了从八种不同初级生产者中沥出的光转化溶解有机物（DOM）上的细菌生长情况。沥出液（10毫克碳/升）分别接受人工UVA + UVB辐射或置于黑暗中20小时。随后向DOM溶液中接种湖水细菌。在紫外线照射下，所有沥出液均观察到溶解无机碳（DIC）的光生成，范围为3至16微克碳/升·小时，同时DOM的吸收特性也发生了变化。辐照暴露对DOM生物可利用性的影响差异很大，这取决于沥出液和细菌生长标准的类型。相对于未辐照沥出液中的碳利用情况，陆地叶片沥出液的紫外线辐射增强了整个培养期（120小时）内的细菌碳利用（生物量生产加呼吸作用）。相反，水生大型植物沥出液的辐射降低了碳利用。在另一个实验中，估算了在辐照和未辐照DOM上生长的细菌的稳定碳和氮同位素组成。相对于未辐照处理中的细菌，在紫外线辐照DOM上生长的细菌的（13）C含量有所富集；这一结果可能是由于光化学产生的、同位素富集的不稳定化合物的选择性同化作用所致。
