Digestion and residue stabilization of bacterial and fungal cells, protein, peptidoglycan, and chitin by the geophagous earthworm Metaphire guillelmi
Digestion and residue stabilization of bacterial and fungal cells, protein, peptidoglycan, and chitin by the geophagous earthworm Metaphire guillelmi
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DOI：
10.1016/j.soilbio.2013.03.009
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发表时间：
2013-09
影响因子：
9.7
通讯作者：
J. Shan;Jie Liu;Yongfeng Wang;Xiaoyuan Yan;Hongyan Guo;Xiangzhen Li;R. Ji
中科院分区：
文献类型：
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作者：
J. Shan;Jie Liu;Yongfeng Wang;Xiaoyuan Yan;Hongyan Guo;Xiangzhen Li;R. Ji
微生物生物量是土壤有机质的重要来源，对维持土壤肥力和粮食安全起着至关重要的作用。然而，蚯蚓对土壤微生物生物量的矿化和转化作用尚不清楚。我们使用14c标记的细菌（大肠杆菌和巨芽孢杆菌）细胞、真菌（黄化青霉）细胞、蛋白质、肽聚糖和几丁质对食土蚯蚓进行饲养试验。土壤中微生物细胞和细胞组分的矿化率在7 d内显著高于无蚯蚓土壤的1.2 ~ 4.0倍，高于新鲜蚯蚓铸体材料的1 ~ 11倍。去除蚯蚓后，土壤中微生物生物量剩余碳的矿化程度显著低于未去除蚯蚓的土壤，说明吉列密菌从两个方面影响土壤生物量的矿化：首先是刺激，然后是减少，这是由于微生物生物量通过蚯蚓的肠道，而铸型中的微生物在刺激的微生物生物量矿化和剩余稳定中只起很小的作用。大量（8-29%）被测微生物生物量的放射性标记在蚯蚓组织中被同化。真菌细胞（11%）和细胞壁成分几丁质（29%）在组织中的积累量显著高于细菌细胞（8%）和细胞壁成分肽聚糖（15%）。14c标记的微生物细胞和细胞成分的摄食痕迹提供了直接证据，证明微生物生物量是食土蚯蚓的食物来源，真菌生物量可能比细菌生物量更重要。本研究结果对土食蚯蚓在土壤微生物生物量变化中的作用具有重要意义。
Microbial biomass is an important source of soil organic matter, which plays crucial roles in the maintenance of soil fertility and food security. However, the mineralization and transformation of microbial biomass by the dominant soil macrofauna earthworms are still unclear. We performed feeding trials with the geophagous earthworm Metaphire guillelmi using14C-labelled bacteria (Escherichia coli and Bacillus megaterium) cells, fungal (Penicillium chrysogenum) cells, protein, peptidoglycan, and chitin. The mineralization rate of the microbial cells and cell components was significantly 1.2–4.0-fold higher in soil with the presence of M. guillelmi for seven days than in earthworm-free soil and 1–11-fold higher than in fresh earthworm cast material. When the earthworms were removed from the soil, the mineralization of the residual carbon of the microbial biomass was significantly lower than that in the earthworm-free soil, indicating that M. guillelmi affects the mineralization of the biomass in soil in two aspects: first stimulation and then reduction, which were attributed to the passage of the microbial biomass through the earthworm gut, and that the microorganisms in the cast could play only minor roles in the stimulated mineralization and residual stabilization of microbial biomass. Large amounts (8–29%) of radiolabel of the tested microbial biomass were assimilated in the earthworm tissue. Accumulation of fungal cells (11%) and cell wall component chitin (29%) in the tissue was significantly higher than that of bacterial cells (8%) and cell wall component peptidoglycan (15%). Feeding trails with14C-lablled microbial cells and cell components provided direct evidence that microbial biomass is a food source for geophagous earthworm and fungal biomass is likely a more important food source for earthworms than bacterial biomass. Findings of this study have important implications for the roles of geophagous earthworms in the fate of microbial biomass in soil.