State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan, China.
PLoS One. 2013 Sep 12;8(9):e73778. doi: 10.1371/journal.pone.0073778. eCollection 2013.
Manganese-oxidizing bacteria in the aquatic environment have been comprehensively investigated. However, little information is available about the distribution and biogeochemical significance of these bacteria in terrestrial soil environments. In this study, stratified soils were initially examined to investigate the community structure and diversity of manganese-oxidizing bacteria. Total 344 culturable bacterial isolates from all substrata exhibited Mn(II)-oxidizing activities at the range of 1 µM to 240 µM of the equivalent MnO2. The high Mn(II)-oxidizing isolates (>50 mM MnO2) were identified as the species of phyla Actinobacteria, Firmicutes and Proteobacteria. Seven novel Mn(II)-oxidizing bacterial genera (species), namely, Escherichia, Agromyces, Cellulomonas, Cupriavidus, Microbacterium, Ralstonia, and Variovorax, were revealed via comparative phylogenetic analysis. Moreover, an increase in the diversity of soil bacterial community was observed after the combined enrichment of Mn(II) and carbon-rich complex. The phylogenetic classification of the enriched bacteria represented by predominant denaturing gradient gel electrophoresis bands, was apparently similar to culturable Mn(II)-oxidizing bacteria. The experiments were further undertaken to investigate the properties of the Mn oxide aggregates formed by the bacterial isolates with high Mn(II)-oxidizing activity. Results showed that these bacteria were closely encrusted with their Mn oxides and formed regular microspherical aggregates under prolonged Mn(II) and carbon-rich medium enrichment for three weeks. The biotic oxidation of Mn(II) to Mn(III/IV) by these isolates was confirmed by kinetic examinations. X-ray diffraction assays showed the characteristic peaks of several Mn oxides and rhodochrosite from these aggregates. Leucoberbelin blue tests also verified the Mn(II)-oxidizing activity of these aggregates. These results demonstrated that Mn oxides were formed at certain amounts under the enrichment conditions, along with the formation of rhodochrosite in such aggregates. Therefore, this study provides insights into the structure and diversity of soil-borne bacterial communities in Mn(II)-oxidizing habitats and supports the contribution of soil-borne Mn(II)-oxidizing bacteria to Mn oxide mineralization in soils.
水生环境中的锰氧化细菌已得到全面研究。然而，关于这些细菌在陆地土壤环境中的分布和生物地球化学意义的信息却很少。在本研究中，我们首先对分层土壤进行了研究，以调查锰氧化细菌的群落结构和多样性。从所有基质中总共分离出 344 株可培养细菌，这些细菌在 1 µM 至 240 µM 当量 MnO2 的范围内具有 Mn(II)氧化活性。高 Mn(II)氧化菌（>50 mM MnO2）被鉴定为放线菌、厚壁菌门和变形菌门的物种。通过比较系统发育分析，揭示了 7 种新的 Mn(II)氧化细菌属（种），即 Escherichia、Agromyces、Cellulomonas、Cupriavidus、Microbacterium、Ralstonia 和 Variovorax。此外，在 Mn(II)和富碳复合物的联合富集后，观察到土壤细菌群落的多样性增加。通过主要变性梯度凝胶电泳带代表的富集细菌的系统发育分类，与可培养的 Mn(II)氧化细菌明显相似。进一步进行实验以研究具有高 Mn(II)氧化活性的细菌分离物形成的 Mn 氧化物聚集体的性质。结果表明，这些细菌紧密地包裹着它们的 Mn 氧化物，并在延长的 Mn(II)和富碳培养基中富集三周后形成规则的微球形聚集体。通过动力学研究证实了这些分离物将 Mn(II)生物氧化为 Mn(III/IV)。X 射线衍射分析表明，这些聚集体中存在几种 Mn 氧化物和菱锰矿的特征峰。Leucoberbelin 蓝测试也验证了这些聚集体的 Mn(II)氧化活性。这些结果表明，在富集条件下形成了一定量的 Mn 氧化物，同时在这些聚集体中形成菱锰矿。因此，本研究深入了解了 Mn(II)氧化栖息地中土壤传播细菌群落的结构和多样性，并支持土壤传播的 Mn(II)氧化细菌对土壤中 Mn 氧化物矿化的贡献。
