Silva K J, Vidal-Torrado P, Lambais M R
Department of Soil Science, University of São Paulo, Piracicaba, São Paulo, 13418-900, Brazil.
Microb Ecol. 2015 Feb;69(2):372-82. doi: 10.1007/s00248-014-0493-3. Epub 2014 Sep 16.
Podzols frequently show bleached mottles depleted in organic matter, most readily visible in the Bh horizons. Even though the process of bleached mottles development is not understood, it has been suggested that the selective degradation of organic matter by soil microorganisms has a major contribution. In this study, we examined the bacterial and archaeal communities along three Brazilian coastal podzol profiles, as well as in bleached mottles and their immediate vicinity, using 16S rRNA gene profiling. Our results showed that the bacterial and archaeal community structures in the studied podzols varied with depth and that the bacterial communities in the bleached mottles were significantly different from that in their immediate vicinity. In contrast, the archaeal communities in bleached mottles were significantly different from their vicinity only in the Bertioga (BT) profile, based on sequencing of amplicons of the 16S rRNA gene. Redundancy analyses showed that the bacterial community structures in the bleached mottles of BT were negatively associated mostly with the levels of organic carbon, exchangeable-aluminum (Al), exchangeable potassium, and Al-saturation, whereas in the surrounding soil, the opposite was observed. In the Ilha Comprida (IC) profiles, no such relationships were observed, suggesting distinct drivers of the bacterial community structures in bleached mottles of different podzols. In the bleached mottles of the BT profile, operational taxonomic units (OTUs) phylogenetically related to Pseudomonas were the most abundant Bacteria, whereas in the IC profiles, OTUs related to Acidobacteria were predominant. Thermoprotei (Crenarchaeota) were the most abundant Archaea in the bleached mottles and in their immediate vicinity. Based on the diverse metabolic capabilities of Pseudomonas and Acidobacteria, our data suggest that these groups of bacteria may be involved in the development of bleached mottles in the podzols studied and that the selection of specific bacterial populations in the bleached mottles may depend on the local edaphic conditions.
灰化土常常呈现出有机质含量低的漂白斑纹，在Bh层最为明显。尽管漂白斑纹的形成过程尚不明确，但有观点认为土壤微生物对有机质的选择性降解起到了主要作用。在本研究中，我们利用16S rRNA基因分析，研究了巴西沿海三个灰化土剖面以及漂白斑纹及其紧邻区域的细菌和古菌群落。我们的结果表明，所研究的灰化土中细菌和古菌群落结构随深度变化，且漂白斑纹中的细菌群落与其紧邻区域显著不同。相比之下，基于16S rRNA基因扩增子测序，仅在贝蒂奥加（BT）剖面中，漂白斑纹中的古菌群落与其紧邻区域存在显著差异。冗余分析表明，BT剖面漂白斑纹中的细菌群落结构主要与有机碳、交换性铝（Al）、交换性钾和铝饱和度呈负相关，而在周围土壤中则相反。在伊利亚孔普里达（IC）剖面中，未观察到此类关系，这表明不同灰化土漂白斑纹中细菌群落结构的驱动因素不同。在BT剖面的漂白斑纹中，与假单胞菌系统发育相关的操作分类单元（OTU）是最丰富的细菌，而在IC剖面中，与酸杆菌相关的OTU占主导地位。嗜热栖热菌（泉古菌）是漂白斑纹及其紧邻区域中最丰富的古菌。基于假单胞菌和酸杆菌多样的代谢能力，我们的数据表明，这些细菌群体可能参与了所研究灰化土中漂白斑纹的形成，且漂白斑纹中特定细菌种群的选择可能取决于当地土壤条件。
