title: Pyrosequencing revealed highly microbial phylogenetic diversity in ferromanganese nodules from farmland.
abstract: There is renewed interest in the origin and makeup of ferromanganese nodules (FMNs), long known to soil mineralogists as unusual secondary minerals. However, new evidence suggests that microorganisms play a significant role in the generation of FMNs. The biogenic origin of nodules has remained elusive because until recently, little has been known about the overall microbial community structure in their microbiota. To learn more about the microbial community and to determine the relative abundance, diversity, and composition of the microbial communities present in FMNs and their surrounding soil, we used pyrosequencing to investigate 16S rRNA genes obtained from vertical soil profiles of both paddy fields and sugarcane fields. Using pyrotaq 16S rRNA gene sequencing, we show that the microbial phylogenetic diversity of nodules was higher than those reported in previous studies of this biosphere, and we identified many previously unidentified microorganisms. Here, we show that the microbial community of these nodules is dominated by Burkholderiales, Rhodocyclales, Acidobacteriales, Desulfuromonales, and Clostridiales, and there were no statistically significant differences found when comparing the microbial community structures of FMNs obtained from vertical soil sequences. Although the microbial composition was markedly different between the surrounding soil and the FMNs, the microbes found within the FMNs were very similar to other FMNs from both field types examined here. In addition to their geochemical properties and the microbial community composition of FMNs, we found that the levels of iron (Fe), manganese (Mn), and SiO2 greatly impact the microbial diversity among FMN communities. Our results indicate that the FMN microbial communities from different land-use types are very similar and suggest that natural selection of these microbes is based on the oligotrophic conditions and the high metal content. Researching FMNs in these two land-use patterns, which represent two different redox potentials, deepens our understanding of Fe-Mn biogeochemical cycling in these oligotrophic biospheres and suggests a biogenetical origin for these nodules.
authors.affiliation: Guangdong Key Laboratory of Agricultural Environment Pollution Integrated Control, Guangdong Institute of Eco-Environmental and Soil Sciences, Guangzhou 510650, P. R. China. cefbli@soil.gd.cn.
authors.forename: Min
authors.initials: M
authors.lastname: Hu
authors.forename: Fangbai
authors.initials: F
authors.lastname: Li
authors.forename: Jing
authors.initials: J
authors.lastname: Lei
authors.forename: Yuan
authors.initials: Y
authors.lastname: Fang
authors.forename: Hui
authors.initials: H
authors.lastname: Tong
authors.forename: Weijian
authors.initials: W
authors.lastname: Wu
authors.forename: Chengshuai
authors.initials: C
authors.lastname: Liu
mesh_terms: D000383:Agriculture; D001419:Bacteria / Q000145:classification*; D017753:Ecosystem; D020459:Genes, rRNA; D014644:Genetic Variation; D007501:Iron; D008345:Manganese; D010802:Phylogeny; D012336:RNA, Ribosomal, 16S; D012988:Soil Microbiology
chemical_list: D012336:RNA, Ribosomal, 16S; C083456:ferro-manganese alloy; D008345:Manganese; D007501:Iron