Abstract

16S rRNA sequences from the phylum Acidobacteria have been commonly reported from soil microbial communities, including those from the Brazilian Savanna (Cerrado) and the Atlantic Forest biomes, two biomes that present contrasting characteristics of soil and vegetation. Using 16S rRNA sequences, the present work aimed to study acidobacterial diversity and distribution in soils of Cerrado savanna and two Atlantic forest sites. PCA and phylogenetic reconstruction showed that the acidobacterial communities found in “Mata de galeria” forest soil samples from the Cerrado biome have a tendency to separate from the other Cerrado vegetation microbial communities in the direction of those found in the Atlantic Forest, which is correlated with a high abundance of Acidobacteria subgroup 2 (GP2). Environmental conditions seem to promote a negative correlation between GP2 and subgroup 1 (GP1) abundance. Also GP2 is negatively correlated to pH, but positively correlated to high Al3+ concentrations. The Cerrado soil showed the lowest Acidobacteria richness and diversity indexes of OTUs at the species and subgroups levels when compared to Atlantic Forest soils. These results suggest specificity of acidobacterial subgroups to soils of different biomes and are a starting point to understand their ecological roles, a topic that needs to be further explored.

Highlights

  • Acidobacteria are one of the most abundant phyla in the soil habitats [1]

  • The analysis of 16S rRNA gene clone libraries and pyrosequencing demonstrated that the abundance of Acidobacteria is usually correlated with low values of soil pH [22] and that subgroups GP2 and subgroup 1 (GP1), genera from subgroup 4 (GP4), and GP6 are predominant in soil [1, 23]

  • Aiming to compare the diversity and structure of acidobacterial communities in contrasting Brazilian ecosystems, here we present the analysis of 16S rRNA gene sequences from three works that describe soil acidobacterial communities from the Cerrado and the Atlantic Forest [26, 27]

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Summary

Introduction

Acidobacteria are one of the most abundant phyla in the soil habitats [1]. More than 30% or even 50% of the sequences obtained in 16S rRNA gene clone libraries from soil belong to the phylum Acidobacteria [2] and a great part (4 to 16% transcripts of 16S rRNA from 9 to 31% 16S rRNA genes of Acidobacteria) of these are physiologically active [3]. The genus Thermotomaculum is the only cultured representative of subgroup 10 [21] These isolates were obtained from distinct environments ranging from acidic environments [5, 13, 18] to marine hydrothermal vents [21], to the tundra soil [9], they are usually considered to be slow-growing organisms that thrive in oligotrophic habitats. The analysis of 16S rRNA gene clone libraries and pyrosequencing demonstrated that the abundance of Acidobacteria is usually correlated with low values of soil pH [22] and that subgroups GP1, GP4, and GP6 are predominant in soil [1, 23] These works consider mostly soils from the northern hemisphere and Acidobacteria from Brazilian biomes have not been compared yet.

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