Distinct bacterial communities across a gradient of vegetation from a preserved Brazilian Cerrado

Abstract

The Cerrado biome in the Sete Cidades National Park, an Ecological Reserve in Northeastern Brazil, has conserved its native biodiversity and presents a variety of plants found in other savannas in Brazil. Despite this finding the soil microbial diversity and community structure are poorly understood. Therefore, we described soil bacterial diversity and distribution along a savanna vegetation gradient taking into account the prevailing environmental factors. The bacterial composition was retrieved by sequencing a fragment of the 16S ribosomal RNA gene. The bacterial operational taxonomic units (OTUs) were assigned to 37 different phyla, 96 classes, and 83 genera. At the phylum level, a core comprised by Proteobacteria, Acidobacteria, Actinobacteria, Firmicutes, Verrucomicrobia and Planctomycetes, was detected in all areas of Cerrado. 'Cerrado stricto sensu' and 'Cerradao' share more similarities between edaphic properties and vegetation and also present more similar bacterial communities, while 'Floresta decidual' and 'Campo graminoide' show the largest environmental differences and also more distinct bacterial communities. Proteobacteria (26%), Acidobacteria (21%) and Actinobacteria (21%) were the most abundant phyla within the four areas. All the samples present similar bacteria richness (alpha diversity) and the observed differences among them (beta diversity) were more related to the abundance of specific taxon OTUs compared to their presence or absence. Total organic C, N and P are the main abiotic factors structuring the bacterial communities. In summary, our findings show the bacterial community structure was clearly different across the Cerrado gradient, but that these environments share a bacterial phylum-core comprising Proteobacteria, Acidobacteria, Actinobacteria, Verrucomicrobia and Planctomycetes with other Brazilian savannas.

Protist species richness and soil microbiome complexity increase towards climax vegetation in the Brazilian Cerrado

“…This is in line with patterns observed for other microbiome components, i.e. bacteria 13 , 15 , 18 , archaea 16 and fungi 17 , 18 . These patterns can be attributed to abiotic differences, such as lower fertility and soil moisture, but higher acidity and soil temperature, in the grass compared to the tree zone.…”

“…Non-random co-occurrence analyses were performed using SparCC, a tool capable of estimating correlation values from compositional data 67 . For this, data tables affiliated to family level, including 18S rRNA data (protists, fungi, nematodes and animal) and 16S rRNA data (bacteria 15 and archaea 16 ), were used in the analysis. We performed the analyses on family level as previously suggested to remove artefacts from inaccurate annotation of lower taxonomic levels and the discrepancy of OTUs to sometimes consist of multiple species, while sometimes species can contain multiple OTUs 68 .…”

“…Increasing knowledge on soil biodiversity is obtained from more agriculture dominated regions, especially Europe and North America 11 , 12 , while the soil biodiversity in southern hemisphere soils, such as the tropical Cerrado, is much less studied. Only recently have microbial groups, including bacteria 13 – 15 , archaea 16 and fungi 17 , 18 , been investigated in the Cerrado. These studies have revealed differences in the community composition of microbial groups between the four vegetation zones with diversity increasing from primary grass to climax tree vegetation.…”

Archaea diversity in vegetation gradients from the Brazilian Cerrado

“…The varied soil conditions found across the gradients of vegetation have influenced the bacterial diversity. 18 Interestingly, our results highlight the soil pH as a significant driver of archaea communities in these soils. According to Gorres, 29 soil pH is the main driver of archaeal community structure in soils.…”

“…Previous studies have shown differences between bacterial diversity in the soils obtained from Cerrado in the Northeast when compared to those from the Central Plateau. 18 Therefore, we used next-generation sequencing of the 16S rRNA gene in soil samples from vegetation gradients obtained from Campo graminoide, Cerrado stricto sensu, Cerradao and Floresta decidual to understand the diversity of Archaea in the soils of Cerrado in Northeastern Brazil.…”