Abstract
The Cerrado biome corresponds to an extensive area of Brazil and is considered a biodiversity hotspot. Frequent fires are a natural feature in this biome and have influences on vegetation structure and composition. However, continuous anthropogenic actions are promoting changes in fire frequency and seasonality. Despite the high biodiversity of the Cerrado, little is known about its microbiome, with few publications describing some aspects of the bacterial and fungal communities found on this biome and almost no references about archaea. In this study, we describe the archaeal diversity in Cerrado sensu stricto soils, comparing the archaeal communities from soils of an area long protected from fires to one exposed to biennial fires, using both 16S rRNA and amoA genes as molecular markers. Almost all 16S rRNA sequences from both studied areas were affiliated with I.1b and 1.1c Thaumarchaeota, groups commonly detected in terrestrial environments. A higher relative abundance of I.1b thaumarchaeal subgroup was detected in the frequently burned area even though no statistically significant differences were observed in archaeal 16S rRNA richness and diversity between the investigated areas. Many ammonia-oxidizing archaea (AOA) are affiliated with this group, which is consistent with the higher amoA diversity and OTU numbers detected in the area periodically burned. Taken together, our results suggest that, although total archaeal community richness and diversity do not seem to greatly differ between the investigated conditions, alterations in wood cover and vegetation structure caused by frequent fires likely cause long-term effects in AOA diversity in Cerrado soils.
Highlights
It is well established that organisms of the Archaea domain are ubiquitously distributed and represent a significant fraction of the prokaryotic cells found in aquatic and terrestrial ecosystems [1, 2]
Most archaea found in soils were initially classified as Group I Crenarchaeota [11], they are classified as members of the Thaumarchaeota phylum [12], which contains all ammonia-oxidizing archaea (AOA) known so far [13]
Our study revealed that I.1b and I.1c Thaumarchaeota are dominant in typical Cerrado sensu stricto soils from areas long protected from fire or submitted to frequent fire regime
Summary
It is well established that organisms of the Archaea domain are ubiquitously distributed and represent a significant fraction of the prokaryotic cells found in aquatic and terrestrial ecosystems [1, 2]. In spite of its notable biodiversity, studies focusing on archaeal diversity in natural Brazilian environments are still scarce, with only about 50 studies published in the last 20 years according to a recent review by Rodrigues et al [14] Most of these studies investigated archaeal communities in soils from the Amazon or Atlantic Forest biomes, but very few have focused on archaeal diversity of the Brazilian savanna, known as Cerrado [15,16,17,18,19]. Due to the Archaea large number of endemic species and the continuous degradation of its habitats, the Cerrado is considered a hotspot for conservation priorities [20] This biome presents different physiognomic forms, ranging from grassland to forest-like vegetation [21]. The seasonality of rains, poor nutrient soils, and fires are considered the determinants of this biome vegetation [22, 23]
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