Abstract
Eusocial animals, such as the termites, often build a nest-like structure called a mound that provides shelter with stable internal conditions and protection against predators. Termites are important components of the Brazilian Cerrado biota. This study aimed to investigate the bacterial community composition and diversity of the Syntermes wheeleri termite-mound soil using culture-independent approaches. We considered the vertical profile by comparing two different mound depths (mound surface and 60 cm) and seasonality with samplings during the rainy and dry seasons. We compared the mound soil microbiota to the adjacent soil without the influence of the mound to test the hypothesis that the Cerrado soil bacterial community was more diverse and more susceptible to seasonality than the mound soil microbiota. The results support the hypothesis that the Cerrado soil bacterial community is more diverse than the mound soil and also has a higher variability among seasons. The number of observed OTUs (Operational Taxonomic Units) was used to express bacterial richness, and it indicates that soil moisture has an effect on the community distribution and richness of the Cerrado samples in comparison to mound samples, which remain stable across seasons. This could be a consequence of the protective role of the mound for the termite colony. The overall community taxonomic profile was similar between soil samples, especially when compared to the taxonomic composition of the Syntermes wheeleri termite’s gut, which might be explained by the different characteristics and functionality between the soil and the gut microbial community.
Highlights
Cerrado is the richest tropical savanna in the world [1]
The number of observed OTUs (Operational Taxonomic Units) was used to express bacterial richness, and it indicates that soil moisture has an effect on the community distribution and richness of the Cerrado samples in comparison to mound samples, which remain stable across seasons
The Syntermes wheeleri termite species was identified by its soldier caste, and mound soil was collected at two different depths: at the mound surface (0–10 cm) and at a depth interval of 50–60 cm (Figure 1B)
Summary
Cerrado is the richest tropical savanna in the world [1] It represents 24% of the Brazilian territory and it is the second largest biome after the Amazon rainforest [2,3]. The Cerrado soils are predominantly Oxisols characterized by their acidity, red color, low nutrient concentrations, and high clay content and aluminum concentration [3,4,5]. This biome is characterized by dry winters and rainy summers, with markedly seasonal rainfall having a great impact on the soil microbiology function [6,7]. The presence of the termites in the Cerrado soil is associated with higher pH values, Calcium (Ca), Phosphorus (P), and Potassium (K) concentrations and lower Aluminum (Al) concentrations [11]
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