Testing the stress gradient hypothesis in soil bacterial communities associated with vegetation belts in the Andean Atacama Desert

Abstract

Background Soil microorganisms are in constant interaction with plants, and these interactions shape the composition of soil bacterial communities by modifying their environment. However, little is known about the relationship between microorganisms and native plants present in extreme environments that are not affected by human intervention. Using high-throughput sequencing in combination with random forest and co-occurrence network analyses, we compared soil bacterial communities inhabiting the rhizosphere surrounding soil (RSS) and the corresponding bulk soil (BS) of 21 native plant species organized into three vegetation belts along the altitudinal gradient (2400–4500 m a.s.l.) of the Talabre–Lejía transect (TLT) in the slopes of the Andes in the Atacama Desert. We assessed how each plant community influenced the taxa, potential functions, and ecological interactions of the soil bacterial communities in this extreme natural ecosystem. We tested the ability of the stress gradient hypothesis, which predicts that positive species interactions become increasingly important as stressful conditions increase, to explain the interactions among members of TLT soil microbial communities. Results Our comparison of RSS and BS compartments along the TLT provided evidence of plant-specific microbial community composition in the RSS and showed that bacterial communities modify their ecological interactions, in particular, their positive:negative connection ratios in the presence of plant roots at each vegetation belt. We also identified the taxa driving the transition of the BS to the RSS, which appear to be indicators of key host-microbial relationships in the rhizosphere of plants in response to different abiotic conditions. Finally, the potential functions of the bacterial communities also diverge between the BS and the RSS compartments, particularly in the extreme and harshest belts of the TLT. Conclusions In this study, we identified taxa of bacterial communities that establish species-specific relationships with native plants and showed that over a gradient of changing abiotic conditions, these relationships may also be plant community specific. These findings also reveal that the interactions among members of the soil microbial communities do not support the stress gradient hypothesis. However, through the RSS compartment, each plant community appears to moderate the abiotic stress gradient and increase the efficiency of the soil microbial community, suggesting that positive interactions may be context dependent.

Bacterial Community Composition and Presence of Plasmids in the Endosphere- and Rhizosphere-Associated Microbiota of Sea Fig (Carpobrotus aequilaterus)

“…In this context, it was also indicated that limited nutrient and water in soils can influence the microbiome recruitment by plants, leading to the selection of specific soil bacterial communities with beneficial functions that might help plants under harsh environmental conditions [46,47]. Thus, plant roots can modulate positive and negative bacterial interactions, as observed across the altitudinal vegetation belt in the Atacama Desert by Mandakovic et al [48]. Similarly, studies on two cactus species, Myrtillocactus geometrizans and Opuntia robusta, in arid ecosystems revealed that plant compartments, plant species, site, and season played a crucial role in the assembly of the microbiota [49].…”

Metabolic Characterization and Geochemical Drivers of Active Hydrocarbon‐Degrading Microorganisms

“…Wang et al, 2022), or other factors such as vegetation, plant species, soil texture, sampling effects, and ecologically neutral diversification processes (J. Li et al, 2021;Liang et al, 2011;Mandakovic et al, 2023;Rüger et al, 2023). These considerations expand our understanding of the complexities driving functional microbial community variations in oil-polluted environments.…”

“…Consistent with previous research on total microbial communities, this is reasonable, given that a considerable portion of soil microbial community variation cannot be explained by measured environmental variables or geographical distance (He et al., 2023; Liang et al., 2011; Ramette & Tiedje, 2007). This gap in explanation may be attributed to unmeasured environmental variables, like the type of petroleum pollutants affecting microbial genetic diversity (H. Y. Wang et al., 2022), or other factors such as vegetation, plant species, soil texture, sampling effects, and ecologically neutral diversification processes (J. Li et al., 2021; Liang et al., 2011; Mandakovic et al., 2023; Rüger et al., 2023). These considerations expand our understanding of the complexities driving functional microbial community variations in oil‐polluted environments.…”

Topsoil and subsoil bacterial community assemblies across different drainage conditions in a mountain environment

“…For example, taxonomic analysis revealed an abrupt change between the rhizosphere and the rest of the non-rhizospheric soils of Chilean altiplanic native plants from the Andean grasslands soils [ 36 ]. In addition analysis of 21 native plant species organized into three vegetation belts in the Andes in the Atacama Desert showed that plants appears to determine plant-specific microbial community composition in the soil associated to root system and showed that bacterial communities modify their ecological interactions, in particular, their positive:negative connection ratios in the presence of plant roots [ 37 ]. Thus, spatial differentiation of TS and SS as environments must be interpreted with caution, especially in studies of bacterial community assembly processes along a soil depth gradient.…”