Non-Specific Interactions of Rhizospheric Microbial Communities Support the Establishment of Mimosa acutistipula var. ferrea in an Amazon Rehabilitating Mineland

Abstract

Mimosa acutistipula var. ferrea (Fabaceae) is endemic to ferruginous tropical rocky outcrops in the eastern Amazon, also known as canga. Canga are often associated with mining activities and are the target of protection and rehabilitation projects. M. acutistipula stands out in this biodiversity hotspot with high growth rates, even in rehabilitating minelands (RMs). However, little is known about the diversity of soil microorganisms interacting with M. acutistipula in canga and RMs. This study analyzed the rhizosphere-associated bacterial and fungal microbial communities associated with M. acutistipula growing in an RM and a native shrub canga. The fungal phylum Ascomycota was the dominant taxa identified in the rhizosphere of the canga (RA: 98.1) and RM (RA: 93.1). The bacterial phyla Proteobacteria (RA: 54.3) and Acidobacteria (RA: 56.2) were the dominant taxa identified in the rhizosphere in the canga and RM, respectively. Beneficial genera such as Bradyrhizobium, Rhodoplanes, and Paraconiothyrium were identified in the rhizosphere of M. acutistipula in both areas. However, the analyses showed that the fungal and bacterial diversity differed between the rhizosphere of the canga and RM, and that the microbial taxa adapted to the canga (i.e., Rasamsonia, Scytalidium, Roseiarcus, and Rhodomicrobium) were lacking in the RM. This influences the microbe-mediated soil processes, affecting long-term rehabilitation success. The results showed that M. acutistipula established non-specific interactions with soil microorganisms, including beneficial taxa such as nitrogen-fixing bacteria, mycorrhizal fungi, and other beneficial endophytes, well known for their importance in plant adaptation and survival. High levels of microbe association and a plant’s ability to recruit a wide range of soil microorganisms help to explain M. acutistipula’s success in rehabilitating minelands.

Proteomic Profiling and Rhizosphere-Associated Microbial Communities Reveal Adaptive Mechanisms of Dioclea apurensis Kunth in Eastern Amazon’s Rehabilitating Minelands

“…Proteobacteria and Ascomycota were the most abundant bacterial and fungal phyla, respectively, in both rhizosphere and bulk soil substrates ( Figure 5 ). Recent studies have reported similar results in plants growing in ecosystems affected by mining activities, where the soil microbial communities and specific mechanisms of abiotic stress tolerance can be considered key to promoting the phytostabilization towards rehabilitation of ecosystems services [ 8 , 56 ]. Among the preferential microorganisms identified in this study, several beneficial saprophytic, free-living, symbiotic, and endophytic taxa were directly identified in the rhizospheric soil, especially in plants from canga , where specific fungal and bacterial taxa belonging to plant growth-promoting microorganisms were detected (e.g., Paraconiothyrium , Rasamsonia , Scytalidium , Rhodoplanes , Bradyrhizobium , Rhizobium , Roseiarcus , and Actinotalea ) ( Table S3 ; Figure 5 ).…”

“…Additionally, several beneficial bacterial and fungal genera with key roles in nutrient solubilization, plant growth promotion, and defense against phytopathogens were detected (e.g., Glomeromycetes, Sphingomonas , Actinotalea , Rhizobium , Rasamsonia , Paraconiothyrium ) [ 61 , 62 , 63 ]. Despite the higher diversity of rhizosphere-associated microorganisms identified in plants growing in RM, they were mostly different from those detected in canga , denoting that D. apurensis can associate with beneficial soil microorganisms inhabiting soil substrates in RM without an apparent specificity, similar to what has been described in Mimosa acutistipula [ 8 ]. Accordingly, the specific rhizosphere-associated microbial communities of D. apurensis , which is related to better performance under abiotic stress conditions in canga [ 64 ], must be considered in mineland rehabilitation projects to preserve essential microbe-mediated processes that can contribute to later successional stages of rehabilitation in Amazonian canga .…”

“…The amplicon libraries for bacteria and fungi were prepared according to Costa et al [ 8 ], with minor modifications. The 16S rRNA gene was amplified by PCR using the bacterial primer set S-D-Bact-0341-b-S-17-N (5′-TCGTCGGCAGCGTCAGATGTGTATAAGAGACAGCCTACGGGNGGCWGCAG-3′) and S-D-Bact-0785-a-A-21-N (5′-GTCTCGTGGGCTCGGAGATGTGTATAAGAGACAGGACTACHVGGGTATCTAATCC-3′).…”

“…These species have a crucial role in the success of mineland rehabilitation, reducing local biodiversity loss and contributing to the progressive recovery of ecological services associated with canga . Considering that revegetation is a fundamental technique for the rehabilitation of minelands, there is a need to identify native species able to cope with the stressful environmental conditions of post-mining areas in canga and understand the adaptive mechanisms used by such plants [ 7 , 8 , 9 ].…”

Cross-species transcriptomes reveal species-specific and shared molecular adaptations for plants development on iron-rich rocky outcrops soils

“…The canga plant community also presents metal tolerance by excluding or accumulating (or hyper-accumulating) metals in their shoots [ 2 , 3 , 9 ]. Some studies also demonstrated the importance of soil microorganisms in the maintenance and growth of plant species in metal-rich canga environments [ 10 – 12 ]. Although several species in the Carajás' cangas shows metal accumulation [ 9 ], there is no study evaluating the plants' adaptive genetic responses that allows them to thrive in such a stressful environment.…”