Abstract
Metallophytes microbiota play a key role in plant growth and resistance to heavy metal stress. Comparing to the well-studied single or some specific plant growth-promoting (PGP) bacterial strains, our current understanding of the structural and functional variations of microbiome of metallophytes is still limited. Here, we systematically investigated the endophytic and rhizosphere bacterial community profiles of a metallophyte Commelina communis growing in different Cu-polluted soils by high-throughput sequencing technology. The results showed that the rhizosphere communities of C. communis exhibited a much higher level of diversity and richness than the endosphere communities. Meanwhile, shifts in the bacterial community composition were observed between the rhizosphere and endosphere of C. communis, indicating plant compartment was a strong driver for the divergence between rhizosphere and endosphere community. Among the environmental factors, soil Cu content, followed by OM, TP and TN, played major roles in shaping the bacterial community structure of C. communis. At the highly Cu-contaminated site, Pseudomonas and Sphingomonas were the predominant genera in the endophytic and rhizospheric bacterial communities, respectively, which might enhance copper tolerance as PGP bacteria. In summary, our findings will be useful to better understand metallophyte–microbe interactions and select suitable bacterial taxa when facilitating phytoremediation.
Highlights
Heavy metals in soil pose a serious threat to the entire ecosystem due to their high toxicity and non-biodegradable characteristics
Specific questions we address include: (1) what is the structure and composition of endosphere and rhizosphere microbial communities in C. communis? (2) How do the endophytic and rhizospheric microbial communities of C. communis vary along a Cu contamination gradient? (3) what are the key drivers if such variations exist? Our results provide a comprehensive insight into the complex bacterial community associated with metallophytes, which may be crucial for further application of the beneficial bacteria in phytoremediation
We found that the parameters evaluating microbial diversity and richness were higher in the rhizosphere soil bacterial community than in the endophytic bacterial communities of C. communis (Figure 1 and Figure S3), which was consistent with the previous reports in other plant species [13,40,41]
Summary
Heavy metals in soil pose a serious threat to the entire ecosystem due to their high toxicity and non-biodegradable characteristics. The elevated concentrations of heavy metals are continuously entering into the food chain through agriculture, leading to considerable health risks to humans and animals; this issue requires urgent remediation [1,2]. Compared to other conventional physico-chemical remediation methods, phytoremediation has been considered as an alternative cost-effective and eco-friendly remediation strategy for in situ toxic-metal cleanup, attracting a lot of attention [3]. High excessive concentrations of metal ions in the soil can significantly induce oxidative damages, reduce the photosynthetic rate, and inhibit the plant growth and development [3]. High excessive concentrations of metal ions in the soil can significantly induce oxidative damages, reduce the photosynthetic rate, and inhibit the plant growth and development [3]. 4.0/).
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