Responses of microbial communities in rhizocompartments of king grass to phytoremediation of cadmium-contaminated soil

Abstract

King grass has been recognized as a potential phytoremediation plant species due to its high biomass and resistance to heavy metals (HMs). However, the possible impacts of cadmium (Cd) contamination on rhizocompartments' microbial activities in association with king grass have not been extensively explored. The utilization of 16S rRNA gene and ITS sequencing was carried out to examine alterations in the bacterial and fungal communities in the rhizosphere and rhizoplane of king grass in response to low and high Cd stress. Results demonstrated that both bacterial and fungal communities' diversity and richness were negatively impacted by Cd stress, regardless of its concentration. However, evenness did not exhibit any significant response to either of the concentrations. Additionally, nonmetric multidimensional scaling (NMDS) ordination demonstrated a significant difference (p < 0.001) in microbial communities under different treatments. The abundance of bacterial taxa such as Steroibacter, Nitrospira, Pseudoxanthomonas, Cellvirio, Phenylobacterium, Mycobacterium, Pirellula and Aquicella was adversely affected under Cd stress while Flavobacterium, Gemmata, Thiobacillus and Gemmatimonas showed no prominent response, indicating their resistance to Cd stress. Like that, certain fungal taxa for instance, Cladosporium, Cercophora, Acremonium, Mortierella, Aspergillus, Penicillium, Glomus and Sebacina were also highly reduced by low and high Cd stress. In contrast, Fusarium, Thanatephorus, Botrytis and Curvularia did not show any response to Cd stress. The identified taxa may have a crucial role in the growth of king grass under heavy metal contamination, making them promising candidates for developing bioinoculants to encourage plant performance and phytoremediation capability in HM-contaminated soils.