Effects of Cr Stress on Rhizosphere Soil Bacterial Community Structure and Diversity of Iris Pseudacorus

Abstract

Rhizosphere microorganisms play an important role in improving soil microenvironment, which contributes to plant growth under heavy metal stress. However, the effect of chromium (Cr) on plant rhizosphere bacterial community is still unknown. In this paper, sole-cultivated pattern, two-cultivated pattern and three-cultivated pattern, combined with 16S rRNA high-throughput sequencing technology, the effects of Cr stress on bacterial community structure and diversity in rhizosphere soil of Iris Pseudacorus were analyzed. The results showed that under Cr stress, I. Pseudacorus showed good tolerance and enrichment. However, under Cr stress, the Alpha diversity indices (Shannon, Chao and Sobs) of rhizosphere bacterial community decreased by 9.1%, 30.3% and 28.0% on average, respectively. The change of bacterial community was 22.6% due to Cr stress, and the common species of bacterial community decreased by 4.2%. Proteobacteria, Actinobacteria, Acidobacteria, Firmicutes and Gemmatimonadetes accounted for more than 78.2% of the total sequence. With the increase of plant diversity, Bacteroides and Pseudomonas appeared successively, and the abundance of the dominant species increased obviously. Through the symbiotic network diagram, it was found that the synergistic effect between dominant species in two-cultivated pattern was significantly enhanced, and the soil microenvironment was significantly improved. In conclusion, the results of this study will provide a reference for understanding the response of rhizosphere bacterial community to heavy metal Cr and the interaction between wetland plants and rhizosphere bacteria during wetland phytoremediation.

Keywords: Cr stress, Rhizosphere bacterial community, Iris pseudacorus, 16S rRNA sequencing technology, phytoremediation