Effects of Cr stress on bacterial community structure and composition in rhizosphere soils of Iris tectorum 

Abstract

Heavy metal Cr pollution caused serious stress to soil bacterial community. However, the joint effects of Cr stress and different cultivation patterns on bacterial communities of rhizosphere soils remain unclear. In this study, Iris tectorum was selected as the research object, and combined with 16S rRNA high-throughput sequencing technology, the effects of high Cr levels and different cultivation patterns on the structure and diversity of rhizosphere soil bacterial community of I. tectorum were analyzed. The results showed that iris had strong tolerance and enrichment to Cr. However, under Cr stress, the diversity and abundance index of rhizosphere bacteria decreased by 8.5% and 6.8% on average, and Sobs index decreased by 7.6%. Moreover, bacterial community changed by 20.1% due to the addition of Cr, further leading to a 15.9% decrease in the common species of the bacterial community, among which Proteobacteria, Actinobacteriota, Chloroflexi and Acidobacteriota accounted for more than 74.8% of the total sequence. The abundance of bacterial community was significantly improved under two-cultivated pattern and three-cultivated pattern. Moreover, the two-cultivated pattern significantly enhanced the synergistic effect among the dominant species, thus improving the rhizosphere soil microenvironment. In conclusion, this study revealed that different cultivation patterns can change the composition and symbiotic relationship of rhizosphere bacterial communities of iris, thus alleviating the negative effects of Cr stress on diversity and abundance. These results provided a reference for understanding the response of rhizosphere bacterial communities under Cr stress under different cultivation modes.