The relationship between the oxidative stress reaction and the microbial community by a combinative method of PA and CCA.

Earthworms, as the first choice for soil monitoring and bio-remediation of cadmium (Cd)-contaminated soil, need to identify its mechanism under Cd stress. In this study, an artificial soil test method was used to determine the oxidative stress reaction indices, amino acid composition, and microbial community changes in earthworms under different stress durations and concentrations. For the first time, the canonical correlation analysis model and path analysis model were innovatively introduced into the data analysis to determine the mechanism that drives earthworm physiological functions after Cd stress. The results showed that in the low-stress concentration treatments (50-125 mg.kg DW), there was a driving relationship between oxidative stress reaction and microbial community in earthworm, and the driving factor was glycyl-L-glutamic acid at 50 mg.kg DW. With the increase of Cd stress intensity, the enzymes of oxidative stress promoted the survival microbes to begin to proliferate, and SOD became the main driving factor under 125 mg.kg DW Cd stress. In the high-stress concentration treatments (250-500 mg.kg DW), the driving effects were weakened or disappeared; while Cd-resistant microbial population appeared. This study provides a theoretical basis for the driving mechanism between oxidative stress effect and microbial community after Cd stress.