Enterobacter sp. FM-1 inoculation influenced heavy metal-induced oxidative stress in pakchoi ( Brassica campestris L. ssp. Chinensis Makino) and water spinach ( Ipomoea aquatic F.) cultivated in cadmium and lead co-contaminated soils

The current study investigated the potential influence of Enterobacter sp. FM-1 on plant growth and the accumulation of Cd and Pb in plants growing in highly contaminated soils. Moreover, the potential mechanism by which Enterobacter sp. FM-1 helps vegetable species alleviate heavy metal (HM)-induced oxidative stress was investigated. Each pot experiment involved a full factorial randomized design which included two types of soils, two vegetable species (Brassica campestris L. and Ipomoea aquatic F.) and four bacterium inoculation concentrations (control (0), 6.4 × 106, 1.3 × 107 and 3.8 × 107 CFU g soil− 1). The results indicated that in both soils, while Cd and Pb accumulation caused oxidative stress in both vegetables, inoculation with FM-1 (3.8 × 107 CFU g soil− 1) promoted the height and weight of both plant species. FM-1 inoculation significantly increased the Chla, Chlb, t-Chl and carotenoid contents in both vegetables, which could help to alleviate the intracellular oxidative stress of vegetables caused by Cd and Pb. Additionally, FM-1 (3.8 × 107 CFU g soil− 1) inoculation significantly increased the CAT and POD activities in both vegetables (by 24.0%~88.0% and 17.4%~178.2%, respectively). Moreover, inoculation with FM-1 promoted the conversion of a large amount of GSH into PCs, and the PC content in both vegetables increased by 18.9%~22.1% and 14.3%~22.8%, respectively. Our findings indicated that Enterobacter sp. FM-1 inoculation of soils co-contaminated with Cd and Pb helps activate the scavenging mechanism of these vegetable species to alleviate the oxidative toxicity stress caused by Cd and Pb.