The Difference between Rhizosphere and Endophytic Bacteria on the Safe Cultivation of Lettuce in Cr-Contaminated Farmland

Abstract

Chromium (Cr) is a major pollutant affecting the environment and human health and microbial remediation is considered to be the most promising technology for the restoration of the heavily metal-polluted soil. However, the difference between rhizosphere and endophytic bacteria on the potential of crop safety production in Cr-contaminated farmland is not clearly elucidated. Therefore, eight Cr-tolerant endophytic strains of three species: Serratia (SR-1~2), Lysinebacillus (LB-1~5) and Pseudomonas (PA-1) were isolated from rice and maize. Additionally, one Cr-tolerant strain of Alcaligenes faecalis (AF-1) was isolated from the rhizosphere of maize. A randomized group pot experiment with heavily Cr-contaminated (a total Cr concentration of 1020.18 mg kg−1) paddy clay soil was conducted and the effects of different bacteria on plant growth, absorption and accumulation of Cr in lettuce (Lactuca sativa var. Hort) were compared. The results show that: (i) the addition of SR-2, PA-1 and LB-5 could promote the accumulation of plant fresh weight by 10.3%, 13.5% and 14.2%, respectively; (ii) most of the bacteria could significantly increase the activities of rhizosphere soil catalase and sucrase, among which LB-1 promotes catalase activity by 224.60% and PA-1 increases sucrase activity by 247%; (iii) AF-1, SR-1, LB-1, SR-2, LB-2, LB-3, LB-4 and LB-5 strains could significantly decrease shoot the Cr concentration by 19.2–83.6%. The results reveal that Cr-tolerant bacteria have good potential to reduce shoot Cr concentration at the heavily contaminated soil and endophytic bacteria have the same or even better effects than rhizosphere bacteria; this suggests that bacteria in plants are more ecological friendly than bacteria in soil, thus aiming to safely produce crops in Cr-polluted farmland and alleviate Cr contamination from the food chain.

Exploring the potential of halotolerant bacteria from coastal regions to mitigate salinity stress in wheat: physiological, molecular, and biochemical insights

“…While seed germination outcomes displayed variability based on the source of isolated bacteria, the overall growth of wheat plants suggested that the bacterial source might not be a decisive factor, except for water isolates, which hindered various plant growth parameters. Earlier research on endophytic and rhizospheric bacteria similarly concluded that the original ecological niches might not be the primary determinant of growth-promoting attributes ( Wang et al., 2022 ; Wen et al., 2023 ). Previous reports have indicated that PGPR foster plant growth through diverse mechanisms, including hormone production such as IAA, ABA, GA, and cytokinins ( Patten and Glick, 2002 ; Dobbelaere et al., 2003 ), symbiotic nitrogen fixation ( Kennedy et al., 1997 ; Kennedy et al., 2004 ), and nutrient solubilization ( Richardson, 2001 ; Hayat et al., 2010 ; Kang et al., 2017 ).…”

Microbial mediated remediation of heavy metals toxicity: mechanisms and future prospects

“…Moreover, different Cr-tolerant bacteria including Bacillus , Enterobacter , Pseudomonas , and Streptomyces have been identified and they can remove the Cr by 50-90% ( Ramesh and Winkler, 2010 ; Bansal et al., 2019 ; Elahi and Rehman, 2019 ; Murthy et al., 2022 ). The study findings of Wen et al. (2023) showed that the addition of SR-2, PA-1, and LB-5 improved the plant fresh weight by 10.3%, 13.5%, and 14.2% and increased the soil enzymatic (catalase and sucrose) activities and significantly decreased the shoot Cr concentration by 19.2-83.6%.…”

Biochar and organic fertilizer drive the bacterial community to improve the productivity and quality of Sophora tonkinensis in cadmium-contaminated soil

“…In practice, biochar is commonly used with supplemental nutrients, such as organic fertilizer, to enhance soil quality, mitigate heavy metal stress, and increase crop productivity ( Muhammad et al, 2017 ; Saeed et al, 2021 ). Notably, this fertilization method is often accompanied by changes in the soil bacterial community ( Wei et al, 2020 ; Liu et al, 2022 ; Wen et al, 2023 ). However, to date, the alterations and effects of the soil bacterial community in most soil remediation processes are still poorly understood.…”