Root colonization by heavy metal resistant Enterobacter and its influence on metal induced oxidative stress on Cajanus cajan

Abstract

BACKGROUND: Heavy metal resistant bacterium Enterobacter sp. C1D was evaluated for cadmium (Cd) mediated exopolysaccharide production, biofilm formation and legume root colonization ability under Cd stress to alleviate metal induced stress. RESULTS:The plant was sensitive to Cd (IC 50 3-4 g mL −1 ), whereas the bacterium showed high Cd tolerance (MIC 99 120 g mL −1 ). Confocal laser scanning microscopy of the Cajanus cajan roots showed heavy loads of green fluorescence protein labelled Enterobacter sp. C1D on the surface of plant root, specifically at the point of root hair/lateral root formation along with cortex, even under metal stress. The root colonizing ability of Enterobacter sp. C1D was not affected by the presence of Rhizobium and the bacteria could be observed after 30 days of incubation in soil. Various plant growth parameters, antioxidant metabolites and oxidative stress indicator were significantly influenced by bacterial treatment, which, overall, reduced the adverse effect of Cd. CONCLUSION: Heavy metal tolerant bacteria may be a good choice for the development of biofertilizers and may work well with the native soil microbes such as Rhizobium under the metal polluted soil. Soil experimentsSterilized soil was amended with 0 or 50 or 100 mg kg −1 of Cd and/or inoculated and incubated in a greenhouse for 30 days. Root length, shoot length, fresh weight, number of pods, number of seeds, dry weight of pods, chlorophyll, H 2 O 2 and malondialdehyde (MDA) content, cellular glutathione, and non-protein thiol, protein and antioxidant enzyme from leaf extract were estimated.

A potent cadmium bioaccumulating Enterobacter cloacae strain displays phytobeneficial property in Cd-exposed rice seedlings

“…This result also positively correlated with the results of Enterobacter sp. ( Abbas et al, 2014 ; Sharma et al, 2020 ).

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“…Increment of the shoot and root length in rice plants after application of Serratia marcescens ( Kotoky et al, 2019 ) was observed under Cd stress. Moreover, the biomass increasing property (under Cd stress) of AS10 indicates the bioremediation capability of the isolate ( Lin et al, 2016 ; Sharma et al, 2020 ). PGPR-mediated improvement in morphological growth indices under Cd stress has also been narrated earlier by other workers in this field ( Ahmad et al, 2016 ; Li et al, 2019 ).…”

Microorganisms in Plant Growth and Development: Roles in Abiotic Stress Tolerance and Secondary Metabolites Secretion

“…They are also involved in nitrogen fixation, phytohormones secretion, and acquisition of nutrients, thereby improving the growth of the plant. Root exudates are known to be produced by plants that act as the source of energy for endophytic microbes associated with them [72]. While endophytic organisms were colonizing the plants at an early stage, there is the production of exopolysaccharides (EPS) from bacterial cells that alleviate its attachment to the surface of the root and likewise prevent bacterial cells from oxidative damage [73].…”

Bioaugmented Phytoremediation of Metal-Contaminated Soils and Sediments by Hemp and Giant Reed

“…A strong resistance to heavy metals was reported for Enterobacter spp. found in contaminated soil and sediments (Neeta et al, 2016;Chen et al, 2017;Sharma et al, 2020). Moreover, this Gram-negative enteric bacteria have already been successfully inoculated to alleviated HM stress in other crops: soybean (Kang et al, 2015), rice (Mitra et al, 2018), and hyperaccumulator plants (Whiting et al, 2001).…”