Antioxidative Enzyme Responses to Antimony Stress of Serratia marcescens – an Endophytic Bacteria of Hedysarum pallidum Roots

International audienceStudies on bacterial endophytes resistant to antimony (Sb), a pollutant deemed alarming, are virtually non-existent. An endophytic bacterial strain showing resistance to high antimony concentrations was isolated for the first time from the roots of Hedysarum pallidum Desf., a Sb accumulator Fabacea growing on mining spoils. With the combined use of morphological, biochemical and molecular methods, the isolated strain was identified as Serratia marcescens species. It showed a minimum inhibitory concentration (MIC) to its growth at 450 mM of Sb. In the presence of excessive concentrations of Sb, corresponding to 30 mM of Sb, i.e., 3652.8 mg/L of Sb, the strain maintained important growth compared to the control. The Sb toxicity caused a significant increase (p<0.05) in the hydrogen peroxide (H2O2) amount and malondialdehyde (MDA) content. The oxidative stress induced significant increases (p<0.05) in the strain antioxidant biomarkers such as proline, catalase (CAT), ascorbate peroxidase (APX), peroxidase (POD) and superoxide dismutase (SOD). Significant and positive correlations (p<0.05) were found between oxidative and antioxidant biomarkers and between antioxidant biomarkers, highlighting the interrelationships between them in oxidative stress fighting. Results show an important adaptation of the strain to high Sb levels that can be used in the Sb-contaminated soils bioremediation

Effects of antimony and arsenic on antioxidant enzyme activities of two steppic plant species in an old antimony mining area

The present work was undertaken to determine strategies and antioxidant enzyme activities involved in the adaptation of two wild steppic plants (Hedysarum pallidum Desf. and Lygeum spartum L.) to the toxic environment of the abandoned antimony mining area of Djebel Hamimat (Algeria). For this purpose, soils and plants were collected in different zones coinciding with a Sb and As concentrations gradient in the soil. Antimony (Sb) and arsenic (As) were analyzed by ICP-OES in the soils and the aboveground parts and roots of the plants. Malondialdehyde (MDA) and antioxidant enzyme activities were measured by spectrometry. Results show levels of Sb and As exceptionally high in most soil and plant samples. The two species accumulate differently Sb and As in their above and belowground parts. MDA levels, in the two parts of both species, increase significantly with increasing soil Sb and As concentrations, but they are significantly higher in H. pallidum than in L. spartum. The activities of antioxidant enzymes differ significantly according to the soil metalloid concentrations, the plant species considered and the plant part. Apart from superoxide dismutase (SOD) whose activity is, overall, higher in H. pallidum than in L. spartum, the activities of all the other enzymes studied (glutathione S-transferase (GST), catalase (CAT), peroxidase (POD), and ascorbate peroxidase (APX)) are generally higher in L. spartum than in H. pallidum. For both species, APX and GST are overall more active in the upper parts than in the roots, while it is the reverse for SOD and CAT. POD is more active in the upper parts than in the roots of L. spartum and the reverse applies to H. pallidum. It appears that the two studied plant species use different tolerance strategies to protect themselves against elevated As and Sb concentrations

Assessment of metal contamination in soil banks of the Rhumel wadi (Northeast Algeria)

Levels of six trace metals were assessed in bank soils of the Rhumel wadi (Northeast Algeria) and their association with soil properties was investigated. Samples were collected at 10 sites. The soils are neutral to moderately alkaline, have high contents of carbonate, and are low in organic carbon and clay. Mean metal concentrations are 1.1 (Cd), 63 (Cr), 20 (Cu), 26 (Ni), 31 (Pb), and 98 (Zn) mg kg(-1). The Cd, Cu, Pb, and Zn contents in soil from sites closest to Constantine City were higher than in uncontaminated soils worldwide, indicating accumulation due to human activities (residential, industrial, and agricultural). Statistical analyses (correlation and principal component analysis) demonstrated that Cd, Pb, and Zn are of anthropogenic origin in the urban areas, whereas Cr and Cu enrichment in some situations is caused by industrial activities, while Ni was geogenic