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

Abstract

Studies 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 (H 2 O 2 ) 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.

Differential Expression of Antioxidant Enzymes in Chlorine-Resistant Acinetobacter and Serratia spp. Isolated from Water Distribution Sites in Mumbai: A Study on Mechanisms of Chlorine Resistance for Sustainable Water Treatment Strategies

“…An increase in GPX and APX enzyme activity is observed under environmental stress, such as osmotic stress and dehydration [27]. Researchers have previously stated that an increased production of APX enzyme activity indicates that the bacteria are able to fight against pollutants like antimony (Sb) [28]. In this study, the stress can be attributed to chlorine, resulting in excessive production of H 2 0 2 .…”

Effects of Antimony on Rice Growth and Its Existing Forms in Rice Under Arbuscular Mycorrhizal Fungi Environment

“…Interestingly, as shown in Figure 7C , when the concentration of Sb was below 1,200 mg/kg, the enzyme activity of CAT was not significantly changed, but when the concentration of Sb increased to 1,200 mg/kg, the enzyme activity of CAT increased rapidly. This may have occurred because the function of CAT and POD are to degrade hydrogen peroxide produced by SOD, and the response sensitivity of CAT may be poorer than that of POD ( Kassa-Laouar et al, 2019 ). Therefore, when POD reached the upper limit of Sb tolerance, the stress response function of CAT was more activated.…”