Effect of Acridine and Ascorbic Acid on Rhizobia of Legume Trees

Abstract

Abstract:The present study aimed to induce a great variation exists among Rhizobium spp. that nodulate Leucaena leucocephala and Sesbania sesban, through the treatment with acridine and ascorbic acid and selection of strains for efficiency of the symbiotic association appears possible. Bacteria were isolated from nodules of both hosts growing in Egyptian soil, subcultured and verified to be rhizobia. The isolates varied significantly in their resistance to antibiotics and NaCI, their growth on different carbohydrate sources and their effect on the pH of culture media. Most isolates showed intermediate antibiotic resistance, the capacity to use numerous carbohydrates and a neutral to acid pH response. The mean generation times of these isolates ranged from 4.813 to 6.437 and 4.600 to 6.523 for Sesbania sesban and Leucaena leucocephala, respectively. Both acridine orange and ascorbic acid appeared genotoxic hazards effect on all rhizobial strains examined here. They demonstrated a dose-response for decreasing cell survival at the levels that are not excessively toxic to the bacteria. The standard assay with pie-incubation was quite toxic to the bacteria than plate incorporation test. Acridine orange and ascorbic acid shows an increase in the number of auxotrophic mutants over the spontaneous value this is evidence for their mutagenicity caused by DNA damage. The biochemical mutants obtained in this study were identified using nine plates of minimal medium each was supplemented with different combinations of four growth factors. From the results reported here, it can be concluded that acridine mutagenesis is due to an enhancement of mismatch repair. In addition, ascorbic acid may be mutagenic and cytotoxic through the generation of hydrogen peroxide.