Effect of Al and heavy metals on enzymes of nitrogen metabolism of fast and slow growing rhizobia under explanta conditions

Abstract

Most of the legume crops are affected by metal stress present in the soil mainly due to contaminated agrochemicals and sewage sludge. The effect of aluminium, and heavy metals copper, iron and molybdenum on growth and activity of enzymes of fast and slow growing rhizobial sps. was studied. Sinorhizobium meliloti RMP 5 was found to be more tolerant to metal stress than Bradyrhizobium BMP 1 . Both the strains were extremely sensitive to Al than other metals. Al was much more deleterious for the enzymatic activities (nitrate reduction, nitrite reduction, nitrogenase and uptake hydrogenase) of strain RMP 5 and BMP 1 . Cu showed inhibitory effect on growth and enzyme activities of Bradyrhizobium strain at all concentrations. However, in S. meliloti RMP 5 all the tested enzymatic activities increased up to the concentration of 0.1 mM Cu. Fe enhanced the growth and enzyme activities of S. meliloti RMP 5 and Bradyrhizobium BMP 1 up to 100 mM concentration. Mo enhanced all the tested enzymatic activities of S. meliloti RMP 5 up to 1 mM. Nitrate and nitrite reduction activities of Bradyrhizobium BMP 1 increased up to 1 mM concentration. However, nitrogenase and hydrogenase activities of Bradyrhizobium BMP 1 got enhanced only up to 0.5 mM Mo. Both Fe and Mo are the key components of the enzyme nitrogenase and nitrate reductase and enhanced the growth and enzyme activities of both the sps. The study of physiology of nitrogen fixing ability of both fast and slow growing rhizobial strains reported that the supplementation of Mo and Fe in soils along with the biological formulations will enhance the process of symbiotic nitrogen fixation.

Practical use of CMC-amended rhizobial inoculant for <I>Mucuna pruriens</I> cultivation to enhance the growth and protection against <I>Macrophomina phaseolina</I>

“…In comparison to E. meliloti RMP 6 , Bradyrhizobium BMP7 Tet+Kan+ showed better PGP and symbiotic potential. Similar results were reported in earlier studies by Arora et al (2000Arora et al ( , 2010. Production of ACC deaminase by RMP6 Ery+Kan+ may contribute to the nodulation ability.…”

Screening metal-dye-tolerant photoautotrophic microbes from textile wastewaters for biohydrogen production

“…Nitrogenase activity in the cells was, however, reduced significantly in the presence of the dyes and metals with just 15 to 25 % activity of that in the control (4.46 nmol C 2 H 4 h −1 mg −1 dry wt). A sharp reduction in nitrogenase in differently growing rhizobia has also been reported by Arora et al (2010) in the presence of heavy metals. Increased hydrogenase activity and downregulated nitrogenase activity in the presence of metals/dyes need to be investigated in detail to understand the mechanism of their action.…”

Toxic Effects of Heavy Metals on Germination and Physiological Processes of Plants

“…Apart from the effects of heavy metals on plants, numerous studies have also shown that long-term accumulation of heavy metal in soils deleteriously affects community diversity including those of denitrifying community (Sobolev and Begonia 2008) or soil microbial activities (Doelman and Haanstra 1984;Hemida et al 1997;Solanki and Dhankhar 2011) including those of hydrogenase activity of Rhizobium leguminosarum biovar viciae (Ureta et al 2005). For example, in a study, the impact of aluminum and heavy metals such as copper, iron, and molybdenum on growth and activity of enzymes of fast-and slow-growing rhizobial species was determined (Arora et al 2010). Of these, copper had inhibitory effect on growth and enzyme activities of Bradyrhizobium strain at all concentrations.…”