Effects of monosulfuron-ester on metabolic processes of nitrogen-fixing cyanobacteria Anabaena flos-aquae and Anabaena azotica

Abstract Presence of the relatively new sulfonylurea herbicide monosulfuron-ester at 0.03-300 nmol/L affected the growth of two non-target nitrogen-fixing cyanobacteria (Anabaena flos-aquae and Anabaena azotica) and substantially inhibited in vitro Acetolactate synthase activity, with IC50 of 3.3 and 101.3 nmol/L for A. flos-aquae and A. azotica, respectively. Presenting in 30-300 nmol/L, it inhibited protein synthesis of the cyanobacteria with less amino acids produced as its concentration increased. Our findings support the view that monosulfuron-ester toxicity in both nitrogen-fixing cyanobacteria is due to its interference with protein metabolism via inhibition of branch-chain amino acid biosynthesis, and particularly Acetolactate synthase activity.

Iron induced metabolic changes in the diazotrophic cyanobacterium Anabaena PCC 7120.

Iron induced changes in growth, N2-fixation, CO2 fixation and photosynthetic activity were studied in a diazotrophic cyanobacterium Anabaena PCC 7120. Iron at 50 microM concentration supported the maximum growth, heterocyst frequency, CO2 fixation, photosystem I (PS I), photosystem II (PS II) and nitrogenase activities in the organism. Higher concentration of iron inhibited these processes. Chl a and PS II activities were more sensitive to iron than the protein and PS I activity.

Effect of butachlor on growth and nitrogen fixation by Anabaena sphaerica.

Present study was carried out to examine the effect of Butachlor on growth and nitrogen fixation by Anabaena sphaerica. The increased concentration of the pesticide did not have any adverse effect on the alga. Rather it accelerated the algal contribution in terms of biomass and nitrogen fixation.

Efecto de la adición de lectina específica sobre la simbiosis Rhizobium leguminosarum--Phaseolus vulgaris / Effect of the addition of specific lectin on the symbiosis of Rhizobium leguminosarum and Phaseolus vulgaris

The effect of specific lectin addition on Rhizobium leguminosarum-Phaseolus vulgaris symbiosis characteristics was studied. Two alternatives were selected for comparison: a) P. vulgaris seedling roots treated with lectin were inoculated with R. leguminosarum and b) P. vulgaris seedling roots were inoculated with R. leguminosarum incubated with lectin for 3 h and 72 h. The following parameters were evaluated: number and dry weight of nodules and dry matter and nitrogen content of shoot. In lectin treatments, the weight of nodules (from 13 to 35), dry matter (from 6 to 18) and nitrogen content (from 5 to 28) increased significantly. The results suggest a stimulation in the formation of functional-nodules, specially in root (a) and Rhizobium (b) 72 h treatments. That is consistent with a model in which the lectin functions as an extracellular matrix component of the root interacting with roots and Rhizobium s.p. receptors.

Effect of nitrate on nitrogen fixation and nitrate assimilation in Azorhizobium-Sesbania rostrata symbiotic system.

Root nodule formation was inhibited by 30% and 50% respectively at low concentration of 1 mM and 2 mM nitrate, while stem nodule formation was enhanced by 50% only at 1 mM nitrate. The nodule specific nitrogenase activity decreased with the increasing concentration of nitrate. At 1 mM nitrate nitrogenase activity per plant stem nodule was not affected, but it was less than 50% in the root nodules as compared to control. Increasing concentration of nitrate increased in vivo activity of nitrate reductase (NR) significantly in stem, root nodules and leaves. Nodule cytosolic NR utilized both NADH and succinate as electron donor, but not reduced MV. However bacteroidal NR utilised reduced MV as reductant more efficiently than succinate.