Disruption of the Gut Ecosystem by Antibiotics

The intestinal microbiota is a complex ecosystem consisting of various microorganisms that expands human genetic repertoire and therefore affects human health and disease. The metabolic processes and signal transduction pathways of the host and intestinal microorganisms are intimately linked, and abnormal progression of each process leads to changes in the intestinal environment. Alterations in microbial communities lead to changes in functional structures based on the metabolites produced in the gut, and these environmental changes result in various bacterial infections and chronic enteric inflammatory diseases. Here, we illustrate how antibiotics are associated with an increased risk of antibiotic-associated diseases by driving intestinal environment changes that favor the proliferation and virulence of pathogens. Understanding the pathogenesis caused by antibiotics would be a crucial key to the treatment of antibiotic-associated diseases by mitigating changes in the intestinal environment and restoring it to its original state.

Influence of lead in soil on mycorrhizal development and plant growth of Cyamopsis tetragonoloba (Linn.) Taub.

Growth of C. tetragonoloba suffered with increase in concentration of Pb in soil. Plant biomass declined significantly at concentrations above 60 ppm of Pb. Roots showed more pronounced impact as compared to shoots. At highest applied concentration of lead (100 ppm), fresh weight of fruits decreased by 33% and dry weight by 52% as compared to control. No significant impact was noticed on the development of mycorrhiza at lower concentrations (15-45 ppm) of lead contamination. At higher concentrations of Pb (60 and 75 ppm), there was a decrease in VAM colonization. VAM hyphae had irregular size and terminated abruptly in outer cortex of root. Number of VAM fungal spores in rhizosphere also decreased with increase in the edaphic Pb concentration.

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.