REMEDIATION OF TETRACYCLINE FROM WATER SOURCES USING VETIVER GRASS (Chrysopogon zizanioides L. Nash) AND TETRACYCLINE-TOLERANT ROOT-ASSOCIATED BACTERIA

Antibiotics are emerging contaminants worldwide. Due to insufficient policy regulations, public awareness, and the constant exposure of the environment to antibiotic sources has created a major environmental concern. Wastewater treatment plants (WWTP) are not equipped to filter-out these compounds before the discharge of the disinfected effluent into water sources (e.g., lakes and streams) and current available technologies are not equipped to remediate these compounds from environmental sources. Hence, the challenge remains to establish a biological system to remove these antibiotics from wastewater. An invitro hydroponic remediation system was developed using vetiver grass (Chrysopogon zizanioides L. Nash) to remediate tetracycline (TC) from water. Comparative metabolomics studies were conducted to investigate the metabolites/pathways associated with tetracycline metabolism in plants and TC-degrading bacteria. The results show that vetiver plants effectively uptake tetracycline from water sources. Vetiver root-associated bacteria recovered during the hydroponic remediation trial were highly tolerant to TC (as high as 600 ppm) and could use TC as a sole carbon and energy source. Growth conditions (pH, temperature, and oxygen requirement) for TC-tolerant bacteria were optimized for higher TC remediation capability from water sources. The plant (roots and shoots) and bacterial species were further characterized for the metabolites produced during the TC degradation process using GC-MS to identify the possible biochemical mechanism involved. Also, the plant root zone was screened for metabolites/enzymes that were secreted during antibiotic degradation and could potentially enhance the degradation process. The root zone was selected for this analysis because this region of the plant has shown a greater capacity for antibiotic degradation compared to the shoot zone. The role of antioxidant enzymes in TC degradation process revealed glutathione-S-transferase (GSTs) as an important group of enzymes in both plant and bacteria potentially involved in TC degradation process. Metabolomics results also suggest potential GST activity in the TC remediation/ transformation process used by plants. This information could be useful in gaining insights for the application of biological remediation systems for the mitigation of antibiotics from waste-water.

Effects of soluble humic acids on the uptake of heavy metals by Vetiveria zizanioides (L.) Nash in contaminated mining soils

In the past, mining wastes were left wherever they might lie in the surroundings of the mine area. Unfortunately, inactive and abandoned mines continue to pollute our environment, reason why these sites should be restored with minimum impact. Phytoextraction is an environmental-friendly and cost-effective technology less harmful than traditional methods that uses metal hyperaccumulator or at least tolerant plants to extract heavy metals from polluted soils. One disadvantage of hyperaccumulator species is their slow growth rate and low biomass production. Vetiveria zizanioides (L.) Nash, perennial species adapted to Mediterranean climate has a strong root system which can reach up to 3 m deep, is fast growing, and can survive in sites with high metal levels (Chen et al., 2004). Due to the fact that metals in abandoned mine tailings become strongly bonded to soil solids, humic acids used as chelating agents could increase metal bioavailability (Evangelou et al., 2004; Wilde et al., 2005) and thereby promote higher accumulation in the harvestable parts of the plant. The objective of this study was to examine the performance of humic acid assisted phytoextraction using Vetiveria zizanioides (L.) Nash in heavy metals contaminated soils.

Pages de vérité : l'offensive de 1917 et le commandement du général Nivelle.

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Notes d'un chasseur à pied (1915-1917), publiées avec une notice et des discours sur l'auteur par M. Hauvette ...

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Diplomatie de la France et de l'Espagne depuis l'avénement de la maison de Bourbon, 1698-1846 /

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L'Ebreo di Verona; racconto storico dall'anno 1846 al 1849.

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Les origines de l'ancienne France: Xe et XIe siècles ...

Imprint varies slightly.

Mémoires du général Guillaume Pépé, 1783-1846; la Révolution, l'Empire, la Restauration, et le royaume de Naples.

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L'effort serbe : discours prononcés à la Sorbonne le 8 février 1917 dans la conférence organisée par le Comité "pour l'effor de la France et de ses alliés," /

"Extrait de la Revue des sciences politiques du 15 avril 1917."

Masaccio : orazione di Melchior Missirini, letta nel giorno della solenne distribuzione dei premj maggiori nell'I. e R. Accademia delle belle arti, in Firenze l'anno 1846.

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