Enhancing the effectiveness of zinc, cadmium, and lead phytoextraction in polluted soils by using amendments and microorganisms.

For remediating polluted soils, phytoextraction of metals received considerable attention in recent years, although slow removal of metals remained a major constraint in this approach. We, therefore, studied the effect of selected organic and inorganic amendments on the solubility of zinc (Zn), cadmium (Cd), and lead (Pb) in polluted soil and enhancing the efficacy of phytoextraction of these metals by Indian mustard (Brassica juncea cv. Pusa Vijay). For this purpose, a greenhouse experiment was conducted using a metal-polluted soil to evaluate the effect of amendments, viz. green manure (T2), EDTA (T3), sulfur (S)+S oxidizing bacteria (Thiobacillus spp.) (T4), metal-solubilizing bacteria (Pseudomonas spp.) (T5), and green manure + metal-solubilizing bacteria (T6), on solubility and bioavailability of Zn, Cd, and Pb. Distribution of metals in different soil fractions revealed that Cd content in water soluble + exchangeable fraction increased to the extent of 34.1, 523, 133, 123, and 75.8% in T2, T3, T4, T5, and T6 treatments, respectively, over control (T1). Cadmium concentrations in soil solution as extracted by Rhizon sampler were recorded as 3.78, 88.1, 11.2, 6.29, and 4.27 µg L-1in T2, T3, T4, T5, and T6, respectively, whereas soil solution concentration of Cd in T1 was 0.99 µg L-1. Activities of Cd (pCd2+) in Baker soil extract were 12.2, 10.9, 6.72, 7.74, 7.67, and 7.05 for T1, T2, T3, T4, T5, and T6, respectively. Cadmium contents in shoot were recorded as 2.74, 3.12, 4.03, 4.55, 4.68, and 4.63 mg kg-1 in T1, T2, T3, T4, T5, and T6 treatments, respectively. Similar trend in Zn and Pb content with different magnitude was also observed across the different amendments. Cadmium uptake by shoot of mustard was enhanced to the extent of 125, 62.5, 175, 175, and 212% grown on T2-, T3-, T4-, T5-, and T6-treated soil, respectively, over T1. By and large, free ion activity of metals as measured by Baker soil test proved to be the most effective index for predicting Zn, Cd, and Pb content in shoot of mustard, followed by EDTA and DTPA. Among the metal fractions, only water soluble + exchangeable metal contributed positively towards plant uptake, which explained the variation in shoot Zn, Cd, and Pb content to the extent of 74, 81, and 87%, respectively, along with other soil metal fractions. Risk to human health for intake of metals through the consumption of leafy vegetable (mustard) grown on polluted soil in terms of hazard quotient (HQ) ranged from 0.64 to 1.10 for Cd and 0.11 to 0.34 for Pb, thus rendering mustard unfit for the human consumption. Novelty of the study mainly consisted of the use of natural means and microorganisms for enhancing solubility of metals in soil with the ultimate aim of hastening the phytoremediation.

Cadinene sesquiterpenes from Eupatorium adenophorum and their antifungal activity.

Bioactive constituents of Eupatorium adenophorum were investigated for antifungal activity. A structure-antifungal activity relationship of cadinene sesquiterpenes was predicted by evaluating individual derivatives. Cadinene derivatives were extracted from leaves of Eupatorium adenophorum using ethyl acetate. Five cadinene sesquiterpenes were isolated by column chromatography and Preparative Thin Layer Chromatography. Bioactivity of these cadinene sesquiterpenes were evaluated in vitro against four phytopathogenic fungi using poison food technique. Purified sesquiterpenes were spectroscopically elucidated as cadinan-3-ene-2,7-dione (1), 7-hydroxycadinan-3-ene-2-one (2), 5,6-dihydroxycadinan-3-ene-2,7-dione (3), cadinan-3,6-diene-2,7-dione (4) and 2-acetyl-cadinan-3,6-diene-7-one (5). Antifungal evaluation of these compounds against pathogenic fungi was found to be selective. Compound 1 was highly inhibitory towards S. rolfsii (ED50 181.60 ± 0.58 µgmL(-1)) and R. solani (ED50 189.74 ± 1.03 µgmL(-1)). Availability of plant material and significant antifungal activity makes the plant a potential source of antifungal agent and that can be exploited for the development of a natural fungicide.

Isolation of Rhizobacteria from Jatropha curcas and characterization of produced ACC deaminase.

Decreased levels of ACC (1-aminocyclopropane-1-carboxylic acid) result in lower levels of endogenous ethylene, which eliminate the potentially inhibitory effects of stress-induced higher ethylene concentrations. It is worth noting the substantial ability of the bacterial species to colonize different environments, including taxonomically distinct plants cultivated in distantly separated geographical regions. For example, Enterobacter cloacae, designated as MSA1 and Enterobacter cancerogenus, designated as MSA2 were recovered from the rhizosphere of Jatropha in the present work. This study first time confirms the ACC deaminase activity in the Enterobacter cancerogenus on the preliminary basis. Several bacterial plant growth-promoting mechanisms were analyzed and detected like phosphate solubilization, siderophore production, IAA production, GA(3) (gibberellic acid) production and ACC deaminase activity in the isolated cultures. Isolates were grown until exponential growth phase to evaluate their ACC deaminase activity and the effect of pH, temperature, salt, metals and substrate concentration after the partial purification of enzyme by ion exchange chromatography. The FOURIER TRANSFORM INFRARED (FT-IR) spectra were recorded for the confirmation of α-ketobutyrate production. By using lineweaver Burk plot K(m) and V(max) value for ACC deaminase of both the organism was calculated in the different fractions. In this work, we discuss the possible implications of these bacterial mechanisms on the plant growth promotion or homeostasis regulation in natural conditions.