Copper-resistant bacteria from industrial effluents and their role in remediation of heavy metals in wastewater

Six copper-resistant bacterial strains were isolated from wastewater of tanneries of Kasur and Rohi Nala. Two strains tolerated copper at 380 mg/L, four up to 400 mg/L. Three strains were identified as members of the genusSalmonella; one strain was identified asStreptococcus pyrogenes, one asVagococcus fluvialis and the last was identified asEscherichia coli. The pH and temperature optimum for two of them were 7.0 and 30 °C, respectively; four strains had corresponding optima at 7.5 and 37 °C, respectively. All bacterial isola-tes showed resistance against Ag⁺ (280–350 mg/L), Co²⁺ (200–420), Cr^VI (280–400), Cd²⁺ (250–350), Hg²⁺ (110–200), Mn²⁺ (300–380), Pb²⁺ (300–400), Sn²⁺ (480–520) and Zn²⁺ (300–450). Largesized plasmids (>20 kb), were detected in all of the strains. After the isolates were cured of plasmids with ethidium bromide, the efficiency of curing was estimated in the range of 60–90%. Reference strain ofE. coli was transformed with the plasmids of the bacterial isolates which grew in Luria-Bertani medium containing 100 mg/L Cu²⁺. The capability to adsorb and afterwards accumulate Cu²⁺ inside their cells was assayed by atomic absorption spectrophotometer; all bacterial cells had the ability to adsorb 50–80 % of the Cu²⁺ and accumulate 30–45 % Cu²⁺ inside them after 1 d of incubation.     

The Effect of Thermophoresis on Unsteady Oldroyd-B Nanofluid Flow over Stretching Surface

There are currently only a few theoretical studies on convective heat transfer in polymer nanocomposites. In this paper, the unsteady incompressible flow of a polymer nanocomposite represented by an Oldroyd-B nanofluid along a stretching sheet is investigated. Recent studies have assumed that the nanoparticle fraction can be actively controlled on the boundary, similar to the temperature. However, in practice, such control presents significant challenges and in this study the nanoparticle flux at the boundary surface is assumed to be zero. We have used a relatively novel numerical scheme; the spectral relaxation method to solve the momentum, heat and mass transport equations. The accuracy of the solutions has been determined by benchmarking the results against the quasilinearisation method. We have conducted a parametric study to determine the influence of the fluid parameters on the heat and mass transfer coefficients.     

Genotoxic potential of copper oxide nanoparticles in human lung epithelial cells

Copper oxide nanoparticles (CuO NPs) are increasingly used in various applications. Recent studies suggest that oxidative stress may be the cause of the cytotoxicity of CuO NPs in mammalian cells. However, little is known about the genotoxicity of CuO NPs following exposure to human cells. This study was undertaken to investigate CuO NPs induced genotoxic response through p53 pathway in human pulmonary epithelial cells (A549). In addition, cytotoxicity and oxidative stress markers were also assessed. Results showed that cell viability was reduced by CuO NPs and degree of reduction was dose dependent. CuO NPs were also found to induce oxidative stress in dose-dependent manner indicated by depletion of glutathione and induction of lipid peroxidation, catalase and superoxide dismutase. The expression of Hsp70, the first tier biomarker of cellular damage was induced by CuO NPs. Further, CuO NPs up-regulated the cell cycle checkpoint protein p53 and DNA damage repair proteins Rad51 and MSH2 expression. These results demonstrate that CuO NPs possess a genotoxic potential in A549 cells which may be mediated through oxidative stress. Our short-term exposure study of high level induction of genotoxic response of CuO NPs will need to be further investigated to determine whether long-term exposure consequences may exist for CuO NPs application.     

Identification of novel genomic islands associated with small RNAs

Genome evolution in prokaryotes is assisted by integration of gene pools from phages and plasmids. Regions downstream of tRNAs and tmRNAs are considered as hot spots for the integration of these gene pools or genomic islands. Till date, genomic islands have been identified only at tRNA/tmRNA genes in the enterobacterial genomes. Present work reports 10 distinct small RNAs as potent integration sites for genomic islands. A known tool tRNAcc 1.0 has been used to identify genomic islands associated with small RNAs c0362, oxyS, ryaA, rybB, rybD, ryeB, ryeE, rtT, sraE and tmRNA. The coordinates of 25 such small RNA associated genomic islands in three E. coli (strains: CFT073, EDL933 and K12) and Shigella flexneri (strain: 301) genomes are presented. Moreover cross-verification of the genomic sequences encoded within the identified genomic islands in horizontal gene transfer database, GenBank annotation features and atypical sequence compositions support our results. Again, all of the identified 25 genomic integration sites do exhibit genomic block rearrangements with respect to the associated small RNA. Similar to tRNAs/tmRNAs, the downstream regions of the small RNAs are found to be hotspots of integration.     

Production of hydrocarbon compounds by endophytic fungi Gliocladium species grown on cellulose

Endophytic fungi belonging to the genus Gliocladium are able to degrade plant cellulose and synthesize complex hydrocarbons under microaerophilic conditions. These fungi could thus be used to produce biofuels from cellulosics without the need for hydrolytic pretreatments. Gas chromatography-mass spectrometry-solid-phase micro-extraction (GC-MS-SPME) of head space gases from Gliocladium cultures demonstrated the production of C(6)-C(19) hydrocarbons including hexane, benzene, heptane, 3,4-dimethyl hexane, 1-octene, m-xylene, 3-methyl nonane, dodecane, tridecane, hexadecane and nonadecane directly from the cellulosic biomass. Hydrocarbon production was 100-fold higher in co-cultures of Gliocladium and Escherichia coli than in pure Gliocladium cultures. The dry mycelia weight is stable at stationary period in co-culture condition which may lead to synthesize more hydrocarbons. These fungi could potentially be developed into cost-effective biocatalysts for production of biofuels.     

Ability to use the diazo dye, C.I. Acid Black 1 as a nitrogen source by the marine cyanobacterium Oscillatoria curviceps BDU92191

Ten different strains of marine cyanobacteria were tested for their ability to decolourise and degrade a recalcitrant diazo dye, C.I. Acid Black 1. Of them, Oscillatoria curvicepsBDU92191 was able to grow up to a tested concentration of 500 mG L⁻¹. The organism degraded 84% of the dye at 100 mG L⁻¹ in 8 days in a medium free of combined nitrogen. The dye degrading ability is attributed to the activities of the enzymes: laccase, polyphenol oxidase and azoreductase. The absence of the doublet amine peak in addition to the overall reduction of absorption in the IR spectra confirmed the mineralisation of the tested azo dye. The nitrogen assimilating enzyme studies along with nitrogenase assay strongly suggested the ability of the non-heterocystous, filamentous marine cyanobacterium, O. curvicepsBDU92191 to use C.I. Acid Black 1 as a nitrogen source in an oligotrophic environment.     

Synthesis and evaluation of cytotoxic effects of hanultarin and its derivatives

One of the known cytotoxic lignans is (-)-1-O-feruloyl-secoisolariciresinol designated as hanultarin, which was isolated from the seeds of Trichosanthes kirilowii. In this Letter, we described the first synthesis of 1-O-feruloyl-secoisolariciresinol, 1,4-O-diferuloyl-secoisolariceresinol and their analogues. The cytotoxicities of these compounds were evaluated against several cancer cell lines. Interestingly, we found that the feruloyl diester derivative of secoisolariciresinol was the most active cytotoxic compound against all the cancer cells tested in this experiment. The IC(50) values of the1,4-O-diferuloyl-secoisolariceresinol were in the range of 7.1-9.8μM except one cell line. In considering that both ferulic acid and secoisolariciresinol are commonly found in many plants and have no cytotoxicity, this finding is remarkable in that simple covalent bonds between the ferulic acid and secoisolariciresinol cause a cytotoxic effect.