Microbial diversity and hydrocarbon degrading gene capacity of a crude oil field soil as determined by metagenomics analysis

Soils contaminated with crude oil are rich sources of enzymes suitable for both degradation of hydrocarbons through bioremediation processes and improvement of crude oil during its refining steps. Due to the long term selection, crude oil fields are unique environments for the identification of microorganisms with the ability to produce these enzymes. In this metagenomic study, based on Hiseq Illumina sequencing of samples obtained from a crude oil field and analysis of data on MG‐RAST, Actinomycetales (9.8%) were found to be the dominant microorganisms, followed by Rhizobiales (3.3%). Furthermore, several functional genes were found in this study, mostly belong to Actinobacteria (12.35%), which have a role in the metabolism of aliphatic and aromatic hydrocarbons (2.51%), desulfurization (0.03%), element shortage (5.6%), and resistance to heavy metals (1.1%). This information will be useful for assisting in the application of microorganisms in the removal of hydrocarbon contamination and/or for improving the quality of crude oil. © 2016 American Institute of Chemical Engineers Biotechnol. Prog., 32:638–648, 2016     

Toxicity and bioaccumulation of iron in soil microalgae

Microalgae are extensively used in the remediation of heavy metals like iron. However, factors like toxicity, bioavailability and iron speciation play a major role in its removal by microalgae. Thus, in this study, toxicity of three different iron salts (FeSO₄, FeCl₃ and Fe(NO₃)₃) was evaluated towards three soil microalgal isolates, Chlorella sp. MM3, Chlamydomonas sp. MM7 and Chlorococcum sp. MM11. Interestingly, all the three iron salts gave different EC50 concentrations; however, ferric nitrate was found to be significantly more toxic followed by ferrous sulphate and ferric chloride. The EC₅₀ analysis revealed that Chlorella sp. was significantly resistant to iron compared to other microalgae. However, almost 900 μg g^?1 iron was accumulated by Chlamydomonas sp. grown with 12 mg L^?1 ferric nitrate as an iron source when compared to other algae and iron salts. The time-course bioaccumulation confirmed that all the three microalgae adsorb the ferric salts such as ferric nitrate and ferric chloride more rapidly than ferrous salt, whereas intracellular accumulation was found to be rapid for ferrous salts. However, the amount of iron accumulated or adsorbed by algae, irrespective of species, from ferrous sulphate medium is comparatively lower than ferric chloride and ferric nitrate medium. The Fourier transform infrared spectroscopy (FTIR) analysis shows that the oxygen atom and P?=?O group of polysaccharides present in the cell wall of algae played a major role in the bioaccumulation of iron ions by algae.     

Abandoned metalliferous mines: ecological impacts and potential approaches for reclamation

The lack of awareness for timely management of the environment surrounding a metal mine site results in several adverse consequences such as rampant business losses, abandoning the bread-earning mining industry, domestic instability and rise in ghost towns, increased environmental pollution, and indirect long-term impacts on the ecosystem. Although several abandoned mine lands (AMLs) exist globally, information on these derelict mines has not been consolidated in the literature. We present here the state-of-the-art on AMLs in major mining countries with emphasis on their impact towards soil health and biodiversity, remediation methods, and laws governing management of mined sites. While reclamation of metalliferous mines by phytoremediation is still a suitable option, there exist several limitations for its implementation. However, many issues of phytoremediation at the derelict mines can be resolved following phytostabilization, a technology that is effective also at the modern operational mine sites. The use of transgenic plant species in phytoremediation of metals in contaminated sites is also gaining momentum. In any case, monitoring and efficacy testing for bioremediation of mined sites is essential. The approaches for reclamation of metalliferous mines such as environmental awareness, effective planning and assessment of pre- and post-mining activities, implementation of regulations, and a safe and good use of phytostabilizers among the native plants for revegetation and ecological restoration are discussed in detail in the present review. We also suggest the use of microbially-enhanced phytoremediation and nanotechnology for efficient reclamation of AMLs, and identify future work warranted in this area of research. Further, we believe that the integration of science of remediation with mining policies and regulations is a reliable option which when executed can virtually balance economic development and environmental destruction for safer future.     

Role of copper in poly R-478 decolorization by the marine cyanobacterium Phormidium valderianum BDU140441

The marine cyanobacterium Phormidium valderianum BDU140441 was tested for its capability of decolorizing Poly R-478 in the presence of copper. The rate of dye decolorization was decreased when the concentration of copper was increased in the medium, whereas copper in low amount (10 μM) enhanced the decolorization. To analyse the fate of dye-decolorizing and stress-stabilizing enzymes upon copper and dye exposure, four different conditions were maintained. The conditions were (A) only the organism P. valderianum BDU140441, (B) organism + Poly R-478 (0.0075%), (C) organism + copper (10 μM) and (D) organism + Poly R-478 (0.0075%) + copper (10 μM). After 16 h of exposure to Poly R-478 and copper, an increased trend in the activity of laccase and peroxidase was observed. In contrast, polyphenol oxidase revealed only a mild increase in activity along with the induction of a new isoform. The tested cellular antioxidants carotenoid and reduced glutathione were found to be reduced in varying percentage in accordance to the degree of stress bared by the cyanobacterium. Dye and copper exposure divulged an increased pattern in the production of reactive oxygen species (ROS). Concomitant with ROS, esterase activity was also found to increase. Towards copper and dye exposure, the activity of the primary stress-stabilizing enzymes catalase and superoxide dismutase were found to be increased in varied degrees. Upon copper exposure glutathione S-transferase and glutathione peroxidase expressed new isoforms. The results suggest that copper at this juncture played a role as inducer for dye-decolorizing copper oxidases and subjugated the antioxidant system to the objective of Poly R-478 decolorization.     

Transport and fate of microplastics in wastewater treatment plants: implications to environmental health

Global studies of microplastic (MP) pollution confirm wastewater treatment plants serve as pathways for microplastics entering terrestrial and aquatic ecosystems. The behaviour, transport and fate of microplastics in wastewater effluents remain mostly unknown, rendering wastewater-derived microplastics as a contaminant of significant concern. We critically examine the literature to understand the sources and fate of microplastics in wastewater treatment plants (WWTPs) and the implications of treated effluents admitted to soil and aquatic systems. The transport of chemical and biological contaminants is also discussed in detail, using fundamental principles of vector relationships. For the removal and reduction of microplastics, profound knowledge is required from source to solution. This review presents a comprehensive overview of the significance of microplastics as a vector of water-borne contaminants in WWTPs.     

Laccase and polyphenol oxidase activities of marine cyanobacteria: a study with Poly R-478 decolourization

The various marine cyanobacterial strains tested showed wide variation in growth patterns and decolourization patterns of the lignin model polymeric dye Poly R-478. The study revealed the presence of laccases (LACs) and polyphenol oxidases (PPOs) in marine cyanobacteria. All the ten tested strains were found to possess constitutive PPOs, whereas only four strains showed the presence of constitutive laccases. Within 7 days of incubation the highest percentage of decolourization was shown by Phormidium valderianum BDU140441 (65%), and Oscillatoria chlorina BDU 140691 (12%) showed the least. Isoforms of LACs were found to be induced by the laccase elicitors veratryl aldehyde, caffeic acid, guaiacol and tannic acid. Cyanobacterial strains that possess both LACs and PPOs were relatively more efficient in decolourizing the dye. Altering the concentrations of nitrogen, phosphorus, potassium and sulphur from the basal medium influenced the efficiency of dye decolourization.     

Defense responses in tomato landrace and wild genotypes to early blight pathogen Alternaria solani infection and accumulation of pathogenesis-related proteins

Plants dispense localised and systemic defense responses against biotic colonisers and plant resistance to pathogens depends upon timely recognition of pathogen infection and subsequent rapid activation of defense responses through signal transduction pathways. Induction of host defense responses involving compatible and incompatible interactions in tomato landrace, LE996, LE150 and LE1165 (Solanum lycopersicum), and wild relatives, Seijima Jeisei and I979 (S. hirsutum) genotypes, and early blight (EB) pathogen, Alternaria solani were studied. Accumulation patterns of different defense related proteins in resistant genotypes (LE996, Seijima jeisei and I979) and susceptible genotypes (LE150 and LE1165) are reported here. Challenge inoculation led to similar protein profiles in resistant genotypes yielding 11 proteins, unique are 14, 54, and 58 kD proteins that are absent with susceptible genotypes. Resistant genotypes accumulated more proteins well in advance, 6-h after challenge inoculation. Resistant genotype LE996 expressed 54%, 90%, and 52% enhanced enzymatic activity of peroxidase, polyphenol oxidase and phenylalanine ammonia lyase respectively than susceptible LE150 and correlated phenolics accumulation peaked 2-d after challenge inoculation. Activity gel assay indicated the unique expression of PO1 and PO2 in LE996 upon challenge inoculation. Significant increase in expression of chitinases (63%) and β-1,3-glucanase (71%) upon challenge inoculation than susceptible LE150 control was recorded. Western blotting indicated the unique presence of less than 30 kD chitinase in resistant LE996 and Seijima Jeisei and was absent in susceptible LE150. The results demonstrate the importance of pathogenesis-related (PR) proteins in EB resistance and their use as biochemical markers for genotype selection.     

A theoretical study on the stability of CNT encased cyclic peptide beyond hydrogen bond cut-off

The Carbon nanotubes (CNT) are potential candidate for many biomedical applications especially in targeted drug delivery for cancer diseases. However, the use of CNT has limitations due to its insolubility in aqueous media. The self-assembly of cyclic peptide encased on the CNT has enhanced its dispersion in aqueous medium which extend their applications as antibacterial and drug delivery agents. To understand this process, an attempt has been made to investigate the dynamics and stability of trimer cyclic peptide encasing with CNT using classical molecular dynamics. The model cyclic peptide monomer constitutes 14 series of amino acids viz.; (cyclo-[(D-ARG-L-VAL-D-ARG-L-THR-D-AGR-L-LYS-D-GLY-L-ARG-D-ARG-L-ILE-D-ARG-L-ILE-D-PRO-L-PRO)]). Each cyclic peptide in the assembly stacking far apart at approximately 15 Å each other beyond hydrogen bond cut-off distance. The trimer was observed to be stable only over 10 ns of entire MD trajectory. But when there is electrostatic interaction between cyclic peptides at 6.5 Å distance then assembly is stable for entire 50 ns. Our result reveals that for a stable assembly, beyond the hydrogen bond cut-off distance, the electrostatic interaction plays significant role.