Ecotoxicological Effects of Aflatoxins on Earthworms under Different Temperature and Moisture Conditions.

Aflatoxin contamination remains one of the most important threats to food safety and human health. Aflatoxins are mainly found in soil, decaying plant material and food storage systems and are particularly abundant during drought stress. Regulations suggest the disposal of aflatoxin-contaminated crops by incorporation into the soil for natural degradation. However, the fate and consequences of aflatoxin in soil and on soil organisms providing essential ecological services remain unclear and could potentially pose a risk to soil health and productivity. The protection of soil biodiversity and ecosystem services are essential for the success of the declared United Nations Decade on Ecosystem Restoration. The focus of this study was to investigate the toxicological consequences of aflatoxins to earthworms' survival, growth, reproduction and genotoxicity under different temperature and moisture conditions. Results indicated an insignificant effect of aflatoxin concentrations between 10 and 100 µg/kg on the survival, growth and reproduction but indicated a concentration-dependent increase in DNA damage at standard testing conditions. However, the interaction of the toxin with different environmental conditions, particularly low moisture, resulted in significantly reduced reproduction rates and increased DNA damage in earthworms.

Global Trends of Green Pesticide Research from 1994 to 2019: A Bibliometric Analysis.

The fast-growing world population places food production under enormous pressure to ensure food security. One of the most common methods to increase food production is the use of pesticides, but the continuous use thereof has numerous detrimental effects on the environment. The interest in biopesticides for a possible substitute has grown over the past two decades. To determine the research evolution of biopesticides (green pesticides), a bibliometric analysis from 1994 to 2019 was carried out. A total of 580 documents were found eligible in the Scopus database for this analysis. Parameters such as the number of articles, article citations, keywords, source impact, and countries of publication were used to analyse the documents and rank countries based on authors, productivity, article citations, and co-authorship. The analysis reveals production increased significantly from 2009 and has the most published documents in 2019 with a total of 74 articles. Asia's most populous countries, India and China, were ranked first and second, respectively, and the USA third in terms of the most productive countries in the field of plant biopesticides. Countries in Europe and Africa however have fewer publications than expected in this field, given the fact that they are high consumers of pesticides. India, China, and the USA have 4.08%, 2.94%, and 12.5% multiple country publications (MCPs), respectively, with the USA having a stronger collaboration. Finally, there is a clear indication in this study that India and China are taking the lead in substituting synthetic pesticides with the alternative natural plant biopesticide.

Heavy metal tolerance traits of filamentous fungi isolated from gold and gemstone mining sites

ABSTRACT Increased environmental pollution has necessitated the need for eco-friendly clean-up strategies. Filamentous fungal species from gold and gemstone mine site soils were isolated, identified and assessed for their tolerance to varied heavy metal concentrations of cadmium (Cd), copper (Cu), lead (Pb), arsenic (As) and iron (Fe). The identities of the fungal strains were determined based on the internal transcribed spacer 1 and 2 (ITS 1 and ITS 2) regions. Mycelia growth of the fungal strains were subjected to a range of (0-100 Cd), (0-1000 Cu), (0-400 Pb), (0-500 As) and (0-800 Fe) concentrations (mgkg-1) incorporated into malt extract agar (MEA) in triplicates. Fungal radial growths were recorded every three days over a 13-days' incubation period. Fungal strains were identified as Fomitopsis meliae, Trichoderma ghanense and Rhizopus microsporus. All test fungal exhibited tolerance to Cu, Pb, and Fe at all test concentrations (400-1000 mgkg-1), not differing significantly (p > 0.05) from the controls and with tolerance index >1. T. ghanense and R. microsporus demonstrated exceptional capacity for Cd and As concentrations, while showing no significant (p > 0.05) difference compared to the controls and with a tolerance index >1 at 25 mgkg-1 Cd and 125 mgkg-1 As. Remarkably, these fungal strains showed tolerance to metal concentrations exceeding globally permissible limits for contaminated soils. It is envisaged that this metal tolerance trait exhibited by these fungal strains may indicate their potentials as effective agents for bioremediative clean-up of heavy metal polluted environments.

Tolerance and growth kinetics of bacteria isolated from gold and gemstone mining sites in response to heavy metal concentrations.

Response and growth kinetics of microbes in contaminated medium are useful indices for the screening and selection of tolerant species for eco-friendly bio-augmentative remediation of polluted environments. In this study, the heavy metal (HM) tolerance, bioaccumulation and growth kinetics of seven bacterial strains isolated from mining sites to 10 HMs (Cd, Hg, Ni, Al, Cr, Pb, Cu, Fe, Mn and Zn) at varied concentrations (25-600 mgL-1) were investigated. The isolates were phylogenetically (16S rRNA gene) related to Lysinibacillus macroides, Achromobacter spanius, Bacillus kochii, B. cereus, Klebsiella pneumoniae, Pseudomonas mosselii and P. nitroreducens. Metal tolerance, effects on lag phase duration and growth rates were assessed using the 96-well micro-titre method. Furthermore, metal bioaccumulation and quantities within cells were determined by transmission electron microscopy and electron dispersive x-ray analyses. Tolerance to Ni, Pb, Fe and Mn occurred at highest concentrations tested. Growth rates increased with increasing Fe concentrations, but reduced significantly (p < .05) with increasing Zn, Cu, Hg, Cd and Al. Significantly higher (p < .05) growth rates (compared to controls) was found with some isolates in Hg (25 mgL-1), Ni (100 mgL-1), Cr (150 mgL-1), Mn (600 mgL-1), Pb (100 mgL-1), Fe (600 mgL-1) and Al (50 mgL-1). Lag phase urations were isolate- and heavy metal-specific, in direct proportion to concentrations. A. spanius accumulated the most Mn and Zn, while B. cereus accumulated the most Cu. Metals accumulated intra-cellularly without cell morphology distortions. The isolates' multi-metal tolerance, intra-cellular metal bioaccumulation and growth kinetics suggest potentials for application in the synergetic biodegradation and bioremediation of polluted environments, especially HM-rich sites.

Heavy metal tolerance traits of filamentous fungi isolated from gold and gemstone mining sites.

Increased environmental pollution has necessitated the need for eco-friendly clean-up strategies. Filamentous fungal species from gold and gemstone mine site soils were isolated, identified and assessed for their tolerance to varied heavy metal concentrations of cadmium (Cd), copper (Cu), lead (Pb), arsenic (As) and iron (Fe). The identities of the fungal strains were determined based on the internal transcribed spacer 1 and 2 (ITS 1 and ITS 2) regions. Mycelia growth of the fungal strains were subjected to a range of (0-100 Cd), (0-1000 Cu), (0-400 Pb), (0-500 As) and (0-800 Fe) concentrations (mgkg-1) incorporated into malt extract agar (MEA) in triplicates. Fungal radial growths were recorded every three days over a 13-days' incubation period. Fungal strains were identified as Fomitopsis meliae, Trichoderma ghanense and Rhizopus microsporus. All test fungal exhibited tolerance to Cu, Pb, and Fe at all test concentrations (400-1000mgkg-1), not differing significantly (p>0.05) from the controls and with tolerance index >1. T. ghanense and R. microsporus demonstrated exceptional capacity for Cd and As concentrations, while showing no significant (p>0.05) difference compared to the controls and with a tolerance index >1 at 25mgkg-1 Cd and 125mgkg-1 As. Remarkably, these fungal strains showed tolerance to metal concentrations exceeding globally permissible limits for contaminated soils. It is envisaged that this metal tolerance trait exhibited by these fungal strains may indicate their potentials as effective agents for bioremediative clean-up of heavy metal polluted environments.