Halotolerant and metalotolerant bacteria strains with heavy metals biorestoration possibilities isolated from Uburu Salt Lake, Southeastern, Nigeria

Environmental contaminations by heavy metals are currently an increasing public health concern globally. One key challenge of these toxic metals is the extremely difficulties involved in their detoxification from the environment and effluents because of their non-degradability. An efficient biologic agent with potentials of remediating these toxic metals may ease these ever-increasing problems. We reported toxic metals tolerance and bioremediation potentials of novel bacteria sp. Strains USL2S, USL4W and USL5W isolated from Uburu salt lake, Ebonyi State, Nigeria. The phenotypic characteristics and the 16S rRNA gene analyses revealed that USL2S strain belongs to the genus Klebsiella, whereas USL4W and USL5W strains belong to the genus Pseudomonas. The bacteria isolates grew well in media containing 5–15 % of sodium chloride. The bacteria isolate showed capacity to tolerate 50.0 mM Hg⁺² and Pb⁺², 17.0, 12.50 and 4.0mM Ni⁺², Cd⁺², and Zn⁺² respectively in solid media. Pseudomonas putida A4W Strain also tolerated 16.0 mM Cu⁺², while Klebsiella sp. Strain USL2S, Pseudomonas putida USL5W Strain tolerated 4.0 mM each. AAS analyses showed 85, 95, and 95 % Hg; 97.13, 98.89, and 97.55 % Pb; 73.33, 77.42 and 69.72 Cd; 88.06, 99.54, and 97.91 % Ni; 100, 100 and 83.62% Cu; 42.30, 84.52 and 98.80 % Zn removal from media broth incorporated with the tested metals by Klebsiella sp. USL2S, Pseudomonas sp. Strain USL5W and Pseudomonas sp. USL4W respectively. We therefore recommend these novel moderately halophilic and metal tolerant isolates as possible biologic agents for effective bioremediation of mercury, lead, cadmium, nickel, copper and zinc in contaminated environments and effluents.

Assessment of Levels and Health Risks of Trace Metals in Soils and Food Crops Cultivated on Farmlands Near Enyigba Mining Sites, Ebonyi State, Nigeria

ABSTRACT

In most developing countries, mining is one of the major sources of toxic heavy metals, some of which are a major health concern to the surrounding populace through soil pollution and food contamination. We investigated the levels of Ti, Mn, Ni, Cu, Zn, Pb, Rb, Sr, Se, Nb, and V in 64 soil samples, 320 samples of regularly consumed staple food crops and vegetables (Manihot esculenta [cassava] tubers, Dioscorea rotundata [white yam], Arachi hypogea [groundnut] seed, Telfariria occidentalis [fluted pumpkin leaf]), and leaves of the medical plant Zanthoxulum zanthoxyloides on farmlands near Enyigba mining sites in Ebonyi state, Nigeria. We also examined the possible health risks due to consumption of these staple foods. Energy dispersive X-ray fluorescence was used to determine the metals present in the samples. The mean levels of metals, except for Mn, Pb, and Zn, were below the threshold limits recommended by various institutions for agricultural soils. Our data also showed that food crops cultivated near these sites bioaccumulated toxic levels of these metals above the proposed values set by the World Health Organization, National Agency for Food and Drug Administration and Control, and Codex Alimentarius Commission, especially for Pb, Zn, Cu, Ni, Se, and Rb. These findings may have potential health implications for the local dwellers. The estimated daily intakes of the toxic metals through the consumption of the crop samples were below the maximum tolerable daily intakes, except for Pb and Ni, by eating groundnut, cassava, and white yam. Furthermore, the target hazard quotient, computed based on the estimated daily intake of the heavy metals, was above unity for the metals for cassava, white yam, and groundnut consumption, suggesting significant health risk. Elevated amounts of heavy metals in cassava and groundnut samples, as revealed by their metal extraction coefficient computed in this study, hint that they may be used as bioindicators of ecological and health hazards and phytoremediators of Mn, Zn, Cu, and Pb.

HIGHLIGHTS

Ethanolic extract of Cnidoscolus aconitifolius leaves alleviates insulin resistance by modulating oxidative stress and inflammation in albino rats exposed to heavy metal mixture

Exposure to heavy metals significantly contributes to insulin resistance, a major factor in type 2 diabetes. This study investigated the antioxidant and therapeutic potential of ethanol leaf extract of Cnidoscolus aconitifolius in mitigating heavy metal-induced insulin resistance, oxidative stress and inflammation in albino rats. Thirty rats were divided into five groups: Groups I and II received normal saline and a lead-mercury mixture, respectively, while Groups III, IV and V were treated with the extract (200, 400 and 600 mg/kg) for four weeks after exposure. The extract, rich in catechin, rutin, gallic acid and kaempferol, exhibited strong antioxidant activity. Heavy metal exposure induced hepatic insulin resistance, dyslipidaemia, oxidative stress and inflammation, as shown by elevated HOMA-IR values. Extract treatment reversed these effects in a dose-dependent manner, restoring insulin sensitivity via oxidative stress and inflammation modulation. This highlights the potential of C. aconitifolius as a nutraceutical for heavy metal-induced metabolic disorders.