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Reuben N. Okechi
Edna I. Chukwura
Christian O. Nweke



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Original Research Article

Reuben N. Okechi1*Edna I. Chukwura2 and Christian O. Nweke3


1Department of Biotechnology, Federal University of Technology Owerri, Imo State, Nigeria
2Department of Applied Microbiology and Brewing, Nnamdi Azikiwe University, Awka, Anambra State, Nigeria
3Department of Microbiology, Federal University of Technology Owerri, Imo State, Nigeria

*Corresponding Author E-mail: reuben.okechi(at)futo.edu.ng

Tel.+2348035086155

Reuben N. Okechi

Edna I. Chukwura

Christian O. Nweke


Article Number: ibspr.20.009  |   Pages: 72-84  |   Vol. 8 (5), November 2020   |   DOI: https://doi.org/10.15739/ibspr.20.009

 Received: September 3, 2020  Accepted: October 24, 2020  Published: November 21, 2020

Abstract

The toxicities of Sodium Dodecyl Sulfate (SDS) and heavy metal ions (Ni2+, Co2+, Cd2+, Zn2+ and Pb2+), as individual and SDS + metal ion binary mixtures to Acinetobacter seifertii isolated from Otamiri river sediment, Owerri, in southeastern Nigeria were assessed, on the basis of dehydrogenase activity (DHA) inhibition. The responses of the bacterium to the toxic effects of the toxicants were concentration-dependent. The EC50S observed ranged from 0.011 ± 0.000 mM for Cd2+ to 2.810 ± 0.140 mM for SDS. The EC50S of the individual toxicants were statistically different from each other. The heavy metals were more toxic than SDS and the decreasing order of toxicity was Cd2+ > Co2+ > Zn2+ > Pb2+ > Ni2+ > SDS. Fixed ratio mixtures based on EC50 equi-effect concentration ratio (EECR50 mixtures) and arbitrary combinations (ABCR mixtures) were designed to assess the combined toxicities of SDS and metals. All the dose-response relationships of the ABCR and EECR50 mixtures and the individual toxicants could be described by logistic function. Toxicities predicted from concentration addition (CA) and independent action (IA) models were statistically different from the experimentally-derived toxicities. In SDS + Ni2+ binary mixture, CA and IA models overestimated the toxicity at low concentrations, while under estimating at high concentrations. Furthermore, both models predicted identical toxicities in SDS + Ni2+ and SDS + Co2+ mixtures and there was also no statistical difference between CA and IA-predicted EC50S for the two binary mixtures. In all but ABCR3 mixture ratio of SDS + Cd2+ mixture, both models significantly predicted lower toxicities. SDS + Zn2+ binary mixture was hormetic at low concentrations. The binary mixtures were generally synergistic to A. seifertii. This synergistic interaction of SDS and metals ions highlights the environmental implications of SDS and metal ions co-contamination.

Keywords:

Inhibition, equi-effect concentration, dose-response, models, synergistic interaction, toxicant

How to Cite this Article

Okechi RN, Chukwura EI Nweke CO (2020). Toxicity of binary mixtures of sodium dodecyl sulfate and heavy metals to Acinetobacter seifertii from tropical river sediment. Issues Biol. Sci. Pharma. Res.8(5):72-84.

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