International Science Community Association International Research Journal of Biological Sciences 2278 - 3202 6 4 2017 04 10 Combined effects of metals and chlorophenols on dehydrogenase activity of bacterial consortium 10 20 EN M. Sreenivas 1 Department of Zoology, Kakatiya University, Warangal-506009, Telangana, India G. Shamitha 2 Department of Zoology, Kakatiya University, Warangal-506009, Telangana, India Nwanyanwu C.E. 1 Department of Microbiology, Federal University of Technology, P.M.B. 1526, Owerri, Nigeria Adieze I.E. 2 Department of Microbiology, Federal University of Technology, P.M.B. 1526, Owerri, Nigeria Nweke C.O. 3 Department of Microbiology, Federal University of Technology, P.M.B. 1526, Owerri, Nigeria Nzeh B.C. 4 Department of Microbiology, Federal University of Technology, P.M.B. 1526, Owerri, Nigeria > Research Paper 2017 1 27 2017 04 10 Toxicity of Zinc, Cadmium, 4-Chlorophenol (4-CP), 2,4-Dichlorophenol (2,4-DCP) and their binary and quaternary mixtures were determined based on inhibition of dehydrogenase activity of a consortium of Pseudomonas, Bacillus, Micrococcus and Staphylococcus species. The toxicity of chemicals and their mixtures were evaluated in the concentration range of 0-3mM while Cadmium and 2,4-Dichlorophenol binary mixture range was 0-1.8mM. Zinc, 4-CP and 2,4-DCP exhibited hormetic effect at low concentration. The IC50 were determined using monotonic and hormesis dose-response models. The binary and quaternary mixtures of the pollutants evaluated showed progressive inhibition of the enzyme activity. The combined effects of the mixtures on the enzyme activity of the bacterial consortium were evaluated with isobolographic representation and toxic index (TI) model. The isobolographic analysis indicated additive, synergistic and antagonistic interactions for the various binary mixtures evaluated. However, the TI of most mixtures was within the range of 0.5-2.0 and are considered additive. Modulation of the toxic interactions by the components of the mixture through synergistic and antagonistic interaction of the heavy metals and phenolic compounds against the dehydrogenase activity of the bacterial consortium were possible depending on the relative amount of the components. Copyright@ International Science Community Association