Journal of Environmental Biology

Effect of bacterial growth period on the sensitivity

of the MTT assay for silver

M.I.E. Halmi¹, F. Ahmad¹, A.K. Hashim², N.A. Shamaan³, M.A. Syed¹ and M.Y. Shukor¹*

¹Department of Biochemistry, Faculty of Biotechnology and Biomolecular Sciences, University Putra,

Malaysia-43400 UPM Serdang, Selangor, Malaysia

²Department of Cell and Molecular Biology, Faculty of Biotechnology and Biomolecular Sciences,

University Putra Malaysia, 43400 UPM Serdang, Selangor, Malaysia

³Faculty of Medicine and Health Sciences, Islamic Science University of Malaysia, Pandan Indah-55100 Kuala Lumpur, Malaysia

*Corresponding Author E-mail: yunus@biotech.upm.edu.my

Publication Data

Paper received:

04 March 2013

Revised received:

07 May 2013

Accepted:

01 June 2013

Abstract

Respiratory activity inhibition by toxic compounds in bacteria and yeast has been used to detect toxic compounds in the environment. Often the age of culture contributes towards the sensitivity of detection. In the present work, the effect of growth period on the sensitivity of an inhibitive assay for heavy metals using bacterial respiratory assay system based on the reduction of the water soluble tetrazolium dye MTT is reported. A silver-sensitive isolate was discovered to exhibit different sensitivities towards silver at different growth periods. An exponential decay model adequately described the inhibition due to silver. Analysis using ANOVA with post-hoc Tukey's test showed that the IC₅₀ obtained by strain DRYS8 grown at the 12 hr-period in nutrient broth at 28 ^oC gave the lowest value compared to other growth periods. This study highlights the importance of taking into accounts growth conditions and age of culture in developing cellular-based bioassays.

 Key words

MTT assay, Bacterium, Growth Period, Silver

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