Toxicity of Zinc to Heterotrophic Bacteria From a Tropical River Sediment

Abstract

Abstract. Tolerance to Zn 2+ by pure cultures of Bacillus, Salmonella and Arthrobacter species isolated from New Calabar River sediment was assessed through dehydrogenase assay. The cultures were exposed to Zn 2+ concentrations of 0.2 to 2.0 mM in a nutrient broth-glucose-TTC medium. The responses of the bacterial strains varied with Zn 2+ concentration. In Salmonella sp. SED2, Zn 2+ stimulated dehydrogenase activity at 0.2 mM. In Bacillus sp. SED1 and Arthrobacter sp. SED4, dehydrogenase activity was progressively inhibited with increasing Zn 2+ concentration. The IC 50 ranges from 0.206 ± 0.030 to 0.807 ± 0.066 mM. Total inhibition of dehydrogenase activity was observed at concentrations ranging from 1.199 ± 0.042 to 1.442 ± 0.062. The order of zinc tolerance is: Salmonella sp. SED2 > Arthrobacter sp. SED4 > Bacillus sp. SED1. The result of the in vitro study indicated that Zinc is potentially toxic to sediment bacteria and could pose serious threat to their metabolism in natural environments.

Inhibition of dehydrogenase activity in bacterial isolates from palm wine by extracts of <i>Vernonia amygdalina</i>

“…These variations may be due to differences in bacterial physiology, including cell wall components or dehydrogenase systems, since different microorganisms have been reported to have different dehydrogenase systems (PraveenKumar, 2003) . However, the present study is in consonance with reports of earlier studies (Nweke et al, 2007;Nwaogu et al, 2007;Nwaogu et al, 2008;Alisi et al, 2008). The effect of the different concentrations of the extracts on the bacterial isolates with respect to the dehydrogenase activity is shown in Figure 1.…”

“…The dehydrogenase assay method as described by Alisi et al (2008) and Nweke et al (2007) was adopted for this study. The dehydrogenase activity (DHA) was determined using 2,3,5-triphenyltetrazolium chloride (TTC) as the artificial electron acceptor, which was reduced to the redcoloured triphenylformazan (TPF).…”

“…In this regard, dehydrogenase activity has been widely used. The dehydrogenase assay is an effective primary test for assessing the potential toxicity of metals to soil microbial activities (Aoyama and Nagumo, 1997;Chander and Brookes, 1995;Kelly and Tate, 1989;Rogers and Li, 1985), toxicity of metals to planktonic (Nweke et al, 2006) and heterotrophic (Nweke et al, 2007) bacteria from tropical river sediments. Toxicity of plant extracts to pathogenic bacteria has been assessed using the dehydrogenase assay (Nwaogu et al, 2007;Nwaogu et al, 2008;Alisi et al, 2008) The aim of the study is to examine the inhibitory activity of dehydrogenase of bacteria isolates in palm wine as a means of control of microbial load in palm wine.…”

Determination of Antimicrobial Potentials of Ethanol Extract of <i>Combretum dolichopentalum</i> Leaves by Total Dehydrogenase Activity Assay

“…Formazan produced from the test is used as a measure of the amount of the living cells [28]. Dehydrogenase activity (DHA) is an effective primary test for the assessment of ecotoxicological impacts of environmental substrates such as toxicity of metals to planktonic [31], heterotrophic bacteria [32], and pathogenic organisms in wounds [29,33,6]]. The viability of microorganisms is represented by the total dehydrogenase activity, thus a reduction in total dehydrogenase activity is an indication of the bactericidal effect of the plant extract on the microorganisms.…”

Influence of Physicochemical Factors on Dehydrogenase Activity of Bacillus Subtilis Imb B-7023

“…На показники його активності спричиняє помітний вплив концентрація джерел вуглецевого живлення і енергії, темпера-тура середовища, вміст різних хімічних речовин, які можуть інтенсифікувати або сповільнювати метаболічні процеси мікроорганізмів [8][9][10][11][12]. Тому дегідро-геназна активність вважається індикатором функціонального стану мікробних популяцій і їх окиснювальної активності [10][11][12].Вплив цих факторів на дегідрогеназну активність Bacillus subtilis ІМВ В-7023, що є компонентом комплексного бактеріального препарату для рос-линництва [2], не визначався, що не дозволяє прогнозувати можливі зміні …”