Rapid Amperometric Assessment of Substrate Oxidation and Acute Toxicant Responses in Acidithiobacillus Strain Thio1

Obligate acidophilic bacteria of the genus Acidithiobacillus are widely used and well known in the biomining industry. Over the past decade, it has been shown that bacterial activity can be determined in short-term experiments via amperometric measurements of microbial oxygen consumption, as changes in the Clark electrode current are proportional to changes in the concentration of dissolved oxygen. This article presents a study of Acidithiobacillus sp. strain Thio1, which was isolated from pyrite–chalcopyrite copper ore and is closely related to A. ferrooxidans. Oxygen consumption by strain Thio1 was measured during the bacterial oxidation of substrates as changes in the electrode current. To evaluate the acute respiratory response of the bacteria to Cu, Zn, and As, respiration suppression was measured at increasing concentrations of the toxicants. The proposed amperometric method is not a substitute for the long-term biogeotechnological evaluation of strain activity using specific ore or pulp samples. At the same time, it can be used as a complementary microbiological method. The proposed approach offers distinct advantages: testing takes mere minutes (rapid analysis), and comparisons of substrates or toxicants can be performed using a single biomass sample (standardization). The amperometric method also demonstrated that oxygen was consumed during the corrosion of solid specimens (steel and chalcopyrite) by Acidithiobacillus sp. strain Thio1. However, applying this method to biocorrosion requires further study because the proportion of oxygen consumption directly related to microbial corrosion remains unknown.