Effects of Low-Level Inorganic Selenium on Selenium Bioaccumulation in Escherichia coli: A Bioanalytical Study Using Graphite Furnace Atomic Absorption Spectrometry (GFAAS)

Abstract

This study aimed to assess the bioaccumulation of selenite – Se(IV) – and selenate – Se(VI) – in Escherichia coli ATCC 11775 biomass. Escherichia coli cultures were exposed to low selenium concentrations (0.3–30.0 µM), and subsequent effects on growth and viability were evaluated. Selenium content in biomass was quantified using graphite furnace atomic absorption spectroscopy (GFAAS) and inductively coupled plasma mass spectrometry (ICP-MS), with Se recovery assessed through mass balance analysis. The average percentage of bioaccumulated Se exhibited variability depending on the Se species at different concentrations. At a concentration of 30.0 μM, elemental selenium formation emerged within the Se(IV) assay, leading to a significantly higher mean percentage of bioaccumulated selenium for Se(IV) (41.1%) compared to Se(VI) (15.8%). While the mean percentage of bioaccumulated selenium showed no significant variance across the Se(VI) concentrations, a significant difference was observed across the Se(IV) concentrations (ranging from 6.1% to 41.1%). Considering the percentage of Se recovered in the solid and liquid phases, the mass balance ranged from 82.1% to 94.5%. These findings underscore the ability of Escherichia coli ATCC 11775 to accumulate notable quantities of selenium, with the amount of bioaccumulated Se influenced by Se(IV) concentration but not by Se(VI). Furthermore, bacterial viability remained unaffected by selenium species and concentrations. This study contributes valuable insights into the bioaccumulation dynamics of Se(IV) and Se(VI) in non-genetically modified Escherichia coli, shedding light on factors governing selenium accumulation in bacterial biomass, particularly regarding natural biological representation, standardization, comparability, and applicability to environmental studies.