Monitoring the metabolic activity of sulphate-reducing bacteria

Abstract

Sulphate-reducing bacteria (SRB) are critically important for industry and the environment due to their role as hydrogen sulphide (H₂S) producers. Traditional monitoring methods include culture-based techniques, microscopy, enzymatic, and molecular biology approaches, which vary in complexity, cost, and time, limiting widespread use. Despite this, the culture-dependent Most Probable Number (MPN) method remains prevalent due to its simplicity. This study introduces the use of an Ag/Ag₂S electrode to detect SRB in aqueous environments by monitoring changes in open circuit potential caused by biogenic sulphide production. The method enabled SRB detection within 72 h—significantly faster than the 28 days required by MPN—with detection limits of ~10 in tap water and ~ 20 correlation (R2 μM in seawater. Experiments were conducted at 32 μ◦M C and pH 7.0 ± 0.1. A strong linear = 0.99) was observed between sulphide accumulation and bacterial growth. The electrode's response exhibited three regimes: non-detection, non-Nernstian (2 × 106–5 × 105 mol L1), and Nernstian behaviour, the former likely linked to kinetic limitations or competitive anion adsorption. Reduced sensitivity in seawater may arise from chloride or metal–sulphide interactions, suggesting the need for further optimization in high-salinity environments. The Ag/Ag₂S electrode offers a simple, cost-effective, and practical solution for monitoring SRB activity, requiring minimal equipment and operator training. Furthermore, it has the potential to enhance operational efficiency and mitigate risks associated with SRB-induced microbial contamination.