The Loligo® microplate respirometry system has a strong track record for high‑throughput oxygen consumption measurements in small aquatic organisms such as Daphnia, zebrafish embryos, and aquatic invertebrates.

Here we show how the same system can be used to measure microbial respiration in suspension, using samples dominated by Acidithiobacillus thiooxidans.

At low pH, A. thiooxidans oxidizes hydrogen sulfide (H₂S) to sulfuric acid (H₂SO₄), a key driver of biogenic sulfuric acid (BSA) corrosion in concrete. Because this process consumes oxygen, microbial activity can be quantified by monitoring O₂ decline in sealed microplate wells.

The aim of this study was to evaluate the inhibitory effect of nitrite (NO₂⁻) on sulfide oxidation under acidic conditions (~pH 2).

Experimental Approach

Corroded concrete material, expected to be dominated by A. thiooxidans, was mixed with water, sulfuric acid, sulfide and increasing concentrations of nitrite (NaNO₂)

Samples were vortexed to homogenize and aerate the suspension before being transferred to a glass microplate wih 1,700 µL wells. Each well contained a glass bead to support continuous agitation on an orbital shaker.

Oxygen saturation in 24 wells was logged using the MicroResp software - the first column being the control (no nitrite) and consecutive columns having increasing nitrite concentrations (see below).

Key Findings

Inhibition of oxygen consumption:

• Oxygen consumption decreased as nitrite concentration increased.
• Control wells and low‑nitrite wells consumed most oxygen within ~1 hour.
• High‑nitrite wells showed minimal oxygen decline over the same period.

Dose–Response Relationship

Data from the first 30 minutes were used to generate dose–response curves, clearly showing nitrite‑dependent inhibition of microbial respiration.

Inhibition of oxygen consumption compared to controls (without added nitrite) at increasing
nitrite concentration after the first 30 minutes. Values are average of the four replicates ± 1 SD.

These results demonstrate that the microplate system is well suited for high‑throughput microbial respiration assays, even in low‑pH, corrosion‑related environments.

Project Background

This work was conducted as part of a master’s thesis by Sune Popp Hinke and Line Gade Frahm supervised by Associate Professor Asbjørn Haaning Nielsen, Department of the Built Environment, Aalborg University.

The study highlights how microplate respirometry can provide rapid, parallel insight into microbial activity driving biogenic sulfuric acid corrosion, and how inhibitors such as nitrite can modulate this process.

Interested in Microbial Respirometry?

The microplate system is suitable for oxygen consumption measurements in suspensions of:

• Bacteria
• Algae
• Yeast
• Protozoa
• Other microorganisms

Should you also be interested in the microplate respirometry system for oxygen consumption measurements of microorganisms in suspension then please reach out to our product specialist Dr Rune Hertz Larsen (rhl@loligosystems.com), who will be happy to discuss your experimental needs and considerations. 

Click here for a more detailed application note with extended data