Author Correction: Ammonia sets limit to life and alters physiology independently of pH in Halomonas meridiana

Correction to: Scientific Reports https://doi.org/10.1038/s41598-025-03858-z, published online 04 June 2025.

The original version of this Article was revised to correct outdated information.

Firstly, in the Introduction, the statement:

“The small size and non-polar properties of NH₃ facilitates passive permeation through membranes^12,13,14,15, causing significant intracellular disruption^16,17,18.”

now reads:

“The small size and unchanged nature of NH₃ facilitates passive permeation through membranes^12,13,14,15, causing significant intracellular disruption^16,17,18.”

And where:

“With a pH predicted at or above 9^29,30, the ocean of Enceladus would bear appreciable amounts of toxic NH₃.”

now reads:

“With a pH predicted at or above 9^29,30,31, the ocean of Enceladus would bear appreciable amounts of toxic NH₃.”

Furthermore, in the Results section, under the subheading ‘Ammonia exposure elicits a unique metabolomic response’, where:

“Multivariate analysis also revealed exposure to 0.25 M ammonia increased the relative abundance of pantothenate (F = 28.839, p < 0.001) (Fig. 6c), and amino acids D-allo-isoleucine (F = 28.686, p < 0.001) (Fig. 6d), and alanine (F = 25.391, p < 0.01) (Fig. 6e), compared to those in NaOH pH 10.18 and control conditions.”

now reads:

“Univariate analysis also revealed exposure to 0.25 M ammonia increased the relative abundance of pantothenate (F = 28.839, p < 0.001) (Fig. 6c), and amino acids D-allo-isoleucine (F = 28.686, p < 0.001) (Fig. 6d), and alanine (F = 25.391, p < 0.01) (Fig. 6e), compared to those in NaOH pH 10.18 and control conditions.”

In addition, under the Materials and Methods section, under the subheading ‘Bacterial culture’, where:

“Thus, H. meridiana Slthf1 was grown in a yeast media consisting of 1 g/100 mL Bacto™ yeast extract (Becton, Dickinson and Company), 0.2 M NaCl (1.17% salinity) (Thermo Fisher Scientific, CAS Number: 7647-14-5) and deionised water (dH₂O).”

now reads,

“Thus, H. meridiana Slthf1 was grown in a yeast media consisting of 1 g/100 mL Bacto™ yeast extract (Becton, Dickinson and Company), 0.2 M NaCl (1.17% salinity) (Thermo Fisher Scientific, CAS Number: 7647-14-5) and distilled water (dH₂O).”

And Eq. 3, where:

$$NH_{3} = NH_{3} + NH_{4}^{ + } /(1 + 10^{{\left( {pKa^{s} + 0.0324\left( {298 - T} \right) + 0.0415\left( P \right)/T - 1} \right)}}$$

(3)

now reads,

$$\% NH_{3} = 100/\left[ {1 + 10^{{\left( {pKa^{s} + 0.0324\left( {298 - T} \right) + 0.0415\left( {P/T} \right) - pH} \right)}} } \right]$$

(3)

In the Discussion section, where:

Interpreted from the point of view of planetary habitability, the closed-air system is the most applicable representation of icy moon subsurface oceans as ammonia concentrations are presumed to remain constant. The ammonia toxicity limit at 0.05 M established in the closed-air system is higher than the lowest predicted concentration of ammonia at 0.01 M for the Enceladus ocean, but lower than the highest predicted concentration at 0.1 M^25,30. With oceanic temperatures estimated at 0 ºC²⁸ and salinity at 4% ²⁹, the Enceladus ocean would require a pH of < 9.96 to satisfy a relative abundance of NH₃ at < 62% suggested as a habitability boundary in this study, which is in the range of current estimations^29,30.

now reads,

Interpreted from the point of view of planetary habitability, the closed-air system is the most applicable representation of icy moon subsurface oceans, as ammonia concentrations are presumed to remain constant. The ammonia toxicity limit at 0.05 M established in the closed-air system is higher than the lowest predicted concentration of ammonia at 0.01 M for the Enceladus ocean, but lower than the highest predicted concentration at 0.1 M^25,30,31. When considering the proportion of more toxic NH₃, the pKa of the NH₃/NH₄⁺ system can be presumed to increase as temperature decreases; a pKa of ~ 10.1 at 0 °C has been approximated³². The pKa of the NH₃/NH₄⁺ equilibrium is also influenced by ionic strength³³. Thus, with oceanic temperatures estimated at 0 ºC²⁸ and ionic strength at 0.333 molal³¹, it can be calculated that the Enceladus ocean would require a pH of ≤ 10.6 to satisfy a relative abundance of NH₃ at < 62% suggested as a habitability boundary in this study. This is in the range of the lower pH estimations currently modelled for Enceladus, where phosphate speciation in the waters constrains the ocean to pH 10.1 to 11.6, with a most consistent value of pH 10.6 ³¹."

And finally, the following References have been included:

31. Glein, C. R. & Truong, N. Phosphates reveal high pH ocean water on Enceladus. Icarus 441, 116,717 (2025).

32. Bates, R. G. & Pinching, G. D. Acidic dissociation constant of ammonium ion at 0 to 50 °C, and the base strength of ammonia. J. Res. Natl. Bur. Stan. 42, 419 (1949).

33. Bower, C. E. & Bidwell, J. P. Ionization of ammonia in seawater: effects of temperature, pH, and salinity. J. Fish. Res. Bd. Can. 35, 1012–1016 (1978).

The original version of this Article has been corrected.