Correction for Oshiki et al., "Determination of 15N/ 14N of Ammonium, Nitrite, Nitrate, Hydroxylamine, and Hydrazine Using Colorimetric Reagents and Matrix-Assisted Laser Desorption Ionization-Time-of-Flight Mass Spectrometry (MALDI-TOF MS)". Determination of 15N/14N of Ammonium, Nitrite, Nitrate, Hydroxylamine, and Hydrazine Using Colorimetric Reagents and Matrix-Assisted Laser Desorption Ionization-Time-of-Flight Mass Spectrometry (MALDI-TOF MS) (Applied and Environmental Microbiology (2022) 88:7 (e02416-21) DOI: 10.1128/aem.02416-21)

The last sentence of the fourth paragraph of the introduction (beginning, "To our knowledge, MALDI-TOF MS has not been applied . . .") should be replaced with the following: "To our knowledge, MALDI-TOF MS has not been applied for determining 15N atom% of the NH4 1, NO2 2, and NO3 2 complex dyes thus far, and no previous studies have described any MS method to determine the 15N atom% of NH2OH-derived dyes, although NH2OH is an intermediate of the aerobic ammonia oxidation process (3). Apart from NH2OH, N2H4 is an intermediate of the anaerobic ammonium oxidation (anammox) process (4). It is notable that the accumulation of 15N-labeled N2H4 in anammox bacterial culture was previously examined by MALDI-TOF MS analysis of N2H4-derived dye (72), while quantitative measurement of the 15N atom% of N2H4 using this method has still been limited."