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Structural Changes in Cell-Wall and Cell-Membrane Organic Materials Following Exposure to Free Nitrous Acid
journal contribution
posted on 2020-08-06, 22:00 authored by Mariella Chislett, Jianhua Guo, Philip L. Bond, Alun Jones, Zhiguo YuanPrevious
studies demonstrate that free nitrous acid (FNA, i.e.,
HNO2) is biocidal for a range of microorganisms. The biocidal
mechanisms of FNA are largely unknown. In this work, it is hypothesized
that FNA will break bonds in molecules found in the cell envelope,
thus causing cell lysis. Selected molecules representing components
found in the cell envelope were treated with FNA at 6.09 mg N/L (NO2– = 250 mg N/L, pH 5.0) for 24 h (conditions
typically used in applications) to evaluate the hypothesized chemical
interactions. Molecular changes were observed using analytical techniques
including proton (1H) nuclear magnetic resonance spectroscopy
(NMR) and electrospray ionization mass spectrometry (ESI-MS). It was
found that FNA broke down a range of cell envelope molecules. The
spectral data demonstrated that the FNA reactions proceeded via two
general pathways. One consisted of electrophilic substitution, whereby
the nitrosonium ion (NO+) was the reactive electrophile.
The other was via oxidative reactions involving nitrogen radicals
(e.g., •NO2 and •NO) formed from the decomposition
of FNA. We further revealed that it was HNO2 that caused
the breakdown, rather than the exclusive action of the acid (H+) or nitrite (NO2–) counterparts.
The fragmentation of these representative cell envelope molecules
provides insight into the biocidal effects of FNA on microorganisms.