Academic article

Responses of Staphylococcus aureus exposed to HCl and organic acid stress

Rode, Tone Mari; Møretrø, Trond; Langsrud, Solveig; Langsrud, Øyvind; Vogt, Kjell gjermund; Holck, Askild Lorentz

Publication details

Journal: Canadian Journal of Microbiology (print), vol. 56, p. 777–792–16, 2010

Issue: 9

International Standard Numbers:
Printed: 0008-4166
Electronic: 1480-3275

Open Access: none

Links:
DOI

Staphylococcus aureus is an important food poisoning bacterium. In food preservation, acidification is a well-known method. Permeant weak organic acids, like lactic and acetic acids, are known to be more effective against bacteria than inorganic strong acids (e.g., HCl). Growth experiments and metabolic and transcriptional analyses were used to determine the responses of a food pathogenic S. aureus strain exposed to lactic acid, acetic acid, and HCl at pH 4.5. Lactic and acetic acid stress induced a slower transcriptional response and large variations in growth patterns compared with the responses induced by HCl. In cultures acidified with lactic acid, the pH of the medium gradually increased to 7.5 during growth, while no such increase was observed for bacteria exposed to acetic acid or HCl. Staphylococcus aureus increased the pH in the medium mainly through accumulation of ammonium and the removal of acid groups, resulting in increased production of diacetyl (2,3-butanedione) and pyrazines. The results showed flexible and versatile responses of S. aureus to different types of acid stress. As measured by growth inhibition, permeant organic acid stress introduced severe stress compared with the stress caused by HCl. Cells exposed to lactic acid showed specific mechanisms of action in addition to sharing many of the mechanisms induced by HCl stress.