Role of organic acids in tolerance

ATR as a function of the acid used may be due to the maintenance of internal pH (pH,) of the cell (Alvarez-Ordonez et al., 2009). Some organic acids enter the cell more easily than others, and, as a result, may alter the pH of the cell more easily (Greenacre et al., 2003). The pH is crucial for maintenance of acid tolerance. The ATR complex phenomenon is strongly affected by environmental factor interaction, prevailing during acid adaptation and acid inactivation (Alvarez-Ordonez et al., 2009). 

An inorganic acid (H+) can signal a decrease in the proteolysis of 6s. Inorganic acid stress, therefore leads to an accumulation of 8s by downregulating proteolysis. Organic acids increase 6s stability, and also stimulate translation of the rpoS message. Exponential-phase cultures, grown at pH7 and adapted with 100 mM acetate exhibit a 5x increase in rpoS translation, but not transcription (Audia, Webb, and Foster, 2001). 

Gram-negative bacteria have developed various devices to protect themselves from acid stress (Barua et al., 2002). For example, studies have shown that propionic acid and butyric acid can promote extreme acid resistance of nonpathogenic E. coli, as well as the extreme acid resistant E. coli 0157 H7 (Guilfoyle and Hershfield, 1996), whereas benzoate, on the other hand, is much less active in promoting survival of E. coli 0157 H7 than acetate (Diez-Gonzalez and Russell, 1999). 

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