Table 1.

Acid-tolerant mechanisms utilized by various microorganisms

Mechanisms	Bacteria	Yeasts
F0F1-ATPase proton pumps	E. coli (Foster 2004; Sun et al. 2012b) Lactococcus (O’Sullivan and Condon 1999) Lactobacillus (Koponen et al. 2012) Streptococcus (Martin-Galiano et al. 2005; Kuhnert and Quivey 2003) Corynebacterium glutamicum (Jakob et al. 2007) P. acidipropionici (Zhang and Yang 2009; Guan et al. 2013) Bacillus (Shobharani and Halami 2014)	S. cerevisiae (Casal et al. 2016) C. glabrata (Zhou et al. 2011) Zygosaccharomyces bailii (Palma et al. 2015)
Decarboxylation and deamination	E. coli (Iyer et al. 2003; Sun et al. 2012a; Lu et al. 2013) Lactococcus (Budin-Verneuil et al. 2006) Lactobacillus (Su et al. 2011) P. acidipropionici (Guan et al. 2013)
Cell membrane modification	E. coli (Chang and Cronan 1999) Lactococcus (Wu et al. 2012b) Lactobacillus (Broadbent et al. 2010)	S. cerevisiae (Ding et al. 2009; Zhao and Bai 2009) Z. bailii (Palma et al. 2015)
Metabolic regulation	P. acidipropionici (Guan et al. 2014)	S. cerevisiae (Wu et al. 2016) Z. bailii (Palma et al. 2015)
Macromolecule protection and repair	E. coli (Hong 2012; Mujacic and Baneyx 2007) Lactococcus (Weidmann et al. 2017) Lactobacillus (Koponen et al. 2012) Streptococcus (Shabayek and Spellerberg 2017) C. glutamicum (Jakob et al. 2007) A. pasteurianus (Zheng et al. 2018)	S. cerevisiae (Ding et al. 2009) Z. bailii (Palma et al. 2015)
Protection from organelle		S. cerevisiae (Ding et al. 2015a; Kumar et al. 2015; Cheng et al. 2016)