Table 4.

An overview of the reported substrates and degradation pathways in Sa. solfataricus and S. acidocaldarius.

Substrate	Organism		Reference
Carbohydrates	Cellulose	Sa. solfataricus	(Girfoglio, Rossi and Cannio 2012)
	Xylan	Sa. solfataricus	(Cannio et al. 2004)
	Glucose	Sa. solfataricus,S. acidocaldarius	(De Rosa et al. 1984; Ahmed et al. 2005)
	Galactose	Sa. solfataricus	(Lamble et al. 2003)
	d-Arabinose	Sa. solfataricus	(Brouns et al. 2006)
	l-Arabinose	Sa. solfataricus,S. acidocaldarius	(Nunn et al. 2010; Wagner et al. 2017)
	d-Xylose	Sa. solfataricus,S. acidocaldarius	(Nunn et al. 2010; Wagner et al. 2017)
	l-Fucose	Sa. solfataricus	(Wolf et al. 2016)
Proteins/peptides/amino acids	Proteins/peptides	Sa. solfataricus,S. acidocaldarius	(Lin and Tang 1990; Gogliettino et al. 2014)
	Glutamate, methionine, leucine, phenylalanine, isoleucine, threonine, alanine, asparagine, glycine, tyrosine and serine	Sa. solfataricus	(Stark et al. 2017)
Lipids/fatty acids	Olive oil, corn oil, p-nitrophenyl (PNP)-butyrate, PNP-caprylate, PNP-palmitate	Sa. solfataricus	(Choi et al. 2016)
	Tributyrin, tricaproin	S. acidocaldarius	(Zweerink et al. 2017)
	Butyrate, hexanoate	S. acidocaldarius	(Wang et al. 2019c)
Other substrates	Ethanol	Sa. solfataricus	(Chong et al. 2007a)
	Phenol	Sa. solfataricus	(Izzo et al. 2005)