Table 1.

Physiological membrane adaptations by core lipid modifications typically found in bacterial and archaeal extremophiles

Bacteria	Temperature					pH				Pressure
	T min <15 °C			T max >75 °C		pHmin <3		pHmax >10		>70 MPa
Level of chain length			Ref		Ref		Ref		Ref		Ref
shorter chain ≤C14	+		(7,8)			+	(31, 33)	+	(42, 43)
longer chain ≥C18
Level of unsaturation
PUFA	+		(1–3)							+	(39)
MUFA-cis	+		(7,8, 40)	+	(21)	+	(33)	+	(44)
MUFA-trans	+		(8)
Level of branching
BCFA-iso				+	(4,15,41)	+	(29)	+	(38, 42–44)
BCFA-anteiso				+	(4)	+	(29, 32)	+	(44)
Diabolic acid				+	(18, 45)	+	(35)
(β)-hydroxy FA	+		(8)			+	(30, 33)
Level of cyclization
Ω-Cyclohexyl						+	(29, 32)
Cyclopropyl	+		(7)	+	(21)	+	(30, 33)
Level of tetraester and etherlipids
Tetraesters				+	(22, 46)
Mono- di- tetraethers				+	(18–21)	+	(34, 35)
Level of terpenes
Polar carotenoid	+		(5,6)	+	(16, 17)
Non-polar terpenes								+	(44)
Other modifications
Cardiolipins	+		(7)					+	(44)
Glycolipids	+		(7)	+	(16)
BMP								+	(44)

Archaea	Temperature				pH				Pressure
	T min <15 °C		T max >75 °C		pHmin <3		pHmax >10		>40 MPa
Level of chain length		Ref		Ref		Ref		Ref		Ref
C20-chain	+	(9)	+	(24–26)			+	(47–53)	+	(28, 54–55)
C25-chain			+	(56)			+	(47–53)
Level of saturation
Unsaturated diethers	+	(9, 10)	+	(11)
Level of branching
Hydroxyarchaeol	+	(9)
Level of cyclization
Pentacyclic TE			+	(13, 27)	+	(13,27, 36, 37)
Macrocyclic			+	(57)					+	(28, 57)
Level of tetraether lipids
Tetraethers	–	(9)	+	(12,23)	+	(14,36, 60)	–	(61, 62, 63)	–	(28)
Other modifications
Glycolipids			+	(11)	+	(27, 37)	–	(48, 50, 53, 58, 59)

References: 1: Russell (1997), 2: Shivaji and Prakash (2010), 3: Zsiros et al. (2000), 4: Oshima and Miyagawa (1974), 5: Chattopadhyay et al. (1997), 6: Jagannadham et al. (2000), 7: Guan et al. (2013), 8: Wan et al. (2016), 9: Nichols et al. (2004), 10: Gibson et al. (2005), 11: Sprott et al. (1997), 12: Cario et al. (2015), 13: De Rosa et al. (1980), 14: Uda et al. (2004), 15: Patel et al. (1991), 16: Ray et al. (1971), 17: Yokoyama et al. (1996), 18: Damsté et al. (2007), 19: Langworthy et al. (1983), 20: Huber et al. (1992), 21: Jahnke et al. (2001), 22: Huber et al. (1989), 23: Matsuno et al. (2009), 24: De Rosa et al. (1987), 25: Hafenbradl et al. (1996), 26: Ulrih et al. (2009), 27: Schleper et al. (1995), 28: Kaneshiro and Clark (1995), 29: De Rosa et al. (1974), 30: Wichlacz et al. (1986), 31: Wakao et al. (1994), 32: Matsubara et al. (2002), 33: Mykytczuk et al. (2010), 34: Weijers et al. (2006), 35: Damste et al. (2011), 36: Macalady et al. (2004), 37: Uda et al. (2001), 38: Clejan et al. (1986), 39: Nogi and Kato (1999), 40: Knoblauch et al. (1999), 41: Heinen et al. (1970), 42: Li et al. (1994), 43: Prowe and Antranikian (2001), 44: Clejan et al. (1986), 45: Balk et al. (2009), 46: Lee et al. (2002), 47: Namwong et al. (2007), 48: Feng et al. (2005), 49: Castillo et al. (2006), 50: Xu et al. (2001), 51: Xu et al. (1999), 52: Lanzotti et al. (1989), 53: Tindall et al. (1984), 54: Grant et al. (1985), 55: Takai et al. (2000), 56: Sako et al. (1996), 57: Sprott et al. (1991), 58: Hu et al. (2008), 59: Bowers and Wiegel (2011), 60: Schleper et al. (1995), 61: Feng et al. (2005), 62: Xu et al. (2001), 63: Lanzotti et al. (1989)

PUFA polyunsaturated fatty acids, MUFA-cis cis-monounsaturated fatty acids, MUFA-trans trans-monounsaturated fatty acids, BCFA-iso iso-branched chain fatty acids, BCFA-anteiso anteiso-branched chain fatty acids, BMP bis-mono-acylglycero-phosphate, TE tetraethers, + increased production, − decreased production