Table 2.

Occurrence of energy spilling in microbes^a.

Species	Ruminal isolate	Heat production or growth yield evidence	Mechanism (type of cycling)	Notes	References
BACTERIA
Escherichia coli	N	Lower growth yield per ATP under Mg, P, S, K vs. C-limitation	NH3/NH+4/H+	Mechanism applies during high NH3/NH4 and low K+	Buurman et al., 1991
	N	Lower growth yield per ATP of wild-type vs. K+ transport mutant	K+	Mechanism applies during low K+	Mulder et al., 1986
	N	ND	NH3/NH+4/H+/K+	Mechanism applies during low NH3/NH+4	Russell and Cook, 1995
Klebsiella aerogenes	N	Lower growth yield per ATP under NH3, P, S, or K vs. C-limitation	ND		Neijssel and Tempest, 1976; Teixeira de Mattos and Tempest, 1983
Fibrobacter intestinalis	N	ND	Glycogen		Matheron et al., 1998
Fibrobacter succinogenes	Y	ND	Glycogen		Gaudet et al., 1992; Matheron et al., 1998
Prevotella bryantii	Y	Heat production rose rapidly during glucose excess	ND	Growth and reserve carbohydrate not accounted explicitly	Russell, 1986
Selemonas ruminantium	Y	Heat production rose rapidly during glucose excess	ND	Growth and reserve carbohydrate not accounted explicitly	Russell, 1986
Streptococus bovis	Y	Heat production not accounted by maintenance energy or growth	H+		Russell and Strobel, 1990; Cook and Russell, 1994; Bond and Russell, 1996, 1998
Mixed rumen bacteria	Y	Lower growth yield per hexose under NH3-N vs. amino-N	Not defined	Reserve carbohydrate or other cell composition changes not accounted explicitly	Van Kessel and Russell, 1996
PROTOZOA
Isotricha protostoma	Y	ND	Glycogen		Prins and Van Hoven, 1977
Dasytricha ruminantium	Y	ND	Glycogen		Van Hoven and Prins, 1977
FUNGI
Saccharomyces cerevisiae	N	Lower growth yield per ATP under glucose excess	ND		Van Urk et al., 1988
	N	Higher heat production and lower growth yield under N vs. glucose-limitation	ND	Reserve carbohydrate not accounted explicitly	Larsson et al., 1993
	N	ND	Trehalose	Mechanism applies under heat shock	Hottiger et al., 1987
ARCHAEA
Methanobacterium thermoautotrophicum	N	Lower growth yield per CH4 under H2- or CO2- excess vs. limitation	ND	Reserve carbohydrate or other cell composition changes not accounted explicitly	Schönheit et al., 1980; Morgan et al., 1997
MIXED OR UNDEFINED
Mixed rumen microbes	Y	Heat production not accounted by endogenous metabolism or reserve carbohydrate	ND	Endogenous metabolism used as proxy for maintenance energy	Hackmann et al., 2013a

^aN, no; Y, yes; ND, Not determined.