TABLE 2.

Balances of electrons and [¹³C]carbon for the anaerobic conversion of uniformly labeled [¹³C]toluene with AQDS and HPSHA as terminal electron acceptors by enriched APH sediment after 2 weeks of incubation^a

Balance	Culture	[13C]toluene added	Product and toluene remaining	Total recovery (%)b
Electron equivalent (meq/liter)c	Unsupplemented	3.7	[13C]toluene remaining (3.4)
			Fe(III) citrate reduced (0.1)
			Total (3.5)	95
	AQDS supplemented	3.4	[13C]toluene remaining (NDd)
			AH2QDS (2.9)
			Total (2.9)	85
	HPSHA supplemented	3.5	[13C]toluene remaining (0.9)
			Fe(III) citrate reduced (1.7)
			Total (2.6)	74
[13C]carbon (mmol of 13C/liter)e	Unsupplemented	0.75	[13C]toluene remaining (0.69)
			13CO2 (0.05)
			Total (0.74)	99
	AQDS supplemented	0.69	[13C]toluene remaining (ND)
			13CO2 (0.63)
			Total (0.63)	91
	HPSHA supplemented	0.71	[13C]toluene remaining (0.18)
			13CO2 (0.39)
			Total (0.57)	80

^aData represent means obtained from triplicate incubations for the different conditions applied, and standard deviations were, in general, within 10% of the means. Negligible conversion of [¹³C]toluene and reduction of the corresponding electron acceptor occurred in sterilized incubations with autoclaved sediment. 

^bTotal recovery of electrons = (electrons recovered in electron acceptor + [¹³C]toluene not consumed)/[¹³C]toluene added. Total recovery of [¹³C]carbon = (carbon recovered as ¹³CO₂ + [¹³C]toluene not consumed)/[¹³C]toluene added. 

^cCorrected for endogenous controls. Less than 2% of endogenous reduction occurred in all instances. 

^dND, not detected. 

^eCorrected for the background level of ¹³CO₂ found in the absence of [¹³C]toluene.