TABLE 5.

Methane, sulfate, ferric iron, and nitrate concentrations in benzene-degrading cultures^a

Cultures	Day	Concn (μmol/vial) ofb:
		Methane	Sulfate	Fe(III)c	Nitrate
Background control cultures containing nitrate but no benzene	0	0.002 ± 0.00	0.71 ± 0.10	<10d	113.1 ± 0.9
	66	0.012 ± 0.002 (+0.010)	0.84 ± 0.00 (+0.13)	<10 (<10)	89.5 ± 0.5 (−23.6)
Active cultures containing nitrate and benzene	0	0.004 ± 0.001	0.71 ± 0.10	<10	113.1 ± 0.9
	66	0.013 ± 0.002 (+0.011)	0.91 ± 0.21 (+0.21)	<10 (<10)	53.9 ± 0.03 (−59.2)

^aThe theoretical values based on the amount of benzene actually degraded (3.38 μmol/vial) and the stoichiometries shown in Table 4 were as follows: methane production, 13 μmol/vial; sulfate consumption, 13 μmol/vial; Fe(III) consumption, 101 μmol/vial; and nitrate consumption, 20 μmol/vial. 

^bData are means ± standard deviations. The values in parentheses are the differences between the day 0 values and the day 66 values. The sulfate and nitrate values can be converted to aqueous concentrations (micromolar) by dividing by the liquid volume (0.01 liter). 

^cFe(III) concentrations were determined by calculating the difference between the total iron concentration and the Fe(II) concentration. 

^dThe concentration was below the detection limit (0.1 mM or 10 μmol/10-ml vial). Both the Fe(II) concentration and the total iron concentration were below the detection limit.