Table 3.

Quantification of 4-methylbenzoate (substrate) and nitrate consumption and of produced biomass by strain pMbN1^a

Experiment	Amt of substrate added (mmol)	Amt of substrate disappearedb (mmol)	Amt of nitrate disappeared (mmol)	Amt of cell dry mass formedc (mg)	Amt of substrate dissimilatedd (mmol)	Amt of electrons from substrate dissimilatede (mmol)	Amt of electrons consumed by nitrate reductionf (mmol)
Cells with limiting amt of substrate	0.34 (0.05)	0.34 (0.13)	1.4 (0.4)	21 (3)	0.25 (0.06)	9.0 (2.0)	7.0 (1.8)
Cells with excess amt of substrate	0.89 (0.07)	0.83 (0.17)	3.4 (0.2)	56 (6)	0.57 (0.05)	20.7 (2.0)	17.1 (1.2)
Cells without substrate (control)	0.00g	0g	0.0g	0.0g			0.0g
Sterile medium without cells (control)	0.83g	0g	0.0g				0.0g

^aIncubation experiments were carried out in anoxic flat glass bottles with a culture volume of 400 ml containing 3.4 mmol nitrate. Numbers in parentheses represent the standard deviation calculated from triplicate experiments.

^bDifference between substrate added and substrate recovered at the end of incubation in the culture supernatant.

^cThe amount of cell dry mass added with the inoculum has been subtracted.

^dDifferences between substrate dissimilated and substrate assimilated. The assimilated amount of 4-methylbenzoate was calculated according to the following equation: 17 C₈H₇O₂⁻ + 8 HCO₃⁻ + 25 H⁺ + 50 H₂O → 36 C₄H₇O₃. Thus, 1 mg of cell dry mass requires 0.00458 mmol 4-methylbenzoate.

^eThirty-six moles of electrons are derived from 1 mol of 4-methylbenzoate if oxidized to CO₂.

^fElectrons consumed = 5 × (nitrate added − nitrate remaining). Nitrite has not been observed in detectable quantities during growth.

^gNo detectable deviations in duplicate experiments.