TABLE 1.

Comparisons of the quantities of amino acids taken up or released by S. aureus at mid-exponential and stationary phases, during growth under optimal conditions (mean ± SD, P < 0.05).

	Amino acids	Mid-exponential phase (nmole/100 μL) n = 4 biological replicates		Stationary phase (nmole/100 μL) n = 3 biological replicates
		Taken up	Released	Taken up	Released
Amino acids with significantly higher levels of	LYS	74.2 ± 14.9		154 ± 4.6
uptake measured at the stationary phase compared	LEU	70.9 ± 28.8		292 ± 1.2
with mid-exponential phase	SER	56.3 ± 5.8		135 ± 0.0
	PHE	41.9 ± 11.6		63.8 ± 2.4
	GLU	34.2 ± 3.8		98.8 ± 1.5
	THR	29.6 ± 3.4		86.9 ± 0.1
	ALA	28.5 ± 4.5		108 ± 0.2
	ASN	27.3 ± 2.0		52.0 ± 0.3
	GLY	25.9 ± 1.9		50.4 ± 0.0
	HIS	5.2 ± 1.5		18.3 ± 0.1
	PRO	3.2 ± 0.9		14.6 ± 0.0
	AAA		1.5 ± 2.5	6.3 ± 0.0
	GLN		5.0 ± 6.7	12.7 ± 7.2
	ORN		0.45 ± 0.4	1.3 ± 0.5
Amino acids with significantly lower levels of uptake	ILE	23.0 ± 5.5		11.8 ± 4.6
measured at the stationary phase compared with	TRP	10.7 ± 2.9		5.5 ± 2.0
mid-exponential phase
Amino acids which did not show any further	MET	18.8 ± 3.5		23.8 ± 1.4
significant up-take after mid-exponential phase	ASP	10.7 ± 1.8		8.8 ± 1.2
	TPR	4.6 ± 2.1		6.6 ± 0.0
	HYP	4.1 ± 0.0		2.8 ± 0.9
	ABA	2.4 ± 1.9		2.4 ± 0.3
Amino acids that were taken up by mid-exponential	VAL	30.0 ± 8.4			81.8 ± 6.5
phase and then released by stationary phase	TYR	19.1 ± 4.3			17.0 ± 3.7

The amino acids have been ranked in the order of their magnitudes of uptake measured at the mid-exponential phase of growth. Amino acid uptake/release was calculated by subtracting the initial concentrations of amino acids in TSB from those evaluated at mid-exponential and stationary phase.