TABLE 3.

Melanin production and pH of K-12 ΔpheA ΔtyrR/pTrcmelA^mut1 in MOPS minimal medium with supplementation

Supplementationa	Melanin production (mg/liter)		Culture pH
	72 h	96 h	72 h	96 h
None	25	37	4.60	4.57
Sodium phosphate, dibasic (Na2HPO4)	305	401	6.57	6.55
Sodium chloride (NaCl)	74	117	4.91	4.91
Potassium phosphate, dibasic (K2HPO4)	303	392	6.65	6.67
Sodium phosphate, monobasic (NaH2PO4)	22	34	4.74	4.76
Sodium phosphate, monobasic and dibasic (NaH2PO4 + Na2HPO4)b	85	136	5.04	5.04

^aAll cultures were supplemented with 500 mg/liter l-tyrosine. Where used, Na₂HPO₄ was added at a final concentration of 20 mM. For all other medium formulations, supplemental components were added such that the sodium (Na⁺) or phosphate (HPO₄²⁻ or H₂PO₄⁻) ion concentrations were equivalent to those found in 20 mM Na₂HPO₄.

^bNaH₂PO₄ and Na₂HPO₄ contributed equal amounts of HPO₄²⁻ or H₂PO₄⁻.