Essentiality of Arginine for Growth of L. hongkongensis HLHK9 L. hongkongensis HLHK9 cells were grown in minimal medium M63 [51] supplemented with 20 mM L-malate as carbon source and 19 mM potassium nitrate as nitrogen source, and 1 mM each of vitamin B1 and vitamin B12. The pH of all media was adjusted to 7.0 with KOH. Essentiality of arginine for growth of L. hongkongensis HLHK9 was determined by transferring the bacterial cells to the modified M63 medium with or without 100 mM of Larginine. Escherichia coli ATCC 25922 and JW5553-1 (argB deletion mutant) [52] were used as positive and negative controls respectively. All cultures were incubated at 37uC with shaking for 5 days. Growth in each medium was determined by measuring absorbance spectrophotometrically at OD 600 . The experiment was performed in duplicate.