Technical Advantage: Effective against both Gram-positive and -negative bacteria Penicillin-Streptomycin-L-glutamine combines two antibiotics with a nutrient which is essential for cell growth, L-glutamine. Penicillin inhibits bacterial growth by inhibiting peptidoglycan synthesis (essential for the bacterial cell wall), and streptomycin inhibits bacterial growth by inhibiting protein synthesis. L-Glutamine is essential as an energy source for most mammalian cells in culture because of its amino acid carbon skeleton. This antibiotic-nutrient combination is effective against Gram-negative and Gram-positive bacteria. Technical Advantage: Effective against both Gram-positive and -negative bacteria Penicillin-Streptomycin-L-glutamine combines two antibiotics with a nutrient which is essential for cell growth, L-glutamine. Penicillin inhibits bacterial growth by inhibiting peptidoglycan synthesis (essential for the bacterial cell wall), and streptomycin inhibits bacterial growth by inhibiting protein synthesis. L-Glutamine is essential as an energy source for most mammalian cells in culture because of its amino acid carbon skeleton. This antibiotic-nutrient combination is effective against Gram-negative and Gram-positive bacteria.