What is the purpose of using Penicillin Streptomycin (Pen-Strep)?

What is the purpose of using Penicillin Streptomycin (Pen-Strep)?

This is a “staple” reagent used to prepare wash medium for PBMC isolation and sometimes in cell culture. The concentration of this reagent can vary depending on the purpose of the cell culture or isolation method. The main purpose of this reagent is to prevent and eliminate bacterial contaminants in cell culture. As the name implies, it contains both Penicillin (Penicllin G) and Streptomycin which are antibodies against bacteria.

Penicillin (Penicillin G) has effective bactericidal properties against gram-positive and gram-negative aerobic and anaerobic bacteria. Penicillin was originally purified from the fungi Penicillium. Due to its high affinity with penicillin-binding proteins (PBPs) located inside the bacterial cell wall, it can purposefully inhibit peptidoglycan synthesis which subsequently interferes with the third and last stage of bacterial cell wall synthesis. In addition, it also indirectly triggers the release of autolytic enzymes such as autolysins to activate bacteria cell lysis.

Streptomycin on the other hand is an aminoglycoside antibiotics that was originally purified from Streptomyces griseus. Likewise it is a useful broad spectrum antibiotics against both Gram-positive and Gram-negative bacteria. It functions as a protein synthesis inhibitor by making strong affinity bonds with the small 16S rRNA of the 30S subunit of the bacterial ribosome, interfering with the binding of formyl-methionyl-tRNA to the 30S subunit. Subsequently, this will lead to codon misreading and the eventual inhibition of protein synthesis or production of defective aberrant proteins. The resulting aberrant proteins may be inserted into the cell membrane, altering permeability and further stimulating aminoglycoside transport. Moreover, incorporation of mistranslated, misfolded proteins into the cell membrane stimulates the formation of lethal hydroxyl radicals by activating the bacterial envelope stress response system and interfering with the electron transport chain.

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