Mode of action of lactococcin produced by Lactococcus lactis R

Lactococcin R test edilen tüm gram-pozltlf bakterilere adsorbe olmasına karşın gram-negatlf bakterilere adsorbe olmadığı ve adsorpsiyonun pH'ya bağlı olduğu bulunmuştur. Lactococcin R'in adsorpslyonu, bazı tuzların aniyonları ($CI^{-}$, $PO^{-3}4$) ve lipotelchoic asit tarafından önlendiği tespit edilmiştir. Hücrelerin ve hücre duvarlarının deterjan, organik solventier veya enzimlerle ön işleme tabi tutulması lactococcin R'm bunlara bağlanmasını azaltmadığı gözlenmiştir. Fakat, metanol-kloroform ve sıcak %20 TCA ile muamele edilen hücre duvarı preparatları lactococcin R'ı bağlama yeteneklerini kaybettiği tespit edilmiştir. Lactococcin R ile muamele edilmiş duyarlı hücreler çok fazla miktarda intrasellüler K+ iyonu ve UV-absorbe edilebilen materyalleri kaybettiği, ve ONPG'ye karşı daha çok geçirgen olduğu bulunmuştur. Farklı lactococcin R konsantrasyonları (0-2560 AU/ml), Listerai monocytegenes koloni sayısını yaklaşık %99 oranında azaltığı ve ayrıca L. monocytogenes'in absorbans değerinde de azalmaya neden olduğu tespit edilmiştir. Bu sonuçlar lactococcin R' ın etki mekanizmasının bakteriyostatikten daha ziyade bacteriyosidal olduğunu göstermektedir.

Lactococcus lactis R tarafından üretilen Lactococcin R' in etkisi mekanizması

It was found that lactococcln R adsorbed to all gram-positive but not to the gram-negative bacteria tested and Its adsorption was dependent on pH. It was observed that the binding of lactococcin R was prevented by anlons of several salts ($CI^{-}$, $PO^{-3}4$) and lipoteicholc acid. It was determined that pretreatments of sensitive cells and cell walls with detergents, organic solvents or enzymes did not reduce subsequent binding of lactococcin R. However, treatment of cell wall preparations with methanol:chloroform and hot 20% TCA caused such walls to lose their ability to adsorb lactococcin R. It was found sensitive cells treated with lactococcin R lost high amounts of intracellular K+ ions, UV-absorbing materials and became more permeable to ONPQ. In addition, It was observed that different lactococcin R concentrations (0-2560 AU/ml) decreased the colony counts of Llsteria monocytogenes by 99% and also caused a reduction In the absorbance values of L. monocytogenes. This results show that the mode of action of lactococcin R Is bactericidal rather than bacteriostatic.

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