Fig 4.

Potassium efflux induced by phages HK97 and λ as measured by a potassium-selective electrode. (A) Phage genome injection into wild-type E. coli by HK97 (♢) leads to efflux of potassium out of the cell and into the surrounding medium. This effect is abrogated in cells lacking the HK97 receptor (lamB) on their surface (+). The expression of pEx15-FLAG is able to block the entry of the HK97 (▲) genome but not the λ (×) genome. This effect is alleviated when pEx15-FLAG carries a nonsense mutation in gp15 (●). (B) The resistance to phage DNA injection is provided by gp15 expressed from an HK97 prophage. The presence of a wild-type HK97 lysogen in E. coli blocks the injection of the HK97 (▲) genome but not λ (×). The introduction of a nonsense mutation into gp15 relieves the inhibition for HK97 DNA injection (●).