Involvement of calcium in the transient depolarization of E.coli cytoplasmic membrane induced by phage adsorption: a study with the fluorescent calcium indicator QUIN2.

Adsorption of phage T4 to its outer membrane receptor (the lipopolysaccharide) triggers a transient depolarization of the cytoplasmic membrane which is prevented upon addition of EGTA, suggesting that calcium is necessary for the transmission of the signal between the two membranes. Using the fluorescent indicator QUIN2, we show that T4 adsorption triggers the release of envelope-bound calcium, the amount of which increases with the number of infecting phages. Since this amount was the same whether the cells were pretreated or not with EDTA-Tris, this suggests that this calcium originated from the high affinity sites of the lipopolysaccharide.