Transmembrane cation movements during infection of Lactobacillus lactis by bacteriophage LL-H.

Phage LL-H-induced cation (K+, Na+, Mg2+, Ca2+, Cd2+) movements in Lactobacillus lactis bacteria have been studied. The effects of the m.o.i. and external cation concentration have been quantified. LL-H-induced effluxes showed cation specificity: K+ but practically no Mg2+ was lost during LL-H infection at low and moderate m.o.i. (up to about 100). Simultaneously to K+ efflux, divalent cation influxes were observed. These were dependent on the m.o.i. and on concentrations of external divalent cations and were concomitant with phage DNA transport, as concluded from the timing of the first phage-promoted biochemical changes in host cell metabolism and from electron microscopical observations. Host energy was not mobilized with phage-induced divalent cation influx. Several features of divalent cation influxes support the view that divalent cations have to be cotransported into the cell as counterions of LL-H DNA. Phage DNA associated with divalent cations may be the basic feature of the divalent cation dependence of LL-H infection.