Mechanism of Adsorption and Eclipse of Bacteriophage φX174 II. Attachment and Eclipse with Isolated Escherichia coli Cell Wall Lipopolysaccharide

Abstract

A mixture of aqueous phenol, choloroform, and ether extracts the lipopolysaccharides (LPS) from the φX174-sensitive strain, Escherichia coli C/1, and resistant strains, C/φX and K12. Interaction of the C/1 LPS with φX in a starvation buffer containing 10 −3 M CaCl 2 at 37 C, but not at 15 C, results in a first-order inactivation that is specific for C/1 LPS. After interaction for 60 min at 15 C, followed by centrifugation, 37 and 20% of a 14 C-φX preparation are bound to the C/1 and C/φX LPS pellets, respectively. The results for intact cells are 75 and 10%. Supporting the conclusion that this represents specific attachment of φX to its receptor site in the LPS is the fact that EDTA-borate buffer is required to elute 85% of the 14 C-φX from the C/1 LPS, whereas starvation buffer elutes the same amount from C/φX LPS. Moreover, 95% of the PFU are found in the C/1 LPS pellets as compared with 50% in the resistant strain LPS pellets. When the products of interaction between φX and LPS at 37 C are examined by sucrose density gradients in EDTA-borate, a single 60 to 90 S peak is observed in the C/1 sample, and the single peak cosediments with the 120 S marker φX in the C/φX sample. This change in S 20, w is very similar to that reported for the eclipse of φX in vivo. If the inactivation at 37 C is carried out on φX-LPS complexes first formed at 15 C, the first-order kinetics are biphasic and nearly identical to that observed for the eclipse kinetics of φX attached to intact cells. Thus, the φX-LPS system is suitable for in vitro studies on the early events in φX infection.