Characterization of some pneumococcal bacteriophages

Abstract
The growth of pneumococcal phages at high cell and phage densities is enhanced strongly by the substitution of K for Na in the medium. Initial titers of 2 .times. 1010 to 4 .times. 1010 PFU[plaque-forming units]/ml are readily obtained and concentrated stocks are stable in a storage buffer described. The mechanism of the cation effect is obscure. Phages .omega.3 and .omega.8 each have linear double-stranded DNA of 33 .times. 106 daltons/particle, with an apparent guanine plus cytosine content of 47-49 mol%, as determined by buoyancy and melting temperature, but with an unusual absorbance spectrum. Efficiency of plating is high if sufficient time is allowed for a relatively slow adsorption, which differs several-fold in rate between the 2 phages. Morphologically, these and other pneumococcal phages are similar to coliphage lambda but with a longer tail and tail fiber. Upon UV inactivation, .omega.3 and .omega.8 have D37 [37% survival dose] values of 33 and 55 J/m2, respectively, and each shows multiplicity reactivation. A total of 13 ts mutants were isolated from the 2 phages, representing only 2 complementation groups; complementation and recombination occur between .omega.3 and .omega.8 mutants. Both phages provoke high-titer antisera with extensive cross-reactivity against a number of newly isolated pneumococcal phages.