Can Bacteriophage Be Detached From the Carrier-Particles?

Abstract

It has been found earlier that residue remaining on the membrane after ultrafiltration of bacteriophage through collodion retains a large proportion of the active agent and does not give it off freely into the filtrate on repeated washing with water. But, if broth is substituted for water in washing, the active agent reappears in the filtrate in high concentration. 1

This finding suggested at first that passage of broth through the membrane resulted in coating the filtering bed by the colloids present in the broth, thus rendering it permeable for coarser particles which were held up by the membrane when suspended in water. However, further experiments have shown that preliminary passage of broth through a new membrane similar to that used above failed to increase its permeability to the residual fraction of the phage. On the basis of these findings the results of the earlier experiments were interpreted as indicating that the addition of broth directly to the residue caused detachment (elution) of some of the active agent from the coarser particles and its adsorption on and passage with the finer particles of the broth.

The existence of a method 2 permitting the measurement of the particles which carry phage suggested the means of inquiring into the validity of this tentative conclusion. We determined by this method the size of ordinary broth-phage filtered through Berkefeld filter as being in the average 12 mμ in diameter. 2 Using the same procedure, we now find that particles held back by the membrane after ultrafiltration measure 28mμ in diameter (average). When broth (free from phage) is added to this residue and ultrafiltration repeated, the particles which come through measure 20mμ in diameter (average)—that is, they are smaller than the original particles kept back by the membrane.