The Bacteriophage: A Method of Isolation

Efforts to determine the intimate nature of the bacteriophage have been complicated by the problem of freeing it from substances, known and unknown, which are necessarily present in the filtrates. Being in a colloidal state, or at least being closely associated with the proteins of the culture medium or of the products of bacterial lysis, the bacteriophage is most certainly influenced in its reactions by these accompanying colloids and objection may be made to the results of any studies which fail to take this source of error into account. Two methods have been developed to purify the bacteriophage, removal of the proteins of the filtrate by passing it through membranes of gradually decreasing permeability (1), and fractional precipitation by certain general precipitating agents (2). By either of these methods bacteriophage solutions are obtained which are of sufficient purity for therapeutic purposes as they do not cause allergic reactions.