Protective effects af various materials against the drying inactivation of Xanthomonas oryzae phage (OP₁ phage).

Abstract

This investigation deals with protective effects of several materials against inactivation of Xanthomonas oryzae phage (OP₁ phage) during desiccation.
OP₁ phage particles are mostly inactivated during any one of the following procedures: freeze-drying, vacuum drying, or drying in an ordinary desiccator under normal room temperatures, when the phage particles are suspended in distilled water. If the phage particles are suspended in a solution of protein such as gelatin or albumin, at a concentration of 10^-3 gram per ml or more, about 70 per cent of the phage activity is protected in the case of freeze-drying, and 20per cent in the case of vacuum drying.
Concentrated (10per cent) solution of gelatin hydrolysate protects the phage activity almost completely against inactivation, in the case of freeze drying; 50per cent or more, in the case of vacuum drying. When the phage particles are dried together with semi-synthetic media containing potato extract, peptone, sugar and certain inorganic salts, about half of the activity is protected in the case of freeze drying; about 35 to 40per cent in the case af vacuum drying.
If the phage suspensions, are dried under ordinary atmospheric pressure and temperature, the phage activities decrease rapidly, even when protective materials are added (Table 1).
Ten per cent solution of mixed amino acids is equivalent to gelatin hydrolysate, protects ca. 20per cent of the phage activity, in the case of vacuum drying (Table 8).
Among amino acids which constitute gelatin hydrolysate, glycine, alanine and proline (two per cent solution in each case) show a certain protective effect against inactivation of the phage, in the case of vacuum drying (Table 9).
Histidine, glutamic acid and aspartic acid (at the same concentration), protects 10per cent, 6per cent and 3per cent, respectively, at pH 7.2.
These protective effects are retained for more then 4 days (Table 9).
Mode of action of these proteins, protein hydrolysates and amino acids in protecting the OP₁ phage against inactivation during drying procedures seems likely to be the protection of the phage particles, not only by forming protein- or peptide- monomolecular membrane, but also by somehow combining with active portions of the particles.
Neither carbohydrates such as soluble starch, sucrose, glucose, nor inorganic salts such as CaCl₂ and NaCl show protective effects. For the preservation of the phages, the most favourable method is the freeze drying of the phages with 0.001 to 0.1per cent solutions of protein, protein hydrolysate, or with semisynthetic media. Phage preparations with constant high titres are thus available, whenever required.