332 THE BACTERIOPHAGE 



The fact that phages will grow only in the presence of multiplying or living 

 bacteria renders the study of their metabolic activities exceedingly difficult. Apart 

 from the work of Schiller (see Editorial 1935), which suggests that phosphatase is 

 the only hydrolytic enzyme possessed by the bacteriophage, such studies as have 

 been recorded have, in fact, yielded negative or ambiguous results (Bronfenbrenner 

 1924-25, 1926, Gozony and Suianyi 1925, Kauffmann 1925-26, Bronfenbrenner and 

 Reichert 1926-27, Schwartzman 1926-27, Bachmann and Wohlfeil 1927). 



The resistance of various phages to heat and to other physical or chemical 

 agents has been studied in some detail. Certain early statements ascribed to lytic 

 filtrates a degree of resistance to heat, and to such chemical agents as chloroform, 

 toluene, alcohol, acetone, etc., that seemed to place them in a category apart from 

 other living things, except the spore-bearing bacteria (see Kabeshima 1920). These 

 statements played a not-inconsiderable part in the controversy as to whether the 

 phage was a living or non-living agent ; but they were not in accord with all the 

 records existing at the time — Twort (1915), for instance, had stated that his lytic 

 agent was inactivated by heating at 60° C. for 1 hour— and they have since been 

 shown to have no general validity. All the evidence suggests that different strains 

 of phage, like different species of bacteria, differ from one another in their resistance 

 to heat, to drying and freezing (see Knorr and Ruf 1935, Campbell-Renton 1941), 

 to shaking (Campbell-Renton 1942) and to various other physical and chemical 

 reagents, and that the range of sensitivity, taken as a whole, is much the same 

 in the two cases. 



A few observations of general interest in regard to this particular problem may be 

 briefly noted. Baker and Nanavutty ( 1929) found that the time relations of the inactiva- 

 tion of a Shiga phage by ultra-violet Ught were closely similar to the killing of Bad. colt 

 by the same agent. The time required to inactivate the Shiga phage, or a staphylococcal 

 phage, did not differ greatly from that required to kill BacL coli ; but the time required to 

 inactivate trj^sin was 20-30 times as long, and for the inactivation of diastase about 120 

 times as long. In this respect, therefore, the phages studied behaved as Uving things, not 

 as ferments (see also Gates 1934). Wright and Kersten (1937) and CampbeU-Renton 

 (1937) noted a wide variation in the sensitivity of different phages to ultra-violet Ught. 



Schultz and Krueger (1928) recorded the inactivation of a staphylococcus phage by 

 methylene blue. Chfton (1931) found that this inactivation occurred when the mixture 

 was exposed to sunUght, but not in the dark, and concluded that it was due to the oxidation 

 of the phage by the photodynamicaUy activated dye. Perdrau and Todd (1933), using 

 more exact methods, record similar results. Different phages have been found to vary 

 widely in their sensitiveness to this photodynamic action, though none is entirely resistant 

 (Burnet 19336, 1934). Staphylococcus phage may also be inactivated by safranine ; 

 the inactivation is partly photodynamic (Krueger and Baldwin 1935). 



Phage is inactivated by aldehydes and the inactivation reversed by the addition of 

 substances with free amino or imino groups, which compete with the phage for the aldehyde 

 (Kendall and Colwell 1938, lOigler and Oleinik 1943). The activity of the phage appears 

 to depend in part upon certain of the free — NHg or — NH groups on its surface. Levin 

 and Lominski (1936) record reversible inactivation of phage by lecithin, which appears 

 to prevent access of phage to sensitive bacteria. Williams, Sandholzer and Berry (1940) 

 record the inactivation of a phage by cholesterol and cephahn, by bacterial and certain 

 non-bacterial phosphohpins, but not by lecithin, sphingomyehn or plasma phospholipins. 



A well-marked antagonistic action on the viability of phages, of Ca, Mg. Ba and Sr 

 ions on the one hand, and of Na and K ions on the other, can be demonstrated (Burnet 

 and McKie 1930a, Sertic^l937a, Gratia 1940), suggesting that these ions are acting on a 

 protein constituent at the"surface of a Uving ceU. Diminution in phage counts are also 



