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THE ACTIXO.MVCKTES. Vol. II 



si rains of which show a very different sensi- 

 tivity pattern against certain phages. 



It is true, likewise, of the separation of 

 streptomycin-producing strains from grisein- 

 producers and other members of the former 

 S. griseus, which is now regarded as a species 

 group rather than ;i single species (Waks- 

 man, 1951)). There have been various reports 

 concerning phages which are active upon 

 st rcptomycin-producing strains, but do not 

 at lack grisein-producers or nonantibiotic- 

 forming cultures (Woodruff et al., 1 1)47 ; 

 Waksman et al, 1947; Reilly et al, 1947; 

 Waksman and Harris, 1949; Hoehn, 1949; 

 Carvajal, 1953; Burkholder et al, 1954). 

 Some streptomycin-producing cultures have 

 been found, however, that are resistant to 

 these specific phages (Okami, 1950; Carva- 

 jal, 1953; Kutzner, 1960). Other phages have 

 been discovered that are specific against S. 

 coelicolor (Kutzner and Waksman, 1959a; 

 Kutzner, I960), S. lavendulae (Gause et al., 

 1957; Shirling, 1959), and S. olivaceus (Kha- 

 vina and Rautenstein, 1958). 



2. No general conclusion can be drawn 

 from the spectrum of a polyvalent phage in 

 regard to relationships between lysed strains. 

 However, a polyvalent phage can be useful 

 in taxonomic studies if it shows specificity 

 within a particular group of organisms that 

 are very similar in their other properties 

 and therefore hardly distinguishable. Fur- 

 ther, testing several polyvalent phages might 

 result in typical sensitivity patterns of the 

 organisms which might be of some value in 

 recognizing whether one has to do with 

 closely related or unrelated organisms. 



::. Actinophages vary greatly when toted 

 againsl numerous strains. In some cases dif- 

 ferences in plaque counts might be due to 

 host range mutants which are present at a 

 concentration of 10' to 10"' particles. These 

 mutants would attack a "new host" resist- 

 ant to the parent phage, as shown by Welsch 

 (1954, 1957) and Welsch et al. (1957). In 

 numerous other cases, however, the devel- 



opment of host range mutants cannot ex- 

 plain the wide host range, and the phages 

 retain their polyvalent nature even after 

 several serial passages on heterologous hosts 

 (Chang, 1953; Shirling, 1959a; Bradley, 

 1959; Gilmour et al., 1959). It is necessary 

 to carry out phage tests with different dilu- 

 tions of the original phage preparation, 

 which should contain about 10 7 to 10 9 par- 

 t icles per milliliter. 



4. A survey of the literature shows that 

 almost every investigator uses a different 

 medium for phage typing. The methods 

 comprise either spot tests or single plaque 

 counts. In a comparative study of different 

 media for phage typing, Kutzner (1900) 

 found that some phages gave similar plaque 

 counts on a variety of media. However, 

 counts of phages that formed tiny plaques 

 were found to be quite dependent on media 

 composition. Inorganic salt content of media 

 was found to influence plaque counts most 

 strikingly. Some phages gave no plaques on 

 media containing XaCl hut gave high 

 plaque counts when plated on the same me- 

 dium without NaCI (with or without CaCl 2 ), 

 while other phages showed higher activity 

 on NaCI than on CaCl 2 media. The expres- 

 sion of phage activity is apparently influ- 

 enced by a great many unknown factors. 

 One of the phages lysed some strains with a 

 medium containing NaCI and gave high 

 plaque counts, but showed no activity 

 against other strains on the same medium. 

 These results suggest that a medium found 

 optimal for one host-phage system might be 

 quite unsuitable for another. Before a phage 

 is typed against a large number of strains, 

 an optimal medium must be developed. Bet- 

 ter still, tests should be carried out with 

 several different media, selected for their 

 usefulness with particular strains. 



Serological Reactions 



Use of serological techniques, particularly 

 those of agglutination and precipitation, has 



