142 BENZER ET AL. 



XII. Lysis from Without 



39. When a large number (100 or more) of phage particles are 

 adsorbed to a bacterium, no phage multiplication occurs. Instead, the 

 bacterium quickly becomes spherical and eventually lyses (Delbriick, 

 1940b). Since this lysis occurs without phage growth it has been called 

 lysis from without (LFW) in contrast to normal lysis. More recently 

 LFW has been observed under the following additional conditions: 



( 1 ) Infection of a bacterium by only a few phage particles in the 

 presence of cyanide, iodoacetate, or dinitrophenol results in LFW 

 (Cohen, 1949; Doermann, 1948; Heagy, 1950). Lack of oxygen 

 or of a carbon source also causes LFW. This suggests that LFW 

 occurs at low multiplicities when a suitable energy source is absent. 

 Bacteria heavily irradiated with UV lyse prematurely when singly 

 infected (Anderson, 1945b). This may also be due to a disruption 

 of the normal energy supply by the UV irradiation. The r+ phages 

 are more effective than the r phages in inducing LFW in the 

 presence of metabolic inhibitors (Cohen, 1949; Heagy, 1950). The 

 speed at which LFW occurs (measured by decrease in bacterial 

 turbidity) increases with the multiplicity of the infection (Watson, 

 1950). 



(2) LFW occurs without disruption of the bacterial nuclei (see 

 36). This is further evidence that LFW is independent of phage 

 growth (Watson and Human, unpublished). Furthermore, "non- 

 killing" X-ray inactivated phage (see 21) can cause LFW (Wat- 

 son, 1950). Therefore LFW is not due to invasion of the phage 

 into the bacteria. 



(3) "Non-killing" X-ray inactivated T2 is much more effective 

 than active T2 in causing LFW (Watson, 1950). 



LITERATURE CITED 



In general only the paper has been cited in which a given point has been treated 

 most recently or most satisfactorily. 



*The asterisk marks review papers. 



Adams, M. H., 1948. Surface inactivation of bacterial viruses and of proteins. /. Gen. 



Physiol, 31:417-431. 

 Adams, M. H., 1949. The calcium requirement of coliphage T5. J. Immunology, 



62:505-516. 

 Adams, M. H., 1949. The stability of bacterial viruses in solutions of salts. 7. Gen. 



Physiol, 32:579-594- 

 * Adams, M. H., 1950. Methods of study of bacterial viruses in "Methods in Medical 



Research" Vol. II, The Year Book Publishers, Chicago. 



