442 BACTERIOPHAGES 



Resistant bacteria: Bacteria not killed by a given phage, usually owing to fail- 

 ure to adsorb, also called nonreceptive bacteria. See immunity. 



Sensitive bacteria: Bacteria killed by a given phage (or other agent). Sensitiv- 

 ity to phage is usually tested by plaque formaticjn, when al)ility t(j sup- 

 port growth of phage may also be inferred. 



Single infection: Multiplicity of infection considerably less than one, so that 

 most of the infected bacteria in a culture are infected with only one phage 

 particle. 



Superinfection: Reinfection of bacteria already infected some minutes before, 

 or reinfection of lysogenic bacteria. 



Temperate phage: A phage capable of lysogenizing some fraction, often small, of 

 the bacteria it infects. 



Vegetative phage: The form in which phage (or phage genes) multiply during 

 the lytic cycle of phage growth. 



Viable: Viable bacteria are able to form colonies. Viable phage particles are 

 able to form plaques following single infection. Viability depends on the 

 conditions of test. 



Virulent phage: A phage that lacks the ability to lysogenize. When known to 

 have originated by mutation from a temperate phage, it is called a viru- 

 lent mutant. 



