Abstract
A temperate phage coding for constitutive hypertoxigenicity has been constructed in Vibrio cholerae strain 569B and used to lysogenise the low-toxin-producing strain MAK 757; 18% of lysogens showed 10-100-fold increase in toxin production. This property was also transmitted at low frequency to second generation lysogens. Thus temperate phage can increase toxin production in a low-toxin-producing strain.