Temperature influences induction of a J7W-1-related phage in Bacillus thuringiensis serovar indiana

Induction of a plasmid-integrative J7W-1-related phage in Bacillus thuringiensis serovar indiana by ethidium bromide was influenced by the temperature at which the host cells were cultured. Under optimal growth conditions, the maximum titer of the phage produced by the serovar indiana reached 1.2 x 10(6) PFU/ml at 37 degrees C while at 27 degrees C it was lower by an order of magnitude (1.3 x 10(5) PFU/ml). The temperature-sensitive period was estimated to occur early during the phage induction. However, the temperature effect observed with the serovar indiana did not occur with the serovar israelensis. In the latter case, the phage induction was the same at 37 degrees C or 27 degrees C. Thus we assume that the temperaturesensitive phage induction observed with the serovar indiana as host was not a phenomenon caused by the phage genome but rather by product(s) encoded by certain host gene(s).