TRAPPING OF PHAGE GENOMES IN SPORES OF BACILLUS-SUBTILIS-168 - RECIPROCAL EXCLUSION OF PHAGE-PHI-29 AND PHAGE-PHI-E DURING OUTGROWTH OF SPORES

The trapping of phages φ29 and φe by spores of Bacillus subtilis 168 has been studied. The optimal time and the efficiency of trapping were different for each phage. The efficiency of φ29 was maximum (0.01-0.02) when infection occurred at stage I of sporulation; that of φe (0.5-1) 1.5 to 2 hr later. A single phage genome was sufficient to infect a spore and there is neither cooperation nor competition between genomes in the trapping event. Viral DNA synthesis is not required for trapping. A single spore may trap two viral genomes, either from the same phage or from the two unrelated phages, φ29 and φe. During outgrowth, spores carrying both genomes, φ29 and φe, produced particles of one or the other phage, but never of both. Normally φ29 multiplied but φe developed when expression of φ29 was impaired by a lethal mutation in cistron 2. However in doubly infected exponentially growing cells φe dominated and prevented reproduction of φ29. © 1979.