Replication of viral DNA in SPO1-infected Bacillus subtilis: II. DNA maturation during abortive infection

Abstract

Previously described work ( Levner and Cozzarelli, 1972) has indicated that the replication of bacteriophage SPO1 DNA in infected Bacillus subtilis involves the sequential conversion of two intermediate DNA species, “VF” and “F”, to produce mature progeny DNA. These intermediates both appear to consist of multigenome size DNA concatemers, which in “VF” are complexed with cellular protein and RNA, and the conversion of “VF” to “F” involves removal of this DNA from the complex. As described here, it is possible to disrupt this viral DNA maturation sequence either by the addition of chloramphenicol (CM) to infected cells, or by abortive infection with a suppressible pleiotropic SPO1 mutant (sus F4), which fails te direct the synthesis of a large class of late viral proteins. In both cases, an accumulation of “VF” results, accompanied by an accumulation of viral DNA strands several times the size of mature strands. The time-dependence of the CM effect shows that the capacity to produce mature viral DNA appears nearly 10 min later than the capacity for viral DNA replication, and at least one late viral protein whose synthesis is blocked by the sus F4 mutation is essential to this maturation capacity. During abortive infection by a second SPO1 mutant (sus F7). defective in the synthesis of phage heads, viral DNA maturation proceeds normally. Possible implications of this result are discussed.