FUNCTIONAL-ANALYSIS OF PSM19035-DERIVED REPLICONS IN BACILLUS-SUBTILIS

We determined the effect of various Bacillus subtilis dna(Ts) mutation s on pSM19035 replication. At non-permissive temperature, plasmid repl ication depends on the dnaB, dnaC, dnaG and dnaI initiation replicatio n products, but does not require the dnaA function. DNA elongation is performed by DNA polymerase III, since replication is blocked at non-p ermissive temperature in dna(Ts) mutants impaired in different subunit s of the enzyme. Single-stranded plasmid replication inter-mediates, c orresponding to the leading strand, accumulate in the dnaD strain. On the basis of electron microscopic analysis of replication intermediate s, we confirmed that the plasmid replicates unidirectionally by a thet a mechanism.