No abstract

Linear multigenome-length double and single stranded plasmid DNA was identified in a Bacillus subtilis ATP-dependent DNAase mutant strain (addA5) bearing plasmids pC194 or pBD95ts. Plasmid pBC30, a seg mutant of pC194, as well as some pUB110 derivatives with rearrangements external to the minimal replicon, produce high amounts of such a concatemeric DNA, even in Rec+ cells. The synthesis of this type of plasmid DNA occurs in the absence of an active plasmid-encoded Rep protein and is markedly affected in polA5 and recE4 genetic backgrounds. To account for these observations, we propose that the AddAB complex serves to prevent a sigma-type replication of plasmid DNA.

The differences in sensitivity between NAT assays can be explained by the input of isolated viral nucleic acid in the amplification reactions. The FDA requirements for sensitivity of NAT blood screening assays can be met by the Gen-probe TMA, as well as by the AmpliScreen assays, particularly when combined with the NucliSens Extractor.

No abstract

The origin of lagging strand synthesis in pUB110, oriL, has been localized within 140 bases outside the pUB110 minimal replicon. The oriL DNA sequence is a cis-acting and orientation dependent determinant required for normal plasmid replication. Rearrangements affecting oriL cause plasmid instability, lead to the accumulation of replication intermediates and result in a marked reduction of the plasmid copy number in some recombination deficient mutant strains. In addition, deletion of oriL triggers a dnaB-dependent mode of replication. Insertion of the functionally asymmetric oriL region in the proper orientation into pC194 reduces the accumulation of single-stranded DNA during the replication of this plasmid.