Polyploidy, regular patterning of genome copies, and unusual control of DNA partitioning in the Lyme disease spirochete.

Borrelia burgdorferi, the tick-transmitted spirochete agent of Lyme disease, has a highly segmented genome with a linear chromosome and various linear or circular plasmids. Here, by imaging several chromosomal loci and 16 distinct plasmids, we show that B. burgdorferi is polyploid during growth in culture and that the number of genome copies decreases during stationary phase.

HBsu Is Required for the Initiation of DNA Replication in Bacillus subtilis.

Nucleoid-associated proteins (NAPs) help structure bacterial genomes and function in an array of DNA transactions, including transcription, recombination, and repair. In most bacteria, NAPs are nonessential in part due to functional redundancy. In contrast, in Bacillus subtilis the HU homolog HBsu is essential for cell viability.

Conformation and dynamic interactions of the multipartite genome in .

Bacterial species from diverse phyla contain multiple replicons, yet how these multipartite genomes are organized and segregated during the cell cycle remains poorly understood. has a 2.8-Mb circular chromosome (Ch1), a 2.

DNA-loop-extruding SMC complexes can traverse one another in vivo.

Chromosome organization mediated by structural maintenance of chromosomes (SMC) complexes is vital in many organisms. SMC complexes act as motors that extrude DNA loops, but it remains unclear what happens when multiple complexes encounter one another on the same DNA in living cells and how these interactions may help to organize an active genome. We therefore created a crash-course track system to study SMC complex encounters in vivo by engineering defined SMC loading sites in the Bacillus subtilis chromosome.

XerD unloads bacterial SMC complexes at the replication terminus.

Bacillus subtilis structural maintenance of chromosomes (SMC) complexes are topologically loaded at centromeric sites adjacent to the replication origin by the partitioning protein ParB. These ring-shaped ATPases then translocate down the left and right chromosome arms while tethering them together. Here, we show that the site-specific recombinase XerD, which resolves chromosome dimers, is required to unload SMC tethers when they reach the terminus.