Distinct activities of bacterial condensins for chromosome management in Pseudomonas aeruginosa

Abstract

Bacteria encompass three types of structurally related SMC complexes referred to as condensins. Smc-ScpAB is present in most bacteria while MukBEF is found in enterobacteria and MksBEF is scattered over the phylogenic tree. The contributions of these condensins to chromosome management were characterized in Pseudomonas aeruginosa that carries both Smc-ScpAB and MksBEF. In this bacterium, SMC-ScpAB controls chromosome disposition by juxtaposing chromosome arms. In contrast, MksBEF is critical for chromosome segregation in the absence of the main segregation system and affects the higher-order architecture of the chromosome by promoting DNA contacts in the megabase range.Strikingly, our results reveal a prevalence of Smc-ScpAB over MksBEF involving a coordination of their activities with the DNA replication process. They also show that E. coli MukBEF can substitute for MksBEF in P. aeruginosa while prevailing over Smc-ScpAB. Altogether, our results reveal a hierarchy between activities of bacterial condensins on the same chromosome.

Condensins are essential for Pseudomonas aeruginosa corneal virulence through their control of lifestyle and virulence programs

“…Given the primary function of condensins in chromosome folding, the location of condensin‐dependent genes could be linked to the fine structure of the chromosome. Recently, a DNA interaction map of P. aeruginosa chromosome has been constructed using chromosome conformation capture, Hi‐C (Lioy et al, 2020). In Figure 9, we mapped the genes significantly affected by smc or mksB mutations (>2‐ fold, FDR < 0.1) to the interaction map of the PAO1 chromosome.…”

“…Hi-C maps of P. aeruginosa (GEO: GSM4560142) were analyzed using MATLAB. The map represents a table of normalized contact frequencies of each 10 kb bin of the PAO1-Orsay genome (Lioy et al, 2020). Each column of the table was fit to a Gaussian distribution, and the width of the distribution used as a measure of the interaction range.…”

DNA-loop extruding SMC complexes can traverse one anotherin vivo

“…In eukaryotes, the cohesin and condensin SMC complexes are loaded at multiple chromosomal loci, at estimated densities between ~1/200 kb - 1/40 kb and extrude loops of 100’s of kilobases (reviewed in 18 ). In many bacteria, condensin SMC complexes are loaded by the protein ParB primarily at centromeric sequences called parS sites 13–17 . These sites often exist in multiple copies close to one another 20 .…”

“…Here, we set up a “crash-course track” system to study what happens when SMC complexes encounter one another. Using the parS /ParB system, which loads SMC complexes in a targeted manner 13–17 , we engineered the Bacillus subtilis chromosome to have multiple SMC loading sites. Chromosome conformation capture (Hi-C) analyses of over 20 engineered strains show an amazing variety of never-before-seen chromosome folding patterns.…”

Chromosomal position of ribosomal protein genes impacts long term evolution ofVibrio cholerae

“…The simplest model to tackle this issue is the bacterial cell due to its relatively small genome size and chromosome number. The bacterial chromosome is tightly organized within the confined space of the cytoplasm and along the cell cycle (6)(7)(8)(9)(10)(11)(12)(13). This is physiologically relevant since DNA simultaneously serves as template for replication, transcription, segregation and the repair of the genetic material (1,4,14).…”