Maintenance of chromosome structure in Pseudomonas aeruginosa

Abstract

Replication and segregation of genetic information are the activities central to the well-being of all living cells. Concerted mechanisms have evolved that ensure that each cellular chromosome is replicated once and only once per cell cycle and then faithfully segregated into daughter cells. Despite remarkable taxonomic diversity, these mechanisms are largely conserved across eubacteria, although species-specific distinctions can often be noted. Here, we provide an overview of the current state of knowledge about maintenance of the chromosome structure in Pseudomonas aeruginosa. We focus on global chromosome organization and its dynamics during DNA replication and cell division. Special emphasis is made on contrasting these activities in P. aeruginosa and other bacteria. Among unique P. aeruginosa, features are the presence of two distinct autonomously replicating sequences and multiple condensins, which suggests existence of novel regulatory mechanisms.

Keywords: MksBEF; PA4685; Pseudomonas aeruginosa; SMC; chromosome structure; condensins.

Fig. 1

Comparison of genomic context for various bacterial origins of replication. The origin of replication (C, red) and a DnaA box clusters with DUE (D; blue) are often found embedded within the dnaA or gidA cassettes. rH, rpmH; rA, rnpA; yD, yidD; v8, VC0008; v9, VC0009; v10, VC0010; p66, PA5566; yyB, yyaB; yA, yaaA; yB, yaaB.

Fig. 2

A working model of bacterial chromosome. Chromosome structure is stabilized by various NAPs that bend and bridge DNA, supercoiling, which energizes and compacts DNA, and condensins, which stabilize giant loops and tether them to extrachromosomal elements.

Fig. 3

Subcellular organization of the chromosome in E. coli and P. aeruginosa prior to (A) or during (B) replication. Newly replicated DNA is shown in gray.

Fig. 4

Comparison of the E. coli and P. aeruginosa condensins. The P. aeruginosa condensins differ in the length of their coiled coil region, which are all shorter than in MukB. One of the condensins, Mks2BEFG, encodes a Toprim protein MksG and is postulated to form a similar complex with MksB2 as ParC with MukB.