The parAB gene products of Pseudomonas putida exhibit partition activity in both P. putida and Escherichia coli

Abstract

Summary The bacteria for which there is evidence that proteins of the ParAB family act in chromosome segregation also undergo developmental transitions that involve the ParAB homologues, raising the question of whether the partition activity is equivalent to that of plasmid partition systems. We have investigated the role in partition of the parAB locus of a free‐living bacterium, Pseudomonas putida, not known to pass through developmental phases. A parAB deletion mutant, compared with wild type, showed slightly higher frequencies of anucleate cells in exponen‐tially growing cultures but much higher frequencies in deceleration phase. This increase was growth medium dependent. Oversupply of ParA and ParB proteins also raised anucleate cell levels, specifically in the deceleration phase, in wild‐type and mutant strains and regardless of medium, as well as generating abnormal cell morphologies. Absence or oversupply of ParAB function had either slight or considerable effects on growth rate, depending on temperature and medium. The need for the Par proteins in chromosome partition thus appears to be subject to the cell’s physiological state. Three sequences similar to cis‐acting stabilization sites of Bacillus subtilis are present in the P. putida oriC–parAB region. One was inserted into an unstable mini‐F and shown to stabilize it in E. coli in a ParAB‐dependent manner.

Towards understanding the molecular basis of bacterial DNA segregation

“…Importantly, the chromosomal partitioning proteins can be engineered to function in the same way as plasmid par proteins to stabilize an otherwise unstable replicon and direct its correct positioning within the cell (Godfrin-Estevenon et al 2002;Lin & Grossman 1998;Yamaichi & Niki 2000). Furthermore, null mutants of ParB are lethal in Caulobacter crescentus (Mohl et al 2001), and mutations in spo0J in B. subtilis result in the formation of up to 3% anucleate cells (Ireton et al 1994).…”

“…Furthermore, null mutants of ParB are lethal in Caulobacter crescentus (Mohl et al 2001), and mutations in spo0J in B. subtilis result in the formation of up to 3% anucleate cells (Ireton et al 1994). Spo0J/ParB mutants of B. subtilis and Pseudomonas aeruginosa are viable but display perceptible defects in chromosome segregation in both vegetative and sporulating cells (Godfrin-Estevenon et al 2002;Ireton et al 1994;Lewis et al 2002;Sharpe & Errington 1996). During vegetative growth, deletion of the parAB genes of Pseudomonas putida slightly increases the formation of anucleate cells, but during both the transition from exponential to stationary growth conditions and during overexpression of parAB, high levels of anucleate cells were formed (Godfrin-Estevenon et al 2002).…”

“…Spo0J/ParB mutants of B. subtilis and Pseudomonas aeruginosa are viable but display perceptible defects in chromosome segregation in both vegetative and sporulating cells (Godfrin-Estevenon et al 2002;Ireton et al 1994;Lewis et al 2002;Sharpe & Errington 1996). During vegetative growth, deletion of the parAB genes of Pseudomonas putida slightly increases the formation of anucleate cells, but during both the transition from exponential to stationary growth conditions and during overexpression of parAB, high levels of anucleate cells were formed (Godfrin-Estevenon et al 2002). Deletion of parAB in Streptomyces coelicolor had no detectable effect in vegetatively growing cells, but also resulted in the production of significant numbers of anucleate spores (Kim et al 2000).…”

“…Research has shown that 8 of the 10 sequences are bound by Spo0J in vivo, and that the presence of one such site on an otherwise unstable plasmid stabilizes the plasmid in a Soj-and Spo0J-dependent manner, demonstrating that the site, parS, can function as a partitioning site (Lin & Grossman 1998). Moreover, it has since been shown that both the B. subtilis and P. aeruginosa partitioning machineries can function in E. coli (Godfrin-Estevenon et al 2002;Yamaichi & Niki 2000).…”

Characterization of the mycobacterial chromosome segregation protein ParB and identification of its target in Mycobacterium smegmatis

“…(Bartosik et al, 2004;Godfrin-Estevenon et al, 2002;Lewis et al, 2002), and Streptomyces coelicolor (Jakimowicz et al, 2002;Kim et al, 2000). Homologues of ParAB proteins are encoded in most bacterial chromosomes (the E. coli chromosome is one of the few exceptions) (Bartosik & Jagura-Burdzy, 2005;Bignell & Thomas, 2001).…”