ParB deficiency in Pseudomonas aeruginosa destabilizes the partner protein ParA and affects a variety of physiological parameters

Abstract

Deletions leading to complete or partial removal of ParB were introduced into the Pseudomonas aeruginosa chromosome. Fluorescence microscopy of fixed cells showed that ParB mutants lacking the C-terminal domain or HTH motif formed multiple, less intense foci scattered irregularly, in contrast to the one to four ParB foci per cell symmetrically distributed in wild-type P. aeruginosa. All parB mutations affected both bacterial growth and swarming and swimming motilities, and increased the production of anucleate cells. Similar effects were observed after inactivation of parA of P. aeruginosa. As complete loss of ParA destabilized its partner ParB it was unclear deficiency of which protein is responsible for the mutant phenotypes. Analysis of four parB mutants showed that complete loss of ParB destabilized ParA whereas three mutants that retained the N-terminal 90 aa of ParB did not. As all four parB mutants demonstrate the same defects it can be concluded that either ParB, or ParA and ParB in combination, plays an important role in nucleoid distribution, growth and motility in P. aeruginosa.

Participation of Chromosome Segregation Protein ParAI ofVibrio choleraein Chromosome Replication

“…In summary, the results from bacterial and yeast two-hybrid systems indicate that V. cholerae ParAI, ParBI, and DnaA can interact with each other. Interactions between the ParA and ParB proteins have been found in other bacteria (7,8,10). DnaA interaction with ParA (Soj) has been found in B. subtilis (54).…”

“…Also, when the B. subtilis parS sites are moved away from their natural originproximal positions, they no longer localize to cell quarter positions, implying that the par system might not be sufficient for their localization to cell quarter positions (43). In P. aeruginosa and in P. putida, anucleate cells account for up to 10% of the population in the absence of Par proteins (8,30,41,46). The role of par can be more important under certain growth conditions.…”

“…Chromosomal Par proteins have been studied in many bacteria, including B. subtilis (35,48), Burkholderia cenocepacia (19), Caulobacter crescentus (12,21,53), Helicobacter pylori (42), Mycobacterium smegmatis (36,37), Pseudomonas aeruginosa (8,41), Pseudomonas putida (30,46), Streptomyces coelicolor (37), and Vibrio cholerae (25,64). These studies revealed several features of the par genes.…”

ParB spreading requires DNA bridging

“…Further complicating genetic analysis, chromosomal ParA and ParB have additional species-specific functions, including regulation of replication initiation, growth, and motility (Ireton et al 1994;Bartosik et al 2009;Scholefield et al 2011).…”

From spores to antibiotics via the cell cycle

“…spo0J null mutants do have a mild segregation defect but, based on our recent results, this does not seem to be connected at all to Soj function (see below). The situation is complicated by the fact that mutations in the soj (parA) and spo0J (parB) homologues in other bacteria generate a plethora of different phenotypic effects, including motility and virulence, as well as different aspects of the cell cycle (and sporulation) (Bartosik et al, 2009;Kim et al, 2000;Mohl et al, 2001). …”