In these conditions, the localization of the AidB-YFP fusion protein displayed three patterns,

depending on the presence or the absence of a constriction site. In bacteria without detectable constriction, AidB-YFP localized at the new pole and PdhS-mCherry at the old pole in 66% of the bacteria (n = 125), with 34% of bacteria labelled only with polar AidB-YFP and not PdhS-mCherry. In the bacteria displaying a constriction site, 65% (n = 84) displayed a single AidB-YFP focus at the constriction site, while the remaining 35% have two foci of AidB-YFP, one at the “”young”" pole and one at the constriction site. Here we define a “”young”" pole as a new pole that is becoming old, because bacteria show a detectable constriction, meaning that there is uncertainty about the completion of cytokinesis,

and therefore uncertainty about the status of this pole (either new or old). We JQ1 molecular weight never observed the PdhS-mCherry and AidB-YFP fusions at the same pole (n = 256) (Figure 2A). Western blots analysis using an anti-GFP antibody on this strain MK-8669 manufacturer suggested that AidB-YFP fusion was stable when it was produced from the low-copy plasmid pDD001 (data not shown). As proposed in the model depicted in the discussion, the cells labelled with polar AidB-YFP without polar PdhS-mCherry could correspond to bacteria produced by division of cells carrying PdhS-mCherry at the old pole and AidB-YFP Janus kinase (JAK) at the constriction site. Indeed, after cell division, one of the two cells does not inherit PdhS-mCherry from the mother cell, but AidB-YFP at the constriction site is proposed to be transmitted to the new pole of this daughter cell. Figure 2 The B. abortus AidB-YFP is localized at new poles and at constriction sites, in culture and in macrophages.

The B. abortus XDB1128 strain was carrying an aidB-yfp fusion on a low copy plasmid, and pdhS-mCherry at the pdhS chromosomal locus. (A) Bacteria were grown in rich medium and the pictures were taken in exponential phase. Differential interference contrast (DIC) is shown on the left. The white arrowheads indicate the dividing cell in which two AidB-YFP foci are detectable. Each scale bar represents 2 μm. The bacterial types are schematically drawn on the right side of the pictures, as they are represented in figure 6. The two upper panels were made with non-diving bacteria, and counting was made with 125 bacteria. The two lower panels were made with dividing bacteria, and counting was made on 84 dividing bacteria. (B) RAW264.7 macrophages were infected for 2, 4, 6, or 24 h with the B. abortus strain expressing aidB-yfp (XDB1120). The infected cells were fixed and immunostained with 12G12 anti-lipopolysaccharide (“”α-LPS”") primary antibody and anti-mouse secondary antibody coupled to Texas Red.