Asymmetry and Inequity in the Inheritance of a Bacterial Adhesive

Pseudomonas aeruginosa is an opportunistic human pathogen that forms biofilm infections in a wide variety of contexts. Biofilms initiate when bacteria attach to a surface, which triggers changes in gene expression leading to the biofilm phenotype.Wehave previously shown, for the P. aeruginosa lab strain PAO1, that the self-produced polymer Psl is the most dominant adhesive for attachment to the surface but that another self-produced polymer, Pel, controls the geometry of attachment of these rod-shaped bacteria—strains that make Psl but not Pel are permanently attached to the surface but adhere at only one end (tilting up off the surface), whereas wild-type bacteria that make both Psl and Pel are permanently attached and lie down flat with very little or no tilting (Cooley et al 2013 Soft Matter 9 3871–6). Here we show that the change in attachment geometry reflects a change in the distribution of Psl on the bacterial cell surface. Bacteria that make Psl and Pel have Psl evenly coating the surface, whereas bacteria that make only Psl have Psl concentrated at only one end.Weshow that Psl can act as an inheritable, epigenetic factor. Rod-shaped P. aeruginosa grows lengthwise and divides across the middle.Wefind that asymmetry in the distribution of Psl on a parent cell is reflected in asymmetry between siblings in their attachment to the surface. Thus, Pel not only promotes P. aeruginosa lying down