Heterogeneity in surface sensing suggests a division of labor in Pseudomonas aeruginosa populations

Abstract

The second messenger signaling molecule cyclic diguanylate monophosphate (c-di-GMP) drives the transition between planktonic and biofilm growth in many bacterial species. Pseudomonas aeruginosa has two surface sensing systems that produce c-di-GMP in response to surface adherence. Current thinking in the field is that once cells attach to a surface, they uniformly respond by producing c-di-GMP. Here, we describe how the Wsp system generates heterogeneity in surface sensing, resulting in two physiologically distinct subpopulations of cells. One subpopulation has elevated c-di-GMP and produces biofilm matrix, serving as the founders of initial microcolonies. The other subpopulation has low c-di-GMP and engages in surface motility, allowing for exploration of the surface. We also show that this heterogeneity strongly correlates to surface behavior for descendent cells. Together, our results suggest that after surface attachment, P. aeruginosa engages in a division of labor that persists across generations, accelerating early biofilm formation and surface exploration.

Social Cooperativity of Bacteria during Reversible Surface Attachment in Young Biofilms: a Quantitative Comparison of Pseudomonas aeruginosa PA14 and PAO1

“…Different strains of P. aeruginosa, such as PAO1 and PA14, utilize these surface-sensing mechanisms to various extents. The PAO1 strain uses predominantly the Wsp system (21), leading to the surface deposition of the EPS Psl (22,23), while PA14 uses predominantly the Pil-Chp system, leading to the suppression of surface motility (17) and production of a Pel-dominant biofilm matrix (24).…”

Phenotypic differences in reversible attachment behavior reveal distinctP. aeruginosasurface colonization strategies

“…For the flagellum localization data, PA14 WT and Δ pilA (deleting the major subunit of the TFP filament) (48) with FliC (the major subunit of the flagellum filament) modified to FliC(T394C) (49) were used. PAO1 was cultured as previously described (21, 23), and PA14 was cultured as previously described (8). Culturing protocols are summarized as follows.…”

“…Different medium conditions were chosen for PAO1 and PA14 based on the medium optimized for flow cell early biofilm formation experiments for each individual strain in prior work. For PAO1, overnight and regrowth media consisted of FAB medium with 30 mM glutamate, while flow cell media consisted of FAB medium with 0.6 mM glutamate (21, 23). For PA14, overnight and regrowth media consisted of M63 medium with 1 mM magnesium sulfate, 0.2% glucose, and 0.5% casamino acids (CAA), while flow cell media consisted of M63 medium with 1 mM magnesium sulfate, 0.05% glucose, and 0.125% CAA (8, 48).…”

“…Different strains of P. aeruginosa , such as PAO1 and PA14, utilize these surface sensing mechanisms to varying extents. The PAO1 strain predominantly uses the Wsp system (21) leading to the surface deposition of the EPS Psl (22, 23), while PA14 predominantly uses the Pil-Chp system leading to the suppression of surface motility (17) and production of a Pel-dominant biofilm matrix (24).…”

Taming the flagellar motor of pseudomonads with a nucleotide messenger

“…While MotA functions as a mechano-sensitive ion channel, MotB may also play a role in mechano-sensing because it regulates the proton ion flux by displacing an inhibiting extracellular plug with its peptidoglycan binding domain (Kojima et al, 2018). It should be stressed that P. aeruginosa also uses the laterally localized Wsp and polarly localized Pil-Chp signalling systems to sense surfaces and promote surface attachment via cAMP and c-di-GMP-dependent mechanisms (O'Connor et al, 2012;Luo et al, 2015;Lee et al, 2018;Armbruster et al, 2019). If the Wsp, Pil-Chp and flagellar motor-mediated surface sensing mechanisms are all dependent on c-di-GMP, how does the bacterial cell integrate the signalling systems to synchronize cellular responses?…”