Heterogeneity in surface sensing produces a division of labor inPseudomonas aeruginosapopulations

Abstract

16The second messenger signaling molecule cyclic diguanylate monophosphate (c-di-GMP) 17 drives the transition from planktonic to biofilm growth in many bacterial species. 18 Pseudomonas aeruginosa has two surface sensing systems that produce c-di-GMP in 19 response to surface adherence. The current thinking in the field is that once cells attach to 20 a surface, they uniformly respond with elevated c-di-GMP. Here, we describe how the 21 Wsp system generates heterogeneity in surface sensing, resulting in two physiologically 22 distinct subpopulations of cells. One subpopulation has elevated c-di-GMP and produces 23 2 biofilm matrix, serving as the founders of initial microcolonies. The other subpopulation 24 has low c-di-GMP and engages in surface motility, allowing for exploration of the 25 surface. We also show that this heterogeneity strongly correlates to surface behavior for 26 descendent cells. Together, our results suggest that after surface attachment, P. 27 aeruginosa engages in a division of labor that persists across generations, accelerating 28 early biofilm formation and surface exploration. 29 3 30 Introduction 31Pseudomonas aeruginosa is an opportunistic pathogen that engages in a range of 32 surface-associated behaviors and is a model bacterium for studies of surface-associated 33 communities called biofilms. Biofilms are dense aggregates of cells producing 34 extracellular matrix components that hold the community together. The biofilm mode of 35 growth confers cells protection from a variety of environmental stresses including 36 nutrient limitation, desiccation, and shear forces, as well as engulfment by protozoa in the 37 environment or phagocytes in a host (1). 38The secondary messenger signaling molecule cylic-di-GMP (c-di-GMP) drives 39 the transition from the planktonic to the biofilm mode of growth. In many bacterial 40 species, including P. aeruginosa, elevated c-di-GMP results in repression of flagellar 41 motility genes, while promoting expression of genes involved in producing a biofilm 42 matrix(2). The P. aeruginosa biofilm matrix is composed of a combination of 43 polysaccharides (including Pel and Psl), proteins (including the adhesin CdrA), and 44 extracellular DNA (3-8). Biofilm matrix production is an energetically costly process 45 that is regulated at multiple levels (9). The cdrA, pel and psl genes are all 46 transcriptionally induced under conditions of high c-di-GMP(10). 47 For many species, the initial step in biofilm formation involves adherence of free 48 swimming planktonic cells to a surface and the initiation of surface sensing. P. 49 aeruginosa has at least two distinct surface sensing systems, the Wsp and the Pil-Chp 50 systems, that when activated, lead to biofilm formation. The Wsp system senses an 51 unknown surface-related signal (recently proposed to be membrane perturbation (11)) 52 through WspA, a membrane-bound protein homologous to methyl-accepting chemotaxis 53 4 proteins (MCPs). Activation of this system stimulates phosphorylation of the digu...

Differential surface competition and biofilm invasion strategies of Pseudomonas aeruginosa PA14 and PA01

“…The two common laboratory strains of P. aeruginosa, abbreviated PAO1 and PA14, represent two distinct lineages based on whole genome phylogenetic analysis (30). PAO1 and PA14 preferentially use the WspR and Pil-Chip signaling pathways to enhance EPS production and repress surface motility, respectively, during early events in biofilm formation (24,31).…”

The Diguanylate Cyclase YfiN of Pseudomonas aeruginosa Regulates Biofilm Maintenance in Response to Peroxide

“…P. aeruginosa forms robust biofilms, multicellular surface-attached aggregates that are recalcitrant to antimicrobial therapy and environmental insults (4,5). For motile organisms such as P. aeruginosa, biofilms form through a multistep process that requires motility and motility appendages, surface-sensing and the production of extracellular polysaccharides (EPS) (6)(7)(8)(9). Flagella mediate initial polar attachment of a cell to a surface, while pili facilitate irreversible surface attachment and microcolony formation (10,11).…”