Role of Cyclic Di-GMP and Exopolysaccharide in Type IV Pilus Dynamics

Ribbe, Jan; Baker, Amy E.; Euler, Sebastian; O’Toole, George A.; Maier, Berenike

doi:10.1128/jb.00859-16

Cited by 39 publications

(38 citation statements)

References 54 publications

(86 reference statements)

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“…However, it is likely that one of the pilT paralogues powers retraction for this specific strain. On the other hand, T4P retraction powered by the retraction ATPase shows a wide range of forces, from 8 pN up to 150 pN (2,5,20,41). Taken together, we conclude that the retraction ATPase PilT consistently increases the force generated by T4P retraction in different bacterial species.…”

Section: Discussionmentioning

confidence: 60%

Motor Properties of PilT-Independent Type 4 Pilus Retraction in Gonococci

2019

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Bacterial type 4 pili (T4P) belong to the strongest molecular machines. The gonococcal T4P retraction ATPase PilT supports forces exceeding 100 pN during T4P retraction. Here, we address the question of whether gonococcal T4P retract in the absence of PilT. We show that pilT deletion strains indeed retract their T4P, but the maximum force is reduced to 5 pN. Similarly, the speed of T4P retraction is lower by orders of magnitude compared to that of T4P retraction driven by PilT. Deleting the pilT paralogue pilT2 further reduces the speed of T4P retraction, yet T4P retraction is detectable in the absence of all three pilT paralogues. Furthermore, we show that depletion of proton motive force (PMF) slows but does not inhibit pilTindependent T4P retraction. We conclude that the retraction ATPase is not essential for gonococcal T4P retraction. However, the force generated in the absence of PilT is too low to support important functions of T4P, including twitching motility, fluidization of colonies, and induction of host cell response. IMPORTANCE Bacterial type 4 pili (T4P) have been termed the "Swiss Army knives" of bacteria because they perform numerous functions, including host cell interaction, twitching motility, colony formation, DNA uptake, protein secretion, and surface sensing. The pilus fiber continuously elongates or retracts, and these dynamics are functionally important. Curiously, only a subset of T4P systems employ T4P retraction ATPases to power T4P retraction. Here, we show that one of the strongest T4P machines, the gonococcal T4P, retracts without a retraction ATPase. Biophysical characterization reveals strongly reduced force and speed compared to retraction with ATPase. We propose that bacteria encode retraction ATPases when T4P have to generate high-force-supporting functions like twitching motility, triggering host cell response, or fluidizing colonies.

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Section: Discussionmentioning

confidence: 60%

Motor Properties of PilT-Independent Type 4 Pilus Retraction in Gonococci

2019

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“…In P. aeruginosa , surface exploration is mainly accomplished by twitching motility, mediated by type IV pili, and does not appear to be influenced by levels of intracellular c-di-GMP when analyzing single cells ( 24 ). Interestingly, we found that correlations between c-di-GMP and motility during the lifetime of individual cells are weak.…”

Section: Resultsmentioning

confidence: 99%

Heterogeneity in surface sensing produces a division of labor inPseudomonas aeruginosapopulations

Armbruster

Lee

Parker-Gilham

et al. 2019

Preprint

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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...

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“…Elongation and retraction are driven by dedicated ATPases (11,12). During the process of retraction, the T4P is capable of generating a very high force (13,14). Interestingly, the fact that the T4P elongate and retract dynamically affects the shape, dynamics, and sorting behavior of bacterial colonies (7,15,16).…”

Section: Introductionmentioning

confidence: 99%

Type IV Pilin Post-Translational Modifications Modulate Material Properties of Bacterial Colonies

Zöllner

Cronenberg

Kouzel

et al. 2019

Biophysical Journal

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Bacterial type 4 pili (T4P) are extracellular polymers that initiate the formation of microcolonies and biofilms. T4P continuously elongate and retract. These pilus dynamics crucially affect the local order, shape, and fluidity of microcolonies. The major pilin subunit of the T4P bears multiple post-translational modifications. By interfering with different steps of the pilin glycosylation and phosphoform modification pathways, we investigated the effect of pilin post-translational modification on the shape and dynamics of microcolonies formed by Neisseria gonorrhoeae. Deleting the phosphotransferase responsible for phosphoethanolamine modification at residue serine 68 inhibits shape relaxations of microcolonies after perturbation and causes bacteria carrying the phosphoform modification to segregate to the surface of mixed colonies. We relate these mesoscopic phenotypes to increased attractive forces generated by T4P between cells. Moreover, by deleting genes responsible for the pilin glycan structure, we show that the number of saccharides attached at residue serine 63 affects the ratio between surface tension and viscosity and cause sorting between bacteria carrying different pilin glycoforms. We conclude that different pilin post-translational modifications moderately affect the attractive forces between bacteria but have severe effects on the material properties of microcolonies.

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Role of Cyclic Di-GMP and Exopolysaccharide in Type IV Pilus Dynamics

Cited by 39 publications

References 54 publications

Motor Properties of PilT-Independent Type 4 Pilus Retraction in Gonococci

Motor Properties of PilT-Independent Type 4 Pilus Retraction in Gonococci

Heterogeneity in surface sensing produces a division of labor inPseudomonas aeruginosapopulations

Type IV Pilin Post-Translational Modifications Modulate Material Properties of Bacterial Colonies

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