Flagellar Mutants Have Reduced Pilus Synthesis in
            <i>Caulobacter crescentus</i>

Ellison, Courtney K.; Rusch, Douglas B.; Brun, Yves V.

doi:10.1128/jb.00031-19

Cited by 19 publications

(17 citation statements)

References 37 publications

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“…Phage sensitivity assays in tubes were performed by adding ~10 6 cfu of indicated strains with ~10 11 pfu of ɸCb5 phage for a MOI of 10 5 in three ml PYE where indicated. A final concentration of 500 µM methoxypolyethylene glycol maleimide, MW 5000 (PEG5000-mal) (Sigma) was added to tubes where indicated to block pilus retraction as shown previously 8,52 . Cultures were then grown shaking at 30 °C overnight before imaging.…”

Section: Methodsmentioning

confidence: 99%

A bifunctional ATPase drives tad pilus extension and retraction

Ellison

Kan

Chlebek

et al. 2019

Preprint

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16Molecular motors convert chemical energy directly into mechanical work 1 and are found in all 17domains of life 2 . These motors are critical to intracellular transport 3 , motility 4,5 , macromolecular 18protein assembly 3,6 , and many essential processes 7 . A wide-spread class of related bacterial 19 motors drive the dynamic activity of extracellular fibers, such as type IV pili (T4P), that are 20 extended and retracted using so-called secretion motor ATPases. Among these, the tight 21 adherence (tad) pili are critical for surface sensing, surface attachment, and biofilm formation 8-22 10

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Section: Methodsmentioning

confidence: 99%

A bifunctional ATPase drives tad pilus extension and retraction

Ellison

Kan

Chlebek

et al. 2019

Preprint

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“…Phage sensitivity assays were performed as described previously [36]. Briefly, five μl of ΦCbK phage dilutions were spotted onto lawns of growing C. crescentus strains.…”

Section: Methodsmentioning

confidence: 99%

Surface Sensing Stimulates Cellular Differentiation inCaulobacter crescentus

Snyder

Ellison

Severin

et al. 2019

Preprint

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Cellular differentiation is a fundamental strategy used by cells to generate specialized functions at specific stages of development. The bacterium C. crescentus employs a specialized dimorphic life cycle consisting of two differentiated cell types. How environmental cues, including mechanical inputs such as contact with a surface, regulate this cell cycle remain unclear. Here, we find that surface sensing by the physical perturbation of retracting extracellular pilus filaments accelerates cell cycle progression and cellular differentiation. We show that physical obstruction of dynamic pilus activity by chemical perturbation or by a mutation in the outer membrane pilus pore protein, CpaC, stimulates early initiation of chromosome replication. In addition, we find that surface contact stimulates cell cycle progression by demonstrating that surface-stimulated cells initiate early chromosome replication to the same extent as planktonic cells with obstructed pilus activity. Finally, we show that obstruction of pilus retraction stimulates the synthesis of the cell cycle regulator, cyclic diguanylate monophosphate (c-di-GMP) through changes in the activity and localization of two key regulatory histidine kinases that control cell fate and differentiation. Together, these results demonstrate that surface contact and mechanosensing by alterations in pilus activity stimulate C. crescentus to bypass its developmentally programmed temporal delay in cell differentiation to more quickly adapt to a surface-associated lifestyle.SignificanceCells from all domains of life sense and respond to mechanical cues [1–3]. In eukaryotes, mechanical signals such as adhesion and surface stiffness are important for regulating fundamental processes including cell differentiation during embryonic development [4]. While mechanobiology is abundantly studied in eukaryotes, the role of mechanical influences on prokaryotic biology remains under-investigated. Here, we demonstrate that mechanosensing mediated through obstruction of the dynamic extension and retraction of tight adherence (tad) pili stimulates cell differentiation and cell cycle progression in the dimorphic α-proteobacterium Caulobacter crescentus. Our results demonstrate an important intersection between mechanical stimuli and the regulation of a fundamental aspect of cell biology.

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“…Flagella and pili are important factors for the colonization of solid surfaces in C. crescentus (23,26) and other species (39)(40)(41). Recently published data provide support for a complex interplay between the flagellum, type IV pili, and the control of holdfast development in C. crescentus (25,31,(42)(43)(44)(45). Given the clear role of the pilus and flagellum in attachment to solid surfaces and the regulatory connection between these structures and holdfast development, I tested the contribution of these appendages to C. crescentus pellicle development at the air-liquid interface.…”

Section: Figmentioning

confidence: 98%

Role of Caulobacter Cell Surface Structures in Colonization of the Air-Liquid Interface

Fiebig

2019

J Bacteriol

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In aquatic environments, Caulobacter spp. can be found at the boundary between liquid and air known as the neuston. I report an approach to study temporal features of Caulobacter crescentus colonization and pellicle biofilm development at the air-liquid interface and have defined the role of cell surface structures in this process. At this interface, C. crescentus initially forms a monolayer of cells bearing a surface adhesin known as the holdfast. When excised from the liquid surface, this monolayer strongly adheres to glass. The monolayer subsequently develops into a three-dimensional structure that is highly enriched in clusters of stalked cells known as rosettes. As this pellicle film matures, it becomes more cohesive and less adherent to a glass surface. A mutant strain lacking a flagellum does not efficiently reach the surface, and strains lacking type IV pili exhibit defects in organization of the three-dimensional pellicle. Strains unable to synthesize the holdfast fail to accumulate at the boundary between air and liquid and do not form a pellicle. Phase-contrast images support a model whereby the holdfast functions to trap C. crescentus cells at the air-liquid boundary. Unlike the holdfast, neither the flagellum nor type IV pili are required for C. crescentus to partition to the air-liquid interface. While it is well established that the holdfast enables adherence to solid surfaces, this study provides evidence that the holdfast has physicochemical properties that allow partitioning of nonmotile mother cells to the air-liquid interface and facilitate colonization of this microenvironment. IMPORTANCE In aquatic environments, the boundary at the air interface is often highly enriched with nutrients and oxygen. Colonization of this niche likely confers a significant fitness advantage in many cases. This study provides evidence that the cell surface adhesin known as a holdfast enables Caulobacter crescentus to partition to and colonize the air-liquid interface. Additional surface structures, including the flagellum and type IV pili, are important determinants of colonization and biofilm formation at this boundary. Considering that holdfast-like adhesins are broadly conserved in Caulobacter spp. and other members of the diverse class Alphaproteobacteria, these surface structures may function broadly to facilitate colonization of air-liquid boundaries in a range of ecological contexts, including freshwater, marine, and soil ecosystems.

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Flagellar Mutants Have Reduced Pilus Synthesis in Caulobacter crescentus

Cited by 19 publications

References 37 publications

A bifunctional ATPase drives tad pilus extension and retraction

A bifunctional ATPase drives tad pilus extension and retraction

Surface Sensing Stimulates Cellular Differentiation inCaulobacter crescentus

Role of Caulobacter Cell Surface Structures in Colonization of the Air-Liquid Interface

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