Involvement of Type IV Pili in Pathogenicity of Plant Pathogenic Bacteria

ABSTRACTBacteria utilize dynamic appendages called type IV pili (T4P) to interact with their environment and mediate a wide variety of functions. Pilus extension is mediated by an extension ATPase motor, commonly called PilB, in all T4P. Pilus retraction, however, can either occur with the aid of an ATPase motor, or in the absence of a retraction motor. While much effort has been devoted to studying motor-dependent retraction, the mechanism and regulation of motor-independent retraction remains poorly characterized. We have previously demonstrated that Vibrio cholerae competence T4P undergo motor-independent retraction in the absence of the dedicated retraction ATPases PilT and PilU. Here, we utilize this model system to characterize the factors that influence motor-independent retraction. We find that freshly extended pili frequently undergo motor-independent retraction, but if these pili fail to retract immediately, they remain statically extended on the cell surface. Importantly, we show that these static pili can still undergo motor-dependent retraction via tightly regulated ectopic expression of PilT, suggesting that these T4P are not broken, but simply cannot undergo motor-independent retraction. Through additional genetic and biophysical characterization of pili, we suggest that pilus filaments undergo conformational changes during dynamic extension and retraction. We propose that only some conformations, like those adopted by freshly extended pili, are capable of undergoing motor-independent retraction. Together, these data highlight the versatile mechanisms that regulate T4P dynamic activity and provide additional support for the long-standing hypothesis that motor-independent retraction occurs via spontaneous depolymerization.SIGNIFICANCEExtracellular pilus fibers are critical to the virulence and persistence of many pathogenic bacteria. A crucial function for most pili is the dynamic ability to extend and retract from the cell surface. Inhibiting this dynamic pilus activity represents an attractive approach for therapeutic interventions, however, a detailed mechanistic understanding of this process is currently lacking. Here, we use the competence pilus of Vibrio cholerae to study how pili retract in the absence of dedicated retraction motors. Our results reveal a novel regulatory mechanism of pilus retraction that is an inherent property of the external pilus filament. Thus, understanding the conformational changes that pili adopt under different conditions may be critical for the development of novel therapeutics that aim to target the dynamic activity of these structures.

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Structure and function of minor pilins of type IV pili

Medical Microbiology and Immunology ◽

10.1007/s00430-019-00642-5 ◽

2019 ◽

Vol 209 (3) ◽

pp. 301-308 ◽

Cited By ~ 4

Author(s):

Theis Jacobsen ◽

Benjamin Bardiaux ◽

Olivera Francetic ◽

Nadia Izadi-Pruneyre ◽

Michael Nilges

Keyword(s):

Pathogenic Bacteria ◽

Type Iv Pili ◽

Host Cells ◽

Type Ii Secretion ◽

Type Iv Pilus ◽

Type Iv ◽

Flexible Fibers ◽

Multiple Copies ◽

Species Specific ◽

And Function

AbstractType IV pili are versatile and highly flexible fibers formed on the surface of many Gram-negative and Gram-positive bacteria. Virulence and infection rate of several pathogenic bacteria, such as Neisseria meningitidis and Pseudomonas aeruginosa, are strongly dependent on the presence of pili as they facilitate the adhesion of the bacteria to the host cell. Disruption of the interactions between the pili and the host cells by targeting proteins involved in this interaction could, therefore, be a treatment strategy. A type IV pilus is primarily composed of multiple copies of protein subunits called major pilins. Additional proteins, called minor pilins, are present in lower abundance, but are essential for the assembly of the pilus or for its specific functions. One class of minor pilins is required to initiate the formation of pili, and may form a complex similar to that identified in the related type II secretion system. Other, species-specific minor pilins in the type IV pilus system have been shown to promote additional functions such as DNA binding, aggregation and adherence. Here, we will review the structure and the function of the minor pilins from type IV pili.

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Expression of Type IV Pili by Moraxella catarrhalis Is Essential for Natural Competence and Is Affected by Iron Limitation

Infection and Immunity ◽

10.1128/iai.72.11.6262-6270.2004 ◽

2004 ◽

Vol 72 (11) ◽

pp. 6262-6270 ◽

Cited By ~ 48

Author(s):

Nicole R. Luke ◽

Amy J. Howlett ◽

Jianqiang Shao ◽

Anthony A. Campagnari

Keyword(s):

Moraxella Catarrhalis ◽

Pathogenic Bacteria ◽

Type Iv Pili ◽

Protein Subunit ◽

Electron Microscopic ◽

Type Iv ◽

Wide Range ◽

Genes Encoding ◽

Microscopic Studies

ABSTRACT Type IV pili, filamentous surface appendages primarily composed of a single protein subunit termed pilin, play a crucial role in the initiation of disease by a wide range of pathogenic bacteria. Although previous electron microscopic studies suggested that pili might be present on the surface of Moraxella catarrhalis isolates, detailed molecular and phenotypic analyses of these structures have not been reported to date. We identified and cloned the M. catarrhalis genes encoding PilA, the major pilin subunit, PilQ, the outer membrane secretin through which the pilus filament is extruded, and PilT, the NTPase that mediates pilin disassembly and retraction. To initiate investigation of the role of this surface organelle in pathogenesis, isogenic pilA, pilT, and pilQ mutants were constructed in M. catarrhalis strain 7169. Comparative analyses of the wild-type 7169 strain and three isogenic pil mutants demonstrated that M. catarrhalis expresses type IV pili that are essential for natural genetic transformation. Our studies suggest type IV pilus production by M. catarrhalis is constitutive and ubiquitous, although pilin expression was demonstrated to be iron responsive and Fur regulated. These data indicate that additional studies aimed at elucidating the prevalence and role of type IV pili in the pathogenesis and host response to M. catarrhalis infections are warranted.

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Fresh extension of Vibrio cholerae competence type IV pili predisposes them for motor-independent retraction

Applied and Environmental Microbiology ◽

10.1128/aem.00478-21 ◽

2021 ◽

Author(s):

Jennifer L. Chlebek ◽

Triana N. Dalia ◽

Nicolas Biais ◽

Ankur B. Dalia

Keyword(s):

Cell Surface ◽

Vibrio Cholerae ◽

Conformational Changes ◽

Pathogenic Bacteria ◽

Ectopic Expression ◽

Type Iv Pili ◽

Therapeutic Interventions ◽

Dynamic Activity ◽

Type Iv ◽

Additional Support

Bacteria utilize dynamic appendages called type IV pili (T4P) to interact with their environment and mediate a wide variety of functions. Pilus extension is mediated by an extension ATPase motor, commonly called PilB, in all T4P. Pilus retraction, however, can either occur with the aid of an ATPase motor, or in the absence of a retraction motor. While much effort has been devoted to studying motor-dependent retraction, the mechanism and regulation of motor-independent retraction remains poorly characterized. We have previously demonstrated that Vibrio cholerae competence T4P undergo motor-independent retraction in the absence of the dedicated retraction ATPases PilT and PilU. Here, we utilize this model system to characterize the factors that influence motor-independent retraction. We find that freshly extended pili frequently undergo motor-independent retraction, but if these pili fail to retract immediately, they remain statically extended on the cell surface. Importantly, we show that these static pili can still undergo motor-dependent retraction via tightly regulated ectopic expression of PilT, suggesting that these T4P are not broken, but simply cannot undergo motor-independent retraction. Through additional genetic and biophysical characterization of pili, we suggest that pilus filaments undergo conformational changes during dynamic extension and retraction. We propose that only some conformations, like those adopted by freshly extended pili, are capable of undergoing motor-independent retraction. Together, these data highlight the versatile mechanisms that regulate T4P dynamic activity and provide additional support for the long-standing hypothesis that motor-independent retraction occurs via spontaneous depolymerization. IMPORTANCE Extracellular pilus fibers are critical to the virulence and persistence of many pathogenic bacteria. A crucial function for most pili is the dynamic ability to extend and retract from the cell surface. Inhibiting this dynamic pilus activity represents an attractive approach for therapeutic interventions, however, a detailed mechanistic understanding of this process is currently lacking. Here, we use the competence pilus of Vibrio cholerae to study how pili retract in the absence of dedicated retraction motors. Our results reveal a novel regulatory mechanism of pilus retraction that is an inherent property of the pilus filament. Thus, understanding the conformational changes that pili adopt under different conditions may be critical for the development of novel therapeutics that aim to target the dynamic activity of these structures.

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Characterization of Adhesion Threads of Deinococcus geothermalis as Type IV Pili

Journal of Bacteriology ◽

10.1128/jb.00608-06 ◽

2006 ◽

Vol 188 (19) ◽

pp. 7016-7021 ◽

Cited By ~ 25

Author(s):

C. Saarimaa ◽

M. Peltola ◽

M. Raulio ◽

T. R. Neu ◽

M. S. Salkinoja-Salonen ◽

...

Keyword(s):

Pathogenic Bacteria ◽

Periodic Acid ◽

Bacterial Attachment ◽

Extracellular Proteins ◽

Type Iv Pili ◽

Confocal Laser ◽

Major Protein ◽

Paper Machine ◽

Type Iv ◽

Deinococcus Geothermalis

ABSTRACT Deinococcus geothermalis E50051 forms tenuous biofilms on paper machine surfaces. Field emission electron microscopy analysis revealed peritrichous appendages which mediated cell-to-surface and cell-to-cell interactions but were absent in planktonically grown cells. The major protein component of the extracellular extract of D. geothermalis had an N-terminal sequence similar to the fimbrial protein pilin annotated in the D. geothermalis DSM 11300 draft sequence. It also showed similarity to the type IV pilin sequence of D. radiodurans and several gram-negative pathogenic bacteria. Other proteins in the extract had N-terminal sequences identical to D. geothermalis proteins with conservative motifs for serine proteases, metallophosphoesterases, and proteins whose function is unknown. Periodic acid-Schiff staining for carbohydrates indicated that these extracellular proteins may be glycosylated. A further confirmation for the presence of glycoconjugates on the cell surface was obtained by confocal laser scanning imaging of living D. geothermalis cells stained with Amaranthus caudatus lectin, which specifically binds to galactose residues. The results indicate that the thread-like appendages of D. geothermalis E50051 are glycosylated type IV pili, bacterial attachment organelles which have thus far not been described for the genus Deinococcus.

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THE ACTIVITY OF ESSENTIAL OILS OBTAINED FROM SPECIES AND INTERSPECIES HYBRIDS OF THE Mentha GENUS AGAINST SELECTED PLANT PATHOGENIC BACTERIA

Acta Scientiarum Polonorum Hortorum Cultus ◽

10.24326/asphc.2018.6.17 ◽

2018 ◽

Vol 17 (6) ◽

pp. 167-174 ◽

Cited By ~ 1

Author(s):

Małgorzata Schollenberger ◽

Tomasz M. Staniek ◽

Elżbieta Paduch-Cichal ◽

Beata Dasiewicz ◽

Agnieszka Gadomska-Gajadhur ◽

...

Keyword(s):

Essential Oils ◽

Pseudomonas Syringae ◽

Pathogenic Bacteria ◽

Antimicrobial Effect ◽

Mentha Piperita ◽

Mentha Spicata ◽

Plant Essential Oils ◽

Plant Pathogenic Bacteria ◽

Interspecies Hybrids

Plant essential oils of six aromatic herb species and interspecies hybrids of the family Lamiaceae – chocolate mint (Mentha piperita × ‘Chocolate’), pineapple mint (Mentha suaveolens ‘Variegata’), apple mint (Mentha × rotundifolia), spearmint (Mentha spicata), orange mint (Mentha × piperita ‘Granada’) and strawberry mint (Mentha × villosa ‘Strawberry’) – were investigated for antimicrobial effects against plant pathogenic bacteria: Agrobacterium tumefaciens, Pseudomonas syringae pv. syringae and Xanthomonas arboricola pv. corylina. The screening was carried out in vitro on agar plates filled with the target organism. All essential oils screened exhibited a higher level of antibacterial activity against A. tumefaciens and X. arboricola pv. corylina than streptomycin used as a standard in all tests. The antimicrobial effect of streptomycin and five mint oils was at the same level for P. syringae pv. syringae. There were no significant differences in the influence of the chocolate mint oil on the growth inhibition of all bacteria tested. Plant essential oils from pineapple mint, apple mint, spearmint and strawberry mint showed the weakest antimicrobial activity against P. syringae pv. syringae and the strongest towards A. tumefaciens and X. arboricola pv. corylina. The essential oils from strawberry mint, pineapple mint, spearmint and apple mint had the strongest effect on A. tumefaciens, and the lowest inhibitory activity was exhibited by the chocolate mint and orange mint essential oils. X. arboricola pv. corylina was the most sensitive to the strawberry mint, pineapple mint and spearmint oils. The chocolate mint oil showed the greatest activity against P. syringae pv. syringae.

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