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1.
Adv Exp Med Biol ; 1267: 81-100, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32894478

RESUMO

Many bacteria are able to actively propel themselves through their complex environment, in search of resources and suitable niches. The source of this propulsion is the Bacterial Flagellar Motor (BFM), a molecular complex embedded in the bacterial membrane which rotates a flagellum. In this chapter we review the known physical mechanisms at work in the motor. The BFM shows a highly dynamic behavior in its power output, its structure, and in the stoichiometry of its components. Changes in speed, rotation direction, constituent protein conformations, and the number of constituent subunits are dynamically controlled in accordance to external chemical and mechanical cues. The mechano-sensitivity of the motor is likely related to the surface-sensing ability of bacteria, relevant in the initial stage of biofilm formation.


Assuntos
Bactérias/metabolismo , Flagelos/metabolismo , Biofilmes , Conformação Proteica , Rotação
2.
Phys Rev Lett ; 125(9): 098002, 2020 Aug 28.
Artigo em Inglês | MEDLINE | ID: mdl-32915620

RESUMO

Many biological systems display intriguing chiral patterns and dynamics. Here, we present an active nematic theory accounting for individual spin to explore the collective handedness in chiral rod-shaped aggregations. We show that coordinated individual spin and motility can engender a vortex-array pattern with chirality and drive ordering of topological defects. During this chiral process, the stationary trefoil-like defects self-organize into a periodic, hexagon-dominated polygonal network, which segregates persistently rotating cometlike defects in pairs within each polygon, leading to a translation symmetry at the global scale while a broken reflection symmetry at the local scale. Such defect ordering agrees exactly with the Voronoi tiling of two-dimensional space and the emergence of the hexagonal symmetry is deciphered in analogy with topological charge neutralization. We calculate energy barriers to the topological transition of the defect ordering and explain the existing metastable states with nonhexagonal polygons. Our findings shed light on the chiral morphodynamics in life processes and also suggest a potential route towards tuning self-organization in active materials.


Assuntos
Flagelos/fisiologia , Modelos Biológicos , Espermatozoides/fisiologia , Animais , Fenômenos Fisiológicos Bacterianos , Masculino , Movimento/fisiologia , Ouriços-do-Mar
3.
Nat Commun ; 11(1): 3748, 2020 07 27.
Artigo em Inglês | MEDLINE | ID: mdl-32719311

RESUMO

Flagellotropic bacteriophages engage flagella to reach the bacterial surface as an effective means to increase the capture radius for predation. Structural details of these viruses are of great interest given the substantial drag forces and torques they face when moving down the spinning flagellum. We show that the main capsid and auxiliary proteins form two nested chainmails that ensure the integrity of the bacteriophage head. Core stabilising structures are conserved in herpesviruses suggesting their ancestral origin. The structure of the tail also reveals a robust yet pliable assembly. Hexameric rings of the tail-tube protein are braced by the N-terminus and a ß-hairpin loop, and interconnected along the tail by the splayed ß-hairpins. By contrast, we show that the ß-hairpin has an inhibitory role in the tail-tube precursor, preventing uncontrolled self-assembly. Dyads of acidic residues inside the tail-tube present regularly-spaced motifs well suited to DNA translocation into bacteria through the tail.


Assuntos
Bacteriófagos/fisiologia , Flagelos/fisiologia , Motivos de Aminoácidos , Bacteriófagos/ultraestrutura , Proteínas do Capsídeo/química , Proteínas do Capsídeo/metabolismo , DNA/genética , DNA Viral/genética , Flagelos/ultraestrutura , Herpesviridae/ultraestrutura , Multimerização Proteica , Estrutura Secundária de Proteína , Vírion/ultraestrutura , Vitrificação
4.
Proc Natl Acad Sci U S A ; 117(29): 16985-16991, 2020 07 21.
Artigo em Inglês | MEDLINE | ID: mdl-32641510

RESUMO

Vertebrates, from zebra fish to humans, have an innate immune recognition of many bacterial flagellins. This involves a conserved eight-amino acid epitope in flagellin recognized by the Toll-like receptor 5 (TLR5). Several important human pathogens, such as Helicobacter pylori and Campylobacter jejuni, have escaped TLR5 activation by mutations in this epitope. When such mutations were introduced into Salmonella flagellin, motility was abolished. It was previously argued, using very low-resolution cryoelectron microscopy (cryo-EM), that C. jejuni accommodated these mutations by forming filaments with 7 protofilaments, rather than the 11 found in other bacteria. We have now determined the atomic structure of the C. jejuni G508A flagellar filament from a 3.5-Å-resolution cryo-EM reconstruction, and show that it has 11 protofilaments. The residues in the C. jejuni TLR5 epitope have reduced contacts with the adjacent subunit compared to other bacterial flagellar filament structures. The weakening of the subunit-subunit interface introduced by the mutations in the TLR5 epitope is compensated for by extensive interactions between the outer domains of the flagellin subunits. In other bacteria, these outer domains can be nearly absent or removed without affecting motility. Furthermore, we provide evidence for the stabilization of these outer domain interactions through glycosylation of key residues. These results explain the essential role of glycosylation in C. jejuni motility, and show how the outer domains have evolved to play a role not previously found in other bacteria.


Assuntos
Campylobacter jejuni/ultraestrutura , Flagelos/ultraestrutura , Flagelina/imunologia , Receptor 5 Toll-Like/imunologia , Campylobacter jejuni/imunologia , Epitopos/química , Epitopos/imunologia , Flagelos/química , Flagelos/imunologia , Flagelina/química , Humanos , Imunidade Inata
5.
PLoS Pathog ; 16(7): e1008620, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-32614919

RESUMO

Campylobacter jejuni rotates a flagellum at each pole to swim through the viscous mucosa of its hosts' gastrointestinal tracts. Despite their importance for host colonization, however, how C. jejuni coordinates rotation of these two opposing flagella is unclear. As well as their polar placement, C. jejuni's flagella deviate from the norm of Enterobacteriaceae in other ways: their flagellar motors produce much higher torque and their flagellar filament is made of two different zones of two different flagellins. To understand how C. jejuni's opposed motors coordinate, and what contribution these factors play in C. jejuni motility, we developed strains with flagella that could be fluorescently labeled, and observed them by high-speed video microscopy. We found that C. jejuni coordinates its dual flagella by wrapping the leading filament around the cell body during swimming in high-viscosity media and that its differentiated flagellar filament and helical body have evolved to facilitate this wrapped-mode swimming.


Assuntos
Campylobacter jejuni/fisiologia , Flagelos/fisiologia , Flagelina/metabolismo
6.
Nat Commun ; 11(1): 3210, 2020 06 25.
Artigo em Inglês | MEDLINE | ID: mdl-32587243

RESUMO

The bacterial flagellum is a remarkable molecular motor, whose primary function in bacteria is to facilitate motility through the rotation of a filament protruding from the bacterial cell. A cap complex, consisting of an oligomer of the protein FliD, is localized at the tip of the flagellum, and is essential for filament assembly, as well as adherence to surfaces in some bacteria. However, the structure of the intact cap complex, and the molecular basis for its interaction with the filament, remains elusive. Here we report the cryo-EM structure of the Campylobacter jejuni cap complex, which reveals that FliD is pentameric, with the N-terminal region of the protomer forming an extensive set of contacts across several subunits, that contribute to FliD oligomerization. We also demonstrate that the native C. jejuni flagellum filament is 11-stranded, contrary to a previously published cryo-EM structure, and propose a molecular model for the filament-cap interaction.


Assuntos
Proteínas de Bactérias/química , Campylobacter jejuni , Flagelos , Campylobacter jejuni/fisiologia , Campylobacter jejuni/ultraestrutura , Microscopia Crioeletrônica , Flagelos/fisiologia , Flagelos/ultraestrutura , Modelos Moleculares , Estrutura Molecular
7.
PLoS Genet ; 16(6): e1008848, 2020 06.
Artigo em Inglês | MEDLINE | ID: mdl-32530919

RESUMO

Pseudomonas aeruginosa colonizes the airways of cystic fibrosis (CF) patients, causing infections that can last for decades. During the course of these infections, P. aeruginosa undergoes a number of genetic adaptations. One such adaptation is the loss of swimming motility functions. Another involves the formation of the rugose small colony variant (RSCV) phenotype, which is characterized by overproduction of the exopolysaccharides Pel and Psl. Here, we provide evidence that the two adaptations are linked. Using random transposon mutagenesis, we discovered that flagellar mutations are linked to the RSCV phenotype. We found that flagellar mutants overexpressed Pel and Psl in a surface-contact dependent manner. Genetic analyses revealed that flagellar mutants were selected for at high frequencies in biofilms, and that Pel and Psl expression provided the primary fitness benefit in this environment. Suppressor mutagenesis of flagellar RSCVs indicated that Psl overexpression required the mot genes, suggesting that the flagellum stator proteins function in a surface-dependent regulatory pathway for exopolysaccharide biosynthesis. Finally, we identified flagellar mutant RSCVs among CF isolates. The CF environment has long been known to select for flagellar mutants, with the classic interpretation being that the fitness benefit gained relates to an impairment of the host immune system to target a bacterium lacking a flagellum. Our new findings lead us to propose that exopolysaccharide production is a key gain-of-function phenotype that offers a new way to interpret the fitness benefits of these mutations.


Assuntos
Proteínas de Bactérias/genética , Regulação Bacteriana da Expressão Gênica , Interações Hospedeiro-Patógeno/genética , Infecções por Pseudomonas/microbiologia , Pseudomonas aeruginosa/genética , Proteínas de Bactérias/metabolismo , Biofilmes/crescimento & desenvolvimento , Vias Biossintéticas/genética , Fibrose Cística/complicações , Fibrose Cística/microbiologia , Flagelos/metabolismo , Humanos , Mutagênese Sítio-Dirigida , Mutação , Polissacarídeos Bacterianos/biossíntese , Pseudomonas aeruginosa/patogenicidade , Seleção Genética
8.
Sci Total Environ ; 734: 139233, 2020 Sep 10.
Artigo em Inglês | MEDLINE | ID: mdl-32460071

RESUMO

Arsenic (As) poisoning and its potential reproductive functional lesions are a global environmental concern. Recent studies shown that spermiogenesis tends to be a major target process in arsenic-induced male infertility, however, the underlying mechanisms are not fully illuminated. In the present study, 32 fertility related indices including sperm motility, dynamic acrosome formation and sperm flagellum during spermiogenesis in testes were evaluated in adult male mice treated with 0, 0.2, 2, and 20 ppm As2O3 via drinking water for 180 consecutive days. The results showed that out of 32 indices, 11, 25, and 29 indicators were changed statistically by 0.2-, 2-, and 20- ppm As2O3 treatment compared to the controls (0 ppm As2O3), respectively, which reveals a significant dose-dependent relationship. For details, sperm motilities were significantly decreased by 18.85%, 32.47% and 29.53% in three As2O3 treatment groups compared to the control group. Meanwhile, the ultra-structures of acrosome formation and sperm flagellum in testes have been altered by chronic arsenic exposure. Furthermore, arsenic decreased the mRNA expressions of 11 out of 13 genes associated with acrosome biosynthesis and 11 out of 12 genes related to flagellum formation in testes, particularly, down-regulated DPY19L2, AKAP3, AKAP4, CFAP44 and SPAG16 were further confirmed at the protein levels by western blotting. Taken together, chronic arsenic exposure declines male fertility by disorganizing dynamic acrosome and flagellum formation in testes. Especially, DPY19L2, AKAP3, AKAP4, CFAP44, and SPAG16 maybe the potential targets in this process. These results may offer not only a new insight to the mechanism of arsenic-induced male reproductive toxicity, but also provide a clue for the diagnosis and therapy of arseniasis.


Assuntos
Acrossomo , Proteínas de Ancoragem à Quinase A , Animais , Arsênico , Flagelos , Masculino , Proteínas de Membrana , Camundongos , Motilidade Espermática , Espermatogênese , Espermatozoides
9.
J Med Microbiol ; 69(6): 906-919, 2020 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-32459613

RESUMO

Introduction. Indwelling medical devices such as endotracheal tubes (ETTs), urinary catheters, vascular access devices, tracheostomies and feeding tubes are often associated with hospital-acquired infections. Bacterial biofilm formed on the ETTs in intubated patients is a significant risk factor associated with ventilator-associated pneumonia. Pseudomonas aeruginosa is one of the four frequently encountered bacteria responsible for causing pneumonia, and the biofilm formation on ETTs. However, understanding of biofilm formation on ETT and interventions to prevent biofilm remains lagging. The ability to sense and adapt to external cues contributes to their success. Thus, the biofilm formation is likely to be influenced by the two-component systems (TCSs) that are composed of a membrane-associated sensor kinase and an intracellular response regulator.Aim. This study aims to establish an in vitro method to analyse the P. aeruginosa biofilm formation on ETTs, and identify the TCSs that contribute to this process.Methodology. In total, 112 P. aeruginosa PA14 TCS mutants were tested for their ability to form biofilm on ETTs, their effect on quorum sensing (QS) and motility.Results. Out of 112 TCS mutants studied, 56 had altered biofilm biomass on ETTs. Although the biofilm formation on ETTs is QS-dependent, none of the 56 loci controlled quorum signal. Of these, 18 novel TCSs specific to ETT biofilm were identified, namely, AauS, AgtS, ColR, CopS, CprR, NasT, KdpD, ParS, PmrB, PprA, PvrS, RcsC, PA14_11120, PA14_32580, PA14_45880, PA14_49420, PA14_52240, PA14_70790. The set of 56 included the GacS network, TCS proteins involved in fimbriae synthesis, TCS proteins involved in antimicrobial peptide resistance, and surface-sensing. Additionally, several of the TCS-encoding genes involved in biofilm formation on ETTs were found to be linked to flagellum-dependent swimming motility.Conclusions. Our study established an in vitro method for studying P. aeruginosa biofilm formation on the ETT surfaces. We also identified novel ETT-specific TCSs that could serve as targets to prevent biofilm formation on indwelling devices frequently used in clinical settings.


Assuntos
Proteínas de Bactérias/fisiologia , Biofilmes , Intubação Intratraqueal/instrumentação , Pseudomonas aeruginosa/fisiologia , 4-Butirolactona/análogos & derivados , 4-Butirolactona/fisiologia , Contaminação de Equipamentos , Fímbrias Bacterianas/fisiologia , Flagelos/fisiologia , Pneumonia Associada à Ventilação Mecânica/etiologia , Percepção de Quorum
10.
Nat Commun ; 11(1): 2340, 2020 05 11.
Artigo em Inglês | MEDLINE | ID: mdl-32393772

RESUMO

Living organisms often display adaptive strategies that allow them to move efficiently even in strong confinement. With one single degree of freedom, the angle of a rotating bundle of flagella, bacteria provide one of the simplest examples of locomotion in the living world. Here we show that a purely physical mechanism, depending on a hydrodynamic stability condition, is responsible for a confinement induced transition between two swimming states in E. coli. While in large channels bacteria always crash onto confining walls, when the cross section falls below a threshold, they leave the walls to move swiftly on a stable swimming trajectory along the channel axis. We investigate this phenomenon for individual cells that are guided through a sequence of micro-fabricated tunnels of decreasing cross section. Our results challenge current theoretical predictions and suggest effective design principles for microrobots by showing that motility based on helical propellers provides a robust swimming strategy for exploring narrow spaces.


Assuntos
Escherichia coli/fisiologia , Fenômenos Biomecânicos , Flagelos/fisiologia , Movimento , Fótons , Polimerização , Fatores de Tempo
11.
Gene ; 753: 144778, 2020 Aug 30.
Artigo em Inglês | MEDLINE | ID: mdl-32439377

RESUMO

Several genes are associated with the multiple morphological abnormalities of the sperm flagella (MMAF) syndrome, including QRICH2, CFAP43, CFAP44, CFAP69, CCDC39, and AKAP4 genes. Although previous work has shown that these genes are significantly associated with male reproductive traits in certain species, it is not yet known whether they are associated with reproductive traits in the goat. In this study, we investigated the correlations between 47 putative indel mutations in MMAF- associated genes, and first-born litter sizes in 1479 Shaanbei white cashmere (SBWC) goats. Our analysis showed that five of these indel mutations were polymorphic: QRICH2-P4, CFAP43-P20, CFAP69-P4, CFAP69-P6, and CFAP69-P7. Association analysis revealed that only a 6-bp indel variation within CFAP43 (CFAP43-P20) was strongly significantly associated with litter sizes in SBWC goats (P = 0.000). We also identified a significant difference in the genotypic distribution between the mothers of single lambs and the mothers of multiple lambs (P = 0.001); carriers of the DD genotype had greater litter sizes than carriers of the II or ID genotype. Our analysis also revealed 8-bp and 6-bp indels in CFAP69 (CFAP69-P4 and CFAP69-P6, respectively) that were in complete linkage disequilibrium with each other (D' = 0.99, r2 = 1.00). These findings indicate that the 6-bp indel mutation in the CFAP43 gene can be used as an effective molecular marker for selecting reproductive traits in goat breeding operations.


Assuntos
Tamanho da Ninhada de Vivíparos/genética , Proteínas dos Microtúbulos/genética , Cauda do Espermatozoide/metabolismo , Anormalidades Múltiplas/genética , Animais , Proteínas do Citoesqueleto/genética , Análise Mutacional de DNA , Flagelos/genética , Flagelos/metabolismo , Estudos de Associação Genética , Genótipo , Cabras/genética , Mutação INDEL/genética , Infertilidade Masculina/genética , Masculino , Mutação , Fenótipo , Reprodução , Espermatozoides/metabolismo
12.
Nat Commun ; 11(1): 2013, 2020 04 24.
Artigo em Inglês | MEDLINE | ID: mdl-32332720

RESUMO

The long external filament of bacterial flagella is composed of several thousand copies of a single protein, flagellin. Here, we explore the role played by lysine methylation of flagellin in Salmonella, which requires the methylase FliB. We show that both flagellins of Salmonella enterica serovar Typhimurium, FliC and FljB, are methylated at surface-exposed lysine residues by FliB. A Salmonella Typhimurium mutant deficient in flagellin methylation is outcompeted for gut colonization in a gastroenteritis mouse model, and methylation of flagellin promotes bacterial invasion of epithelial cells in vitro. Lysine methylation increases the surface hydrophobicity of flagellin, and enhances flagella-dependent adhesion of Salmonella to phosphatidylcholine vesicles and epithelial cells. Therefore, posttranslational methylation of flagellin facilitates adhesion of Salmonella Typhimurium to hydrophobic host cell surfaces, and contributes to efficient gut colonization and host infection.


Assuntos
Aderência Bacteriana , Flagelina/metabolismo , Histona-Lisina N-Metiltransferase/metabolismo , Infecções por Salmonella/patologia , Salmonella typhimurium/patogenicidade , Animais , Linhagem Celular , Modelos Animais de Doenças , Células Epiteliais , Flagelos/metabolismo , Humanos , Interações Hidrofóbicas e Hidrofílicas , Mucosa Intestinal/microbiologia , Mucosa Intestinal/patologia , Metilação , Camundongos , Células NIH 3T3 , Processamento de Proteína Pós-Traducional , Infecções por Salmonella/microbiologia , Salmonella typhimurium/metabolismo
13.
PLoS One ; 15(4): e0232116, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32343719

RESUMO

Myosin XXI (Myo21) is a novel class of myosin present in all kinetoplastid parasites, such as Trypanosoma and Leishmania. This protein in Leishmania promastigotes is predominantly localized to the proximal region of the flagellum, and is involved in the flagellum assembly, cell motility and intracellular vesicle transport. As Myo21 contains two ubiquitin associated (UBA)-like domains (UBLD) in its amino acid sequence, we considered it of interest to analyze the role of these domains in the intracellular distribution and functions of this protein in Leishmania cells. In this context, we created green fluorescent protein (GFP)-conjugates of Myo21 constructs lacking one of the two UBLDs at a time or both the UBLDs as well as GFP-conjugates of only the two UBLDs and Myo21 tail lacking the two UBLDs and separately expressed them in the Leishmania cells. Our results show that unlike Myo21-GFP, Myo21-GFP constructs lacking either one or both the UBLDs failed to concentrate and co-distribute with actin in the proximal region of the flagellum. Nevertheless, the GFP conjugate of only the two UBLDs was found to predominantly localize to the flagellum base. Additionally, the cells that expressed only one or both the UBLDs-deleted Myo21-GFP constructs possessed shorter flagellum and displayed slower motility, compared to Myo21-GFP expressing cells. Further, the intracellular vesicle transport and cell growth were severely impaired in the cells that expressed both the UBLDs deleted Myo21-GFP construct, but in contrast, virtually no effect was observed on the intracellular vesicle transport and growth in the cells that expressed single UBLD deleted mutant proteins. Moreover, the observed slower growth of both the UBLDs-deleted Myo21-GFP expressing cells was primarily due to delayed G2/M phase caused by aberrant nuclear and daughter cell segregation during their cell division process. These results taken together clearly reveal that the presence of UBLDs in Myo21 are essentially required for its predominant localization to the flagellum base, and perhaps also in its involvement in the flagellum assembly and cell division. Possible role of UBLDs in involvement of Myo21 during Leishmania flagellum assembly and cell cycle is discussed.


Assuntos
Flagelos/metabolismo , Leishmania donovani/fisiologia , Miosinas/química , Miosinas/metabolismo , Actinas/metabolismo , Ciclo Celular , Proteínas de Fluorescência Verde/genética , Proteínas de Fluorescência Verde/metabolismo , Leishmania donovani/crescimento & desenvolvimento , Leishmania donovani/metabolismo , Miosinas/genética , Domínios Proteicos , Proteínas de Protozoários/metabolismo , Proteínas Recombinantes/metabolismo , Deleção de Sequência , Vesículas Transportadoras/metabolismo , Ubiquitina/metabolismo
14.
Nat Commun ; 11(1): 2041, 2020 04 27.
Artigo em Inglês | MEDLINE | ID: mdl-32341341

RESUMO

How complex, multi-component macromolecular machines evolved remains poorly understood. Here we reveal the evolutionary origins of the chemosensory machinery that controls flagellar motility in Escherichia coli. We first identify ancestral forms still present in Vibrio cholerae, Pseudomonas aeruginosa, Shewanella oneidensis and Methylomicrobium alcaliphilum, characterizing their structures by electron cryotomography and finding evidence that they function in a stress response pathway. Using bioinformatics, we trace the evolution of the system through γ-Proteobacteria, pinpointing key evolutionary events that led to the machine now seen in E. coli. Our results suggest that two ancient chemosensory systems with different inputs and outputs (F6 and F7) existed contemporaneously, with one (F7) ultimately taking over the inputs and outputs of the other (F6), which was subsequently lost.


Assuntos
Substâncias Macromoleculares/química , Methylococcaceae/fisiologia , Pseudomonas aeruginosa/fisiologia , Shewanella/fisiologia , Vibrio cholerae/fisiologia , Evolução Biológica , Quimiotaxia , Biologia Computacional , Tomografia com Microscopia Eletrônica , Escherichia coli/fisiologia , Flagelos/fisiologia , Gammaproteobacteria/fisiologia , Genoma Bacteriano , Proteínas Quimiotáticas Aceptoras de Metil/química , Filogenia
15.
Am J Physiol Cell Physiol ; 318(6): C1092-C1106, 2020 06 01.
Artigo em Inglês | MEDLINE | ID: mdl-32233951

RESUMO

Intraflagellar transport (IFT) is an evolutionarily conserved mechanism that is indispensable for the formation and maintenance of cilia and flagella; however, the implications and functions of IFT81 remain unknown. In this study, we disrupted IFT81 expression in male germ cells starting from the spermatocyte stage. As a result, homozygous mutant males were completely infertile and displayed abnormal sperm parameters. In addition to oligozoospermia, spermatozoa presented dysmorphic and nonfunctional flagella. Histological examination of testes from homozygous mutant mice revealed abnormal spermiogenesis associated with sloughing of germ cells and the presence of numerous multinucleated giant germ cells (symblasts) in the lumen of seminiferous tubules and epididymis. Moreover, only few elongated spermatids and spermatozoa were seen in analyzed cross sections. Transmission electron microscopy showed a complete disorganization of the axoneme and para-axonemal structures such as the mitochondrial sheath, fibrous sheath, and outer dense fibers. In addition, numerous vesicles that contain unassembled microtubules were observed within developing spermatids. Acrosome structure analysis showed normal appearance, thus excluding a crucial role of IFT81 in acrosome biogenesis. These observations showed that IFT81 is an important member of the IFT process during spermatogenesis and that its absence is associated with abnormal flagellum formation leading to male infertility. The expression levels of several IFT components in testes, including IFT20, IFT25, IFT27, IFT57, IFT74, and IFT88, but not IFT140, were significantly reduced in homozygous mutant mice. Overall, our study demonstrates that IFT81 plays an essential role during spermatogenesis by modulating the assembly and elongation of the sperm flagella.


Assuntos
Fertilidade , Flagelos/metabolismo , Infertilidade Masculina/metabolismo , Proteínas Associadas aos Microtúbulos/metabolismo , Proteínas Musculares/metabolismo , Espermatócitos/metabolismo , Espermatogênese , Testículo/metabolismo , Animais , Proteínas do Citoesqueleto/metabolismo , Epididimo/metabolismo , Epididimo/fisiopatologia , Epididimo/ultraestrutura , Flagelos/ultraestrutura , Infertilidade Masculina/genética , Infertilidade Masculina/patologia , Infertilidade Masculina/fisiopatologia , Masculino , Camundongos Endogâmicos C57BL , Camundongos Knockout , Proteínas Associadas aos Microtúbulos/deficiência , Proteínas Associadas aos Microtúbulos/genética , Proteínas Musculares/deficiência , Proteínas Musculares/genética , Transdução de Sinais , Contagem de Espermatozoides , Motilidade Espermática , Espermatócitos/ultraestrutura , Testículo/fisiopatologia , Testículo/ultraestrutura
16.
Proc Natl Acad Sci U S A ; 117(16): 8941-8947, 2020 04 21.
Artigo em Inglês | MEDLINE | ID: mdl-32241888

RESUMO

The bacterial flagellum is an amazing nanomachine. Understanding how such complex structures arose is crucial to our understanding of cellular evolution. We and others recently reported that in several Gammaproteobacterial species, a relic subcomplex comprising the decorated P and L rings persists in the outer membrane after flagellum disassembly. Imaging nine additional species with cryo-electron tomography, here, we show that this subcomplex persists after flagellum disassembly in other phyla as well. Bioinformatic analyses fail to show evidence of any recent horizontal transfers of the P- and L-ring genes, suggesting that this subcomplex and its persistence is an ancient and conserved feature of the flagellar motor. We hypothesize that one function of the P and L rings is to seal the outer membrane after motor disassembly.


Assuntos
Bactérias/genética , Proteínas da Membrana Bacteriana Externa/genética , Proteínas de Bactérias/genética , Flagelos/genética , Especiação Genética , Bactérias/citologia , Bactérias/metabolismo , Membrana Externa Bacteriana/metabolismo , Membrana Externa Bacteriana/ultraestrutura , Proteínas da Membrana Bacteriana Externa/metabolismo , Proteínas de Bactérias/metabolismo , Biologia Computacional , Microscopia Crioeletrônica , Tomografia com Microscopia Eletrônica , Flagelos/metabolismo , Genes Bacterianos , Filogenia
17.
PLoS Genet ; 16(3): e1008561, 2020 03.
Artigo em Inglês | MEDLINE | ID: mdl-32134924

RESUMO

Intraflagellar transport (IFT) is required for ciliary assembly and maintenance. While disruption of IFT may trigger ciliary disassembly, we show here that IFT mediated transport of a CDK-like kinase ensures proper ciliary disassembly. Mutations in flagellar shortening 2 (FLS2), encoding a CDK-like kinase, lead to retardation of cilia resorption and delay of cell cycle progression. Stimulation for ciliary disassembly induces gradual dephosphorylation of FLS2 accompanied with gradual inactivation. Loss of FLS2 or its kinase activity induces early onset of kinesin13 phosphorylation in cilia. FLS2 is predominantly localized in the cell body, however, it is transported to cilia upon induction of ciliary disassembly. FLS2 directly interacts with IFT70 and loss of this interaction inhibits its ciliary transport, leading to dysregulation of kinesin13 phosphorylation and retardation of ciliary disassembly. Thus, this work demonstrates that IFT plays active roles in controlling proper ciliary disassembly by transporting a protein kinase to cilia to regulate a microtubule depolymerizer.


Assuntos
Proteínas de Arabidopsis/metabolismo , Proteína Quinase CDC2/metabolismo , Chlamydomonas/metabolismo , Cílios/metabolismo , Proteínas de Plantas/metabolismo , Proteínas Quinases/metabolismo , Transporte Biológico/fisiologia , Ciclo Celular/fisiologia , Flagelos/metabolismo , Fosforilação/fisiologia , Plantas Geneticamente Modificadas/metabolismo , Transdução de Sinais/fisiologia
18.
PLoS Genet ; 16(3): e1008703, 2020 03.
Artigo em Inglês | MEDLINE | ID: mdl-32176702

RESUMO

The assembly status of the V. cholerae flagellum regulates biofilm formation, suggesting that the bacterium senses a lack of movement to commit to a sessile lifestyle. Motility and biofilm formation are inversely regulated by the second messenger molecule cyclic dimeric guanosine monophosphate (c-di-GMP). Therefore, we sought to define the flagellum-associated c-di-GMP-mediated signaling pathways that regulate the transition from a motile to a sessile state. Here we report that elimination of the flagellum, via loss of the FlaA flagellin, results in a flagellum-dependent biofilm regulatory (FDBR) response, which elevates cellular c-di-GMP levels, increases biofilm gene expression, and enhances biofilm formation. The strength of the FDBR response is linked with status of the flagellar stator: it can be reversed by deletion of the T ring component MotX, and reduced by mutations altering either the Na+ binding ability of the stator or the Na+ motive force. Absence of the stator also results in reduction of mannose-sensitive hemagglutinin (MSHA) pilus levels on the cell surface, suggesting interconnectivity of signal transduction pathways involved in biofilm formation. Strains lacking flagellar rotor components similarly launched an FDBR response, however this was independent of the status of assembly of the flagellar stator. We found that the FDBR response requires at least three specific diguanylate cyclases that contribute to increased c-di-GMP levels, and propose that activation of biofilm formation during this response relies on c-di-GMP-dependent activation of positive regulators of biofilm production. Together our results dissect how flagellum assembly activates c-di-GMP signaling circuits, and how V. cholerae utilizes these signals to transition from a motile to a sessile state.


Assuntos
Biofilmes/crescimento & desenvolvimento , GMP Cíclico/análogos & derivados , Flagelos/metabolismo , Proteínas de Bactérias/genética , GMP Cíclico/metabolismo , Proteínas de Escherichia coli/genética , Proteínas de Escherichia coli/metabolismo , Fímbrias Bacterianas/metabolismo , Flagelos/fisiologia , Regulação Bacteriana da Expressão Gênica/genética , Fósforo-Oxigênio Liases/genética , Fósforo-Oxigênio Liases/metabolismo , Sistemas do Segundo Mensageiro/fisiologia , Transdução de Sinais/fisiologia , Vibrio cholerae/genética , Vibrio cholerae/metabolismo
19.
PLoS Genet ; 16(3): e1008664, 2020 03.
Artigo em Inglês | MEDLINE | ID: mdl-32203505

RESUMO

Motile cilia/flagella are essential for swimming and generating extracellular fluid flow in eukaryotes. Motile cilia harbor a 9+2 arrangement consisting of nine doublet microtubules with dynein arms at the periphery and a pair of singlet microtubules at the center (central pair). In the central system, the radial spoke has a T-shaped architecture and regulates the motility and motion pattern of cilia. Recent cryoelectron tomography data reveal three types of radial spokes (RS1, RS2, and RS3) in the 96 nm axoneme repeat unit; however, the molecular composition of the third radial spoke, RS3 is unknown. In human pathology, it is well known mutation of the radial spoke head-related genes causes primary ciliary dyskinesia (PCD) including respiratory defect and infertility. Here, we describe the role of the primary ciliary dyskinesia protein Rsph4a in the mouse motile cilia. Cryoelectron tomography reveals that the mouse trachea cilia harbor three types of radial spoke as with the other vertebrates and that all triplet spoke heads are lacking in the trachea cilia of Rsph4a-deficient mice. Furthermore, observation of ciliary movement and immunofluorescence analysis indicates that Rsph4a contributes to the generation of the planar beating of motile cilia by building the distal architecture of radial spokes in the trachea, the ependymal tissues, and the oviduct. Although detailed mechanism of RSs assembly remains unknown, our results suggest Rsph4a is a generic component of radial spoke heads, and could explain the severe phenotype of human PCD patients with RSPH4A mutation.


Assuntos
Cílios/metabolismo , Proteínas do Citoesqueleto/metabolismo , Proteínas do Tecido Nervoso/metabolismo , Animais , Axonema/genética , Axonema/metabolismo , Cílios/genética , Transtornos da Motilidade Ciliar/genética , Transtornos da Motilidade Ciliar/metabolismo , Proteínas do Citoesqueleto/genética , Dineínas/metabolismo , Feminino , Flagelos/genética , Flagelos/metabolismo , Humanos , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Microtúbulos/metabolismo , Mutação , Proteínas do Tecido Nervoso/genética
20.
Nature ; 578(7796): 588-592, 2020 02.
Artigo em Inglês | MEDLINE | ID: mdl-32076271

RESUMO

Elucidating elementary mechanisms that underlie bacterial diversity is central to ecology1,2 and microbiome research3. Bacteria are known to coexist by metabolic specialization4, cooperation5 and cyclic warfare6-8. Many species are also motile9, which is studied in terms of mechanism10,11, benefit12,13, strategy14,15, evolution16,17 and ecology18,19. Indeed, bacteria often compete for nutrient patches that become available periodically or by random disturbances2,20,21. However, the role of bacterial motility in coexistence remains unexplored experimentally. Here we show that-for mixed bacterial populations that colonize nutrient patches-either population outcompetes the other when low in relative abundance. This inversion of the competitive hierarchy is caused by active segregation and spatial exclusion within the patch: a small fast-moving population can outcompete a large fast-growing population by impeding its migration into the patch, while a small fast-growing population can outcompete a large fast-moving population by expelling it from the initial contact area. The resulting spatial segregation is lost for weak growth-migration trade-offs and a lack of virgin space, but is robust to population ratio, density and chemotactic ability, and is observed in both laboratory and wild strains. These findings show that motility differences and their trade-offs with growth are sufficient to promote diversity, and suggest previously undescribed roles for motility in niche formation and collective expulsion-containment strategies beyond individual search and survival.


Assuntos
Escherichia coli/fisiologia , Interações Microbianas , Movimento , Biodiversidade , Escherichia coli/citologia , Escherichia coli/crescimento & desenvolvimento , Escherichia coli/isolamento & purificação , Fezes/microbiologia , Flagelos/fisiologia , Modelos Biológicos , Análise Espacial
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