scholarly journals Structure of Vibrio phage XM1, a simple contractile DNA injection machine

2021 ◽  
Author(s):  
Zhiqing Wang ◽  
Andrei Fokine ◽  
Xinwu Guo ◽  
Wen Jiang ◽  
Michael G Rossmann ◽  
...  
Keyword(s):  
Conformational Changes ◽  
Pathogenic Bacteria ◽  
Virus Assembly ◽  
Cell Envelope ◽  
Neck Region ◽  
Secretion Systems ◽  
Atomic Structures ◽  
Dna Injection ◽  
Minimum Requirements ◽  
Cell Envelopes

Antibiotic resistance poses a growing risk to public health requiring new tools to combat pathogenic bacteria. Contractile injection systems, including bacteriophage tails, pyocins, and bacterial type VI secretion systems, can efficiently penetrate cell envelopes and become potential antibacterial agents. Bacteriophage XM1 is a dsDNA virus belonging to the Myoviridae family and infecting Vibrio bacteria. The XM1 virion, made of 18 different proteins, consists of an icosahedral head and a contractile tail, terminated with a baseplate. Here we report cryo-EM reconstructions of all components of the XM1 virion and describe atomic structures of 14 XM1 proteins. The XM1 baseplate is composed of a central hub surrounded by six wedge modules to which twelve spikes are attached. The XM1 tail contains a fewer number of smaller proteins compared with other reported phage baseplates, depicting the minimum requirements for building an effective cell-envelope-penetrating machine. We describe the tail sheath structure in the pre-infection post-infection states and its conformational changes during infection. In addition, we report, for the first time, the in situ structure of the phage neck region to near-atomic resolution. Based on these structures, we propose mechanisms of virus assembly and infection.

scholarly journals Evolutionary Remodeling of the Cell Envelope in Bacteria of the Planctomycetes Phylum

2020 ◽  
Vol 12 (9) ◽  
pp. 1528-1548
Author(s):  
Mayank Mahajan ◽  
Christian Seeger ◽  
Benjamin Yee ◽  
Siv G E Andersson
Keyword(s):  
Cell Wall ◽  
Electron Tomography ◽  
Cell Envelope ◽  
Outer Membrane Proteins ◽  
Cell Wall Proteins ◽  
Secretion Systems ◽  
Peptidoglycan Biosynthesis ◽  
Multiple Copies ◽  
Cellular Phenotypes ◽  
Cell Envelopes

Abstract Bacteria of the Planctomycetes phylum have many unique cellular features, such as extensive membrane invaginations and the ability to import macromolecules. These features raise intriguing questions about the composition of their cell envelopes. In this study, we have used microscopy, phylogenomics, and proteomics to examine the composition and evolution of cell envelope proteins in Tuwongella immobilis and other members of the Planctomycetes. Cryo-electron tomography data indicated a distance of 45 nm between the inner and outer membranes in T. immobilis. Consistent with the wide periplasmic space, our bioinformatics studies showed that the periplasmic segments of outer-membrane proteins in type II secretion systems are extended in bacteria of the order Planctomycetales. Homologs of two highly abundant cysteine-rich cell wall proteins in T. immobilis were identified in all members of the Planctomycetales, whereas genes for peptidoglycan biosynthesis and cell elongation have been lost in many members of this bacterial group. The cell wall proteins contain multiple copies of the YTV motif, which is the only domain that is conserved and unique to the Planctomycetales. Earlier diverging taxa in the Planctomycetes phylum contain genes for peptidoglycan biosynthesis but no homologs to the YTV cell wall proteins. The major remodeling of the cell envelope in the ancestor of the Planctomycetales coincided with the emergence of budding and other unique cellular phenotypes. The results have implications for hypotheses about the process whereby complex cellular features evolve in bacteria.

scholarly journals Effects of rhodomyrtone on Gram-positive bacterial tubulin homologue FtsZ

PeerJ ◽  
2017 ◽  
Vol 5 ◽  
pp. e2962 ◽  
Author(s):  
Dennapa Saeloh ◽  
Michaela Wenzel ◽  
Thanyada Rungrotmongkol ◽  
Leendert Willem Hamoen ◽  
Varomyalin Tipmanee ◽  
...  
Keyword(s):  
Conformational Changes ◽  
Pathogenic Bacteria ◽  
Cell Envelope ◽  
Docking Study ◽  
Bacterial Cell Division ◽  
Molecular Docking Study ◽  
Gram Positive ◽  
Ligand Free

Rhodomyrtone, a natural antimicrobial compound, displays potent activity against many Gram-positive pathogenic bacteria, comparable to last-defence antibiotics including vancomycin and daptomycin. Our previous studies pointed towards effects of rhodomyrtone on the bacterial membrane and cell wall. In addition, a recent molecular docking study suggested that the compound could competitively bind to the main bacterial cell division protein FtsZ. In this study, we applied a computational approach (in silico),in vitro, andin vivoexperiments to investigate molecular interactions of rhodomyrtone with FtsZ. Using molecular simulation, FtsZ conformational changes were observed in both (S)- and (R)-rhodomyrtone binding states, compared with the three natural states of FtsZ (ligand-free, GDP-, and GTP-binding states). Calculations of free binding energy showed a higher affinity of FtsZ to (S)-rhodomyrtone (−35.92 ± 0.36 kcal mol−1) than the GDP substrate (−23.47 ± 0.25 kcal mol−1) while less affinity was observed in the case of (R)-rhodomyrtone (−18.11 ± 0.11 kcal mol−1).In vitroexperiments further revealed that rhodomyrtone reduced FtsZ polymerization by 36% and inhibited GTPase activity by up to 45%. However, the compound had no effect on FtsZ localization inBacillus subtilisat inhibitory concentrations and cells also did not elongate after treatment. Higher concentrations of rhodomyrtone did affect localization of FtsZ and also affected localization of its membrane anchor proteins FtsA and SepF, showing that the compound did not specifically inhibit FtsZ but rather impaired multiple divisome proteins. Furthermore, a number of cells adopted a bean-like shape suggesting that rhodomyrtone possibly possesses further targets involved in cell envelope synthesis and/or maintenance.

Two-step and one-step secretion mechanisms in Gram-negative bacteria: contrasting the type IV secretion system and the chaperone-usher pathway of pilus biogenesis

2010 ◽  
Vol 425 (3) ◽  
pp. 475-488 ◽  
Author(s):  
Ana Toste Rêgo ◽  
Vidya Chandran ◽  
Gabriel Waksman
Keyword(s):  
Pathogenic Bacteria ◽  
Cell Envelope ◽  
Gram Negative Bacteria ◽  
Secretion Systems ◽  
Extracellular Medium ◽  
Gram Negative ◽  
Type Iv ◽  
Pilus Biogenesis ◽  
One Step ◽  
Step Mechanism

Gram-negative bacteria have evolved diverse secretion systems/machineries to translocate substrates across the cell envelope. These various machineries fulfil a wide variety of functions but are also essential for pathogenic bacteria to infect human or plant cells. Secretion systems, of which there are seven, utilize one of two secretion mechanisms: (i) the one-step mechanism, whereby substrates are translocated directly from the bacterial cytoplasm to the extracellular medium or into the eukaryotic target cell; (ii) the two-step mechanism, whereby substrates are first translocated across the bacterial inner membrane; once in the periplasm, substrates are targeted to one of the secretion systems that mediate transport across the outer membrane and released outside the bacterial cell. The present review provides an example for each of these two classes of secretion systems and contrasts the various solutions evolved to secrete substrates.

scholarly journals Assessing the Molecular Targets and Mode of Action of Furanone C-30 on Pseudomonas aeruginosa Quorum Sensing

Molecules ◽  
2021 ◽  
Vol 26 (6) ◽  
pp. 1620
Author(s):  
Victor Markus ◽  
Karina Golberg ◽  
Kerem Teralı ◽  
Nazmi Ozer ◽  
Esti Kramarsky-Winter ◽  
...  
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Antibiotic Resistance ◽  
Quorum Sensing ◽  
Conformational Changes ◽  
Mode Of Action ◽  
Pathogenic Bacteria ◽  
Molecular Targets ◽  
Resistant Bacteria ◽  
Public Healthcare ◽  
C 30

Quorum sensing (QS), a sophisticated system of bacterial communication that depends on population density, is employed by many pathogenic bacteria to regulate virulence. In view of the current reality of antibiotic resistance, it is expected that interfering with QS can address bacterial pathogenicity without stimulating the incidence of resistance. Thus, harnessing QS inhibitors has been considered a promising approach to overriding bacterial infections and combating antibiotic resistance that has become a major threat to public healthcare around the globe. Pseudomonas aeruginosa is one of the most frequent multidrug-resistant bacteria that utilize QS to control virulence. Many natural compounds, including furanones, have demonstrated strong inhibitory effects on several pathogens via blocking or attenuating QS. While the natural furanones show no activity against P. aeruginosa, furanone C-30, a brominated derivative of natural furanone compounds, has been reported to be a potent inhibitor of the QS system of the notorious opportunistic pathogen. In the present study, we assess the molecular targets and mode of action of furanone C-30 on P. aeruginosa QS system. Our results suggest that furanone C-30 binds to LasR at the ligand-binding site but fails to establish interactions with the residues crucial for the protein’s productive conformational changes and folding, thus rendering the protein dysfunctional. We also show that furanone C-30 inhibits RhlR, independent of LasR, suggesting a complex mechanism for the agent beyond what is known to date.

scholarly journals N 1 N 8-bis(γ-glutamyl)spermidine cross-linking in epidermal-cell envelopes. Comparison of cross-link levels in normal and psoriatic cell envelopes

1990 ◽  
Vol 271 (2) ◽  
pp. 305-308 ◽  
Author(s):  
N Martinet ◽  
S Beninati ◽  
T P Nigra ◽  
J E Folk
Keyword(s):  
Epidermal Cell ◽  
Skin Disease ◽  
Envelope Protein ◽  
Cell Envelope ◽  
Human Epidermis ◽  
Cross Linking ◽  
Cross Link ◽  
Gamma Glutamyl ◽  
Cell Envelopes ◽  
Isolated Cell

N1N8-Bis(gamma-glutamyl)spermidine was found in exhaustive proteolytic digests of isolated cell envelopes from human epidermis at levels comparable with those of epsilon-(gamma-glutamyl)lysine. Significantly higher than normal amounts of these compounds, particularly the bis(gamma-glutamyl)polyamine, were observed in envelopes from afflicted areas (scales) of psoriatic patients. These findings support the notions that N1N8-bis(gamma-glutamyl)spermidine, like epsilon-(gamma-glutamyl)lysine, functions in cell envelopes as an enzyme-generated protein cross-link and stabilizing force and that individuals with the chronic, recurrent skin disease, psoriasis, exhibit in involved epidermis abnormal cell-envelope-protein cross-linking.

scholarly journals THE CELL ENVELOPES OF TWO EXTREMELY HALOPHILIC BACTERIA

1963 ◽  
Vol 18 (3) ◽  
pp. 681-689 ◽  
Author(s):  
A. D. Brown ◽  
C. D. Shorey
Keyword(s):  
Single Unit ◽  
Cell Envelope ◽  
Halophilic Bacteria ◽  
Layered Compound ◽  
Halobacterium Halobium ◽  
Chemical Analyses ◽  
Unit Membrane ◽  
Thin Sections ◽  
Whole Cells ◽  
Cell Envelopes

The cell envelope of Halobacterium halobium was seen in thin sections of permanganate-fixed cells to consist of one membrane. This membrane appeared mostly as a unit membrane but in a few preparations it resembled a 5-layered compound membrane. The cell envelope of Halobacterium salinarium at high resolution was always seen as a 5-layered structure different in appearance from the apparent compound membrane of H. halobium. The "envelopes" which were isolated in 12.5 per cent NaCl from each organism were indistinguishable from each other in the electron microscope and comprised, in each case, a single unit membrane with an over-all thickness of about 110 A. Some chemical analyses were made of isolated membranes after freeing them from salt by precipitating and washing with trichloroacetic acid. Such precipitated membranes consisted predominantly of protein, with little carbohydrate and no peptido-aminopolysaccharide (mucopeptide). Sectioned whole cells of H. halobium contained intracellular electron-opaque structures of unknown function.

scholarly journals The presence and absence of periplasmic rings in bacterial flagellar motors correlates with stator type

eLife ◽  
2019 ◽  
Vol 8 ◽  
Author(s):  
Mohammed Kaplan ◽  
Debnath Ghosal ◽  
Poorna Subramanian ◽  
Catherine M Oikonomou ◽  
Andreas Kjaer ◽  
...  
Keyword(s):  
Legionella Pneumophila ◽  
Pathogenic Bacteria ◽  
Bioinformatics Analysis ◽  
Cell Envelope ◽  
Shewanella Oneidensis ◽  
Flagellar Motor ◽  
Flagellar Motors ◽  
A Cell ◽  
Animal Hosts

The bacterial flagellar motor, a cell-envelope-embedded macromolecular machine that functions as a cellular propeller, exhibits significant structural variability between species. Different torque-generating stator modules allow motors to operate in different pH, salt or viscosity levels. How such diversity evolved is unknown. Here, we use electron cryo-tomography to determine the in situ macromolecular structures of three Gammaproteobacteria motors: Legionella pneumophila, Pseudomonas aeruginosa, and Shewanella oneidensis, providing the first views of intact motors with dual stator systems. Complementing our imaging with bioinformatics analysis, we find a correlation between the motor’s stator system and its structural elaboration. Motors with a single H+-driven stator have only the core periplasmic P- and L-rings; those with dual H+-driven stators have an elaborated P-ring; and motors with Na+ or Na+/H+-driven stators have both their P- and L-rings embellished. Our results suggest an evolution of structural elaboration that may have enabled pathogenic bacteria to colonize higher-viscosity environments in animal hosts.

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

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

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.

scholarly journals A family of T6SS antibacterial effectors related to L,D-transpeptidases targets the Peptidoglycan

2020 ◽  
Vol 2 (7A) ◽  
Author(s):  
Stephanie Sibinelli de Sousa ◽  
Julia Takuno Hespanhol ◽  
Bruno Matsuyama ◽  
Stephane Mesnage ◽  
Gianlucca Nicastro ◽  
...  
Keyword(s):  
Cell Envelope ◽  
Point Mutations ◽  
Time Lapse ◽  
Secretion Systems ◽  
Bacterial Antagonism ◽  
New Family ◽  
Type Vi Secretion ◽  
Altered Cell ◽  
Bacterial Effectors ◽  
Insight Into

Type VI secretion systems (T6SSs) are contractile nanomachines widely used by bacteria to intoxicate competitors. Salmonella Typhimurium encodes a T6SS within the Salmonella pathogenicity island 6 (SPI-6) that is used during competition against species of the gut microbiota. We characterized a new SPI-6 T6SS antibacterial effector named Tlde1 (type VI L,D-transpeptidase effector 1). Tlde1 is toxic in target-cell periplasm and its toxicity is neutralized by co-expression with immunity protein Tldi1 (type VI L,D-transpeptidase immunity 1). Time-lapse microscopy revealed that intoxicated cells display altered cell division and lose cell envelope integrity. Bioinformatics analysis showed that Tlde1 is evolutionarily related to L,D-transpeptidases. Point mutations on conserved histidine121 and cysteine131 residues eliminated toxicity. Co-incubation of purified recombinant Tlde1 and peptidoglycan tetrapeptides showed that Tlde1 displays both L,D-carboxypeptidase activity by cleaving GM-tetrapeptides between meso-diaminopimelic acid3 and D-alanine4, and L,D-transpeptidase exchange activity by replacing D-alanine4 for a non-canonical D-amino acid. Tlde1 constitutes a new family of T6SS effectors widespread in Proteobacteria. This work increases our knowledge about the bacterial effectors used in interbacterial competitions and provides molecular insight into a new mechanism of bacterial antagonism.

scholarly journals The Rcs System in Enterobacteriaceae: Envelope Stress Responses and Virulence Regulation

2021 ◽  
Vol 12 ◽  
Author(s):  
Jiao Meng ◽  
Glenn Young ◽  
Jingyu Chen
Keyword(s):  
Stress Response ◽  
Stress Responses ◽  
Bacterial Infections ◽  
Pathogenic Bacteria ◽  
Cell Envelope ◽  
Regulatory System ◽  
Virulence Regulation ◽  
Bacterial Interaction ◽  
Envelope Stress

The bacterial cell envelope is a protective barrier at the frontline of bacterial interaction with the environment, and its integrity is regulated by various stress response systems. The Rcs (regulator of capsule synthesis) system, a non-orthodox two-component regulatory system (TCS) found in many members of the Enterobacteriaceae family, is one of the envelope stress response pathways. The Rcs system can sense envelope damage or defects and regulate the transcriptome to counteract stress, which is particularly important for the survival and virulence of pathogenic bacteria. In this review, we summarize the roles of the Rcs system in envelope stress responses (ESRs) and virulence regulation. We discuss the environmental and intrinsic sources of envelope stress that cause activation of the Rcs system with an emphasis on the role of RcsF in detection of envelope stress and signal transduction. Finally, the different regulation mechanisms governing the Rcs system’s control of virulence in several common pathogens are introduced. This review highlights the important role of the Rcs system in the environmental adaptation of bacteria and provides a theoretical basis for the development of new strategies for control, prevention, and treatment of bacterial infections.

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