scholarly journals Architecture and regulation of an enterobacterial cellulose secretion system

2021 ◽  
Vol 7 (5) ◽  
pp. eabd8049
Author(s):  
Wiem Abidi ◽  
Samira Zouhir ◽  
Meryem Caleechurn ◽  
Stéphane Roche ◽  
Petya Violinova Krasteva
Keyword(s):  
Functional Data ◽  
Second Messenger ◽  
Secretion System ◽  
Low Resolution ◽  
Free Living ◽  
Inner Membrane ◽  
Layered Architecture ◽  
Subunit Stoichiometry

Many free-living and pathogenic enterobacteria secrete biofilm-promoting cellulose using a multicomponent, envelope-embedded Bcs secretion system under the control of intracellular second messenger c-di-GMP. The molecular understanding of system assembly and cellulose secretion has been largely limited to the crystallographic studies of a distantly homologous BcsAB synthase tandem and a low-resolution reconstruction of an assembled macrocomplex that encompasses most of the inner membrane and cytosolic subunits and features an atypical layered architecture. Here, we present cryo-EM structures of the assembled Bcs macrocomplex, as well as multiple crystallographic snapshots of regulatory Bcs subcomplexes. The structural and functional data uncover the mechanism of asymmetric secretion system assembly and periplasmic crown polymerization and reveal unexpected subunit stoichiometry, multisite c-di-GMP recognition, and ATP-dependent regulation.

First report of developmental changes inside the eggs of the Chinese freshwater crab, Sinopotamon yangtsekiense Bott, 1967 (Potamoidea, Potamidae), with comments on its evolutionary significance

2010 ◽  
Vol 79 (2) ◽  
pp. 79-84 ◽  
Author(s):  
Junzeng Xue ◽  
Yan Liu ◽  
Neil Cumberlidge ◽  
Huixian Wu
Keyword(s):  
Outer Membrane ◽  
Morphological Changes ◽  
Zhejiang Province ◽  
Developmental Changes ◽  
Evolutionary Significance ◽  
Freshwater Crab ◽  
Yolk Mass ◽  
Free Living ◽  
Inner Membrane ◽  
Larval Stages

This paper focuses on the developmental changes that take place inside the eggs of the semi-terrestrial freshwater crab, Sinopotamon yangtsekiense, from Qiantang River in Zhejiang Province, China. The egg consists of two layers, a thick outer membrane and a thin inner membrane that encloses the fluidfilled embryonic sac. Development in this species took up to 77 days, after which the free-living juvenile hatchling crab emerged from the egg. During development the embryo underwent a series of morphological changes that corresponded to the free-living larval stages of marine crabs, and the yolk mass decreased in size and changed color (from creamy pale yellow, to orange, and finally grey). The eggs remained attached to the pleopods in the female’s abdominal brood pouch during development and showed a great deal of independence from water. Embryos developed normally whether they were immersed in water or in air. The implications of this adaptation for freshwater crab evolution are discussed.

A high-conductance cation channel from the inner membrane of the free-living soil bacteria Rhizobium etli

2010 ◽  
Vol 192 (7) ◽  
pp. 595-602
Author(s):  
Daniel Balleza ◽  
Carmen Quinto ◽  
David Elias ◽  
Froylán Gómez-Lagunas
Keyword(s):  
Soil Bacteria ◽  
Cation Channel ◽  
Rhizobium Etli ◽  
Free Living ◽  
Inner Membrane ◽  
High Conductance

scholarly journals Agrobacterium tumefaciens VirB9, an Outer-Membrane-Associated Component of a Type IV Secretion System, Regulates Substrate Selection and T-Pilus Biogenesis

2005 ◽  
Vol 187 (10) ◽  
pp. 3486-3495 ◽  
Author(s):  
Simon J. Jakubowski ◽  
Eric Cascales ◽  
Vidhya Krishnamoorthy ◽  
Peter J. Christie
Keyword(s):  
Agrobacterium Tumefaciens ◽  
Outer Membrane ◽  
Secretion System ◽  
Type Iv Secretion ◽  
Type Iv Secretion System ◽  
Substrate Selection ◽  
Inner Membrane ◽  
Protein Substrates ◽  
Type Iv ◽  
Pilus Biogenesis

ABSTRACT Agrobacterium tumefaciens translocates DNA and protein substrates between cells via a type IV secretion system (T4SS) whose channel subunits include the VirD4 coupling protein, VirB11 ATPase, VirB6, VirB8, VirB2, and VirB9. In this study, we used linker insertion mutagenesis to characterize the contribution of the outer-membrane-associated VirB9 to assembly and function of the VirB/D4 T4SS. Twenty-five dipeptide insertion mutations were classified as permissive for intercellular substrate transfer (Tra+), completely transfer defective (Tra−), or substrate discriminating, e.g., selectively permissive for transfer only of the oncogenic transfer DNA and the VirE2 protein substrates or of a mobilizable IncQ plasmid substrate. Mutations inhibiting transfer of DNA substrates did not affect formation of close contacts of the substrate with inner membrane channel subunits but blocked formation of contacts with the VirB2 and VirB9 channel subunits, which is indicative of a defect in assembly or function of the distal portion of the secretion channel. Several mutations in the N- and C-terminal regions disrupted VirB9 complex formation with the outer-membrane-associated lipoprotein VirB7 or the inner membrane energy sensor VirB10. Several VirB9.i2-producing Tra+ strains failed to elaborate T pilus at detectable levels (Pil−), and three such Tra+ Pil− mutant strains were rendered Tra− upon deletion of virB2, indicating that the cellular form of pilin protein is essential for substrate translocation. Our findings, together with computer-based analyses, support a model in which distinct domains of VirB9 contribute to substrate selection and translocation, establishment of channel subunit contacts, and T-pilus biogenesis.

scholarly journals Inner-membrane GspF of the bacterial type II secretion system is a dimeric adaptor mediating pseudopilus biogenesis

2018 ◽  
Author(s):  
Wouter Van Putte ◽  
Tatjana De Vos ◽  
Wim Van Den Broeck ◽  
Henning Stahlberg ◽  
Misha Kudryashev ◽  
...  
Keyword(s):  
Antibiotic Resistance ◽  
Virulence Factors ◽  
Protein Complex ◽  
Secretion System ◽  
Structural Basis ◽  
Type Ii Secretion ◽  
Type Ii ◽  
Secretion Systems ◽  
Inner Membrane ◽  
Type Ii Secretion System

AbstractThe type II secretion system (T2SS), a protein complex spanning the bacterial envelope, is pivotal to bacterial pathogenicity. Central to T2SS function is the extrusion of protein cargos from the periplasm into the extracellular environment mediated by a pseudopilus and motorized by a cytosolic ATPase. GspF, an inner-membrane component of T2SS has long been considered to be a key player in this process, yet the structural basis of its role had remained elusive. Here, we employed single-particle electron microscopy based on XcpS (GspF) from the T2SS of pathogenicP. aeruginosastabilized by a nanobody, to show that XcpS adopts a dimeric structure mediated by its transmembrane helices. This assembly matches in terms of overall organization and dimensions the basal inner-membrane cassette of a T2SS machinery. Thus, GspF is poised to serve as an adaptor involved in the mediation of propeller-like torque generated by the motor ATPase to the secretion pseudopilus.Non-technical author summaryAntibiotic resistance by bacteria imposes a worldwide threat that can only be overcome through a multi-front approach: preventive actions and the parallel development of novel molecular strategies to combat antibiotic resistance mechanisms. One such strategy might focus on antivirulence drugs that prevent host invasion and spreading by pathogenic bacteria, without shutting down essential functions related to bacterial survival. The rationale behind such an approach is that it might limit selective pressure leading to slower evolutionary rates of resistant bacterial strains. Bacterial secretion systems are an appropriate target for such therapeutic approaches as their impairment will inhibit the secretion of a multitude of virulence factors. This study focuses on the structural characterization of one of the proteins residing in the inner-membrane cassette of the type II secretion system (T2SS), a multi-protein complex in multiple opportunistic pathogens that secretes virulence factors. The targeted protein is essential for the assembly of the pseudopilus, a rod-like supramolecular structure that propels the secretion of virulence factors by pathogenic Gram-negative bacteria. Our study crucially complements growing evidence supporting a rotational assembly model of the pseudopilus and contributes to a better understanding of the functioning of the T2SS and the related secretion systems. We envisage that such knowledge will facilitate targeting of these systems for therapeutic purposes.

scholarly journals SecA—a New Twist in the Tale

2016 ◽  
Vol 199 (2) ◽  
Author(s):  
Ian Collinson
Keyword(s):  
Secretion System ◽  
Protein Export ◽  
Inner Membrane ◽  
Link Type ◽  
Sec System ◽  
Bacterial Secretion ◽  
Bacterial Secretion System ◽  
Timely Reminder

ABSTRACT A paper published in this issue of the Journal of Bacteriology (D. Huber, M. Jamshad, R. Hanmer, D. Schibich, K. Döring, I. Marcomini, G. Kramer, and B. Bukau, J Bacteriol 199:e0622-16, 2017, https://doi.org/10.1128/JB.00622-16 ) provides us with a timely reminder that all is not as clear as we had previously thought in the general bacterial secretion system. The paper describes a new mode of secretion through the Sec system—“uncoupled cotranslocation”—for the passage of proteins across the bacterial inner membrane and suggests that we might rethink the nature and mechanism of the targeting and transport steps toward protein export.

scholarly journals Cyclic di-GMP signaling controlling the free-living lifestyle of alpha-proteobacterial rhizobia

2020 ◽  
Vol 401 (12) ◽  
pp. 1335-1348
Author(s):  
Elizaveta Krol ◽  
Simon Schäper ◽  
Anke Becker
Keyword(s):  
Regulatory Network ◽  
Host Plants ◽  
Sinorhizobium Meliloti ◽  
Second Messenger ◽  
Diazotrophic Bacteria ◽  
Free Living ◽  
Environmental Adaptations ◽  
Leguminous Host

AbstractCyclic-di-GMP (c-di-GMP) is a ubiquitous bacterial second messenger which has been associated with a motile to sessile lifestyle switch in many bacteria. Here, we review recent insights into c-di-GMP regulated processes related to environmental adaptations in alphaproteobacterial rhizobia, which are diazotrophic bacteria capable of fixing nitrogen in symbiosis with their leguminous host plants. The review centers on Sinorhizobium meliloti, which in the recent years was intensively studied for its c-di-GMP regulatory network.

scholarly journals The evolutionary origin of host association in an ancient bacterial clade

2021 ◽  
Author(s):  
Max E. Schön ◽  
Joran Martijn ◽  
Julian Vosseberg ◽  
Stephan Köstlbacher ◽  
Thijs J. G. Ettema
Keyword(s):  
Secretion System ◽  
Type Iv Secretion ◽  
Type Iv Secretion System ◽  
Ancestral Genome ◽  
Bacterial Symbionts ◽  
Host Association ◽  
Free Living ◽  
Type Iv ◽  
Genome Content ◽  
Bacterial Clade

AbstractThe evolution of obligate host-association of bacterial symbionts and pathogens remains poorly understood. The Rickettsiales represent an order of obligate alphaproteobacterial endosymbionts and parasites that infect a wide variety of eukaryotic hosts, including humans, livestock, insects and protists. Induced by their host-associated lifestyle, Rickettsiales genomes have undergone reductive evolution, leading to small, AT-rich genomes with limited metabolic capacities. We describe several genomes of deep-branching, environmental alphaproteobacteria that branch basal to previously sampled Rickettsiales, and whose genome content are reminiscent of free-living and biofilm-associated lifestyles. Ancestral genome content reconstruction across the Rickettsiales tree revealed that the free-living to host-association transition of this group occurred more recently than previously anticipated, and likely involved the repurposing of a type IV secretion system.One-Sentence SummaryDeep-branching Rickettsiales provide insights into the evolution of obligate host-associated lifestyle

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