scholarly journals Injectisome T3SS subunits as potential chaperones in the extracellular export of Pectobacterium carotovorum subsp. carotovorum bacteriocins Carocin S1 and Carocin S3 secreted via flagellar T3SS

2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Huang-Pin Wu ◽  
Reymund C. Derilo ◽  
Han-Ling Chen ◽  
Tzu-Rung Li ◽  
Ruchi Briam James S. Lagitnay ◽  
...  
Keyword(s):  
Type Iii Secretion ◽  
Insertional Mutagenesis ◽  
Plant Pathogens ◽  
Soft Rot ◽  
Economic Losses ◽  
Pectobacterium Carotovorum ◽  
Secretion Systems ◽  
Unique Type ◽  
Bacterial Flagellum ◽  
Type Iii

AbstractPectobacterium carotovorum subsp. carotovorum (Pcc) causes soft-rot disease in a wide variety of plants resulting in economic losses worldwide. It produces various types of bacteriocin to compete against related plant pathogens. Studies on how bacteriocins are extracellularly secreted are conducted to understand the mechanism of interbacterial competition. In this study, the secretion of the low-molecular-weight bacteriocins (LMWB) Carocin S1 and Carocin S3 produced by a multiple-bacteriocin producing strain of Pcc, 89-H-4, was investigated. Tn5 insertional mutagenesis was used to generate a mutant, TH22–6, incapable of LMWBs secretion. Sequence and homology analyses of the gene disrupted by transposon Tn5 insertion revealed that the gene sctT, an essential component of the injectisome type III secretion machinery (T3aSS), is required for the secretion of the bacteriocins. This result raised a question regarding the nature of the secretion mechanism of Pcc bacteriocins which was previously discovered to be secreted via T3bSS, a system that utilizes the bacterial flagellum for extracellular secretions. Our previous report has shown that bacteriocin Carocin S1 cannot be secreted by mutants that are defective of T3bSS-related genes such as flhA, flhC, flhD and fliC. We knocked out several genes making up the significant structural components of both T3aSS and T3bSS. The findings led us to hypothesize the potential roles of the T3aSS-related proteins, SctT, SctU and SctV, as flagellar T3SS chaperones in the secretion of Pcc bacteriocins. This current discovery and the findings of our previous study helped us to conceptualize a unique Type III secretion system for bacteriocin extracellular export which is a hybrid of the injectisome and flagellar secretion systems.

scholarly journals Injectisome T3SS Subunits As Potential Chaperones In The Extracellular Export of Pectobacterium Carotovorum Subsp. Carotovorum Bacteriocins Carocin S1 And Carocin S3 Secreted Via Flagellar T3SS

2021 ◽  
Author(s):  
Hang-Cheng Chen ◽  
Reymund C. Derilo ◽  
Han-Ling Chen ◽  
Tzu-Rung Li ◽  
Ruchi Briam James S. Lagitnay ◽  
...  
Keyword(s):  
Type Iii Secretion ◽  
Insertional Mutagenesis ◽  
Plant Pathogens ◽  
Soft Rot ◽  
Economic Losses ◽  
Pectobacterium Carotovorum ◽  
Secretion Systems ◽  
Unique Type ◽  
Bacterial Flagellum ◽  
Type Iii

Abstract Pectobacterium carotovorum subsp. carotovorum (Pcc) causes soft-rot disease in a wide variety of plants resulting in economic losses worldwide. It produces various types of bacteriocin to compete against related plant pathogens. Studies on how bacteriocins are extracellularly secreted are conducted to understand the mechanism of interbacterial competition. In this study, the secretion of the low-molecular-weight bacteriocins (LMWB) Carocin S1 and Carocin S3 produced by a multiple-bacteriocin producing strain of Pcc, 89-H-4, was investigated. Tn5 insertional mutagenesis was used to generate a mutant, TH22-6, incapable of LMWBs secretion. Sequence and homology analyses of the gene disrupted by transposon Tn5 insertion revealed that the gene sctT, an essential component of the injectisome type III secretion machinery (T3aSS), is required for the secretion of the bacteriocins. This result raised a question regarding the nature of the secretion mechanism of Pcc bacteriocins which was previously discovered to be secreted via T3bSS, a system that utilizes the bacterial flagellum for extracellular secretions. Our previous report has shown that bacteriocin Carocin S1 cannot be secreted by mutants that are defective of T3bSS-related genes such as flhA, flhC, flhD and fliC. We knocked out several genes making up the significant structural components of both T3aSS and T3bSS. The findings led us to hypothesize the potential roles of the T3aSS-related proteins, SctT, SctU and SctV, as flagellar T3SS chaperones in the secretion of Pcc bacteriocins. This current discovery and the findings of our previous study helped us to conceptualize a unique Type III secretion system for bacteriocin extracellular export which is a hybrid of the injectisome and flagellar secretion systems.

scholarly journals Bridging the Gap: Type III Secretion Systems in Plant-Beneficial Bacteria

2022 ◽  
Vol 10 (1) ◽  
pp. 187
Author(s):  
Antoine Zboralski ◽  
Adrien Biessy ◽  
Martin Filion
Keyword(s):  
Type Iii Secretion ◽  
Plant Pathogens ◽  
Plant Immunity ◽  
Effector Proteins ◽  
Secretion Systems ◽  
Beneficial Bacteria ◽  
Living Plant ◽  
Pseudomonas Spp ◽  
Type Iii ◽  
Type Iii Secretion Systems

Type III secretion systems (T3SSs) are bacterial membrane-embedded nanomachines translocating effector proteins into the cytoplasm of eukaryotic cells. They have been intensively studied for their important roles in animal and plant bacterial diseases. Over the past two decades, genome sequencing has unveiled their ubiquitous distribution in many taxa of Gram-negative bacteria, including plant-beneficial ones. Here, we discuss the distribution and functions of the T3SS in two agronomically important bacterial groups: the symbiotic nodule-forming nitrogen-fixing rhizobia and the free-living plant-beneficial Pseudomonas spp. In legume-rhizobia symbiosis, T3SSs and their cognate effectors play important roles, including the modulation of the plant immune response and the initiation of the nodulation process in some cases. In plant-beneficial Pseudomonas spp., the roles of T3SSs are not fully understood, but pertain to plant immunity suppression, biocontrol against eukaryotic plant pathogens, mycorrhization facilitation, and possibly resistance against protist predation. The diversity of T3SSs in plant-beneficial bacteria points to their important roles in multifarious interkingdom interactions in the rhizosphere. We argue that the gap in research on T3SSs in plant-beneficial bacteria must be bridged to better understand bacteria/eukaryotes rhizosphere interactions and to support the development of efficient plant-growth promoting microbial inoculants.

scholarly journals Type III Protein Secretion Systems in Bacterial Pathogens of Animals and Plants

1998 ◽  
Vol 62 (2) ◽  
pp. 379-433 ◽  
Author(s):  
Christoph J. Hueck
Keyword(s):  
Host Cell ◽  
Protein Secretion ◽  
Type Iii Secretion ◽  
Plant Pathogens ◽  
Host Cells ◽  
Secretion Systems ◽  
Type Iii ◽  
Type Iii Secretion Systems ◽  
Animal Pathogens ◽  
Type Iii Protein Secretion

SUMMARY Various gram-negative animal and plant pathogens use a novel, sec-independent protein secretion system as a basic virulence mechanism. It is becoming increasingly clear that these so-called type III secretion systems inject (translocate) proteins into the cytosol of eukaryotic cells, where the translocated proteins facilitate bacterial pathogenesis by specifically interfering with host cell signal transduction and other cellular processes. Accordingly, some type III secretion systems are activated by bacterial contact with host cell surfaces. Individual type III secretion systems direct the secretion and translocation of a variety of unrelated proteins, which account for species-specific pathogenesis phenotypes. In contrast to the secreted virulence factors, most of the 15 to 20 membrane-associated proteins which constitute the type III secretion apparatus are conserved among different pathogens. Most of the inner membrane components of the type III secretion apparatus show additional homologies to flagellar biosynthetic proteins, while a conserved outer membrane factor is similar to secretins from type II and other secretion pathways. Structurally conserved chaperones which specifically bind to individual secreted proteins play an important role in type III protein secretion, apparently by preventing premature interactions of the secreted factors with other proteins. The genes encoding type III secretion systems are clustered, and various pieces of evidence suggest that these systems have been acquired by horizontal genetic transfer during evolution. Expression of type III secretion systems is coordinately regulated in response to host environmental stimuli by networks of transcription factors. This review comprises a comparison of the structure, function, regulation, and impact on host cells of the type III secretion systems in the animal pathogens Yersinia spp., Pseudomonas aeruginosa, Shigella flexneri, Salmonella typhimurium, enteropathogenic Escherichia coli, and Chlamydia spp. and the plant pathogens Pseudomonas syringae, Erwinia spp., Ralstonia solanacearum, Xanthomonas campestris, and Rhizobium spp.

scholarly journals Type III Secretion Contributes to the Pathogenesis of the Soft-Rot Pathogen Erwinia carotovora: Partial Characterization of the hrp Gene Cluster

2001 ◽  
Vol 14 (8) ◽  
pp. 962-968 ◽  
Author(s):  
A. Rantakari ◽  
O. Virtaharju ◽  
S. Vähämiko ◽  
S. Taira ◽  
E. T. Palva ◽  
...  
Keyword(s):  
Gene Cluster ◽  
Type Iii Secretion ◽  
Plant Pathogens ◽  
Erwinia Carotovora ◽  
Soft Rot ◽  
Hypersensitive Reaction ◽  
Virulence Determinants ◽  
Type Iii ◽  
Hrp Genes ◽  
Soft Rot Erwinia

The virulence of soft-rot Erwinia species is dependent mainly upon secreted enzymes such as pectinases, pectin lyases, and proteases that cause maceration of plant tissue. Some soft-rot Erwinia spp. also harbor genes homologous to the hypersensitive reaction and pathogenesis (hrp) gene cluster, encoding components of the type III secretion system. The hrp genes are essential virulence determinants for numerous nonmacerating gram-negative plant pathogens but their role in the virulence of soft-rot Erwinia spp. is not clear. We isolated and characterized 11 hrp genes of Erwinia carotovora subsp. carotovora. Three putative σL-dependent Hrp box promoter sequences were found. The genes were expressed when the bacteria were grown in Hrp-inducing medium. The operon structure of the hrp genes was determined by mRNA hybridization, and the results were in accordance with the location of the Hrp boxes. An E. carotovora strain with mutated hrcC, an essential hrp gene, was constructed. The hrcC¯ strain was able to multiply and cause disease in Arabidopsis, but the population kinetics were altered so that growth was delayed during the early stages of infection.

scholarly journals Molecular and cell biological analysis of SwrB in Bacillus subtilis

2021 ◽  
Author(s):  
Andrew M. Phillips ◽  
Sandra Sanchez ◽  
Tatyana A. Sysoeva ◽  
Briana M. Burton ◽  
Daniel B. Kearns
Keyword(s):  
Bacillus Subtilis ◽  
Type Iii Secretion ◽  
Random Mutagenesis ◽  
Basal Bodies ◽  
Secretion Systems ◽  
Swarming Motility ◽  
Bacterial Flagellum ◽  
Type Iii ◽  
Type Iii Secretion Systems ◽  
Critical Residues

Swarming motility is flagellar-mediated movement over a solid surface and Bacillus subtilis cells require an increase in flagellar density to swarm. SwrB is a protein of unknown function required for swarming that is necessary to increase the number of flagellar hooks but not basal bodies. Previous work suggested that SwrB activates flagellar type III secretion but the mechanism by which it might perform this function is unknown. Here we show that SwrB likely acts sub-stoichiometrically as it localizes as puncta at the membrane in numbers fewer than that of flagellar basal bodies. Moreover the action of SwrB is likely transient as puncta of SwrB were not dependent on the presence of the basal bodies and rarely co-localized with flagellar hooks. Random mutagenesis of the SwrB sequence found that a histidine within the transmembrane segment was conditionally required for activity and punctate localization. Finally, three hydrophobic residues that precede a cytoplasmic domain of poor conservation abolished SwrB activity when mutated and caused aberrant migration during electrophoresis. Our data are consistent with a model in which SwrB interacts with the flagellum, changes conformation to activate type III secretion, and departs. IMPORTANCE Type III secretion systems (T3SS) are elaborate nanomachines that form the core of the bacterial flagellum and injectisome of pathogens. The machines not only secrete proteins like virulence factors but also secrete the structural components for their own assembly. Moreover, proper construction requires complex regulation to ensure that the parts are roughly secreted in the order in which they are assembled. Here we explore a poorly understood activator of the flagellar T3SS activation in Bacillus subtilis called SwrB. To aid mechanistic understanding, we determine the rules for subcellular punctate localization, the topology with respect to the membrane, and critical residues required for SwrB function.

scholarly journals Coiled-Coil Domain of Enteropathogenic Escherichia coli Type III Secreted Protein EspD Is Involved in EspA Filament-Mediated Cell Attachment and Hemolysis

2001 ◽  
Vol 69 (6) ◽  
pp. 4055-4064 ◽  
Author(s):  
Sarah J. Daniell ◽  
Robin M. Delahay ◽  
Robert K. Shaw ◽  
Elizabeth L. Hartland ◽  
Mark J. Pallen ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Host Cell ◽  
Type Iii Secretion ◽  
Plant Pathogens ◽  
Cell Attachment ◽  
Coiled Coil ◽  
Secreted Protein ◽  
Secretion Systems ◽  
Host Cell Membrane ◽  
Type Iii

ABSTRACT Many animal and plant pathogens use type III secretion systems to secrete key virulence factors, some directly into the host cell cytosol. However, the basis for such protein translocation has yet to be fully elucidated for any type III secretion system. We have previously shown that in enteropathogenic and enterohemorrhagicEscherichia coli the type III secreted protein EspA is assembled into a filamentous organelle that attaches the bacterium to the plasma membrane of the host cell. Formation of EspA filaments is dependent on expression of another type III secreted protein, EspD. The carboxy terminus of EspD, a protein involved in formation of the translocation pore in the host cell membrane, is predicted to adopt a coiled-coil conformation with 99% probability. Here, we demonstrate EspD-EspD protein interaction using the yeast two-hybrid system and column overlays. Nonconservative triple amino acid substitutions of specific EspD carboxy-terminal residues generated an enteropathogenicE. coli mutant that was attenuated in its ability to induce attaching and effacing lesions on HEp-2 cells. Although the mutation had no effect on EspA filament biosynthesis, it also resulted in reduced binding to and reduced hemolysis of red blood cells. These results segregate, for the first time, functional domains of EspD that control EspA filament length from EspD-mediated cell attachment and pore formation.

scholarly journals Molecular and cell biological analysis of SwrB in Bacillus subtilis

2021 ◽  
Author(s):  
Andrew M. Phillips ◽  
Sandra Sanchez ◽  
Tatyana A. Sysoeva ◽  
Briana M. Burton ◽  
Daniel B. Kearns
Keyword(s):  
Bacillus Subtilis ◽  
Type Iii Secretion ◽  
Random Mutagenesis ◽  
Basal Bodies ◽  
Secretion Systems ◽  
Swarming Motility ◽  
Bacterial Flagellum ◽  
Type Iii ◽  
Type Iii Secretion Systems ◽  
Critical Residues

ABSTRACTSwarming motility is flagellar-mediated movement over a solid surface and Bacillus subtilis cells require an increase in flagellar density to swarm. SwrB is a protein of unknown function required for swarming that is necessary to increase the number of flagellar hooks but not basal bodies. Previous work suggested that SwrB activates flagellar type III secretion but the mechanism by which it might perform this function is unknown. Here we show that SwrB likely acts sub-stoichiometrically as it localizes as puncta at the membrane in numbers fewer than that of flagellar basal bodies. Moreover the action of SwrB is likely transient as puncta of SwrB were not dependent on the presence of the basal bodies and rarely co-localized with flagellar hooks. Random mutagenesis of the SwrB sequence found that a histidine within the transmembrane segment was conditionally required for activity and punctate localization. Finally, three hydrophobic residues that precede a cytoplasmic domain of poor conservation abolished SwrB activity when mutated and caused aberrant migration during electrophoresis. Our data are consistent with a model in which SwrB interacts with the flagellum, changes conformation to activate type III secretion, and departs.IMPORTANCEType III secretion systems (T3SS) are elaborate nanomachines that form the core of the bacterial flagellum and injectisome of pathogens. The machines not only secrete proteins like virulence factors but also secrete the structural components for their own assembly. Moroever, proper construction requires complex regulation to ensure that the parts are roughly secreted in the order in which they are assembled. Here we explore a poorly understood activator the flagellar T3SS activation in Bacillus subtilis called SwrB. To aid mechanistic understanding, we determine the rules for subcellular punctate localization, the topology with respect to the membrane, and critical residues required for SwrB function.

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