Chlamydial Type III Secretion System Is Encoded on Ten Operons Preceded by Sigma 70-Like Promoter Elements

ABSTRACT Many gram-negative bacterial pathogens employ type III secretion systems for infectious processes. Chlamydiae are obligate intracellular bacteria that encode a conserved type III secretion system that is likely requisite for growth. Typically, genes encoding type III secretion systems are located in a single locus; however, for chlamydiae these genes are scattered throughout the genome. Little is known regarding the gene regulatory mechanisms for this essential virulence determinant. To facilitate identification of cis-acting transcriptional regulatory elements, the operon structure was determined. This analysis revealed 10 operons that contained 37 genes associated with the type III secretion system. Linkage within these operons suggests a role in type III secretion for each of these genes, including 13 genes encoding proteins with unknown function. The transcriptional start site for each operon was determined. In conjunction with promoter activity assays, this analysis revealed that the type III secretion system operons encode σ70-like promoter elements. Transcriptional initiation by a sigma factor responsible for constitutive gene expression indicates that undefined activators or repressors regulate developmental stage-specific expression of chlamydial type III secretion system genes.

Download Full-text

Mutations in Salmonella Pathogenicity Island 2 (SPI2) Genes Affecting Transcription of SPI1 Genes and Resistance to Antimicrobial Agents

Journal of Bacteriology ◽

10.1128/jb.180.18.4775-4780.1998 ◽

1998 ◽

Vol 180 (18) ◽

pp. 4775-4780 ◽

Cited By ~ 74

Author(s):

Jörg Deiwick ◽

Thomas Nikolaus ◽

Jaqueline E. Shea ◽

Colin Gleeson ◽

David W. Holden ◽

...

Keyword(s):

Type Iii Secretion ◽

Antimicrobial Agents ◽

Type Iii Secretion System ◽

Polymyxin B ◽

Secretion System ◽

Effector Proteins ◽

Secretion Systems ◽

Type Iii ◽

Genes Encoding

ABSTRACT The Salmonella typhimurium genome contains two pathogenicity islands (SPI) with genes encoding type III secretion systems for virulence proteins. SPI1 is required for the penetration of the epithelial layer of the intestine. SPI2 is important for the subsequent proliferation of bacteria in the spleens of infected hosts. Although most mutations in SPI2 lead to a strong reduction of virulence, they have different effects in vitro, with some mutants having significantly increased sensitivity to gentamicin and the antibacterial peptide polymyxin B. Previously we showed that certain mutations in SPI2 affect the ability of S. typhimurium to secrete SPI1 effector proteins and to invade cultured eukaryotic cells. In this study, we show that these SPI2 mutations affect the expression of the SPI1 invasion genes. Analysis of reporter fusions to various SPI1 genes reveals highly reduced expression of sipC,prgK, and hilA, the transcriptional activator of SPI1 genes. These observations indicate that the expression of one type III secretion system can be influenced dramatically by mutations in genes encoding a second type III secretion system in the same cell.

Download Full-text

Cloning and Transfer of the Salmonella Pathogenicity Island 2 Type III Secretion System for Studies of a Range of Gram-Negative Genera

Applied and Environmental Microbiology ◽

10.1128/aem.00952-07 ◽

2007 ◽

Vol 73 (18) ◽

pp. 5911-5918 ◽

Cited By ~ 14

Author(s):

James W. Wilson ◽

Clint Coleman ◽

Cheryl A. Nickerson

Keyword(s):

Type Iii Secretion ◽

Vaccine Development ◽

Type Iii Secretion System ◽

Pathogenicity Island ◽

Secretion System ◽

Host Cells ◽

Secretion Systems ◽

Gram Negative ◽

Type Iii ◽

Type Iii Secretion Systems

ABSTRACT The engineering of bacterial strains with specific phenotypes frequently requires the use of blocks or “cassettes” of genes that act together to perform a desired function. The potential benefits of utilizing type III secretion systems in this regard are becoming increasingly realized since these systems can be used to direct interactions with host cells for beneficial purposes such as vaccine development, anticancer therapies, and targeted protein delivery. However, convenient methods to clone and transfer type III secretion systems for studies of a range of different types of bacteria are lacking. In addition to functional applications, such methods would also reveal important information about the evolution of a given type III secretion system, such as its ability to be expressed and functional outside of the strain of origin. We describe here the cloning of the Salmonella enterica serovar Typhimurium pathogenicity island 2 (SPI-2) type III secretion system onto a vector that can be easily transferred to a range of gram-negative bacterial genera. We found that expression of the cloned SPI-2 system in different Gammaproteobacteria and Alphaproteobacteria (as monitored by SseB protein levels) is dependent on the bacterial strain and growth medium. We also demonstrate that the cloned system is functional for secretion, can direct interactions with macrophages, and can be used as a novel tool to analyze the predicted interaction of SseB with host cells. This work provides a foundation for future applications where the cloned SPI-2 region (or other cloned type III systems) can provide a desired function to an engineered gram-negative strain.

Download Full-text

Evidence for a Type III Secretion System in Aeromonas salmonicida subsp. salmonicida

Journal of Bacteriology ◽

10.1128/jb.184.21.5966-5970.2002 ◽

2002 ◽

Vol 184 (21) ◽

pp. 5966-5970 ◽

Cited By ~ 74

Author(s):

Sarah E. Burr ◽

Katja Stuber ◽

Thomas Wahli ◽

Joachim Frey

Keyword(s):

Type Iii Secretion ◽

Type Strain ◽

Wild Type Strain ◽

Type Iii Secretion System ◽

Secretion System ◽

Aeromonas Salmonicida ◽

Broad Host Range ◽

Wild Type ◽

Secretion Systems ◽

Type Iii

ABSTRACT Aeromonas salmonicida subsp. salmonicida, the etiological agent of furunculosis, is an important fish pathogen. We have screened this bacterium with a broad-host-range probe directed against yscV, the gene that encodes the archetype of a highly conserved family of inner membrane proteins found in every known type III secretion system. This has led to the identification of seven open reading frames that encode homologues to proteins functioning within the type III secretion systems of Yersinia species. Six of these proteins are encoded by genes comprising a virA operon. The A. salmonicida subsp. salmonicida yscV homologue, ascV, was inactivated by marker replacement mutagenesis and used to generate an isogenic ascV mutant. Comparison of the extracellular protein profiles from the ascV mutant and the wild-type strain indicates that A. salmonicida subsp. salmonicida secretes proteins via a type III secretion system. The recently identified ADP-ribosylating toxin AexT was identified as one such protein. Finally, we have compared the toxicities of the wild-type A. salmonicida subsp. salmonicida strain and the ascV mutant against RTG-2 rainbow trout gonad cells. While infection with the wild-type strain results in significant morphological changes, including cell rounding, infection with the ascV mutant has no toxic effect, indicating that the type III secretion system we have identified plays an important role in the virulence of this pathogen.

Download Full-text

Expression of the Bradyrhizobium japonicum Type III Secretion System in Legume Nodules and Analysis of the Associated tts box Promoter

Molecular Plant-Microbe Interactions ◽

10.1094/mpmi-21-8-1087 ◽

2008 ◽

Vol 21 (8) ◽

pp. 1087-1093 ◽

Cited By ~ 40

Author(s):

Susanne Zehner ◽

Grit Schober ◽

Mandy Wenzel ◽

Kathrin Lang ◽

Michael Göttfert

Keyword(s):

Type Iii Secretion ◽

Bradyrhizobium Japonicum ◽

Response Regulator ◽

Type Iii Secretion System ◽

Secretion System ◽

Symbiotic Efficiency ◽

Type Iii ◽

Genes Encoding ◽

Transcriptional Start Sites ◽

Type Three Secretion

In Bradyrhizobium japonicum, as in some other rhizobia, symbiotic efficiency is influenced by a type III secretion system (T3SS). Most genes encoding the transport machinery and secreted proteins are preceded by a conserved 30-bp motif, the type-three secretion (tts) box. In this study, we found that regions downstream of 34 tts boxes are transcribed. For nopB, nopL, and gunA2, the transcriptional start sites were found to be 12, 11, and 10 bp downstream of their tts boxes, respectively. The deletion of this motif or modification of two or more conserved residues strongly reduced expression of nopB. This indicates that the tts box is an essential promoter element. Data obtained with lacZ reporter gene fusions of five genes preceded by a tts box (gunA2, nopB, rhcV, nopL, and blr1806) revealed that they are expressed in 4-week-old nodules of Macroptilium atropurpureum. These data suggest that the T3SS is active in mature nitrogen-fixing nodules. The two-component response regulator TtsI is required for the expression of rhcV, nopL, and blr1806 in bacteroids. Staining of inoculated roots showed that nopB is also expressed in early infection stages.

Download Full-text

Escherichia coli type III secretion system 2 (ETT2) is widely distributed in avian pathogenic Escherichia coli isolates from Eastern China

Epidemiology and Infection ◽

10.1017/s0950268816000820 ◽

2016 ◽

Vol 144 (13) ◽

pp. 2824-2830 ◽

Cited By ~ 5

Author(s):

S. WANG ◽

X. LIU ◽

X. XU ◽

Y. ZHAO ◽

D. YANG ◽

...

Keyword(s):

Escherichia Coli ◽

Type Iii Secretion ◽

Bacterial Infections ◽

Eastern China ◽

Type Iii Secretion System ◽

Secretion System ◽

Secretion Systems ◽

E Coli ◽

Type Iii ◽

System 2

SUMMARYPathogens utilize type III secretion systems to deliver effector proteins, which facilitate bacterial infections. The Escherichia coli type III secretion system 2 (ETT2) which plays a crucial role in bacterial virulence, is present in the majority of E. coli strains, although ETT2 has undergone widespread mutational attrition. We investigated the distribution and characteristics of ETT2 in avian pathogenic E. coli (APEC) isolates and identified five different ETT2 isoforms, including intact ETT2, in 57·6% (141/245) of the isolates. The ETT2 locus was present in the predominant APEC serotypes O78, O2 and O1. All of the ETT2 loci in the serotype O78 isolates were degenerate, whereas an intact ETT2 locus was mostly present in O1 and O2 serotype strains, which belong to phylogenetic groups B2 and D, respectively. Interestingly, a putative second type III secretion-associated locus (eip locus) was present only in the isolates with an intact ETT2. Moreover, ETT2 was more widely distributed in APEC isolates and exhibited more isoforms compared to ETT2 in human extraintestinal pathogenic E. coli, suggesting that APEC might be a potential risk to human health. However, there was no distinct correlation between ETT2 and other virulence factors in APEC.

Download Full-text

The Type III Secretion System Effector SptP of Salmonella enterica Serovar Typhi

Journal of Bacteriology ◽

10.1128/jb.00647-16 ◽

2016 ◽

Vol 199 (4) ◽

Cited By ~ 13

Author(s):

Rebecca Johnson ◽

Alexander Byrne ◽

Cedric N. Berger ◽

Elizabeth Klemm ◽

Valerie F. Crepin ◽

...

Keyword(s):

Amino Acid ◽

Type Iii Secretion ◽

Salmonella Enterica ◽

Type Iii Secretion System ◽

Secretion System ◽

Binding Domain ◽

Secretion Systems ◽

Content Type ◽

Type Iii ◽

Chaperone Binding

ABSTRACT Strains of the various Salmonella enterica serovars cause gastroenteritis or typhoid fever in humans, with virulence depending on the action of two type III secretion systems (Salmonella pathogenicity island 1 [SPI-1] and SPI-2). SptP is a Salmonella SPI-1 effector, involved in mediating recovery of the host cytoskeleton postinfection. SptP requires a chaperone, SicP, for stability and secretion. SptP has 94% identity between S. enterica serovar Typhimurium and S. Typhi; direct comparison of the protein sequences revealed that S. Typhi SptP has numerous amino acid changes within its chaperone-binding domain. Subsequent comparison of ΔsptP S. Typhi and S. Typhimurium strains demonstrated that, unlike SptP in S. Typhimurium, SptP in S. Typhi was not involved in invasion or cytoskeletal recovery postinfection. Investigation of whether the observed amino acid changes within SptP of S. Typhi affected its function revealed that S. Typhi SptP was unable to complement S. Typhimurium ΔsptP due to an absence of secretion. We further demonstrated that while S. Typhimurium SptP is stable intracellularly within S. Typhi, S. Typhi SptP is unstable, although stability could be recovered following replacement of the chaperone-binding domain with that of S. Typhimurium. Direct assessment of the strength of the interaction between SptP and SicP of both serovars via bacterial two-hybrid analysis demonstrated that S. Typhi SptP has a significantly weaker interaction with SicP than the equivalent proteins in S. Typhimurium. Taken together, our results suggest that changes within the chaperone-binding domain of SptP in S. Typhi hinder binding to its chaperone, resulting in instability, preventing translocation, and therefore restricting the intracellular activity of this effector. IMPORTANCE Studies investigating Salmonella pathogenesis typically rely on Salmonella Typhimurium, even though Salmonella Typhi causes the more severe disease in humans. As such, an understanding of S. Typhi pathogenesis is lacking. Differences within the type III secretion system effector SptP between typhoidal and nontyphoidal serovars led us to characterize this effector within S. Typhi. Our results suggest that SptP is not translocated from typhoidal serovars, even though the loss of sptP results in virulence defects in S. Typhimurium. Although SptP is just one effector, our results exemplify that the behavior of these serovars is significantly different and genes identified to be important for S. Typhimurium virulence may not translate to S. Typhi.

Download Full-text

Evaluation of biofilm production and characterization of genes encoding type III secretion system among Pseudomonas aeruginosa isolated from burn patients

Burns ◽

10.1016/j.burns.2012.07.030 ◽

2012 ◽

Vol 38 (8) ◽

pp. 1192-1197 ◽

Cited By ~ 38

Author(s):

Fereshteh Jabalameli ◽

Akbar Mirsalehian ◽

Babak Khoramian ◽

Marzieh Aligholi ◽

Seyed Sajjad Khoramrooz ◽

...

Keyword(s):

Pseudomonas Aeruginosa ◽

Type Iii Secretion ◽

Type Iii Secretion System ◽

Secretion System ◽

Burn Patients ◽

Type Iii ◽

Biofilm Production ◽

Genes Encoding

Download Full-text

Synchronous Gene Expression of the Yersinia enterocolitica Ysa Type III Secretion System and Its Effectors

Journal of Bacteriology ◽

10.1128/jb.01402-08 ◽

2009 ◽

Vol 191 (6) ◽

pp. 1816-1826 ◽

Cited By ~ 19

Author(s):

Kimberly A. Walker ◽

Virginia L. Miller

Keyword(s):

Yersinia Enterocolitica ◽

Type Iii Secretion ◽

Response Regulator ◽

Solid Surfaces ◽

Dual Function ◽

Secretion Systems ◽

Type Iii ◽

Virulence Plasmids ◽

Type Iii Secretion Systems ◽

Genes Encoding

ABSTRACT Type III secretion systems (T3SSs) are complex units that consist of many proteins. Often the proteins are encoded as a cohesive unit on virulence plasmids, but several systems have their various components dispersed around the chromosome. The Yersinia enterocolitica Ysa T3SS is such a system, where the apparatus genes, some regulatory genes, and four genes encoding secreted proteins (ysp genes) are contained in a single locus. The remaining ysp genes and at least one additional regulator are found elsewhere on the chromosome. Expression of ysa genes requires conditions of high ionic strength, neutral/basic pH, and low temperatures (26°C) and is stimulated by exposure to solid surfaces. The AraC-like regulator YsaE and the dual-function chaperone/regulator SycB are required to stimulate the sycB promoter, which transcribes sycB and probably yspBCDA as well. The putative phosphorelay proteins YsrRS (located at the distal end of the ysa locus) and RcsB, the response regulator of the RcsBCD phosphorelay system, are required to initiate transcription at the ysaE promoter, which drives transcription of many apparatus genes. In this work, we sought to determine which ysp genes were coordinately regulated with the genes within the ysa locus. We found that six unlinked ysp genes responded to NaCl and required YsaE/SycB, YsrRS, and RcsB for expression. Three ysp genes had unique patterns, one of which was unaffected by all elements tested except NaCl. Thus, while the ysp genes were likely to have been acquired independently, most have acquired a synchronous regulatory pattern.

Download Full-text