scholarly journals The role of toxin:antitoxin systems and insertion sequences in the loss of virulence in Shigella sonnei

2020 ◽  
Author(s):  
Jessica E. Martyn ◽  
Giulia Pilla ◽  
Sarah Hollingshead ◽  
Mariya Lobanovska ◽  
Kristoffer S. Winther ◽  
...  
Keyword(s):  
Type Iii Secretion ◽  
High Frequency ◽  
Shigella Flexneri ◽  
Shigella Sonnei ◽  
Single Amino Acid ◽  
Amino Acid Difference ◽  
Insertion Sequences ◽  
Plasmid Loss ◽  
The Impact

SUMMARYThe Shigella plasmid, pINV, contains a 30 kb pathogenicity island (PAI) encoding a Type III secretion system (T3SS) which is essential for virulence. During growth in the laboratory, avirulent colonies of Shigella (which do not express a T3SS) arise spontaneously. Avirulence in Shigella flexneri mostly follows loss of the PAI, following recombination between insertion sequences (ISs) on pINV; toxin:antitoxin (TA) systems on pINV promote its retention through post-segregational killing (PSK). We show that avirulence in Shigella sonnei mainly results from plasmid loss, consistent with previous findings; IS-mediated PAI deletions can occur in S. sonnei, but through different ISs than in S. flexneri. We investigated the molecular basis for frequent loss of the S. sonnei plasmid, pINVSsonn. Introduction into pINVSsonn of CcdAB and GmvAT, toxin:antitoxin TA systems in pINV from S. flexneri but not S. sonnei, reduced plasmid loss and the emergence of avirulent bacteria. However, plasmid loss remained the leading cause of avirulence. We show that a single amino acid difference in the VapC toxin of the VapBC TA system in pINV also contributes to high frequency plasmid loss in S. sonnei compared to S. flexneri. Our findings demonstrate that the repertoire of ISs, complement of TA systems, and polymorphisms in TA systems influence plasmid dynamics and virulence loss in S. sonnei. Understanding the impact of polymorphisms should be informative about how TA systems contribute to PSK, and could be exploited for generating strains with stable plasmids.

scholarly journals Genetic Mechanisms behind the Spread of Reduced Susceptibility to Azithromycin in Shigella Strains Isolated from Men Who Have Sex with Men in Québec, Canada

2018 ◽  
Vol 63 (2) ◽  
pp. e01679-18 ◽  
Author(s):  
Khadidja Yousfi ◽  
Christiane Gaudreau ◽  
Pierre A. Pilon ◽  
Brigitte Lefebvre ◽  
Matthew Walker ◽  
...  
Keyword(s):  
Sequence Analysis ◽  
Shigella Flexneri ◽  
Complete Sequence ◽  
Shigella Sonnei ◽  
Content Type ◽  
Genetic Mechanisms ◽  
Sex With Men

ABSTRACT We analyzed 254 Shigella species isolates collected in Québec, Canada, during 2013 and 2014. Overall, 23.6% of isolates showed reduced susceptibility to azithromycin (RSA) encoded by mphA (11.6%), ermB (1.7%), or both genes (86.7%). Shigella strains with RSA were mostly isolated from men who have sex with men (68.8% or higher) from the Montreal region. A complete sequence analysis of six selected plasmids from Shigella sonnei and different serotypes of Shigella flexneri emphasized the role of IS26 in the dissemination of RSA.

scholarly journals Genetic functions of the NAIP family of inflammasome receptors for bacterial ligands in mice

2016 ◽  
Vol 213 (5) ◽  
pp. 647-656 ◽  
Author(s):  
Yue Zhao ◽  
Jianjin Shi ◽  
Xuyan Shi ◽  
Yupeng Wang ◽  
Fengchao Wang ◽  
...  
Keyword(s):  
Legionella Pneumophila ◽  
Type Iii Secretion ◽  
Physiological Function ◽  
Shigella Flexneri ◽  
Critical Role ◽  
Bacterial Virulence ◽  
Infection Model ◽  
Inflammasome Activation ◽  
Inflammatory Damage

Biochemical studies suggest that the NAIP family of NLR proteins are cytosolic innate receptors that directly recognize bacterial ligands and trigger NLRC4 inflammasome activation. In this study, we generated Naip5−/−, Naip1−/−, and Naip2−/− mice and showed that bone marrow macrophages derived from these knockout mice are specifically deficient in detecting bacterial flagellin, the type III secretion system needle, and the rod protein, respectively. Naip1−/−, Naip2−/−, and Naip5−/− mice also resist lethal inflammasome activation by the corresponding ligand. Furthermore, infections performed in the Naip-deficient macrophages have helped to define the major signal in Legionella pneumophila, Salmonella Typhimurium and Shigella flexneri that is detected by the NAIP/NLRC4 inflammasome. Using an engineered S. Typhimurium infection model, we demonstrate the critical role of NAIPs in clearing bacterial infection and protecting mice from bacterial virulence–induced lethality. These results provide definitive genetic evidence for the important physiological function of NAIPs in antibacterial defense and inflammatory damage–induced lethality in mice.

scholarly journals Tropical Cyclone Interaction with the Ocean: The Role of High-Frequency (Subdaily) Coupled Processes

2017 ◽  
Vol 30 (1) ◽  
pp. 145-162 ◽  
Author(s):  
Enrico Scoccimarro ◽  
Pier Giuseppe Fogli ◽  
Kevin A. Reed ◽  
Silvio Gualdi ◽  
Simona Masina ◽  
...  
Keyword(s):  
Tropical Cyclone ◽  
High Frequency ◽  
Climate Model ◽  
Horizontal Resolution ◽  
Coupled Processes ◽  
Realistic Representation ◽  
Order Of Magnitude ◽  
The Impact ◽  
Coupling Frequency

Through tropical cyclone (TC) activity the ocean and the atmosphere exchange a large amount of energy. In this work possible improvements introduced by a higher coupling frequency are tested between the two components of a climate model in the representation of TC intensity and TC–ocean feedbacks. The analysis is based on the new Centro Euro-Mediterraneo per I Cambiamenti Climatici Climate Model (CMCC-CM2-VHR), capable of representing realistic TCs up to category-5 storms. A significant role of the negative sea surface temperature (SST) feedback, leading to a weakening of the cyclone intensity, is made apparent by the improved representation of high-frequency coupled processes. The first part of this study demonstrates that a more realistic representation of strong TC count is obtained by coupling atmosphere and ocean components at hourly instead of daily frequency. Coherently, the positive bias of the annually averaged power dissipation index associated with TCs is reduced by one order of magnitude when coupling at the hourly frequency, compared to both forced mode and daily coupling frequency results. The second part of this work shows a case study (a modeled category-5 typhoon) analysis to verify the impact of a more realistic representation of the high-frequency coupling in representing the TC effect on the ocean; the theoretical subsurface warming induced by TCs is well represented when coupling the two components at the higher frequency. This work demonstrates that an increased horizontal resolution of model components is not sufficient to ensure a realistic representation of intense and fast-moving systems, such as tropical and extratropical cyclones, but a concurrent increase in coupling frequency is required.

scholarly journals Regulation of the Ysa Type III Secretion System of Yersinia enterocolitica by YsaE/SycB and YsrS/YsrR

2004 ◽  
Vol 186 (13) ◽  
pp. 4056-4066 ◽  
Author(s):  
Kimberly A. Walker ◽  
Virginia L. Miller
Keyword(s):  
Yersinia Enterocolitica ◽  
Type Iii Secretion ◽  
Shigella Flexneri ◽  
Wild Type ◽  
Secretion Systems ◽  
Type Iii ◽  
Regulatory Cascade ◽  
Two Component

ABSTRACT Yersinia enterocolitica biovar 1B contains two type III secretion systems (TTSSs), the plasmid-encoded Ysc-Yop system and the chromosomally encoded Ysa-Ysp system. Proteins secreted from the Ysa TTSS (Ysps) have only been detected in vitro when cells are cultured at 26°C in a high-NaCl medium. However, the exact role of the Ysa TTSS is unclear. Thus, investigations into the regulation of this system may help elucidate the role of the Ysps during the life cycle of Y. enterocolitica. Here we present evidence that the AraC-like regulator YsaE acts together with the chaperone SycB to regulate transcription of the sycByspBCDA operon, a phenomenon similar to that seen in the closely related Salmonella SPI-1 and Shigella flexneri Mxi-Spa-Ipa TTSSs. Deletion of either sycB or ysaE results in a twofold reduction in the activity of a sycB-lacZ fusion compared to the wild type. In a reconstituted Escherichia coli system, transcription of sycB was activated sixfold only when both YsaE and SycB were present, demonstrating that they are necessary for activation. ysrR and ysrS are located near the ysa genes and encode a putative two-component regulatory system. Mutations in either gene indicated that both YsrR and YsrS were required for secretion of Ysps. In addition, transcription from sycB-lacZ and ysaE-lacZ fusions was decreased 6.5- and 25-fold, respectively, in the ysrS mutant compared to the wild type. Furthermore, in the absence of NaCl, the activity of ysaE-lacZ was reduced 25-fold in the wild-type and ΔysrS strains, indicating that YsrS is probably required for the salt-dependent expression of the ysa locus. These results suggest that the putative two-component system YsrRS may be a key element in the regulatory cascade for the Ysa TTSS.

scholarly journals Crystal structure of RahU, an aegerolysin protein from the human pathogen Pseudomonas aeruginosa, and its interaction with membrane ceramide phosphorylethanolamine

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Eva Kočar ◽  
Tea Lenarčič ◽  
Vesna Hodnik ◽  
Anastasija Panevska ◽  
Yunjie Huang ◽  
...  
Keyword(s):  
Pseudomonas Aeruginosa ◽  
High Frequency ◽  
Common Property ◽  
Insect Cell Line ◽  
Single Amino Acid ◽  
Head Group ◽  
Human Pathogens ◽  
Starting Point ◽  
Genome Analyses

AbstractAegerolysins are proteins produced by bacteria, fungi, plants and protozoa. The most studied fungal aegerolysins share a common property of interacting with membranes enriched with cholesterol in combination with either sphingomyelin or ceramide phosphorylethanolamine (CPE), major sphingolipids in the cell membranes of vertebrates and invertebrates, respectively. However, genome analyses show a particularly high frequency of aegerolysin genes in bacteria, including the pathogenic genera Pseudomonas and Vibrio; these are human pathogens of high clinical relevance and can thrive in a variety of other species. The knowledge on bacterial aegerolysin-lipid interactions is scarce. We show that Pseudomonas aeruginosa aegerolysin RahU interacts with CPE, but not with sphingomyelin-enriched artificial membranes, and that RahU interacts with the insect cell line producing CPE. We report crystal structures of RahU alone and in complex with tris(hydroxymethyl)aminomethane (Tris), which, like the phosphorylethanolamine head group of CPE, contains a primary amine. The RahU structures reveal that the two loops proximal to the amino terminus form a cavity that accommodates Tris, and that the flexibility of these two loops is important for this interaction. We show that Tris interferes with CPE-enriched membranes for binding to RahU, implying on the importance of the ligand cavity between the loops and its proximity in RahU membrane interaction. We further support this by studying the interaction of single amino acid substitution mutants of RahU with the CPE-enriched membranes. Our results thus represent a starting point for a better understanding of the role of P. aeruginosa RahU, and possibly other bacterial aegerolysins, in bacterial interactions with other organisms.

An analysis of the representation of cultural content in English coursebooks

2020 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Mahdi Dahmardeh ◽  
Sung-Do Kim
Keyword(s):  
High Frequency ◽  
English Language ◽  
Cultural Representation ◽  
Main Concern ◽  
Content Type ◽  
Cultural Elements ◽  
The Status ◽  
Different Cultures ◽  
The Impact

PurposeThe aim of this article was to understand about cultural representation in these coursebooks and if it is reflected the status of English as a lingua franca.Design/methodology/approachThis article is a report on a case study in the form of content analysis of different categories of culture represented in English language coursebooks used in schools of Iran. In order to do so, references to source, target, international and universal cultures were classified into four aspects: perspectives, products, practices and persons.FindingsGenerally, the findings suggested that despite the high frequency of cultural elements, the representation favoured the source culture, while the target, international and universal cultures were heavily under-represented.Research limitations/implicationsApart from the valuable contributions of the study, the implications of the study are that despite the high frequency of cultural elements, the representation favoured the source culture, while the target, international and universal cultures were heavily under-represented. Therefore, the imbalance in the content of materials on different cultures needs to be redressed. While the main concern of this investigation is the frequency of appearance, which replicates the extent of source, target, international and universal cultures represented in the coursebooks, the impact of the materials, affected by how the cultural elements are used and perceived by teachers and pupils, is beyond the scope of the present study; hence, future studies in this area are deeply encouraged, and it is recommended for further research.Practical implicationsThe implications for resolving the imbalance in cultural representation are also being explained.Originality/valueBearing in mind the importance of coursebooks as well as the role of culture in teaching the English language, this article aims at understanding about cultural representation within the newly developed Iranian English language coursebooks for schools, an issue that has never been studied by Iranian scholars with respect to the newly published materials.

Spa13 of Shigella flexneri has a dual role: chaperone escort and export gate-activator switch of the type III secretion system

Microbiology ◽  
2014 ◽  
Vol 160 (1) ◽  
pp. 130-141 ◽  
Author(s):  
Youness Cherradi ◽  
Abderrahman Hachani ◽  
Abdelmounaaïm Allaoui
Keyword(s):  
Type Iii Secretion ◽  
Shigella Flexneri ◽  
Secretion System ◽  
Dual Role ◽  
Inner Membrane ◽  
Type Iii ◽  
Inner Membrane Protein ◽  
Soluble Components ◽  
Made In

The type III secretion apparatus (T3SA) is used by numerous Gram-negative pathogens to inject virulence factors into eukaryotic cells. The Shigella flexneri T3SA spans the bacterial envelope and its assembly requires the products of ~20 mxi and spa genes. Despite progress made in understanding how the T3SA is assembled, the role of several predicted soluble components, such as Spa13, remains elusive. Here, we show that the secretion defect of the spa13 mutant is associated with lack of T3SA assembly which is partly due to the instability of the needle component MxiH. In contrast to its Yersinia counterpart, Spa13 is not a secreted protein. We identified a network of interactions between Spa13 and the ATPase Spa47, the C-ring protein Spa33, and the inner-membrane protein Spa40. Moreover, we revealed a Spa13 interaction with the inner-membrane MxiA and showed that overexpression of the large cytoplasmic domain of MxiA in the WT background shuts off secretion. Lastly, we demonstrated that Spa13 interacts with the cleaved form of Spa40 and with the translocator chaperone IpgC, suggesting that Spa13 intervenes during the secretion hierarchy switch process. Collectively, our results support a dual role of Spa13 as a chaperone escort and as an export gate-activator switch.

scholarly journals Invasion of Epithelial Cells Is Correlated with Secretion of Biosurfactant via the Type 3 Secretion System (T3SS) of Shigella flexneri

2020 ◽  
Vol 2020 ◽  
pp. 1-10
Author(s):  
Duchel Jeanedvi Kinouani Kinavouidi ◽  
Christian Aimé Kayath ◽  
Etienne Nguimbi
Keyword(s):  
Organic Solvent ◽  
Type Iii Secretion ◽  
Shigella Flexneri ◽  
Secretion System ◽  
Extracellular Medium ◽  
Membrane Interfaces ◽  
Type 3 Secretion System ◽  
Type 3 ◽  
Hydrophobic Areas

Biosurfactants are amphipathic molecules produced by many microorganisms, usually bacteria, fungi, and yeasts. They possess the property of reducing the tension of the membrane interfaces. No studies have been conducted on Shigella species showing the role of biosurfactant-like molecules (BLM) in pathogenicity. The aim of this study is to assess the ability of Shigella environmental and clinical strains to produce BLM and investigate the involvement of biosurfactants in pathogenicity. Our study has shown that BLM are secreted in the extracellular medium with EI24 ranging from 80% to 100%. The secretion is depending on the type III secretion system (T3SS). Moreover, our results have shown that S. flexneri, S. boydii, and S. sonnei are able to interact with hydrophobic areas with 17.64%, 21.42%, and 22.22% hydrophobicity, respectively. BLM secretion is totally prevented due to inhibition of T3SS by 100 mM benzoic and 1.5 mg/ml salicylic acids. P. aeruginosa harboring T3SS is able to produce 100% of BLM in the presence or in the absence of both T3SS inhibitors. The secreted BLM are extractable with an organic solvent such as chloroform, and this could entirely be considered a lipopeptide or polypeptide compound. Secretion of BLM allows some Shigella strains to induce multicellular phenomena like “swarming.”

scholarly journals VscF in T3SS1 Helps to Translocate VPA0226 in Vibrio parahaemolyticus

2021 ◽  
Vol 11 ◽  
Author(s):  
Lele Lian ◽  
Jiao Xue ◽  
Wanjun Li ◽  
Jianluan Ren ◽  
Fang Tang ◽  
...  
Keyword(s):  
Hela Cells ◽  
Type Iii Secretion ◽  
Vibrio Parahaemolyticus ◽  
Shigella Flexneri ◽  
Wild Type ◽  
Infection Mechanism ◽  
Complementation Strain ◽  
Needle Protein ◽  
System 1

In Vibrio parahaemolyticus, type III secretion system 1 (T3SS1) is a major virulence factor that delivers effectors into the host eukaryotic cytoplasm; however, studies on its infection mechanism are currently limited. To determine the function of the vscF gene, we constructed the vscF deletion mutant ΔvscF and complementation strain CΔvscF. Compared with those of wild-type POR-1 and CΔvscF, the cytotoxic, adherent, and apoptotic abilities of ΔvscF in HeLa cells were significantly reduced (P < 0.01). Furthermore, in infected HeLa cells, the mutant strain reduced the translocation rates of VP1683 and VP1686 effectors compared to the wild-type and complementation strains. A BLAST search showed that vscF is homologous to the MixH needle protein of Shigella flexneri, indicating that the vscF gene encodes the needle protein of T3SS1 in V. parahaemolyticus. Additional translocation assays showed that VPA0226 translocated into the HeLa eukaryotic cytoplasm via T3SS1, secretion assays showed that VPA0226 can be secreted to supernatant by T3SS1, indicating that VPA0226 belongs to the unpublished class of T3SS1 effectors. In conclusion, our data indicate an essential role of vscF in V. parahaemolyticus T3SS1 and revealed that VPA0226 can be secreted into the host cell cytoplasm via T3SS1. This study provides insights into a previously unexplored aspect of T3SS1, which is expected to contribute to the understanding of its infection mechanism.

scholarly journals Maintenance of the Shigella sonnei virulence plasmid is dependent on its repertoire and amino acid sequence of toxin:antitoxin systems

2022 ◽  
Author(s):  
Jessica E. Martyn ◽  
Giulia Pilla ◽  
Sarah Hollingshead ◽  
Kristoffer S. Winther ◽  
Susan Lea ◽  
...  
Keyword(s):  
Amino Acid ◽  
Vaccine Development ◽  
Shigella Flexneri ◽  
Amino Acid Sequences ◽  
Shigella Sonnei ◽  
Single Amino Acid ◽  
Multi Drug Resistance ◽  
Virulence Plasmid ◽  
Closely Related Species ◽  
Single Amino Acid Polymorphisms

Shigella sonnei is a major cause of bacillary dysentery, and of increasing concern due to the spread of multi-drug resistance. S. sonnei harbours pINV, a ∼ 210 kb plasmid that encodes a Type III secretion system (T3SS), which is essential for virulence. During growth in the laboratory, avirulence arises spontaneously in S. sonnei at high frequency, hampering studies on and vaccine development against this important pathogen. Here we investigated the molecular basis for the emergence of avirulence in S. sonnei , and show that avirulence mainly results from pINV loss, consistent with previous findings. Ancestral deletions have led to the loss from S. sonnei pINV of two toxin:antitoxin (TA) systems involved in plasmid maintenance, CcdAB and GmvAT, which are found on pINV in Shigella flexneri . We show that introduction of these TA systems into S. sonnei pINV reduced but did not eliminate pINV loss, while single amino acid polymorphisms found in the S. sonnei VapBC TA system compared with S. flexneri VapBC also contribute to pINV loss. Avirulence also results from deletions of T3SS-associated genes on pINV through recombination between insertion sequences (ISs) on the plasmid; these events differ from those observed in S. flexneri due to the different distribution and repertoire of ISs. Our findings demonstrate that TA systems and ISs influence plasmid dynamics and loss in S. sonnei , and could be exploited for the design and evaluation of vaccines. IMPORTANCE Shigella sonnei is the major cause of shigellosis in high-income and industrialising countries, and an emerging multi-drug resistant pathogen. A significant challenge when studying this bacterium is that it spontaneously becomes avirulent during growth in the laboratory, through loss of its virulence plasmid (pINV). Here we decipher the mechanisms leading to avirulence in S. sonnei and how the limited repertoire and amino acid sequences of plasmid-encoded toxin:antitoxin (TA) systems make the maintenance of pINV in this bacterium less efficient compared with Shigella flexneri . Our findings highlight how subtle differences in plasmids in closely-related species have marked effects and could be exploited to reduce plasmid loss in S. sonnei . This should facilitate research on this bacterium and vaccine development.

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