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Fällman, Maria
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Publications (10 of 44) Show all publications
Taheri, N., Fällman, M., Wai, S. N. & Fahlgren, A. (2019). Accumulation of virulence-associated proteins in Campylobacter jejuni Outer Membrane Vesicles at human body temperature. Journal of Proteomics, 195, 33-40
Open this publication in new window or tab >>Accumulation of virulence-associated proteins in Campylobacter jejuni Outer Membrane Vesicles at human body temperature
2019 (English)In: Journal of Proteomics, ISSN 1874-3919, E-ISSN 1876-7737, Vol. 195, p. 33-40Article in journal (Refereed) Published
Abstract [en]

Campylobacter jejuni is the major cause of bacterial gastroenteritis in humans. In contrast, colonization in avian hosts is asymptomatic. Body temperature differs between human (37 °C) and avian (42 °C) hosts, and bacterial growth in 37 °C is therefore a potential cue for higher virulence properties during human infection. The proteome of the bacteria was previously shown to be altered by temperature. Here we investigated whether temperature has an effect on the C. jejuni outer membrane vesicle (OMV) proteome, as OMVs are considered to be bacterial vehicles for protein delivery and might play a role during infection. OMVs isolated from C. jejuni strain 81-176 grown at 37 °C and 42 °C were analyzed by LC-ESI-MS/MS. 181 proteins were detected in both sample groups, one protein was exclusively present, and three were absent in OMVs from 37 °C. Of the 181 proteins, 59 were differentially expressed; 30 proteins were detected with higher abundance, and 29 proteins with lower abundance at 37 °C. Among the more highly abundant proteins, significantly more proteins were predicted to be associated with virulence. These data show that temperature has an impact on the property of the OMVs, and this might affect the outcome of colonization/infection by C. jejuni in different hosts.

Keywords
Campylobacter jejuni, OMVs, Proteomics, Temperature
National Category
Microbiology
Research subject
Microbiology
Identifiers
urn:nbn:se:umu:diva-155499 (URN)10.1016/j.jprot.2019.01.005 (DOI)000459366000004 ()30641234 (PubMedID)
Available from: 2019-01-18 Created: 2019-01-18 Last updated: 2019-04-16Bibliographically approved
Taheri, N., Mahmud, A. K., Sandblad, L., Fällman, M., Wai, S. N. & Fahlgren, A. (2018). Campylobacter jejuni bile exposure influences outer membrane vesicles protein content and bacterial interaction with epithelial cells. Scientific Reports, 8, Article ID 16996.
Open this publication in new window or tab >>Campylobacter jejuni bile exposure influences outer membrane vesicles protein content and bacterial interaction with epithelial cells
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2018 (English)In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 8, article id 16996Article in journal (Refereed) Published
Abstract [en]

Campylobacter jejuni is a prevalent human pathogen and a major cause of bacterial gastroenteritis in the world. In humans, C. jejuni colonizes the intestinal tract and its tolerance to bile is crucial for bacteria to survive and establish infection. C. jejuni produces outer membrane vesicles (OMVs) which have been suggested to be involved in virulence. In this study, the proteome composition of C. jejuni OMVs in response to low concentration of bile was investigated. We showed that exposure of C. jejuni to low concentrations of bile, similar to the concentration in cecum, induced significant changes in the protein profile of OMVs released during growth without affecting the protein profile of the bacteria. This suggests that bile influences a selective packing of the OMVs after bacterial exposure to low bile. A low concentration of bile was found to increase bacterial adhesion to intestinal epithelial cells, likely by an enhanced hydrophobicity of the cell membrane following exposure to bile. The increased bacterial adhesiveness was not associated with increased invasion, instead bile exposure decreased C. jejuni invasion. OMVs released from bacteria upon exposure to low bile showed to increase both adhesion and invasion of non-bile-exposed bacteria into intestinal epithelial cells. These findings suggest that C. jejuni in environments with low concentrations of bile produce OMVs that facilitates colonization of the bacteria, and this could potentially contribute to virulence of C. jejuni in the gut.

Place, publisher, year, edition, pages
Nature Publishing Group, 2018
National Category
Microbiology Cell Biology
Identifiers
urn:nbn:se:umu:diva-153787 (URN)10.1038/s41598-018-35409-0 (DOI)000450411700027 ()
Funder
Carl Tryggers foundation
Available from: 2018-12-03 Created: 2018-12-03 Last updated: 2019-01-18Bibliographically approved
Wang, H., Avican, K., Fahlgren, A., Erttmann, S. F., Nuss, A. M., Dersch, P., . . . Wolf-Watz, H. (2016). Increased plasmid copy number is essential for Yersinia T3SS function and virulence. Science, 353(6298), 492-495
Open this publication in new window or tab >>Increased plasmid copy number is essential for Yersinia T3SS function and virulence
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2016 (English)In: Science, ISSN 0036-8075, E-ISSN 1095-9203, Vol. 353, no 6298, p. 492-495Article in journal (Refereed) Published
Abstract [en]

Pathogenic bacteria have evolved numerous virulence mechanisms that are essential for establishing infections. The enterobacterium Yersinia uses a type III secretion system (T3SS) encoded by a 70-kilobase, low-copy, IncFII-class virulence plasmid. We report a novel virulence strategy in Y. pseudotuberculosis in which this pathogen up-regulates the plasmid copy number during infection. We found that an increased dose of plasmid-encoded genes is indispensable for virulence and substantially elevates the expression and function of the T3SS. Remarkably, we observed direct, tight coupling between plasmid replication and T3SS function. This regulatory pathway provides a framework for further exploration of the environmental sensing mechanisms of pathogenic bacteria.

National Category
Microbiology in the medical area Infectious Medicine
Identifiers
urn:nbn:se:umu:diva-125586 (URN)10.1126/science.aaf7501 (DOI)000380583600042 ()27365311 (PubMedID)
Available from: 2016-09-19 Created: 2016-09-13 Last updated: 2018-06-07Bibliographically approved
Ekestubbe, S., Bröms, J. E., Edgren, T., Fällman, M., Francis, M. S. & Forsberg, Å. (2016). The amino-terminal part of the needle-tip translocator LcrV of Yersinia pseudotuberculosis is required for early targeting of YopH and in vivo virulence. Frontiers in Cellular and Infection Microbiology, 6, Article ID 175.
Open this publication in new window or tab >>The amino-terminal part of the needle-tip translocator LcrV of Yersinia pseudotuberculosis is required for early targeting of YopH and in vivo virulence
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2016 (English)In: Frontiers in Cellular and Infection Microbiology, E-ISSN 2235-2988, Vol. 6, article id 175Article in journal (Refereed) Published
Abstract [en]

Type III secretion systems (T3SS) are dedicated to targeting anti-host effector proteins into the cytosol of the host cell to promote bacterial infection. Delivery of the effectors requires three specific translocator proteins, of which the hydrophilic translocator, LcrV, is located at the tip of the T3SS needle and is believed to facilitate insertion of the two hydrophobic translocators into the host cell membrane. Here we used Yersinia as a model to study the role of LcrV in T3SS mediated intracellular effector targeting. Intriguingly, we identified N-terminal IcrV mutants that, similar to the wild-type protein, efficiently promoted expression, secretion and intracellular levels of Yop effectors, yet they were impaired in their ability to inhibit phagocytosis by J774 cells. In line with this, the YopH mediated dephosphorylation of Focal Adhesion Kinase early after infection was compromised when compared to the wild type strain. This suggests that the mutants are unable to promote efficient delivery of effectors to their molecular targets inside the host cell upon host cell contact. The significance of this was borne out by the fact that the mutants were highly attenuated for virulence in the systemic mouse infection model. Our study provides both novel and significant findings that establish a role for LcrV in early targeting of effectors in the host cell.

Keywords
LcrV, type III secretion system, YopH, translocation, pore formation, Yersinia pseudotuberculosis, virulence
National Category
Microbiology in the medical area Medical Biotechnology (with a focus on Cell Biology (including Stem Cell Biology), Molecular Biology, Microbiology, Biochemistry or Biopharmacy)
Identifiers
urn:nbn:se:umu:diva-130149 (URN)10.3389/fcimb.2016.00175 (DOI)000389194200001 ()
Available from: 2017-01-12 Created: 2017-01-12 Last updated: 2018-06-09Bibliographically approved
Taheri, N., Fahlgren, A. & Fällman, M. (2016). Yersinia pseudotuberculosis Blocks Neutrophil Degranulation. Infection and Immunity, 84(12), 3369-3378
Open this publication in new window or tab >>Yersinia pseudotuberculosis Blocks Neutrophil Degranulation
2016 (English)In: Infection and Immunity, ISSN 0019-9567, E-ISSN 1098-5522, Vol. 84, no 12, p. 3369-3378Article in journal (Refereed) Published
Abstract [en]

Neutrophils are essential components of immunity and are rapidly recruited to infected or injured tissue. Upon their activation, neutrophils release granules to the cell's exterior, through a process called degranulation. These granules contain proteins with antimicrobial properties that help combat infection. The enteropathogenic bacterium Yersinia pseudotuberculosis successfully persists as an extracellular bacterium during infection by virtue of its translocation of virulence effectors (Yersinia outer proteins [Yops]) that act in the cytosol of host immune cells to subvert phagocytosis and proinflammatory responses. Here, we investigated the effect of Y. pseudotuberculosis on neutrophil degranulation upon cell contact. We found that virulent Y. pseudotuberculosis was able to prevent secondary granule release. The blocking effect was general, as the release of primary and tertiary granules was also reduced. Degranulation of secondary granules was also blocked in primed neutrophils, suggesting that this mechanism could be an important element of immune evasion. Further, wild-type bacteria conferred a transient block on neutrophils that prevented their degranulation upon contact with plasmid-cured, avirulent Y. pseudotuberculosis and Escherichia coli Detailed analyses showed that the block was strictly dependent on the cooperative actions of the two antiphagocytic effectors, YopE and YopH, suggesting that the neutrophil target structures constituting signaling molecules needed to initiate both phagocytosis and general degranulation. Thus, via these virulence effectors, Yersinia can impair several mechanisms of the neutrophil's antimicrobial arsenal, which underscores the power of its virulence effector machinery.

Keywords
Yersinia, neutrophil, degranulation
National Category
Immunology Microbiology Other Biological Topics
Identifiers
urn:nbn:se:umu:diva-128892 (URN)10.1128/IAI.00760-16 (DOI)000390128700011 ()27620724 (PubMedID)
Available from: 2016-12-19 Created: 2016-12-19 Last updated: 2019-01-18Bibliographically approved
Bahnan, W., Boettner, D. R., Westermark, L., Fällman, M. & Schesser, K. (2015). Pathogenic Yersinia Promotes Its Survival by Creating an Acidic Fluid-Accessible Compartment on the Macrophage Surface. PLoS ONE, 10(8), Article ID e0133298.
Open this publication in new window or tab >>Pathogenic Yersinia Promotes Its Survival by Creating an Acidic Fluid-Accessible Compartment on the Macrophage Surface
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2015 (English)In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 10, no 8, article id e0133298Article in journal (Refereed) Published
Abstract [en]

Microbial pathogens and host immune cells each initiate events following their interaction in an attempt to drive the outcome to their respective advantage. Here we show that the bacterial pathogen Yersinia pseudotuberculosis sustains itself on the surface of a macrophage by forming acidic fluid-accessible compartments that are partially bounded by the host cell plasma membrane. These Yersinia-containing acidic compartments (YACs) are bereft of the early endosomal marker EEA1 and the lysosomal antigen LAMP1 and readily form on primary macrophages as well as macrophage-like cell lines. YAC formation requires the presence of the Yersinia virulence plasmid which encodes a type III secretion system. Unexpectedly, we found that the initial formation of YACs did not require translocation of the type III effectors into the host cell cytosol; however, the duration of YACs was markedly greater in infections using translocation-competent Y. pseudotuberculosis strains as well as strains expressing the effector YopJ. Furthermore, it was in this translocation- and YopJ-dependent phase of infection that the acidic environment was critical for Y. pseudotuberculosis survival during its interaction with macrophages. Our findings indicate that during its extracellular phase of infection Y. pseudotuberculosis initiates and then, by a separate mechanism, stabilizes the formation of a highly intricate structure on the surface of the macrophage that is disengaged from the endocytic pathway.

National Category
Cell and Molecular Biology
Identifiers
urn:nbn:se:umu:diva-108136 (URN)10.1371/journal.pone.0133298 (DOI)000359493600011 ()
Available from: 2015-09-18 Created: 2015-09-04 Last updated: 2018-06-07Bibliographically approved
Avican, K., Fahlgren, A., Huss, M., Heroven, A. K., Beckstette, M., Dersch, P. & Fällman, M. (2015). Reprogramming of Yersinia from Virulent to Persistent Mode Revealed by Complex In Vivo RNA-seq Analysis. PLoS Pathogens, 11(1), Article ID e1004600.
Open this publication in new window or tab >>Reprogramming of Yersinia from Virulent to Persistent Mode Revealed by Complex In Vivo RNA-seq Analysis
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2015 (English)In: PLoS Pathogens, ISSN 1553-7366, E-ISSN 1553-7374, Vol. 11, no 1, article id e1004600Article in journal (Refereed) Published
Abstract [en]

We recently found that Yersinia pseudotuberculosis can be used as a model of persistent bacterial infections. We performed in vivo RNA-seq of bacteria in small cecal tissue biopsies at early and persistent stages of infection to determine strategies associated with persistence. Comprehensive analysis of mixed RNA populations from infected tissues revealed that Y. pseudotuberculosis undergoes transcriptional reprogramming with drastic down-regulation of T3SS virulence genes during persistence when the pathogen resides within the cecum. At the persistent stage, the expression pattern in many respects resembles the pattern seen in vitro at 26oC, with for example, up-regulation of flagellar genes and invA. These findings are expected to have impact on future rationales to identify suitable bacterial targets for new antibiotics. Other genes that are up-regulated during persistence are genes involved in anaerobiosis, chemotaxis, and protection against oxidative and acidic stress, which indicates the influence of different environmental cues. We found that the Crp/CsrA/RovA regulatory cascades influence the pattern of bacterial gene expression during persistence. Furthermore, arcA, fnr, frdA, and wrbA play critical roles in persistence. Our findings suggest a model for the life cycle of this enteropathogen with reprogramming from a virulent to an adapted phenotype capable of persisting and spreading by fecal shedding.

Keywords
Persistent infection, RNA-seq, PMNs, Yersinia, Transcriptome, wrba, fnr, rovA, arcA, rfaH
National Category
Cell and Molecular Biology Biochemistry and Molecular Biology Bioinformatics and Systems Biology
Research subject
biology, Environmental Science
Identifiers
urn:nbn:se:umu:diva-100980 (URN)10.1371/journal.ppat.1004600 (DOI)000349106100030 ()25590628 (PubMedID)
Available from: 2015-03-16 Created: 2015-03-16 Last updated: 2018-06-07Bibliographically approved
Erttmann, S. F., Gekara, N. O. & Fällman, M. (2014). Bacteria Induce Prolonged PMN Survival via a Phosphatidylcholine-Specific Phospholipase C- and Protein Kinase C-Dependent Mechanism. PLoS ONE, 9(1), e87859
Open this publication in new window or tab >>Bacteria Induce Prolonged PMN Survival via a Phosphatidylcholine-Specific Phospholipase C- and Protein Kinase C-Dependent Mechanism
2014 (English)In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 9, no 1, p. e87859-Article in journal (Refereed) Published
Abstract [en]

Polymorphonuclear leukocytes (PMNs) are essential for the human innate immune defense, limiting expansion of invading microorganisms. PMN turnover is controlled by apoptosis, but the regulating signaling pathways remain elusive, largely due to inherent differences between mice and humans that undermine use of mouse models for understanding human PMN biology. Here, we aim to elucidate signal transduction mediating survival of human peripheral blood PMNs in response to bacteria, such as Yersinia pseudotuberculosis, an enteropathogen that causes the gastro-intestinal disease yersiniosis, as well as Escherichia coli and Staphylococcus aureus. Determinations of cell death reveal that uninfected control cells undergo apoptosis, while PMNs infected with either Gram-positive or -negative bacteria show profoundly increased survival. Infected cells exhibit decreased caspase 3 and 8 activities, increased mitochondrial integrity and are resistant to apoptosis induced by a death receptor ligand. This bacteria-induced response is accompanied by pro-inflammatory cytokine production including interleukin-8 and tumor necrosis factor-a competent to attract additional PMNs. Using agonists and pharmacological inhibitors, we show participation of Toll-like receptor 2 and 4, and interestingly, that protein kinase C (PKC) and phosphatidylcholine-specific phospholipase C (PC-PLC), but not tyrosine kinases or phosphatidylinositol-specific phospholipase C (PI-PLC) are key players in this dual PMN response. Our findings indicate the importance of prolonged PMN survival in response to bacteria, where general signaling pathways ensure complete exploitation of PMN anti-microbial capacity.

National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:umu:diva-87041 (URN)10.1371/journal.pone.0087859 (DOI)000330621900186 ()
Available from: 2014-04-07 Created: 2014-03-18 Last updated: 2018-06-08Bibliographically approved
Fahlgren, A., Avican, K., Westermark, L., Nordfelth, R. & Fällman, M. (2014). Colonization of cecum is important for development of persistent infection by Yersinia pseudotuberculosis. Infection and Immunity, 82(8), 3471-3482
Open this publication in new window or tab >>Colonization of cecum is important for development of persistent infection by Yersinia pseudotuberculosis
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2014 (English)In: Infection and Immunity, ISSN 0019-9567, E-ISSN 1098-5522, Vol. 82, no 8, p. 3471-3482Article in journal (Refereed) Published
Abstract [en]

Yersiniosis is a human disease caused by the bacterium Yersinia pseudotuberculosis or Yersinia enterocolitica. The infection is usually resolved but can lead to postinfectious sequelae, including reactive arthritis and erythema nodosum. The commonly used Yersinia mouse infection model mimics acute infection in humans to some extent but leads to systemic infection and eventual death. Here, we analyzed sublethal infection doses of Y. pseudotuberculosis in mice in real time using bioluminescent imaging and found that infections using these lower doses result in extended periods of asymptomatic infections in a fraction of mice. In a search for the site for bacterial persistence, we found that the cecum was the primary colonization site and was the site where the organism resided during a 115-day infection period. Persistent infection was accompanied by sustained fecal shedding of cultivable bacteria. Cecal patches were identified as the primary site for cecal colonization during persistence. Y. pseudotuberculosis bacteria were present in inflammatory lesions, in localized foci, or as single cells and also in neutrophil exudates in the cecal lumen. The chronically colonized cecum may serve as a reservoir for dissemination of infection to extraintestinal sites, and a chronic inflammatory state may trigger the onset of postinfectious sequelae. This novel mouse model for bacterial persistence in cecum has potential as an investigative tool to unveil a deeper understanding of bacterial adaptation and host immune defense mechanisms during persistent infection.

Place, publisher, year, edition, pages
American Society for Microbiology, 2014
National Category
Immunology in the medical area Infectious Medicine
Identifiers
urn:nbn:se:umu:diva-91821 (URN)10.1128/IAI.01793-14 (DOI)000339161400035 ()
Available from: 2014-09-01 Created: 2014-08-18 Last updated: 2018-06-07Bibliographically approved
Westermark, L., Fahlgren, A. & Fällman, M. (2014). Yersinia pseudotuberculosis Efficiently Escapes Polymorphonuclear Neutrophils during Early Infection. Infection and Immunity, 82(3), 1181-1191
Open this publication in new window or tab >>Yersinia pseudotuberculosis Efficiently Escapes Polymorphonuclear Neutrophils during Early Infection
2014 (English)In: Infection and Immunity, ISSN 0019-9567, E-ISSN 1098-5522, Vol. 82, no 3, p. 1181-1191Article in journal (Refereed) Published
Abstract [en]

The human-pathogenic species of the Gram-negative genus Yersinia preferentially target and inactivate cells of the innate immune defense, suggesting that this is a critical step by which these bacteria avoid elimination and cause disease. In this study, bacterial interactions with dendritic cells, macrophages, and polymorphonuclear neutrophils (PMNs) in intestinal lymphoid tissues during early Yersinia pseudotuberculosis infection were analyzed. Wild-type bacteria were shown to interact mainly with dendritic cells, but not with PMNs, on day 1 postinfection, while avirulent yopH and yopE mutants interacted with PMNs as well as with dendritic cells. To unravel the role of PMNs during the early phase of infection, we depleted mice of PMNs by using an anti-Ly6G antibody, after which we could see more-efficient initial colonization by the wild-type strain as well as by yopH, yopE, and yopK mutants on day 1 postinfection. Dissemination of yopH, yopE, and yopK mutants from the intestinal compartments to mesenteric lymph nodes was faster in PMN-depleted mice than in undepleted mice, emphasizing the importance of effective targeting of PMNs by these Yersinia outer proteins (Yops). In conclusion, escape from interaction with PMNs due to the action of YopH, YopE, and YopK is a key feature of pathogenic Yersinia species that allows colonization and effective dissemination.

National Category
Cell and Molecular Biology
Identifiers
urn:nbn:se:umu:diva-88290 (URN)10.1128/IAI.01634-13 (DOI)000333190900029 ()24379291 (PubMedID)
Available from: 2014-05-02 Created: 2014-04-29 Last updated: 2018-06-07Bibliographically approved
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