scholarly journals in vivo gene expression and the adaptive response: from pathogenesis to vaccines and antimicrobials

2000 ◽  
Vol 355 (1397) ◽  
pp. 633-642 ◽  
Author(s):  
Douglas M. Heithoff ◽  
Robert L. Sinsheimer ◽  
David A. Low ◽  
Michael J. Mahan
Keyword(s):  
Pathogenic Bacteria ◽  
Acid Stress ◽  
Infection Process ◽  
Bacterial Virulence ◽  
Microbial Pathogens ◽  
Virulence Determinants ◽  
Preferential Expression ◽  
Successful Infection ◽  
Dna Adenine Methylase

Microbial pathogens possess a repertoire of virulence determinants that each make unique contributions to fitness during infection. Analysis of these in vivo –expressed functions reveals the biology of the infection process, encompassing the bacterial infection strategies and the host ecological and environmental retaliatory strategies designed to combat them (e.g. thermal, osmotic, oxygen, nutrient and acid stress). Many of the bacterial virulence functions that contribute to a successful infection are normally only expressed during infection. A genetic approach was used to isolate mutants that ectopically expressed many of these functions in a laboratory setting. Lack of DNA adenine methylase (Dam) in Salmonella typhimurium abolishes the preferential expression of many bacterial virulence genes in host tissues. Dam − Salmonella were proficient in colonization of mucosal sites but were defective in colonization of deeper tissue sites. Additionally, Dam − mutants were totally avirulent and effective as live vaccines against murine typhoid fever. Since dam is highly conserved in many pathogenic bacteria that cause significant morbidity and mortality worldwide, Dams are potentially excellent targets for both vaccines and antimicrobials.

scholarly journals Rv3723/LucA coordinates fatty acid and cholesterol uptake inMycobacterium tuberculosis

2017 ◽  
Author(s):  
Evgeniya V. Nazarova ◽  
Christine R. Montague ◽  
Thuy La ◽  
Kaley M. Wilburn ◽  
Neelima Sukumar ◽  
...  
Keyword(s):  
Fatty Acids ◽  
Fatty Acid ◽  
Pathogenic Bacteria ◽  
Bacterial Virulence ◽  
Fatty Acid Transport ◽  
Acid Transport ◽  
Uncharacterized Protein ◽  
Fatty Acid Transporter ◽  
Important Fatty Acid

AbstractPathogenic bacteria have evolved highly specialized systems to extract essential nutrients from their hosts andMycobacterium tuberculosis(Mtb) scavenges lipids (cholesterol and fatty acids) to maintain infection in mammals. While the uptake of cholesterol by Mtb is mediated by the Mce4 transporter, the route(s) of uptake of fatty acids remain unknown. Here, we demonstrate that an uncharacterized protein LucA, integrates the assimilation of both cholesterol and fatty acids in Mtb. LucA interacts with subunits of the Mce1 and Mce4 complexes to coordinate the activities of these nutrient transporters. We also demonstrate that Mce1 functions as an important fatty acid transporter in Mtb and we determine that the integration of cholesterol and fatty acid transport by LucA is required for full bacterial virulencein vivo. These data establish that fatty acid and cholesterol assimilation are inexorably linked in Mtb and reveals a key role for LucA in coordinating both transport activities.

scholarly journals Identification and analysis of bacterial virulence genes in vivo

2000 ◽  
Vol 355 (1397) ◽  
pp. 613-622 ◽  
Author(s):  
Kate E. Unsworth ◽  
David W. Holden
Keyword(s):  
Type Iii Secretion ◽  
Virulence Genes ◽  
Screening Method ◽  
Secretion System ◽  
Bacterial Virulence ◽  
Microbial Pathogens ◽  
Temperature Sensitive ◽  
Approaches To Study

Signature–tagged mutagenesis is a mutation–based screening method for the identification of virulence genes of microbial pathogens. Genes isolated by this approach fall into three classes: those with known biochemical function, those of suspected function and some whose functions cannot be predicted from database searches. A variety of in vitro and in vivo methods are available to elucidate the function of genes of the second and third classes. We describe the use of some of these approaches to study the function of the Salmonella pathogenicity island 2 type III secretion system of Salmonella typhimurium . This virulence determinant is required for intracellular survival. Secretion by this system is induced by an acidic pH, and its function may be to alter trafficking of the Salmonella –containing vacuole. Use of a temperature–sensitive non–replicating plasmid and competitive index tests with other genes show that in vivo phenotypes do not always correspond to those predicted from in vitro studies.

scholarly journals Rv3723/LucA coordinates fatty acid and cholesterol uptake in Mycobacterium tuberculosis

eLife ◽  
2017 ◽  
Vol 6 ◽  
Author(s):  
Evgeniya V Nazarova ◽  
Christine R Montague ◽  
Thuy La ◽  
Kaley M Wilburn ◽  
Neelima Sukumar ◽  
...  
Keyword(s):  
Fatty Acids ◽  
Mycobacterium Tuberculosis ◽  
Fatty Acid ◽  
Pathogenic Bacteria ◽  
Fatty Acid Uptake ◽  
Bacterial Virulence ◽  
Acid Uptake ◽  
Uncharacterized Protein ◽  
Fatty Acid Transporter

Pathogenic bacteria have evolved highly specialized systems to extract essential nutrients from their hosts. Mycobacterium tuberculosis (Mtb) scavenges lipids (cholesterol and fatty acids) to maintain infections in mammals but mechanisms and proteins responsible for the import of fatty acids in Mtb were previously unknown. Here, we identify and determine that the previously uncharacterized protein Rv3723/LucA, functions to integrate cholesterol and fatty acid uptake in Mtb. Rv3723/LucA interacts with subunits of the Mce1 and Mce4 complexes to coordinate the activities of these nutrient transporters by maintaining their stability. We also demonstrate that Mce1 functions as a fatty acid transporter in Mtb and determine that facilitating cholesterol and fatty acid import via Rv3723/LucA is required for full bacterial virulence in vivo. These data establish that fatty acid and cholesterol assimilation are inexorably linked in Mtb and reveals a key function for Rv3723/LucA in in coordinating thetransport of both these substrates.

scholarly journals Bacillus thuringiensistargets the host intestinal epithelial junctions for successful infection ofCaenorhabditis elegans

2018 ◽  
Author(s):  
Liting Wan ◽  
Jian Lin ◽  
Hongwen Du ◽  
Alejandra Bravo ◽  
Mario Soberón ◽  
...  
Keyword(s):  
Virulence Factors ◽  
Pathogenic Bacteria ◽  
Intestinal Barrier ◽  
Infection Process ◽  
Intestinal Epithelial ◽  
Cry Toxins ◽  
Early Stages ◽  
Successful Infection ◽  
Epithelial Junctions ◽  
Sporulation Phase

ABSTRACTPathogenic bacteria use different strategies to infect their hosts including the simultaneous production of pore forming toxins and several virulence factors that help to synergize their pathogenic effects. However, how the pathogenic bacteria are able to complete their life cycle and break out the host intestinal barrier is poorly understood. The infectious cycle ofBacillus thuringiensis(Bt) bacterium inCaenorhabditis elegansis a powerful model system to study the early stages of the infection process. Bt produces Cry pore-forming toxins during the sporulation phase that are key virulence factors involved in Bt pathogenesis. Here we show that during the early stages of infection, the Cry toxins disrupt the midgut epithelial tissue allowing the germination of spores. The vegetative Bt cells then trigger a quorum sensing response that is activated by PlcR regulator resulting in production of different virulence factors, such as the metalloproteinases ColB and Bmp1, that besides Cry toxins are necessary to disrupt the nematode epithelial junctions causing efficient bacterial host infection and dead of the nematode. Overall our work describes a novel mechanism for Bt infection, targeting the epithelial junctions of its host midgut cells.Author summaryThe entomopathogenic bacteriaBacillus thuringiensis(Bt) are used worldwide as biopesticides due to their insecticidal properties. Crystal proteins (Cry) produced by Bt during the sporulation phase of growth are mainly responsible for their insecticidal properties. The infection process of Bt includes three successive steps, virulence, necrotrophic, and sporulation processes. During the virulence process, after ingestion by the susceptible hosts, the Cry toxins form pores in the apical membrane of intestinal cells, inducing favorable conditions for bacterial spore germination. Vegetative bacteria multiply in the host and coordinate their behavior by using the quorum sensor regulator PlcR, which leads to the production of virulence factors allowing the bacteria to kill the host. However, how the bacteria are able to disrupt the host intestinal barrier during the early stages of infection remains unknown. Here we show that Bt employs the nematicidal Cry toxins and additional virulence factors controlled by the PlcR regulon to disrupt the intestinal epithelial junctions ofC. elegansat the early stages of infection allowing that Bt bacteria complete its life cycle in the worms. Our work provides new insights into the pathogenesis of Bt, and highlights the importance of breaking down host epithelial junctions for a successful infection, a similar mechanism could be used by other pathogens-host interactions since epithelial junctions are conserved structures from insects to mammals.

scholarly journals Human Papillomavirus Type 31b Infection of Human Keratinocytes Does Not Require Heparan Sulfate

2005 ◽  
Vol 79 (11) ◽  
pp. 6838-6847 ◽  
Author(s):  
Nicole A. Patterson ◽  
Jessica L. Smith ◽  
Michelle A. Ozbun
Keyword(s):  
High Risk ◽  
Heparan Sulfate ◽  
Human Keratinocytes ◽  
Hpv Infection ◽  
Infection Process ◽  
Human Papillomaviruses ◽  
Viral Attachment ◽  
Successful Infection ◽  
High Risk Hpv

ABSTRACT Oncogenic human papillomaviruses (HPVs) are difficult to study experimentally as they replicate at low levels in vivo. This has precluded the purification of high-risk HPV virions from in vivo lesions. Virus-like particles (VLPs) and pseudovirions from low- and high-risk HPV types can emulate various aspects of HPV virion attachment and infections. These studies suggest that HPV infection is mediated by α6-integrin and/or heparan-sulfonated receptors. However, whether VLPs and pseudovirions accurately reflect the infection process of HPV virions has not been verified. We generated infectious HPV31b virions from organotypic (raft) tissues and performed experimental infections in a variety of cells. Successful infection following viral attachment, internalization, and nuclear transport was assayed by detecting newly synthesized, spliced HPV transcripts using reverse transcription (RT)-PCR or RT-quantitative PCR. Most human epithelial cells were infected with HPV31b at a multiplicity of infection as low as 1 to 10 viral genome equivalents per cell. HPV31b infection was detected in other cell lines, including COS-7 monkey kidney cells, but higher viral multiplicities of infection were required. Heparin preparations of various molecular weights or heparinase I treatment of cells prevented HPV31b infection of COS-7 cells and C-33A human cervical cancer cells in reproducible and dose-dependent manners. However, these reagents were unable to block infection of human keratinocytes, including HaCaT and N/TERT-1 cells and low-passage human foreskin keratinocytes. These data suggest that HPV31b infection of human keratinocytes, the natural host cell for HPV infections in vivo, does not require a heparan-sulfonated receptor, whereas heparan sulfate is important for infection of some other cells.

scholarly journals Bacterial autolysins trim cell surface peptidoglycan to prevent detection by the Drosophila innate immune system

eLife ◽  
2014 ◽  
Vol 3 ◽  
Author(s):  
Magda Luciana Atilano ◽  
Pedro Matos Pereira ◽  
Filipa Vaz ◽  
Maria João Catalão ◽  
Patricia Reed ◽  
...  
Keyword(s):  
Immune System ◽  
Innate Immune System ◽  
Pathogenic Bacteria ◽  
Bacterial Virulence ◽  
Innate Immune ◽  
Molecular Signature ◽  
Host Immune System ◽  
Bacterial Proteins ◽  
Successful Infection ◽  
Bacterial Surfaces

Bacteria have to avoid recognition by the host immune system in order to establish a successful infection. Peptidoglycan, the principal constituent of virtually all bacterial surfaces, is a specific molecular signature recognized by dedicated host receptors, present in animals and plants, which trigger an immune response. Here we report that autolysins from Gram-positive pathogenic bacteria, enzymes capable of hydrolyzing peptidoglycan, have a major role in concealing this inflammatory molecule from Drosophila peptidoglycan recognition proteins (PGRPs). We show that autolysins trim the outermost peptidoglycan fragments and that in their absence bacterial virulence is impaired, as PGRPs can directly recognize leftover peptidoglycan extending beyond the external layers of bacterial proteins and polysaccharides. The activity of autolysins is not restricted to the producer cells but can also alter the surface of neighboring bacteria, facilitating the survival of the entire population in the infected host.

scholarly journals The Degenerate EAL-GGDEF Domain Protein Filp Functions as a Cyclic di-GMP Receptor and Specifically Interacts with the PilZ-Domain Protein PXO_02715 to Regulate Virulence in Xanthomonas oryzae pv. oryzae

2014 ◽  
Vol 27 (6) ◽  
pp. 578-589 ◽  
Author(s):  
Fenghuan Yang ◽  
Fang Tian ◽  
Xiaotong Li ◽  
Susu Fan ◽  
Huamin Chen ◽  
...  
Keyword(s):  
Gene Expression ◽  
Pathogenic Bacteria ◽  
In Silico Analysis ◽  
Bacterial Virulence ◽  
Xanthomonas Oryzae ◽  
Glutathione S Transferase ◽  
Ggdef Domain ◽  
Domain Protein ◽  
Silico Analysis

Degenerate GGDEF and EAL domain proteins represent major types of cyclic diguanylic acid (c-di-GMP) receptors in pathogenic bacteria. Here, we characterized a FimX-like protein (Filp) which possesses both GGDEF and EAL domains in Xanthomonas oryzae pv. oryzae, the causal agent of bacterial blight of rice. Both in silico analysis and enzyme assays indicated that the GGDEF and EAL domains of Filp were degenerate and enzymatically inactive. However, Filp bound to c-di-GMP efficiently within the EAL domain, where Q477, E653, and F654 residues were crucial for the binding. Deletion of the filp gene in X. oryzae pv. oryzae resulted in attenuated virulence in rice and reduced type III secretion system (T3SS) gene expression. Complementation analysis with different truncated proteins indicated that REC, PAS, and EAL domains but not the GGDEF domain were required for the full activity of Filp in vivo. In addition, a PilZ-domain protein (PXO_02715) was identified as a Filp interactor by yeast two-hybrid and glutathione-S-transferase pull-down assays. Deletion of the PXO_02715 gene demonstrated changes in bacterial virulence and T3SS gene expression similar to Δfilp. Moreover, both mutants were impaired in their ability to induce hypersensitive response in nonhost plants. Thus, we concluded that Filp was a novel c-di-GMP receptor of X. oryzae pv. oryzae, and its function to regulate bacterial virulence expression might be via the interaction with PXO_02715.

scholarly journals In Vitro and In Vivo Characterization of a Bordetella bronchiseptica Mutant Strain with a Deep Rough Lipopolysaccharide Structure

2002 ◽  
Vol 70 (4) ◽  
pp. 1791-1798 ◽  
Author(s):  
Federico Sisti ◽  
Julieta Fernández ◽  
María Eugenia Rodríguez ◽  
Antonio Lagares ◽  
Nicole Guiso ◽  
...  
Keyword(s):  
Parental Strain ◽  
Infection Process ◽  
Bordetella Bronchiseptica ◽  
Host Cells ◽  
Virulence Determinants ◽  
Chronic Infections ◽  
In Vivo Experiments ◽  
Dominant Phenotype

ABSTRACT Bordetella bronchiseptica is closely related to Bordetella pertussis, which produces respiratory disease primarily in mammals other than humans. However, its importance as a human pathogen is being increasingly recognized. Although a large amount of research on Bordetella has been generated regarding protein virulence factors, the participation of the surface lipopolysaccharide (LPS) during B. bronchiseptica infection is less understood. To get a better insight into this matter, we constructed and characterized the behavior of an LPS mutant with the deepest possible rough phenotype. We generated the defective mutant B. bronchiseptica LP39 on the waaC gene, which codes for a heptosyl transferase involved in the biosynthesis of the core region of the LPS molecule. Although in B. bronchiseptica LP39 the production of the principal virulence determinants adenylate cyclase-hemolysin, filamentous hemagglutinin, and pertactin persisted, the quantity of the two latter factors was diminished, with the levels of pertactin being the most greatly affected. Furthermore, the LPS of B. bronchiseptica LP39 did not react with sera obtained from mice that had been infected with the parental strain, indicating that this defective LPS is immunologically different from the wild-type LPS. In vivo experiments demonstrated that the ability to colonize the respiratory tract is reduced in the mutant, being effectively cleared from lungs within 5 days, whereas the parental strain survived at least for 30 days. In vitro experiments have demonstrated that, although B. bronchiseptica LP39 was impaired for adhesion to human epithelial cells, it is still able to survive within the host cells as efficiently as the parental strain. These results seem to indicate that the deep rough form of B. bronchiseptica LPS cannot represent a dominant phenotype at the first stage of colonization. Since isolates with deep rough LPS phenotype have already been obtained from human B. bronchiseptica chronic infections, the possibility that this phenotype arises as a consequence of selection pressure within the host at a late stage of the infection process is discussed.

scholarly journals Intestinal Organoids: New Tools to Comprehend the Virulence of Bacterial Foodborne Pathogens

Foods ◽  
2022 ◽  
Vol 11 (1) ◽  
pp. 108
Author(s):  
Mayra Aguirre Garcia ◽  
Killian Hillion ◽  
Jean-Michel Cappelier ◽  
Michel Neunlist ◽  
Maxime M. Mahe ◽  
...  
Keyword(s):  
Infectious Diseases ◽  
Pathogenic Bacteria ◽  
Foodborne Pathogen ◽  
Extensive Study ◽  
Infection Process ◽  
High Morbidity ◽  
Cell Culture Techniques ◽  
Culture Techniques

Foodborne diseases cause high morbidity and mortality worldwide. Understanding the relationships between bacteria and epithelial cells throughout the infection process is essential to setting up preventive and therapeutic solutions. The extensive study of their pathophysiology has mostly been performed on transformed cell cultures that do not fully mirror the complex cell populations, the in vivo architectures, and the genetic profiles of native tissues. Following advances in primary cell culture techniques, organoids have been developed. Such technological breakthroughs have opened a new path in the study of microbial infectious diseases, and thus opened onto new strategies to control foodborne hazards. This review sheds new light on cellular messages from the host–foodborne pathogen crosstalk during in vitro organoid infection by the foodborne pathogenic bacteria with the highest health burden. Finally, future perspectives and current challenges are discussed to provide a better understanding of the potential applications of organoids in the investigation of foodborne infectious diseases.

Antigens ofAspergillus fumigatusexpressed during infection

1995 ◽  
Vol 73 (S1) ◽  
pp. 1087-1091 ◽  
Author(s):  
Jean-Paul Debeaupuis ◽  
Jacqueline Sarfati ◽  
Hidemitsu Kobayashi ◽  
Drion G. Boucias ◽  
Anne Beauvais ◽  
...  
Keyword(s):  
Invasive Aspergillosis ◽  
Aspergillus Fumigatus ◽  
Virulence Gene ◽  
Culture Conditions ◽  
Infection Process ◽  
Host Cells ◽  
Virulence Determinants

Aspergillus fumigatus secretes an array of antigenic molecules in vitro and in vivo. Recent progresses have been made in the characterization and standardization of A. fumigatus antigens useful for the serodiagnosis of aspergillosis. The chymotrypsin antigen has been purified and can be utilized for the diagnosis of aspergillosis occurring in patients with an immunocompetent B cell population. In the case of immunosuppressed patients suffering from invasive aspergillosis, new methods have been developed to detect the galactofuran containing antigen in the serum. The chemical configuration of this molecule is now known. In contrast to their potential in diagnosis, very little progress has been made on the study of the biochemical and pathoimmunological role of these antigens during the infection process. Two reasons can be advanced for this lack of understanding of the virulence determinants. First of all, antigens studied have been produced in vitro in a dextrose rich medium where pH reaches a value below 5 at maximal growth. These culture conditions are very different from the nutritional environment of the lung, which is a protein-based medium with a slightly basic pH. Antigens expressed under these nutritional conditions are very different from the ones detected in vitro. Second, A. fumigatus is an opportunistic fungus which is characterized by a multifactorial virulence. Gene disruption strategy is not adequate to discriminate the role of a factor in the virulence of the fungus. In contrast, as shown by the studies on two toxins of A. fumigatus, a direct effect of an antigen can be seen directly when several fungal molecules are tested in conjunction on host cells. Key words: Aspergillus fumigatus, antigen, invasive aspergillosis, galactomannan, protease.

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