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F1000Research 2019Morphological changes are critical for the virulence of a range of plant and human fungal pathogens. is a major human fungal pathogen whose ability to switch between... (Review)
Review
Morphological changes are critical for the virulence of a range of plant and human fungal pathogens. is a major human fungal pathogen whose ability to switch between different morphological states is associated with its adaptability and pathogenicity. In particular, can switch from an oval yeast form to a filamentous hyphal form, which is characteristic of filamentous fungi. What mechanisms underlie hyphal growth and how are they affected by environmental stimuli from the host or resident microbiota? These questions are the focus of intensive research, as understanding hyphal growth has broad implications for cell biological and medical research.
Topics: Candida albicans; Humans; Hyphae; Virulence
PubMed: 31131089
DOI: 10.12688/f1000research.18546.1 -
Advances in Experimental Medicine and... 2011The family Xanthomonadaceae is a wide-spread family of bacteria belonging to the gamma subdivision of the Gram-negative proteobacteria, including the two... (Review)
Review
The family Xanthomonadaceae is a wide-spread family of bacteria belonging to the gamma subdivision of the Gram-negative proteobacteria, including the two plant-pathogenic genera Xanthomonas and Xylella, and the related genus Stenotrophomonas. Adhesion is a widely conserved virulence mechanism among Gram-negative bacteria, no matter whether they are human, animal or plant pathogens, since attachment to the host tissue is one of the key early steps of the bacterial infection process. Bacterial attachment to surfaces is mediated by surface structures that are anchored in the bacterial outer membrane and cover a broad group of fimbrial and non-fimbrial structures, commonly known as adhesins. In this chapter, we discuss recent findings on candidate adhesins of plant-pathogenic Xanthomonadaceae, including polysaccharidic (lipopolysaccharides, exopolysaccharides) and proteineous structures (chaperone/usher pili, type IV pili, autotransporters, two-partner-secreted and other outer membrane adhesins), their involvement in the formation of biofilms and their mode of regulation via quorum sensing. We then compare the arsenals of adhesins among different Xanthomonas strains and evaluate their mode of selection. Finally, we summarize the sparse knowledge on specific adhesin receptors in plants and the possible role of RGD motifs in binding to integrin-like plant molecules.
Topics: Adhesins, Bacterial; Bacterial Adhesion; Fimbriae, Bacterial; Gram-Negative Bacterial Infections; Host-Pathogen Interactions; Plant Diseases; Plants; Polysaccharides, Bacterial; Receptors, Immunologic; Virulence; Xanthomonadaceae
PubMed: 21557058
DOI: 10.1007/978-94-007-0940-9_5 -
Current Opinion in Plant Biology Aug 2020Plant pathogens can rapidly overcome resistance of their hosts by mutating key pathogenicity genes encoding for effectors. Pathogen adaptation is fuelled by extensive... (Review)
Review
Plant pathogens can rapidly overcome resistance of their hosts by mutating key pathogenicity genes encoding for effectors. Pathogen adaptation is fuelled by extensive genetic variability in populations and different strains may not share the same set of genes. Recently, such an intra-specific variation in gene content became formalized as pangenomes distinguishing core genes (i.e. shared) and accessory genes (i.e. lineage or strain-specific). Across pathogens species, key effectors tend to be part of the rapidly evolving accessory genome. Here, we show how the construction and analysis of pathogen pangenomes provide deep insights into the dynamic host adaptation process. We also discuss how pangenomes should ideally be built and how geography, niche and lifestyle likely determine pangenome sizes.
Topics: Plant Diseases; Plants; Virulence
PubMed: 32480355
DOI: 10.1016/j.pbi.2020.04.009 -
Frontiers in Cellular and Infection... 2018Iron is an absolute requirement for both the host and most pathogens alike and is needed for normal cellular growth. The acquisition of iron by biological systems is... (Review)
Review
Iron is an absolute requirement for both the host and most pathogens alike and is needed for normal cellular growth. The acquisition of iron by biological systems is regulated to circumvent toxicity of iron overload, as well as the growth deficits imposed by iron deficiency. In addition, hosts, such as humans, need to limit the availability of iron to pathogens. However, opportunistic pathogens such as are able to adapt to extremes of iron availability, such as the iron replete environment of the gastrointestinal tract and iron deficiency during systemic infection. has developed a complex and effective regulatory circuit for iron acquisition and storage to circumvent iron limitation within the human host. As can form complex interactions with both commensal and pathogenic co-inhabitants, it can be speculated that iron may play an important role in these interactions. In this review, we highlight host iron regulation as well as regulation of iron homeostasis in . In addition, the review argues for the need for further research into the role of iron in polymicrobial interactions. Lastly, the role of iron in treatment of infection is discussed.
Topics: Candida albicans; Candidiasis; Gastrointestinal Tract; Gene Expression Regulation, Fungal; Homeostasis; Host-Pathogen Interactions; Humans; Immunity; Iron; Microbial Interactions; Symbiosis; Virulence
PubMed: 29922600
DOI: 10.3389/fcimb.2018.00185 -
Infection and Immunity Dec 2012The emergence of new pathogens and the exploitation of novel pathogenic niches by bacteria typically require the horizontal transfer of virulence factors and subsequent... (Review)
Review
The emergence of new pathogens and the exploitation of novel pathogenic niches by bacteria typically require the horizontal transfer of virulence factors and subsequent adaptation--a "fine-tuning" process--for the successful incorporation of these factors into the microbe's genome. The function of newly acquired virulence factors may be hindered by the expression of genes already present in the bacterium. Occasionally, certain genes must be inactivated or deleted for full expression of the pathogen phenotype to occur. These genes are known as antivirulence genes (AVGs). Originally identified in Shigella, AVGs have improved our understanding of pathogen evolution and provided a novel approach to drug and vaccine development. In this review, we revisit the AVG definition and update the list of known AVGs, which now includes genes from pathogens such as Salmonella, Yersinia pestis, and the virulent Francisella tularensis subspecies. AVGs encompass a wide variety of different roles within the microbe, including genes involved in metabolism, biofilm synthesis, lipopolysaccharide modification, and host vasoconstriction. More recently, the use of one of these AVGs (lpxL) as a potential vaccine candidate highlights the practical application of studying AVG inactivation in microbial pathogens.
Topics: Adaptation, Biological; Animals; Bacteria; Evolution, Molecular; Gene Silencing; Genes, Bacterial; Humans; Mice; Virulence
PubMed: 23045475
DOI: 10.1128/IAI.00740-12 -
The New Phytologist Aug 2009Ecological, evolutionary and molecular models of interactions between plant hosts and microbial pathogens are largely based around a concept of tightly coupled... (Review)
Review
Ecological, evolutionary and molecular models of interactions between plant hosts and microbial pathogens are largely based around a concept of tightly coupled interactions between species pairs. However, highly pathogenic and obligate associations between host and pathogen species represent only a fraction of the diversity encountered in natural and managed systems. Instead, many pathogens can infect a wide range of hosts, and most hosts are exposed to more than one pathogen species, often simultaneously. Furthermore, outcomes of pathogen infection vary widely because host plants vary in resistance and tolerance to infection, while pathogens are also variable in their ability to grow on or within hosts. Environmental heterogeneity further increases the potential for variation in plant host-pathogen interactions by influencing the degree and fitness consequences of infection. Here, we describe these continua of specificity and virulence inherent within plant host-pathogen interactions. Using this framework, we describe and contrast the genetic and environmental mechanisms that underlie this variation, outline consequences for epidemiology and community structure, explore likely ecological and evolutionary drivers, and highlight several key areas for future research.
Topics: Biological Evolution; Ecosystem; Host-Pathogen Interactions; Plants; Species Specificity; Virulence
PubMed: 19563451
DOI: 10.1111/j.1469-8137.2009.02927.x -
Biological Reviews of the Cambridge... Nov 2004Recent studies have provided evolutionary explanations for much of the variation in mortality among human infectious diseases. One gap in this knowledge concerns... (Review)
Review
Recent studies have provided evolutionary explanations for much of the variation in mortality among human infectious diseases. One gap in this knowledge concerns respiratory tract pathogens transmitted from person to person by direct contact or through environmental contamination. The sit-and-wait hypothesis predicts that virulence should be positively correlated with durability in the external environment because high durability reduces the dependence of transmission on host mobility. Reviewing the epidemiological and medical literature, we confirm this prediction for respiratory tract pathogens of humans. Our results clearly distinguish a high-virulence high-survival group of variola (smallpox) virus, Mycobacterium tuberculosis, Cornynebacterium diphtheriae, Bordetella pertussis, Streptococcus pneumoniae, and influenza virus (where all pathogens have a mean percent mortality > or = 0.01% and mean survival time >10 days) from a low-virulence low-survival group containing ten other pathogens. The correlation between virulence and durability explains three to four times of magnitude of difference in mean percent mortality and mean survival time, using both across-species and phylogenetically controlled analyses. Our findings bear on several areas of active research and public health policy: (1) many pathogens used in the biological control of insects are potential sit-and-wait pathogens as they combine three attributes that are advantageous for pest control: high virulence, long durability after application, and host specificity; (2) emerging pathogens such as the 'hospital superbug' methicillin-resistant Staphylococcus aureus (MRSA) and potential bioweapons pathogens such as smallpox virus and anthrax that are particularly dangerous can be discerned by quantifying their durability; (3) hospital settings and the AIDS pandemic may provide footholds for emerging sit-and-wait pathogens; and (4) studies on food-borne and insect pathogens point to future research considering the potential evolutionary trade-offs and genetic linkages between virulence and durability.
Topics: Animals; Bacteria; Disease Transmission, Infectious; Evolution, Molecular; Humans; Mortality; Time Factors; Virulence; Viruses
PubMed: 15682873
DOI: 10.1017/s1464793104006475 -
Cell Host & Microbe May 2016Protozoan parasites colonize numerous metazoan hosts and insect vectors through their life cycles, with the need to respond quickly and reversibly while encountering... (Review)
Review
Protozoan parasites colonize numerous metazoan hosts and insect vectors through their life cycles, with the need to respond quickly and reversibly while encountering diverse and often hostile ecological niches. To succeed, parasites must also persist within individuals until transmission between hosts is achieved. Several parasitic protozoa cause a huge burden of disease in humans and livestock, and here we focus on the parasites that cause malaria and African trypanosomiasis. Efforts to understand how these pathogens adapt to survive in varied host environments, cause disease, and transmit between hosts have revealed a wealth of epigenetic phenomena. Epigenetic switching mechanisms appear to be ideally suited for the regulation of clonal antigenic variation underlying successful parasitism. We review the molecular players and complex mechanistic layers that mediate the epigenetic regulation of virulence gene expression. Understanding epigenetic processes will aid the development of antiparasitic therapeutics.
Topics: Animals; Gene Expression Regulation; Humans; Parasites; Virulence
PubMed: 27173931
DOI: 10.1016/j.chom.2016.04.020 -
ACS Infectious Diseases Jan 2020Natural products from microorganisms are important small molecules that play roles in various biological processes like cellular growth, motility, nutrient acquisition,... (Review)
Review
Natural products from microorganisms are important small molecules that play roles in various biological processes like cellular growth, motility, nutrient acquisition, stress response, biofilm formation, and defense. It is hypothesized that pathogens exploit these molecules to regulate virulence and persistence during infections. Here, we present selected examples of signaling natural products from human pathogenic bacteria that use these metabolites to gain a competitive advantage. Targeting these signaling systems provides novel strategies to antimicrobial treatments.
Topics: Animals; Anti-Bacterial Agents; Bacteria; Biological Products; Host Microbial Interactions; Humans; Secondary Metabolism; Signal Transduction; Virulence
PubMed: 31617342
DOI: 10.1021/acsinfecdis.9b00286 -
Journal of Molecular Biology Nov 2019Recent studies revealed an amazing phenotypic heterogeneity between genetically identical individual cells within populations of microbial pathogens. During the course... (Review)
Review
Recent studies revealed an amazing phenotypic heterogeneity between genetically identical individual cells within populations of microbial pathogens. During the course of an infection, subpopulations occur, which differ in certain virulence-relevant factors, stress adaptation functions or physiological and metabolic abilities. The mechanisms driving this heterogeneity are divergent reactions of the pathogens to differences in host tissue microenvironments. In addition, certain genetic regulatory circuits with positive feedback loops and stochastic differences in gene expression can generate endogenous fluctuations in regulatory components leading to bistable expression of virulence-associated functions. Here, we focus on the occurrence of phenotypic heterogeneity in populations of well-studied examples of pathogens, which enables cooperative, social behavior where a subpopulation of producers shares fitness- and/or virulence-relevant goods and traits with non-producers. We further highlight that this strategy allows preadaptation of a subgroup of cells to recurrent and thus predictable changes of the environment that they encounter during the different stages of the infection. The diversity within bacterial communities has a significant influence on the survival of the pathogens within their hosts and the progression of the disease.
Topics: Adaptation, Physiological; Bacteria; Bacterial Physiological Phenomena; Biological Variation, Population; Host-Pathogen Interactions; Microbiological Phenomena; Nitric Oxide; Oxidation-Reduction; Phenotype; Reactive Oxygen Species; Stress, Physiological; Type III Secretion Systems; Virulence; Virulence Factors
PubMed: 31260693
DOI: 10.1016/j.jmb.2019.06.024