Pleiotropic phenotypes of a Yersinia enterocolitica flhD mutant include reduced lethality in a chicken embryo model

Townsend, Megan K; Carr, Nathan J; Iyer, Jyoti; Horne, Shelley M.; Gibbs, Penelope S.; Prüß, Birgit M.

doi:10.1186/1471-2180-8-12

Cited by 19 publications

(24 citation statements)

References 56 publications

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“…Embryonated eggs have been used for decades as a convenient alternative infection model for studying viruses and for determination of bacterial virulence determinants (2,18,23,55). However, to our knowledge, they have never been used as a model to study the pathogenesis of filamentous fungi, such as A. fumigatus.…”

Section: Discussionmentioning

confidence: 99%

Embryonated Eggs as an Alternative Infection Model To Investigate Aspergillus fumigatus Virulence

Jacobsen

Große²,

Slesiona

et al. 2010

Infect Immun

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Infection models are essential tools for studying microbial pathogenesis. Murine models are considered the "gold standard" for studying in vivo infections caused by Aspergillus species, such as A. fumigatus. Recently developed molecular protocols allow rapid construction of high numbers of fungal deletion mutants, and alternative infection models based on cell culture or invertebrates are widely used for screening such mutants to reduce the number of rodents in animal experiments. To bridge the gap between invertebrate models and mice, we have developed an alternative, low-cost, and easy-to-use infection model for Aspergillus species based on embryonated eggs. The outcome of infections in the egg model is dose and age dependent and highly reproducible. We show that the age of the embryos affects the susceptibility to A. fumigatus and that increased resistance coincides with altered chemokine production after infection. The progress of disease in the model can be monitored by using egg survival and histology. Based on pathological analyses, we hypothesize that invasion of embryonic membranes and blood vessels leads to embryonic death. Defined deletion mutant strains previously shown to be fully virulent or partially or strongly attenuated in a mouse model of bronchopulmonary aspergillosis showed comparable degrees of attenuation in the egg model. Addition of nutrients restored the reduced virulence of a mutant lacking a biosynthetic gene, and variations of the infectious route can be used to further analyze the role of distinct genes in our model. Our results suggest that embryonated eggs can be a very useful alternative infection model to study A. fumigatus virulence and pathogenicity.

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Section: Discussionmentioning

confidence: 99%

Embryonated Eggs as an Alternative Infection Model To Investigate Aspergillus fumigatus Virulence

Jacobsen

Große²,

Slesiona

et al. 2010

Infect Immun

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“…FlhD and FlhC form a heteromeric complex (36) that activates class II flagella genes, including the alternative sigma factor 28 , and leads to expression of class III flagellum genes (37)(38)(39). FlhD 4 C 2 also regulates the expression of genes that are not related to flagellum biogenesis, including cell division and aspects of metabolism (29,(40)(41)(42)(43)(44)(45).…”

Section: Isolating Populations Of Different Cell Morphologiesmentioning

confidence: 99%

Flagellum Density Regulates Proteus mirabilis Swarmer Cell Motility in Viscous Environments

et al. 2013

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cProteus mirabilis is an opportunistic pathogen that is frequently associated with urinary tract infections. In the lab, P. mirabilis cells become long and multinucleate and increase their number of flagella as they colonize agar surfaces during swarming. Swarming has been implicated in pathogenesis; however, it is unclear how energetically costly changes in P. mirabilis cell morphology translate into an advantage for adapting to environmental changes. We investigated two morphological changes that occur during swarming-increases in cell length and flagellum density-and discovered that an increase in the surface density of flagella enabled cells to translate rapidly through fluids of increasing viscosity; in contrast, cell length had a small effect on motility. We found that swarm cells had a surface density of flagella that was ϳ5 times larger than that of vegetative cells and were motile in fluids with a viscosity that inhibits vegetative cell motility. To test the relationship between flagellum density and velocity, we overexpressed FlhD 4 C 2 , the master regulator of the flagellar operon, in vegetative cells of P. mirabilis and found that increased flagellum density produced an increase in cell velocity. Our results establish a relationship between P. mirabilis flagellum density and cell motility in viscous environments that may be relevant to its adaptation during the infection of mammalian urinary tracts and movement in contact with indwelling catheters. Proteus mirabilis is a Gram-negative rod-shaped gammaproteobacterium that is commonly associated with urinary tract infections (1) and the biofouling of catheters (2-4). P. mirabilis may also be present in the human gut microflora (5) and is correlated with the incidence of colitis (6, 7). Broth-grown vegetative cells of P. mirabilis are characteristically ϳ2 m long and have a peritrichous distribution of ϳ4 to 10 flagella. The flagella form a bundle that performs work on the surrounding fluid and propels cells forward via a mechanism that is similar to the motility system of Escherichia coli (8, 9).Broth-grown vegetative cells of P. mirabilis in contact with the surface of agar gels infused with nutrients change their morphology, become "swarmers," and colonize the surface by coordinating the movement of large groups of cells (i.e., "swarming") (see Fig. 1A). P. mirabilis swarm colonies exhibit a terraced pattern of concentric rings (see Fig. S1 in the supplemental material) (10). These rings are produced by alternating phases of consolidation, during which the colony does not expand and cells are dedifferentiated into a vegetative cell-like morphology, and swarming, during which cells are motile and differentiated (11). Motility occurs predominantly at the swarm front and decreases with increasing distance from the front; cells near the center of the swarm are nonmotile. Swarming has several characteristics, including the following: (i) the inhibition of cell division to produce long (10-to 70-m) multinucleate cells, (ii) an increase in the surface dens...

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“…Therefore, we expected that the ⌬pyrF strains of both LVS and Schu S4 would be sharply attenuated for virulence during animal infection. To test this with LVS, we employed the chicken embryo infection model (15,27,42,62). Here, each chicken embryo was infected with ϳ10 3 , ϳ10 5 , or ϳ10 7 bacteria (Fig.…”

Section: F Tularensis Pyrf Encodes a Functional Orotidine-5-phosphatmentioning

confidence: 99%

Francisella tularensisΔpyrFMutants Show that Replication in Nonmacrophages Is Sufficient for PathogenesisIn Vivo

Horzempa¹,

O’Dee²,

Shanks

et al. 2010

Infect Immun

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The pathogenesis of Francisella tularensis has been associated with this bacterium's ability to replicate within macrophages. F. tularensis can also invade and replicate in a variety of nonphagocytic host cells, including lung and kidney epithelial cells and hepatocytes. As uracil biosynthesis is a central metabolic pathway usually necessary for pathogens, we characterized ⌬pyrF mutants of both F. tularensis LVS and Schu S4 to investigate the role of these mutants in intracellular growth. As expected, these mutant strains were deficient in de novo pyrimidine biosynthesis and were resistant to 5-fluoroorotic acid, which is converted to a toxic product by functional PyrF. The F. tularensis ⌬pyrF mutants could not replicate in primary human macrophages. The inability to replicate in macrophages suggested that the F. tularensis ⌬pyrF strains would be attenuated in animal infection models. Surprisingly, these mutants retained virulence during infection of chicken embryos and in the murine model of pneumonic tularemia. We hypothesized that the F. tularensis ⌬pyrF strains may replicate in cells other than macrophages to account for their virulence. In support of this, F. tularensis ⌬pyrF mutants replicated in HEK-293 cells and normal human fibroblasts in vitro. Moreover, immunofluorescence microscopy showed abundant staining of wild-type and mutant bacteria in nonmacrophage cells in the lungs of infected mice. These findings indicate that replication in nonmacrophages contributes to the pathogenesis of F. tularensis.

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Pleiotropic phenotypes of a Yersinia enterocolitica flhD mutant include reduced lethality in a chicken embryo model

Cited by 19 publications

References 56 publications

Embryonated Eggs as an Alternative Infection Model To Investigate Aspergillus fumigatus Virulence

Embryonated Eggs as an Alternative Infection Model To Investigate Aspergillus fumigatus Virulence

Flagellum Density Regulates Proteus mirabilis Swarmer Cell Motility in Viscous Environments

Francisella tularensisΔpyrFMutants Show that Replication in Nonmacrophages Is Sufficient for PathogenesisIn Vivo

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