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Sensing of the microbial neighborhood by Candida albicans.

Mallick EM, Bennett RJ - PLoS Pathog. (2013)

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular Microbiology and Immunology, Brown University, Providence, Rhode Island, United States of America.

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C. albicans uses quorum sensing to react to other Candida cells, pheromone signaling in the context of mating and sexual biofilm formation, and a variety of mechanisms for interkingdom interactions with the bacterial microbiota... Quorum sensing (QS) is used by C. albicans to communicate with other Candida cells, and is driven by soluble quorum-sensing molecules or autoinducers that are secreted into the environment in a density-dependent manner, ... QS regulates several pathogenic traits including hyphal (filamentous) growth... This phenomenon is evident by the “inoculum effect,” in which the formation of hyphae is repressed in cells grown at high densities, while cells grown at low densities are able to germinate, ... Several key QS molecules have been identified that have antagonistic effects, including farnesol and tyrosol... However, farnesol and possibly other filamentation-repressing QS molecules may also promote biofilm-mediated infections by inducing the formation of yeast cells that are then easily dispersed from mature biofilms... Interspecies pheromone signaling between different Candida species can also drive biofilm formation in white cells and sexual mating in opaque cells, indicating a surprising level of promiscuity in sexual signaling... Bacterial species that comprise the normal microbiota can also inhibit C. albicans from colonizing in vivo niches... C. albicans can also increase the virulence of bacterial pathogens such as E. faecalis, Staphylococcus aureus, and Serratia marcescens, as co-infection results in more severe disease than infection with the bacterial species alone... Presumably, unidentified QS molecules and other virulence determinants are responsible for signaling between the different species thereby resulting in increased virulence... In the oral cavity, commensal Streptococcus species adhere to C. albicans cell wall proteins and adhesins including SspA, SspB, and Als3, thereby enhancing biofilm formation, ... Streptococcus species can also absorb protein components from saliva resulting in increased adherence and hyphal development in C. albicans, strengthening the biofilm and providing additional places for Streptococcus cells to bind... Together, these findings reveal the complexities of mixed-species biofilms and the role that these structures play in responses to antimicrobial therapy... It is likely that these interactions represent the proverbial tip of the iceberg, and that further studies will be necessary to define how microbial species affect colonization and infection by Candida species, and for developing medical interventions that target these human pathogens.

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Environmental cues sensed by C. albicans.(A) Schematic representation of how C. albicans morphology and biofilm formation is regulated by quorum sensing and signaling with other microbial species. (B) Farnesol and 3-oxo-C(12)-homoserine lactone both act on the Ras1 pathway to inhibit the yeast-to-hyphal transition by inhibiting Cyr1 and cAMP signaling.
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ppat-1003661-g001: Environmental cues sensed by C. albicans.(A) Schematic representation of how C. albicans morphology and biofilm formation is regulated by quorum sensing and signaling with other microbial species. (B) Farnesol and 3-oxo-C(12)-homoserine lactone both act on the Ras1 pathway to inhibit the yeast-to-hyphal transition by inhibiting Cyr1 and cAMP signaling.

Mentions: C. albicans virulence depends on its ability to switch between distinct morphologic and phenotypic states, and these transitions are directly influenced by its environment. Quorum sensing (QS) is used by C. albicans to communicate with other Candida cells, and is driven by soluble quorum-sensing molecules or autoinducers that are secreted into the environment in a density-dependent manner [3], [4]. QS regulates several pathogenic traits including hyphal (filamentous) growth. This phenomenon is evident by the “inoculum effect,” in which the formation of hyphae is repressed in cells grown at high densities, while cells grown at low densities are able to germinate [5], [6] (Figure 1A). Several key QS molecules have been identified that have antagonistic effects, including farnesol and tyrosol. Farnesol inhibits the yeast-hyphal transition by inhibiting adenylate cyclase (Cyr1), part of a central regulatory pathway that impacts filamentous growth [5]–[8] (Figure 1B). Conversely, tyrosol shortens lag-phase growth in low-density cultures and stimulates germ-tube formation in yeast cells [9]. Other molecules that are potential QS molecules in C. albicans include phenylethyl alcohol, tryptophol, and MARS (morphogenic autoregulatory substance), although the mechanisms of action of these molecules remain unclear [10]–[12]. Thus, multiple QS molecules can impact C. albicans morphology (Figure 1).


Sensing of the microbial neighborhood by Candida albicans.

Mallick EM, Bennett RJ - PLoS Pathog. (2013)

Environmental cues sensed by C. albicans.(A) Schematic representation of how C. albicans morphology and biofilm formation is regulated by quorum sensing and signaling with other microbial species. (B) Farnesol and 3-oxo-C(12)-homoserine lactone both act on the Ras1 pathway to inhibit the yeast-to-hyphal transition by inhibiting Cyr1 and cAMP signaling.
© Copyright Policy
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC3814570&req=5

ppat-1003661-g001: Environmental cues sensed by C. albicans.(A) Schematic representation of how C. albicans morphology and biofilm formation is regulated by quorum sensing and signaling with other microbial species. (B) Farnesol and 3-oxo-C(12)-homoserine lactone both act on the Ras1 pathway to inhibit the yeast-to-hyphal transition by inhibiting Cyr1 and cAMP signaling.
Mentions: C. albicans virulence depends on its ability to switch between distinct morphologic and phenotypic states, and these transitions are directly influenced by its environment. Quorum sensing (QS) is used by C. albicans to communicate with other Candida cells, and is driven by soluble quorum-sensing molecules or autoinducers that are secreted into the environment in a density-dependent manner [3], [4]. QS regulates several pathogenic traits including hyphal (filamentous) growth. This phenomenon is evident by the “inoculum effect,” in which the formation of hyphae is repressed in cells grown at high densities, while cells grown at low densities are able to germinate [5], [6] (Figure 1A). Several key QS molecules have been identified that have antagonistic effects, including farnesol and tyrosol. Farnesol inhibits the yeast-hyphal transition by inhibiting adenylate cyclase (Cyr1), part of a central regulatory pathway that impacts filamentous growth [5]–[8] (Figure 1B). Conversely, tyrosol shortens lag-phase growth in low-density cultures and stimulates germ-tube formation in yeast cells [9]. Other molecules that are potential QS molecules in C. albicans include phenylethyl alcohol, tryptophol, and MARS (morphogenic autoregulatory substance), although the mechanisms of action of these molecules remain unclear [10]–[12]. Thus, multiple QS molecules can impact C. albicans morphology (Figure 1).

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular Microbiology and Immunology, Brown University, Providence, Rhode Island, United States of America.

AUTOMATICALLY GENERATED EXCERPT
Please rate it.

C. albicans uses quorum sensing to react to other Candida cells, pheromone signaling in the context of mating and sexual biofilm formation, and a variety of mechanisms for interkingdom interactions with the bacterial microbiota... Quorum sensing (QS) is used by C. albicans to communicate with other Candida cells, and is driven by soluble quorum-sensing molecules or autoinducers that are secreted into the environment in a density-dependent manner, ... QS regulates several pathogenic traits including hyphal (filamentous) growth... This phenomenon is evident by the “inoculum effect,” in which the formation of hyphae is repressed in cells grown at high densities, while cells grown at low densities are able to germinate, ... Several key QS molecules have been identified that have antagonistic effects, including farnesol and tyrosol... However, farnesol and possibly other filamentation-repressing QS molecules may also promote biofilm-mediated infections by inducing the formation of yeast cells that are then easily dispersed from mature biofilms... Interspecies pheromone signaling between different Candida species can also drive biofilm formation in white cells and sexual mating in opaque cells, indicating a surprising level of promiscuity in sexual signaling... Bacterial species that comprise the normal microbiota can also inhibit C. albicans from colonizing in vivo niches... C. albicans can also increase the virulence of bacterial pathogens such as E. faecalis, Staphylococcus aureus, and Serratia marcescens, as co-infection results in more severe disease than infection with the bacterial species alone... Presumably, unidentified QS molecules and other virulence determinants are responsible for signaling between the different species thereby resulting in increased virulence... In the oral cavity, commensal Streptococcus species adhere to C. albicans cell wall proteins and adhesins including SspA, SspB, and Als3, thereby enhancing biofilm formation, ... Streptococcus species can also absorb protein components from saliva resulting in increased adherence and hyphal development in C. albicans, strengthening the biofilm and providing additional places for Streptococcus cells to bind... Together, these findings reveal the complexities of mixed-species biofilms and the role that these structures play in responses to antimicrobial therapy... It is likely that these interactions represent the proverbial tip of the iceberg, and that further studies will be necessary to define how microbial species affect colonization and infection by Candida species, and for developing medical interventions that target these human pathogens.

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