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Biofilm growth alters regulation of conjugation by a bacterial pheromone.

ABSTRACT: Conjugation is an important mode of horizontal gene transfer in bacteria, enhancing the spread of antibiotic resistance. In clinical settings, biofilms are likely locations for antibiotic resistance transfer events involving nosocomial pathogens such as Enterococcus faecalis. Here we demonstrate that growth in biofilms alters the induction of conjugation by a sex pheromone in E. faecalis. Mathematical modelling suggested that a higher plasmid copy number in biofilm cells would enhance a switch-like behaviour in the pheromone response of donor cells with a delayed, but increased response to the mating signal. Alterations in plasmid copy number, and a bimodal response to induction of conjugation in populations of plasmid-containing donor cells were both observed in biofilms, consistent with the predictions of the model. The pheromone system may have evolved such that donor cells in biofilms are only induced to transfer when they are in extremely close proximity to potential recipients in the biofilm community. These results may have important implications for development of chemotherapeutic agents to block resistance transfer and treat biofilm-related clinical infections.

SUBMITTER: Cook L

PROVIDER: S-EPMC3187857 | biostudies-literature | 2011 Sep

REPOSITORIES: biostudies-literature

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Biofilm growth alters regulation of conjugation by a bacterial pheromone.

Cook Laura L Chatterjee Anushree A Barnes Aaron A Yarwood Jeremy J Hu Wei-Shou WS Dunny Gary G

Molecular microbiology 20110815 6

Conjugation is an important mode of horizontal gene transfer in bacteria, enhancing the spread of antibiotic resistance. In clinical settings, biofilms are likely locations for antibiotic resistance transfer events involving nosocomial pathogens such as Enterococcus faecalis. Here we demonstrate that growth in biofilms alters the induction of conjugation by a sex pheromone in E. faecalis. Mathematical modelling suggested that a higher plasmid copy number in biofilm cells would enhance a switch-l ...[more]

PMID: 21843206

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Project description:Candida albicans can stochastically switch between two phenotypes, white and opaque. Opaque cells are the sexually competent form of C. albicans and therefore undergo efficient polarized growth and mating in the presence of pheromone. In contrast, white cells cannot mate, but are induced - under a specialized set of conditions - to form biofilms in response to pheromone. In this work, we compare the genetic regulation of such "pheromone-stimulated" biofilms with that of "conventional" C. albicans biofilms. In particular, we examined a network of six transcriptional regulators (Bcr1, Brg1, Efg1, Tec1, Ndt80, and Rob1) that mediate conventional biofilm formation for their potential roles in pheromone-stimulated biofilm formation. We show that four of the six transcription factors (Bcr1, Brg1, Rob1, and Tec1) promote formation of both conventional and pheromone-stimulated biofilms, indicating they play general roles in cell cohesion and biofilm development. In addition, we identify the master transcriptional regulator of pheromone-stimulated biofilms as C. albicans Cph1, ortholog of Saccharomyces cerevisiae Ste12. Cph1 regulates mating in C. albicans opaque cells, and here we show that Cph1 is also essential for pheromone-stimulated biofilm formation in white cells. In contrast, Cph1 is dispensable for the formation of conventional biofilms. The regulation of pheromone- stimulated biofilm formation was further investigated by transcriptional profiling and genetic analyses. These studies identified 206 genes that are induced by pheromone signaling during biofilm formation. One of these genes, HGC1, is shown to be required for both conventional and pheromone-stimulated biofilm formation. Taken together, these observations compare and contrast the regulation of conventional and pheromone-stimulated biofilm formation in C. albicans, and demonstrate that Cph1 is required for the latter, but not the former. 4 condition experiment: white and opaque cells in planktonic and pheromone-induced biofilm conditions with and without alpha pheromone. WT strain (P37005), the tec1 mutant strain and the cph1 mutant strain

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Biofilm growth alters regulation of conjugation by a bacterial pheromone.

Publications

Biofilm growth alters regulation of conjugation by a bacterial pheromone.

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