Functions and regulation of quorum-sensing in Agrobacterium tumefaciens

Lang, Julien; Faure, Denis

doi:10.3389/fpls.2014.00014

Cited by 93 publications

(93 citation statements)

References 112 publications

(168 reference statements)

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“…Interestingly, a fadL homolog was not found in Bradyrhizobiaceae. Bradyrhizobium japonicum was reported to produce unusual isovaleryl-HSL QS signals (30) whereas A. tumefaciens QS involves AHLs with C 6 or C 8 acyl chains (27). Thus, we speculate that species synthesizing AHLs with acyl chains of 14 or more carbons, or coming into contact with species producing them, might have evolved FadL to facilitate their sensing.…”

Section: Discussionmentioning

confidence: 99%

“…S6). Because these bacteria use AHL-based QS (8,(25)(26)(27), we asked whether promotion of long-chain AHL sensing is a common trait of their FadL proteins. For this, fadL homologs from these species were ectopically expressed in the S. meliloti sinI fadL mutant by introduction of plasmid-localized heterologous fadL genes driven by an IPTG-inducible lac promoter.…”

Section: Resultsmentioning

confidence: 99%

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Rhizobial homologs of the fatty acid transporter FadL facilitate perception of long-chain acyl-homoserine lactone signals

Krol

Becker

2014

Proc. Natl. Acad. Sci. U.S.A.

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Significance Bacterial intercellular communication is crucial for developing population and community structures and for pathogenic and symbiotic interactions with eukaryotic hosts. Many Gram-negative bacteria use N-acyl-homoserine lactones (AHLs) in quorum sensing-related signaling. Although it is likely that specific transport mechanisms are required for long-chain AHLs to overcome the outer membrane, mechanisms promoting uptake have not been reported so far. Here we present evidence that homologs of the outer membrane long-chain fatty acid transporter FadL facilitate uptake of long-chain AHLs, which closes an important gap in our understanding of quorum sensing signaling. Our findings suggest that bacteria responding to long-chain AHLs have evolved specificity of FadL toward these signal molecules and have partly lost the ability to transport long-chain fatty acid by this protein.

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Section: Discussionmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Rhizobial homologs of the fatty acid transporter FadL facilitate perception of long-chain acyl-homoserine lactone signals

Krol

Becker

2014

Proc. Natl. Acad. Sci. U.S.A.

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“…Agrobacterium tumefaciens is a well known plant pathogen, which efficiently utilizes the QS apparatus to accomplish the process of conjugation and virulencecrown gall tumors [124,125]. A. tumefaciens embodies the tumor-inducing plasmid designated as Ti plasmid which harbours the virulent genes.…”

Section: Agrobacteriummentioning

confidence: 99%

Potential Emergence of Multi-quorum Sensing Inhibitor Resistant (MQSIR) Bacteria

et al. 2015

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Expression of certain bacterial genes only at a high bacterial cell density is termed as quorum-sensing (QS). Here bacteria use signaling molecules to communicate among themselves. QS mediated genes are generally involved in the expression of phenotypes such as bioluminescence, biofilm formation, competence, nodulation, and virulence. QS systems (QSS) vary from a single in Vibrio spp. to multiple in Pseudomonas and Sinorhizobium species. The complexity of QSS is further enhanced by the multiplicity of signals: (1) peptides, (2) acyl-homoserine lactones, (3) diketopiperazines. To counteract this pathogenic behaviour, a wide range of bioactive molecules acting as QS inhibitors (QSIs) have been elucidated. Unlike antibiotics, QSIs don't kill bacteria and act at much lower concentration than those of antibiotics. Bacterial ability to evolve resistance against multiple drugs has cautioned researchers to develop QSIs which may not generate undue pressure on bacteria to develop resistance against them. In this paper, we have discussed the implications of the diversity and multiplicity of QSS, in acting as an arsenal to withstand attack from QSIs and may use these as reservoirs to develop multi-QSI resistance.

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“…Indeed, it has been shown that Agrobacterium tumefaciens cells carrying conjugative Ti plasmids show a donor-density-dependent increase in transfer, which is mediated by an extracellular quorum-sensing acyl-homoserine lactone autoinducer synthesized by the plasmid-encoded TraI autoinducer synthetase (45,46). In contrast, we have demonstrated that high donor density reduced the frequency of pheromone-controlled conjugative transfer of plasmids pAD1 and pAM373 in E. faecalis.…”

Section: Discussionmentioning

confidence: 55%

Antagonistic Donor Density Effect Conserved in Multiple Enterococcal Conjugative Plasmids

Bandyopadhyay

O’Brien

Frank

et al. 2016

Appl Environ Microbiol

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Enterococcus faecalis, a common causative agent of hospital-acquired infections, is resistant to many known antibiotics. Its ability to acquire and transfer resistance genes and virulence determinants through conjugative plasmids poses a serious concern for public health. In some cases, induction of transfer of E. faecalis plasmids results from peptide pheromones produced by plasmid-free recipient cells, which are sensed by the plasmid-bearing donor cells. These plasmids generally encode an inhibitory peptide that competes with the pheromone and suppresses self-induction of donors. We recently demonstrated that the inhibitor peptide encoded on plasmid pCF10 is part of a unique quorum-sensing system in which it functions as a "self-sensing signal," reducing the response to the pheromone in a density-dependent fashion. Based on the similarities between regulatory features controlling conjugation in pAD1 and pAM373 and those controlling conjugation in pCF10, we hypothesized that these plasmids are likely to exhibit similar quorum-sensing behaviors. Experimental findings indicate that for both pAD1 and pAM373, high donor densities indeed resulted in decreased induction of the conjugation operon and reduced conjugation frequencies. This effect was restored by the addition of exogenous inhibitor, confirming that the inhibitor serves as an indicator for donor density. Donor density also affects cross-species conjugative plasmid transfer. Based on our experimental results, we propose models for induction and shutdown of the conjugation operon in pAD1 and pAM373. IMPORTANCEEnterococcus faecalis is a leading cause of hospital-acquired infections. Its ability to transfer antibiotic resistance and virulence determinants by sharing its genetic material with other bacteria through direct cell-cell contact via conjugation poses a serious threat. Two antagonistic signaling peptides control the transfer of plasmids pAD1 and pAM373: a peptide pheromone produced by plasmid-free recipients triggers the conjugative transfer in plasmid-containing donors, and an inhibitor peptide encoded on the plasmid and produced by donor cells serves to modulate the donor response in accordance with the relative abundance of donors and recipients. We demonstrate that high donor density reduces the conjugation frequency of both of these plasmids, which is a consequence of increased inhibitor concentration in high-donor-density cultures. While most antibiotic strategies end up selecting resistant strains and disrupting the community balance, manipulating bacterial signaling mechanisms can serve as an alternate strategy to prevent the spread of antibiotic resistance. E nterococcus faecalis, a bacterium normally present in the human intestinal tract, is a major cause of health care-associated infections. Treatment of these infections has become increasingly difficult with the emergence of E. faecalis strains that are resistant to multiple antibiotics, such as macrolides, tetracyclines, amino glycosides, and glycopeptides, including vancomycin (...

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Functions and regulation of quorum-sensing in Agrobacterium tumefaciens

Cited by 93 publications

References 112 publications

Rhizobial homologs of the fatty acid transporter FadL facilitate perception of long-chain acyl-homoserine lactone signals

Rhizobial homologs of the fatty acid transporter FadL facilitate perception of long-chain acyl-homoserine lactone signals

Potential Emergence of Multi-quorum Sensing Inhibitor Resistant (MQSIR) Bacteria

Antagonistic Donor Density Effect Conserved in Multiple Enterococcal Conjugative Plasmids

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