RESUMO
Biofilms formed by bacteria on plant roots play an important role in maintaining an optimal rhizosphere environment that supports plant growth and fitness. Bacillus subtilis is a potent plant growth promoter, forming biofilms that play a key role in protecting the host from fungal and bacterial infections. In this work, we demonstrate that the development of B. subtilis biofilms is antagonized by specific indole derivatives that accumulate during symbiotic interactions with plant hosts. Indole derivatives are more potent signals when the plant polysaccharide xylan serves as a carbon source, a mechanism to sustain beneficial biofilms at a biomass that can be supported by the plant. Moreover, B. subtilis biofilms formed by mutants resistant to indole derivatives become deleterious to the plants due to their capacity to consume and recycle plant polysaccharides. These results demonstrate how a dynamic metabolite-based dialogue can promote homeostasis between plant hosts and their beneficial biofilm communities.
Assuntos
Bacillus subtilis , Biofilmes , Indóis , Plantas , Bacillus subtilis/fisiologia , Proteínas de Bactérias/genética , Interações Hospedeiro-Patógeno/efeitos dos fármacos , Interações Hospedeiro-Patógeno/fisiologia , Indóis/química , Indóis/farmacologia , Raízes de Plantas/microbiologia , Plantas/microbiologiaRESUMO
Autoinducer-2 (AI-2) has been suggested to serve as a ubiquitous quorum sensing (QS) signal that mediates intra- and interspecies cross-talk between bacteria. To add tools for the study of its function in bacterial communication, we present a new and an improved synthetic route to AI-2 and aromatic analogues. We used this strategy to prepare naphthyl-DPD, and observed remarkably high synergistic activity at low nanomolar concentrations for this analogue in Vibrio harveyi.
Assuntos
Homosserina/análogos & derivados , Lactonas/farmacologia , Percepção de Quorum/efeitos dos fármacos , Vibrio/efeitos dos fármacos , Homosserina/síntese química , Homosserina/química , Homosserina/metabolismo , Homosserina/farmacologia , Lactonas/síntese química , Lactonas/química , Lactonas/metabolismo , Estrutura Molecular , Vibrio/metabolismoRESUMO
Autoinducer-2 (AI-2) has been suggested to serve as a universal interspecies quorum sensing signaling molecule. We have synthesized a set of AI-2 analogs with small incremental changes in alkyl substitution on C-2 and evaluated them for their agonistic and antagonistic potential as quorum sensing (QS) attenuators in two different bacterial species: Pseudomonas aeruginosa and Vibrio harveyi. Unexpectedly, several of the analogs were found to function as synergistic QS agonists in V. harveyi, while two of these analogs inhibit QS in P. aeruginosa.
Assuntos
Antibacterianos/química , Homosserina/análogos & derivados , Lactonas/química , Pentanonas/química , Pseudomonas aeruginosa/efeitos dos fármacos , Percepção de Quorum/efeitos dos fármacos , Antibacterianos/síntese química , Antibacterianos/farmacologia , Homosserina/química , Pentanonas/síntese química , Pentanonas/farmacologia , Pseudomonas aeruginosa/metabolismo , Percepção de Quorum/fisiologia , Vibrio/metabolismoRESUMO
The discovery that plant smoke contains germination stimuli has led to the identification of a new class of signaling molecules named karrikins. Here we report a potential second role for these molecules: in various bacterial species -A. tumefaciens, P. aeruginosa and V. harveyi- they modulate bacterial quorum-sensing (QS), with very different outcomes.
Assuntos
Agrobacterium tumefaciens/efeitos dos fármacos , Furanos/farmacologia , Plantas/metabolismo , Pseudomonas aeruginosa/efeitos dos fármacos , Piranos/farmacologia , Percepção de Quorum/efeitos dos fármacos , Fumaça , Vibrio/efeitos dos fármacosRESUMO
Aggregatibacter actinomycetemcomitans, a Gram-negative bacterium, and Candida albicans, a polymorphic fungus, are both commensals of the oral cavity but both are opportunistic pathogens that can cause oral diseases. A. actinomycetemcomitans produces a quorum-sensing molecule called autoinducer-2 (AI-2), synthesized by LuxS, that plays an important role in expression of virulence factors, in intra- but also in interspecies communication. The aim of this study was to investigate the role of AI-2 based signaling in the interactions between C. albicans and A. actinomycetemcomitans. A. actinomycetemcomitans adhered to C. albicans and inhibited biofilm formation by means of a molecule that was secreted during growth. C. albicans biofilm formation increased significantly when co-cultured with A. actinomycetemcomitans luxS, lacking AI-2 production. Addition of wild-type-derived spent medium or synthetic AI-2 to spent medium of the luxS strain, restored inhibition of C. albicans biofilm formation to wild-type levels. Addition of synthetic AI-2 significantly inhibited hypha formation of C. albicans possibly explaining the inhibition of biofilm formation. AI-2 of A. actinomycetemcomitans is synthesized by LuxS, accumulates during growth and inhibits C. albicans hypha- and biofilm formation. Identifying the molecular mechanisms underlying the interaction between bacteria and fungi may provide important insight into the balance within complex oral microbial communities.
Assuntos
Aggregatibacter actinomycetemcomitans/fisiologia , Antibiose , Biofilmes/crescimento & desenvolvimento , Candida albicans/fisiologia , Homosserina/análogos & derivados , Lactonas/metabolismo , Aderência Bacteriana , Proteínas de Bactérias/genética , Liases de Carbono-Enxofre/genética , Deleção de Genes , Homosserina/metabolismo , Humanos , Hifas , Boca/microbiologia , Mutação , Pentanonas/metabolismo , Percepção de QuorumRESUMO
The human pathogen Vibrio cholerae uses several small molecules to coordinate gene expression in a process termed quorum sensing (QS), and its main autoinducer is CAI-1. We have examined the activity of this signaling molecule in three other species of bacteria. Interestingly, while showing an inhibitory effect on QS in the opportunistic pathogen P. aeruginosa at low micromolar concentrations, it caused also growth inhibition at higher concentrations. In contrast, the two other bacteria were unaffected, and we suggest a possible mechanism for these effects, based on membrane perturbation studies.