Quorum sensing LuxS/autoinducer-2 inhibits Enterococcus faecalis biofilm formation ability

Abstract Objective: To investigate the relation between biofilm formation ability and quorum sensing gene LuxS/AI-2. Materials and Methods: Enterococcus faecalis (E. faecalis) standard strain ATCC 29212 was used in the study. Long flanking homology polymerase chain reaction method was used to build the LuxS gene knockout strain. Sequential culture turbidity measurement and CFU counting were used to assess the proliferation ability of E. faecalis after the depletion of LuxS. 96-well plate assay was used to quantify the biofilm formation ability; CLSM was used to observe the attached bacteria areas, while scanning electron microscopy (SEM) was performed to observe biofilm microstructure conditions. Results: LuxS gene knockout strains were successfully constructed and identified. The results showed that proliferation ability of E. faecalis was not affected by the depletion of the luxS gene, and the biofilm formation ability of ΔLuxS 29212 significantly decreased (P<0.05). Conclusions: Collectively, our studies provide the LuxS gene's key role in controlling biofilm formation of E. faecalis, which presented a negative regulation, and furthermore, providing us a possible way to conquer the persistent apical periodontitis.

Redes de señalización en la producción de biopelículas en bacterias: quorum sensing, di-GMPc y óxido nítrico / Networks involving quorum sensing, cyclic-di-GMP and nitric oxide on biofilm production in bacteria

Las bacterias forman biopelículas de manera ubicua, y esta característica les otorga una flexibilidad que es resultado, en parte, de una matriz compleja construida según las exigencias de las condiciones ambientales. Aunque los estadios de la formación de las biopelículas bacterianas se conocen con detalle, para entender con profundidad la formación de las biopelículas es deseable un conocimiento mayor de los mecanismos de señalización. Las bacterias detectan cambios en la densidad de población por regulación del quórum y condiciones específicas, empleando señales como el di-GMPc y el óxido nítrico. La importancia del conocimiento de estas vías de señalización radica en que controlan una variedad de funciones, como la formación de biopelículas y la movilidad, y proporcionan a las bacterias beneficios en la colonización del hospedador, la defensa contra competidores y los cambios adversos del entorno. Por la trascendencia que revisten estos aspectos, revisamos aquí las redes de regulación y la conexión de la señalización entre quorum sensing, di-GMPc y óxido nítrico

Bacterial biofilms are ubiquitous in nature, and their flexibility is derived in part from a complex extracellular matrix that can be made-to-order to cope with environmental demand. Although common developmental stages leading to biofilm formation have been described, an in-depth knowledge of genetic and signaling is required to understand biofilm formation. Bacteria detect changes in population density by quorum sensing and particular environmental conditions, using signals such as cyclic di-GMP or nitric oxide. The significance of understanding these signaling pathways lies in that they control a broad variety of functions such as biofilm formation, and motility, providing benefits to bacteria as regards host colonization, defense against competitors, and adaptation to changing environments. Due to the importance of these features, we here review the signaling network and regulatory connections among quorum sensing, c-di-GMP and nitric oxide involving biofilm formation

Quorum sensing (QS) as etiological phenomenon: the bacterial paradigm.

Signaling mechanisms that govern physiological and morphological responses to change the cell density are common in bacteria. Quorum sensing is signal transduction processes which involves the production and release of and response to hormone-like molecules (auto-inducers) that accumulate in the external environment as the cell population grows. Quorum sensing is found in a wide variety of bacteria, both Gram-positive and Gram-negative and the spectrum of physiological functions that can be regulated is impressive. Variation in the nature of the extra-cellular signal in the signal detection machinery and in the mechanisms of signal transmission demonstrates the evolutionary adaptability of quorum sensing systems for multiple uses.

Quorum sensing signal profile of Acinetobacter strains from nosocomial and environmental sources / Perfil de sensores de quórum en cepas nosocomiales y ambientales de Acinetobacter

A set of 43 strains corresponding to 20 classified and unclassified genomic Acinetobacter species was analyzed for the production of typical N-acyl homoserine lactone quorum sensing molecules in culture broths. A large percentage of the strains (74%) displayed quorum sensing signals that could be separated into three statistically significantly different chromatographic groups (p < 0.001) based on their retention factor in TLC, i.e. Rf1 (0.22 ± 0.02); Rf2 (0.40 ± 0.02) and Rf3 (0.54 ± 0.02). Noteworthy, 63% of the strains tested produced more than one quorum signal. The frequency of signal appearance was Rf3 > Rf2 > Rf1. None of the three signals could be specifically assigned to a particular species in the genus; furthermore, no distinction could be made between the quorum sensing signals secreted by typical opportunistic strains of the A. calcoaceticus-A. baumannii complex, isolated from patients, with respect to the other species of the genus, except for the Rf1 signal which was present in all the QS positive strains belonging to this complex and DNA group 13 TU. In conclusion, quorum sensors in Acinetobacter are not homogenously distributed among species and one of them is present in most of the A. calcoaceticus-baumannii complex.

Se analizó la producción de moléculas típicas de N-acil homoserina lactona con actividad de quorum sensing en cultivos líquidos de un grupo de 43 cepas correspondientes a 20 especies genómicas clasificadas y no clasificadas de Acinetobacter. Un porcentaje alto de las cepas (74%) mostraron señales de quorum sensing que pudieron ser separadas en tres grupos cromatográficos significativamente diferentes entre sí (p < 0,001) sobre la base de sus factores de retención en TLC, a saber: Rf1 (0.22 ± 0.02); Rf2 (0.40 ± 0.02) y Rf3 (0.54 ± 0.02). Es de notar que 63% de las cepas ensayadas produjeron más de una señal de quorum. La frecuencia de aparición de las señales fue Rf3 > Rf2 > Rf1. Ninguna de las tres señales pudo ser asignada a una especie en particular dentro del género; es más, no se encontró diferencia entre las señales producidas por las cepas típicamente oportunistas (complejo A. calcoaceticus-A. baumannii) aisladas de pacientes respecto de las producidas por otras cepas del mismo género, excepto para el caso de Rf1, que se encontró presente en todos los aislamientos quorum sensing positivos del mencionado complejo y en las cepas del grupo de DNA 13TU. En conclusión, los sensores de quórum en Acinetobacter no están homogéneamente distribuidos entre especies y uno de ellos (Rf1) está presente en la mayoría de los miembros del complejo calcoaceticus-baumannii.