Quorum sensing in biofilms – How to destroy the bacterial citadels or their cohesion/power?

doi:10.1016/j.anaerobe.2011.03.023

Anaerobe

Volume 17, Issue 6, December 2011, Pages 280-285

https://doi.org/10.1016/j.anaerobe.2011.03.023 Get rights and content

Abstract

Biofilms or microbial communities formed by adherent and cohesive cells on cellular or inert substrata (like medical devices), are involved in ∼60% of all infections and characterized by moderate intensity symptoms, chronic evolution and resistance to antibiotics. Biofilms’ pathogenicity, even of those formed by opportunistic microorganisms, is amplified by two major biofilm characteristics: 1) the increased resistance to antimicrobials; 2) the protection of cells against the host’s defence mechanisms. The studies at the molecular level shown that the biofilms formation is controlled by cell-to-cell signalling mechanisms and the gene regulation during biofilm growth is due to the accumulation of signal molecules. In this regard, quorum sensing mechanism (QS) is defined as a cell-density dependent bacterial intercellular communication, involved in gene expression (e.g. virulence genes for exoenzymes, exopolysaccharides) and the consequent changed behaviour of biofilm’s cells, including the resistance to stress conditions; this resistance is different of well known antibioresistance, being named phenotypical resistance or tolerance. Considering the differences in physiology and susceptibility to antibiotics of biofilm embedded bacteria, as well as their increased power against the host defence responses, there are necessary new strategies for prevention and therapy of biofilm associated infections. The dental plaque is a typical example of biofilm, involved in the ethiology of cariogenesis and periodontal diseases associated with local chronic inflammation and cytokines production. The genetical and phenotypical versatility of the biofilm’s cells represent a challenge for discovering new methods of treatment and prevention of biofilm associated infections. A novel class of antibiofilm and antipathogenic therapeutics which are interfering with a new target – the QS pathway, not based on growth inhibition and called QS inhibitors, natural, with different origins or artificial, are now developing as an alternative to antibiotherapy.

Section snippets

Definition and processes governing biofilm formation

A biofilm is a population of microbial cells (predominantly bacteria) in an extracellular polymeric matrix. In a more complex definition, the biofilm is a sessile microbial community composed of cells irreversibly attached to a substratum, to an interface or between them, embedded in a matrix of extracellular polymeric substances produced by themselves and which present a modified phenotype, concerning the growth rate and gene transcription [1]. Biofilms are considered a different growth phase,

The architecture and physiological properties of biofilms

The biofilm formation is a multi-step process; a mature biofilm revels a citadels–like association, with structures type mushroom, column and pillar-like, with spatiotemporal relationships and a synergistic, metabolic cooperation (Fig. 1). A biofilm is considered the most successful and competitive expression of the prokaryotic genome, the biofilm’s cells being metabolically more efficient, well protected and resistant to any kind of stress; it is also considered at present a primitive form of

Intercellular communication by quorum sensing mechanism and their consequences

It was demonstrated that between the cells of a biofilm there is a process of cell-to-cell communication and detection of cellular density called quorum sensing (QS) and response, or more simply QS [5], [6], [7]; this process is mediated by small molecules, produced and secreted by themself: autoinducers (AIs) – their synthesis is dependent on cellular density (Fig. 2). The concentration of these signalling molecules represents a measure of cell’s number; it has been demonstrated that without

The resistance/tolerance of biofilms to antimicrobials

The main mechanisms which can account for the increased antibiotic tolerance: 1) the failure of the antibiotic/antimicrobial agent to penetrate the extracellular matrix with reticular structure, which contains H₂O, minerals, glucides, proteins, small fragments of DNA, and is acting as a diffusion barrier for large molecules (some antibiotics, antibodies, phagocytes) or as an ionic exchange resin; 2) the biofilm matrix which can accumulate nutrients allowing the continuation of log phase or

A new generation of antibiofilm therapeutical agents

Considering the tolerance of biofilm cells to all kind of antimicrobials, new drugs and strategies for fighting against them were searched; these new therapeutics are alternative or complementary to antibiotherapy and based on different mechanisms of action on different targets [32]. For example, one way is the degrading of the matrix by chelators (EDTA), enzymes (dispersines), bacteriophages [4]. At present, there are some new other antiinfectious strategies, which can be successfully used for

Conclusions

Microbial biofilms influence almost all aspects of our lives, being significant from medical, ecological, biotechnological \and economic point of view. Whilst much of this impact is positive, there are many areas in which the presence and activities of biofilms are detrimental. It is in this respect that biofilms reveal their recalcitrance towards a lot of antibiotics and other antimicrobials used in medical and industrial fields. In natural environment the biofilm formation can be beneficial

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Pathogenesis and ToxinsQuorum sensing in biofilms – How to destroy the bacterial citadels or their cohesion/power?

Abstract

Section snippets

Definition and processes governing biofilm formation

The architecture and physiological properties of biofilms

Intercellular communication by quorum sensing mechanism and their consequences

The resistance/tolerance of biofilms to antimicrobials

A new generation of antibiofilm therapeutical agents

Conclusions

The Lancet

FEBS Lett

Fitoterapia

Int J Food Microb

Biofilms: survival mechanisms of clinically relevant microorganisms

Clin Microb Rev

Biomaterials Approaches to combating oral biofims and dental disease

BMC Oral Health

Microbial biofilms

Ann Rev Microbiol

Les biofilms (2)

Bull Soc Fr Microbiol

Quorum sensing in bacteria: the LuxR-LuxI family of cell density-responsive transcriptional regulators

J Bacteriol

Quorum sensing and virulence gene regulation in Pseudomonas aeruginosa

The involvement of cell-to-cell signals in the development of a bacterial biofilm

Science

Bacterial quorum sensing: signals, circuits, and implications for biofilms and disease

Annu Rev Biomed Eng

Antibody interference with N-acyl-homoserine lactone-mediated bacterial quorum sensing

J Am Chem Soc

Immunomodulatory effects of Pseudomonas aeruginosa quorum sensing small molecule probes on mammalian macrophages

Mol Biosyst

Pharmacological inhibition of quorum sensing for the treatment of chronic bacterial infections

J Clin Invest

Microbial biofilms: from ecology to molecular genetics

Microbiol Mol Biol Rev

Attenuation of Pseudomonas aeruginosa virulence by quorum sensing inhibitors

EMBO J

Quorum sensing in bacteria

Annu Rev Microbiol

Formation and dispersal of bacterial biofilms in vivo and in situ, J Appl Bacteriol (Symp Suppl.)

The physiology and collective recalcitrance of microbial biofilm communities

Adv Microb Physiol

Biofilms, a new approach to the microbiology of dental plaque

Odontology

Coaggregation of human oral bacteria: potential role in the accretion of dental plaque, J. Appl. Bacteriol. (Symp. Suppl.)

Dental plaque as a microbial biofilm

Caries Res

Investigation of dental- plaque formers biofilms by optic and confocal laser scanning microscopy and microbiological tools

Rev Med Chir

Bacterial interactions in dental biofilm development

J Dent Res

The microbial challenge in periodontitis

Periodontology

Bacterial biofilms: a common cause of persistent infections

Science

Biofilms: the bacterial way to persist, Abstracts book of The International symposium and the 43rd ESCMID post-graduate course- Bacterial adaptation mechanisms: biofilms, hypermutability and antibiotic resistance

Ps. aeruginosa hypermutability and oxidative stress in biofilms, Abstracts book of The International symposium and the 43rd ESCMID post-graduate course- bacterial adaptation mechanisms: biofilms, hypermutability and antibiotic resistance

Pseudomonas aeruginosa biofilms in the CF lung, Abstracts book of The International symposium at the 43rd ESCMID post-graduate course- bacterial adaptation mechanisms: biofilms, hypermutability and antibiotic resistance

Pathogenesis and Toxins
Quorum sensing in biofilms – How to destroy the bacterial citadels or their cohesion/power?