scholarly journals Extracellular riboflavin induces anaerobic biofilm formation in Shewanella oneidensis

2021 ◽  
Vol 14 (1) ◽  
Author(s):  
Miriam Edel ◽  
Gunnar Sturm ◽  
Katrin Sturm-Richter ◽  
Michael Wagner ◽  
Julia Novion Ducassou ◽  
...  
Keyword(s):  
Quorum Sensing ◽  
Biofilm Formation ◽  
Shewanella Oneidensis ◽  
Model Organism ◽  
Electrical Current ◽  
Growth Conditions ◽  
Threshold Concentration ◽  
Bioelectrochemical Systems ◽  
Riboflavin Production ◽  
Biofilm Growth

Abstract Background Some microorganisms can respire with extracellular electron acceptors using an extended electron transport chain to the cell surface. This process can be applied in bioelectrochemical systems in which the organisms produce an electrical current by respiring with an anode as electron acceptor. These organisms apply flavin molecules as cofactors to facilitate one-electron transfer catalyzed by the terminal reductases and in some cases as endogenous electron shuttles. Results In the model organism Shewanella oneidensis, riboflavin production and excretion trigger a specific biofilm formation response that is initiated at a specific threshold concentration, similar to canonical quorum-sensing molecules. Riboflavin-mediated messaging is based on the overexpression of the gene encoding the putrescine decarboxylase speC which leads to posttranscriptional overproduction of proteins involved in biofilm formation. Using a model of growth-dependent riboflavin production under batch and biofilm growth conditions, the number of cells necessary to produce the threshold concentration per time was deduced. Furthermore, our results indicate that specific retention of riboflavin in the biofilm matrix leads to localized concentrations, which by far exceed the necessary threshold value. Conclusion This study describes a new quorum-sensing mechanism in S. oneidensis. Biofilm formation of S. oneidensis is induced by low concentrations of riboflavin resulting in an upregulation of the ornithine-decarboxylase speC. The results can be applied for the development of strains catalyzing increased current densities in bioelectrochemical systems.

scholarly journals Extracellular riboflavin induces anaerobic biofilm formation in Shewanella oneidensis

2021 ◽  
Author(s):  
Miriam Edel ◽  
Gunnar Sturm ◽  
Katrin Sturm-Richter ◽  
Michael Wagner ◽  
Julia Novion Ducassou ◽  
...  
Keyword(s):  
Quorum Sensing ◽  
Cell Surface ◽  
Biofilm Formation ◽  
Shewanella Oneidensis ◽  
Threshold Concentration ◽  
Electron Acceptors ◽  
Specific Response ◽  
Dependent Manner ◽  
Riboflavin Production ◽  
Electron Shuttles

AbstractSome microorganisms can respire with extracellular electron acceptors using an extended electron transport chain to the cell surface. These organisms apply flavin molecules as cofactors to facilitate one-electron transfer catalysed by the terminal reductases and as endogenous electron shuttles. In the model organism Shewanella oneidensis, riboflavin production and excretion triggers a specific biofilm formation response that is initiated at a specific threshold concentration, similar to canonical quorum sensing molecules. Riboflavin-mediated messaging is based on the overexpression of the gene encoding the putrescin decarboxylase speC which leads to posttranscriptional overproduction of proteins involved in biofilm formation. Using a model of growth-dependent riboflavin production under batch and biofilm growth conditions, the number of cells necessary to produce the threshold concentration per time was deduced. Furthermore, our results indicate that specific retention of riboflavin in the biofilm matrix leads to localized concentrations which by far exceed the necessary threshold value.ImportanceFerric iron is the fourth most abundant element of the earth crust. It occurs at neutral pH in the form insoluble iron minerals. The dissimilatory reduction of these minerals is an import part of global geological cycles and is catalyzed by microorganisms through extended respiratory chains to the cell surface. Shewanella oneidensis is one of the best understood model organisms for this kind of extracellular respiration. Flavins are important for the reduction of extracellular electron acceptors by S. oneidensis. since they have a function as (I) cofactors of the terminal reductases and (II) electron shuttles. In this study we reveal that flavin molecules are further employed as quorum sensing molecules. They are excreted by the organisms in a growth dependent manner and lead to anaerobic biofilm formation as a specific response at a certain threshold concentration. Although we know multiple examples of quorum sensing mechanisms, the use of riboflavin was so far not described and at least in S. oneidensis proceeds via a new regulatory routine that proceeds on the trancriptomic and posttranscriptomic level.

scholarly journals Chemotaxis towards autoinducer 2 mediates autoaggregation in Escherichia coli

2016 ◽  
Vol 7 (1) ◽  
Author(s):  
Leanid Laganenka ◽  
Remy Colin ◽  
Victor Sourjik
Keyword(s):  
Escherichia Coli ◽  
Quorum Sensing ◽  
Biofilm Formation ◽  
Bacterial Species ◽  
Physiological Role ◽  
Growth Conditions ◽  
Signal Molecules ◽  
E Coli ◽  
Autoinducer 2 ◽  
Cell Densities

Abstract Bacteria communicate by producing and sensing extracellular signal molecules called autoinducers. Such intercellular signalling, known as quorum sensing, allows bacteria to coordinate and synchronize behavioural responses at high cell densities. Autoinducer 2 (AI-2) is the only known quorum-sensing molecule produced by Escherichia coli but its physiological role remains elusive, although it is known to regulate biofilm formation and virulence in other bacterial species. Here we show that chemotaxis towards self-produced AI-2 can mediate collective behaviour—autoaggregation—of E. coli. Autoaggregation requires motility and is strongly enhanced by chemotaxis to AI-2 at physiological cell densities. These effects are observed regardless whether cell–cell interactions under particular growth conditions are mediated by the major E. coli adhesin (antigen 43) or by curli fibres. Furthermore, AI-2-dependent autoaggregation enhances bacterial stress resistance and promotes biofilm formation.

scholarly journals Influence of Quorum Sensing and Iron on Twitching Motility and Biofilm Formation in Pseudomonas aeruginosa

2007 ◽  
Vol 190 (2) ◽  
pp. 662-671 ◽  
Author(s):  
Glenn M. Patriquin ◽  
Ehud Banin ◽  
Christie Gilmour ◽  
Rivka Tuchman ◽  
E. Peter Greenberg ◽  
...  
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Quorum Sensing ◽  
Biofilm Formation ◽  
Minimal Medium ◽  
Homoserine Lactone ◽  
Planktonic Cell ◽  
Growth Yields ◽  
Twitching Motility ◽  
Wild Type ◽  
Biofilm Growth

ABSTRACT Reducing iron (Fe) levels in a defined minimal medium reduced the growth yields of planktonic and biofilm Pseudomonas aeruginosa, though biofilm biomass was affected to the greatest extent and at FeCl3 concentrations where planktonic cell growth was not compromised. Highlighting this apparently greater need for Fe, biofilm growth yields were markedly reduced in a mutant unable to produce pyoverdine (and, so, deficient in pyoverdine-mediated Fe acquisition) at concentrations of FeCl3 that did not adversely affect biofilm yields of a pyoverdine-producing wild-type strain. Concomitant with the reduced biofilm yields at low Fe concentrations, P. aeruginosa showed enhanced twitching motility in Fe-deficient versus Fe-replete minimal media. A mutant deficient in low-Fe-stimulated twitching motility but normal as regards twitching motility on Fe-rich medium was isolated and shown to be disrupted in rhlI, whose product is responsible for synthesis of the N-butanoyl homoserine lactone (C4-HSL) quorum-sensing signal. In contrast to wild-type cells, which formed thin, flat, undeveloped biofilms in Fe-limited medium, the rhlI mutant formed substantially developed though not fully mature biofilms under Fe limitation. C4-HSL production increased markedly in Fe-limited versus Fe-rich P. aeruginosa cultures, and cell-free low-Fe culture supernatants restored the twitching motility of the rhlI mutant on Fe-limited minimal medium and stimulated the twitching motility of rhlI and wild-type P. aeruginosa on Fe-rich minimal medium. Still, addition of exogenous C4-HSL did not stimulate the twitching motility of either strain on Fe-replete medium, indicating that some Fe-regulated and RhlI/C4-HSL-dependent extracellular product(s) was responsible for the enhanced twitching motility (and reduced biofilm formation) seen in response to Fe limitation.

Interfacing anoxic Shewanella oneidensis biofilms with electrically conducting nanostructures

2020 ◽  
Author(s):  
Edina Klein ◽  
René Wurst ◽  
David Rehnlund ◽  
Johannes Gescher
Keyword(s):  
Electron Transfer ◽  
Biofilm Formation ◽  
Electronic Communication ◽  
Shewanella Oneidensis ◽  
Model Organism ◽  
Laser Scanning Microscopy ◽  
Extracellular Electron Transfer ◽  
Metal Nanostructures ◽  
Special Importance ◽  
Anoxic Conditions

<p><em>Shewanella oneidensis</em> MR1 is the best understood model organism with regards to dissimilatory metal reduction and extracellular electron transfer onto carbon electrodes in bioelectrochemical systems (BES)<sup>1</sup>. However, under anoxic conditions <em>S. oneidensis</em> is known to form very thin biofilms resulting in low current density output. In contrast, another exoelectrogenic model organism <em>Geobacter surfurreduscens</em> can form electroactive biofilms up to 100 µm in thickness. This organism is known for its ability to transport electrons over a long range (> 10 µm) along a network of protein filaments, called microbial nanowires. Although still controversial, it was recently reported that OmcS has a special importance for the conductivity of these nanowires<sup>2</sup>. One of the key differences between <em>G. surfurreduscens</em> and <em>S. oneidensis</em> lies in how cell-to-cell electronic communication occurs, which dictate the range of electronic communication between distant cells. <em>S. oneidensis</em> relies on direct cell-to-cell communication via electron transfer between outer membrane cytochromes or via soluble redox active flavins that are secreted by the cells<sup>3</sup>. Our research is based on the question, what if the <em>S. oneidensis</em> biofilm formation could be improved by introducing an artificial electronic network, similar to the native microbial nanowires for <em>G. sulfurreducens</em>?</p> <p>We hypothesize that synthetic biofilms containing conductive nanostructure additives would allow <em>S. oneidensis</em> to build multilayer thick biofilms under anoxic conditions on solid electron acceptors. To answer this question of how conductive materials affect the formation of anoxic <em>S. oneidensis</em> biofilms, we integrated both biological and synthetic conductive nanostructures into these biofilms. As biological additive, the <em>c</em>-type cytochrome OmcS purified from<em> G. sulfurreducens</em> was utilized. As synthetic additives, both commercially available biotinylated gold nanorods and in-house electrochemically synthesized metal nanostructures were added to anoxic <em>S. oneidensis</em> biofilms.</p> <p>Cultivation and characterization of the biofilms was performed using our newly developed microfluidic bioelectrochemical platform. Microbial cultivation with the aid of microfluidic flow chambers has a great potential to form biofilms on an easy to handle laboratory scale with simultaneously ongoing multianalytical analysis<sup>4</sup>. In our bioelectrochemical microfluidic, system <em>S. oneidensis</em> biofilms can be grown under anoxic conditions using an anode as sole electron acceptor. The growth behavior and bioelectrochemical performance was evaluated by a combination of electrochemical techniques (chronoamperometry, electrochemical impedance spectroscopy, cyclic voltammetry) and optical analyses (confocal laser scanning microscopy and optical coherence tomography). The strategy of conductive nanostructured additives for improved electroactive biofilm formation could be an important tool for other exoelectrogenic microorganisms in order to exploit their physiological abilities for biotechnology.</p> <p>References:</p> <ol> <li>Beblawy, S. <em>et al</em>. (2018) <em>Molecular Microbiology</em> <strong>109</strong>: 571-583.</li> <li>Wang, F. <em>et al</em>. (2019) <em>Cell </em><strong>177</strong>: 361‐369.</li> <li>Shi, L. <em>et al</em>. (2016) <em>Nature Reviews Microbiology</em> <strong>14</strong>: 651-662.</li> <li>Hansen, S.H. <em>et al</em>. (2019) <em>Scientific Reports</em> <strong>9</strong>: 8933.</li> </ol> <p> </p>

scholarly journals Activity of Streptococcus mutans VicR Is Modulated by Antisense RNA

2018 ◽  
Vol 97 (13) ◽  
pp. 1477-1484 ◽  
Author(s):  
L. Lei ◽  
R.N. Stipp ◽  
T. Chen ◽  
S.Z. Wu ◽  
T. Hu ◽  
...  
Keyword(s):  
Streptococcus Mutans ◽  
Biofilm Formation ◽  
Posttranscriptional Regulation ◽  
Growth Conditions ◽  
Northern Blotting ◽  
Promoter Regions ◽  
Mobility Shift ◽  
Biofilm Growth ◽  
Qrt Pcr ◽  
Rna Transcript

The VicRK 2-component system of Streptococcus mutans regulates genes associated with cell wall biogenesis and biofilm formation. A putative RNase III–encoding gene ( rnc) is located downstream from the vicRKX operon. The goals of this study were to investigate the potential role of VicR in the regulation of adjacent downstream genes and evaluate transcription levels of vicR during planktonic and biofilm growth. Quantitative real-time polymerase chain reaction (qRT-PCR) was used to investigate whether vicRKX and adjacent downstream genes were cotranscribed. Binding of purified recombinant VicR protein to promoter regions of vicR, rnc, and syfA genes was confirmed by electrophoretic mobility shift assay and by chromatin immunoprecipitation analyses. VicR antisense (AS vicR) RNA was detected by Northern blotting and qRT-PCR assays. AS vicR overexpression mutants were constructed, and the biofilm biomass was determined by crystal violet microtiter assay. Adjacent downstream genes rnc, smc, syfA, smu.1511, and syfB were cotranscribed with vicRKX. The predicted promoter regions of vicR, rnc, and syfA genes were directly regulated by VicR. An AS vicR RNA transcript was detected upstream of the rnc gene. Expression of the AS vicR RNA transcript was elevated in planktonic cultures and repressed during biofilm growth. In addition, Western blot data showed that expression of the VicR protein decreased by 35% in planktonic as compared with biofilm cultures. Furthermore, we show that overexpression of AS vicR led to a reduction in biofilm formation. The downstream genes rnc, smc, syfA, smu.1511, and syfB are cotranscribed with vicRKX. VicR is autophosphorylated, and rnc and syfA are directly regulated by VicR. Expression of VicR protein correlated inversely with different levels of AS vicR RNA transcript and growth conditions. The biofilm biomass decreased in the AS vicR overexpression mutant. These data suggest a role for the AS vicR RNA transcript in posttranscriptional regulation of VicR protein production in S. mutans.

scholarly journals Environmental Adaptability and Quorum Sensing: Iron Uptake Regulation during Biofilm Formation byParacoccus denitrificans

2018 ◽  
Vol 84 (14) ◽  
Author(s):  
Yang Zhang ◽  
Jie Gao ◽  
Lushan Wang ◽  
Shuangjiang Liu ◽  
Zhihui Bai ◽  
...  
Keyword(s):  
Quorum Sensing ◽  
Biofilm Formation ◽  
Iron Uptake ◽  
Paracoccus Denitrificans ◽  
Iron Acquisition ◽  
Model Organism ◽  
Ecological Niches ◽  
Content Type ◽  
Excess Iron ◽  
Cell Functions

ABSTRACTParacoccus denitrificansis a valuable model organism due to its versatile respiration capability and bioenergetic flexibility, both of which are critical to its survival in different environments. Quorum sensing (QS) plays a crucial role in the regulation of many cell functions; however, whether QS systems play a role inP. denitrificansis unknown. In this study, we demonstrated that iron uptake systems inP. denitrificanswere directly regulated by a newly identified QS system. Genes coding for TonB-dependent systems, which transport chelated iron, were transcribed at higher levels in the QS-defective mutants. In contrast, genes coding for the Fbp system, which is TonB independent and transports unchelated ferric iron, were downregulated in the mutants. In brief, QS inP. denitrificanstriggers a switch in iron uptake from TonB-dependent to TonB-independent transport during biofilm formation as higher concentrations of iron accumulate in the exopolysaccharide (EPS). Switching from TonB-dependent iron uptake systems to TonB-independent systems not only prevents cells from absorbing excess iron but also conserves energy. Our data suggest that iron uptake strategies are directly regulated by QS inParacoccus denitrificansto support their survival in available ecological niches.IMPORTANCEAs iron is an important trace metal for most organisms, its absorption is highly regulated. Fur has been reported as a prevalent regulator of iron acquisition. In addition, there is a relationship between QS and iron acquisition in pathogenic microbes. However, there have been few studies on the iron uptake strategies of nonpathogenic bacteria. In this study, we demonstrated that iron uptake systems inParacoccus denitrificansPD1222 were regulated by a newly identified PdeR/PdeI QS system during biofilm formation, and we put forward a hypothesis that QS-dependent iron uptake systems benefit the stability of biofilms. This report elaborates the correlation among QS, iron uptake, and biofilm formation and thus contributes to an understanding of the ecological behavior of environmental bacteria.

Quorum Sensing – A Stratagem for Conquering Multi-Drug Resistant Pathogens

2020 ◽  
Vol 26 ◽  
Author(s):  
Madison Tonkin ◽  
Shama Khan ◽  
Mohmmad Younus Wani ◽  
Aijaz Ahmad
Keyword(s):  
Drug Resistance ◽  
Quorum Sensing ◽  
Virulence Factors ◽  
Biofilm Formation ◽  
Cell Communication ◽  
Natural Compounds ◽  
Quorum Sensing Inhibitors ◽  
Communication Technique ◽  
Multicellular Organisms ◽  
Chemical Strategies

: Quorum sensing is defined as cell to cell communication between microorganisms, which enables microorganisms to behave as multicellular organisms. Quorum sensing enables many collaborative benefits such as synchronisation of virulence factors and biofilm formation. Both quorum sensing as well as biofilm formation encourage the development of drug resistance in microorganisms. Biofilm formation and quorum sensing are causally linked to each other and play role in the pathogenesis of microorganisms. With the increasing drug resistance against the available antibiotics and antifungal medications, scientists are combining different options to develop new strategies. Such strategies rely on the inhibition of the communication and virulence factors rather than on killing or inhibiting the growth of the microorganisms. This review encompasses the communication technique used by microorganisms, how microorganism resistance is linked to quorum sensing and various chemical strategies to combat quorum sensing and thereby drug resistance. Several compounds have been identified as quorum sensing inhibitors and are known to be effective in reducing resistance as they do not kill the pathogens but rather disrupt their communication. Natural compounds have been identified as anti-quorum sensing agents. However, natural compounds present several related disadvantages. Therefore, the need for the development of synthetic or semi-synthetic compounds has arisen. This review argues that anti-quorum sensing compounds are effective in disrupting quorum sensing and could therefore be effective in reducing microorganism drug resistance.

Modulation of Gut Microbiota through Dietary Phytochemicals as a Novel Anti-infective Strategy

2020 ◽  
Vol 17 (4) ◽  
pp. 498-506 ◽  
Author(s):  
Pavan K. Mujawdiya ◽  
Suman Kapur
Keyword(s):  
Microbial Community ◽  
Quorum Sensing ◽  
Population Density ◽  
Gut Microbiota ◽  
Biofilm Formation ◽  
Chemical Interaction ◽  
Bacterial Species ◽  
Critical Role ◽  
Bacterial Cells ◽  
Gut Microbes

: Quorum Sensing (QS) is a phenomenon in which bacterial cells communicate with each other with the help of several low molecular weight compounds. QS is largely dependent on population density, and it triggers when the concentration of quorum sensing molecules accumulate in the environment and crosses a particular threshold. Once a certain population density is achieved and the concentration of molecules crosses a threshold, the bacterial cells show a collective behavior in response to various chemical stimuli referred to as “auto-inducers”. The QS signaling is crucial for several phenotypic characteristics responsible for bacterial survival such as motility, virulence, and biofilm formation. Biofilm formation is also responsible for making bacterial cells resistant to antibiotics. : The human gut is home to trillions of bacterial cells collectively called “gut microbiota” or “gut microbes”. Gut microbes are a consortium of more than 15,000 bacterial species and play a very crucial role in several body functions such as metabolism, development and maturation of the immune system, and the synthesis of several essential vitamins. Due to its critical role in shaping human survival and its modulating impact on body metabolisms, the gut microbial community has been referred to as “the forgotten organ” by O`Hara et al. (2006) [1]. Several studies have demonstrated that chemical interaction between the members of bacterial cells in the gut is responsible for shaping the overall microbial community. : Recent advances in phytochemical research have generated a lot of interest in finding new, effective, and safer alternatives to modern chemical-based medicines. In the context of antimicrobial research various plant extracts have been identified with Quorum Sensing Inhibitory (QSI) activities among bacterial cells. This review focuses on the mechanism of quorum sensing and quorum sensing inhibitors isolated from natural sources.

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