scholarly journals AbaM Regulates Quorum Sensing, Biofilm Formation and Virulence in Acinetobacter baumannii

2020 ◽  
Author(s):  
Mario López-Martín ◽  
Jean-Frédéric Dubern ◽  
Morgan R. Alexander ◽  
Paul Williams
Keyword(s):  
Quorum Sensing ◽  
Acinetobacter Baumannii ◽  
Biofilm Formation ◽  
Plant Pathogens ◽  
Galleria Mellonella ◽  
Homoserine Lactone ◽  
Infection Model ◽  
Wild Type ◽  
Surface Motility ◽  
Biofilm Development

ABSTRACTAcinetobacter baumannii possesses a single divergent luxR/luxI-type quorum sensing (QS) locus named abaR/abaI. This locus also contains a third gene located between abaR and abaI which we term abaM that codes for an uncharacterized member of the RsaM protein family known to regulate N-acylhomoserine lactone (AHL) dependent QS in other β- and γ-proteobacteria. Here we show that disruption of abaM via a T26 insertion in A. baumannii strain AB5075 resulted in increased production of N-(3-hydroxydodecanoyl)-L-homoserine lactone (OHC12) and enhanced surface motility and biofilm formation. In contrast to the wild type and abaI::T26 mutant, the virulence of the abaM::T26 mutant was completely attenuated in a Galleria mellonella infection model. Transcriptomic analysis of the abaM::T26 mutant revealed that abaM differentially regulates at least 76 genes including the csu pilus operon and the acinetin 505 lipopeptide biosynthetic operon, that are involved in surface adherence, biofilm formation and virulence. A comparison of the wild type, abaM::T26 and abaI::T26 transcriptomes, indicates that abaM regulates ~21% of the QS regulon including the csu operon. Moreover, the QS genes (abaI/abaR) were among the most upregulated in the abaM::T26 mutant. A. baumannii lux-based abaM reporter gene fusions revealed that abaM expression is positively regulated by QS but negatively auto-regulated. Overall, the data presented in this work demonstrates that abaM plays a central role in regulating A. baumannii QS, virulence, surface motility and biofilm formation.IMPORTANCEAcinetobacter baumanni is a multi-antibiotic resistant pathogen of global healthcare importance. Understanding Acinetobacter virulence gene regulation could aid the development of novel anti-infective strategies. In A. baumannii, the abaR and abaI genes that code for the receptor and synthase components of an N-acylhomoserine (AHL) lactone-dependent quorum sensing system (QS) are separated by abaM. Here we show that although mutation of abaM increased AHL production, surface motility and biofilm development, it resulted in the attenuation of virulence. abaM was found to control both QS-dependent and QS-independent genes. The significance of this work lies in the identification of abaM, an RsaM ortholog known to control virulence in plant pathogens, as a modulator of virulence in a human pathogen.

scholarly journals AbaM Regulates Quorum Sensing, Biofilm Formation and Virulence in Acinetobacter baumannii

2021 ◽  
Author(s):  
Mario López-Martín ◽  
Jean-Frédéric Dubern ◽  
Morgan R. Alexander ◽  
Paul Williams
Keyword(s):  
Quorum Sensing ◽  
Acinetobacter Baumannii ◽  
Biofilm Formation ◽  
Plant Pathogens ◽  
Galleria Mellonella ◽  
Homoserine Lactone ◽  
Infection Model ◽  
Wild Type ◽  
Surface Motility ◽  
Biofilm Development

Acinetobacter baumannii possesses a single divergent luxR/luxI-type quorum sensing (QS) locus named abaR/abaI. This locus also contains a third gene located between abaR and abaI which we term abaM that codes for an uncharacterized member of the RsaM protein family known to regulate N-acylhomoserine lactone (AHL) dependent QS in other β- and γ-proteobacteria. Here we show that disruption of abaM via a T26 insertion in A. baumannii strain AB5075 resulted in increased production of N-(3-hydroxydodecanoyl)-L-homoserine lactone (OHC12) and enhanced surface motility and biofilm formation. In contrast to the wild type and abaI::T26 mutant, the virulence of the abaM::T26 mutant was completely attenuated in a Galleria mellonella infection model. Transcriptomic analysis of the abaM::T26 mutant revealed that AbaM differentially regulates at least 76 genes including the csu pilus operon and the acinetin 505 lipopeptide biosynthetic operon, that are involved in surface adherence, biofilm formation and virulence. A comparison of the wild type, abaM::T26 and abaI::T26 transcriptomes, indicates that AbaM regulates ∼21% of the QS regulon including the csu operon. Moreover, the QS genes (abaI/abaR) were among the most upregulated in the abaM::T26 mutant. A. baumannii lux-based abaM reporter gene fusions revealed that abaM expression is positively regulated by QS but negatively auto-regulated. Overall, the data presented in this work demonstrates that AbaM plays a central role in regulating A. baumannii QS, virulence, surface motility and biofilm formation. Importance Acinetobacter baumanni is a multi-antibiotic resistant pathogen of global healthcare importance. Understanding Acinetobacter virulence gene regulation could aid the development of novel anti-infective strategies. In A. baumannii, the abaR and abaI genes that code for the receptor and synthase components of an N-acylhomoserine (AHL) lactone-dependent quorum sensing system (QS) are separated by abaM. Here we show that although mutation of abaM increased AHL production, surface motility and biofilm development, it resulted in the attenuation of virulence. AbaM was found to control both QS-dependent and QS-independent genes. The significance of this work lies in the identification of AbaM, an RsaM ortholog known to control virulence in plant pathogens, as a modulator of virulence in a human pathogen.

scholarly journals Quorum-Sensing Regulation of the Biofilm Matrix Genes (pel) of Pseudomonas aeruginosa

2007 ◽  
Vol 189 (14) ◽  
pp. 5383-5386 ◽  
Author(s):  
Yumiko Sakuragi ◽  
Roberto Kolter
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Quorum Sensing ◽  
Biofilm Formation ◽  
Homoserine Lactone ◽  
Wild Type ◽  
Wild Type Level ◽  
Dna Release ◽  
Biofilm Development ◽  
Development Regulation ◽  
Biofilm Matrix

ABSTRACT Quorum sensing (QS) has been previously shown to play an important role in the development of Pseudomonas aeruginosa biofilms (D. G. Davies et al., Science 280:295-298, 1998). Although QS regulation of swarming and DNA release has been shown to play important roles in biofilm development, regulation of genes directly involved in biosynthesis of biofilm matrix has not been described. Here, transcription of the pel operon, essential for the production of a glucose-rich matrix exopolysaccharide, is shown to be greatly reduced in lasI and rhlI mutants. Chemical complementation of the lasI mutant with 3-oxo-dodecanoyl homoserine lactone restores pel transcription to the wild-type level and biofilm formation ability. These findings thus connect QS signaling and transcription of genes responsible for biofilm matrix biosynthesis.

scholarly journals Quorum Sensing Influences Burkholderia thailandensis Biofilm Development and Matrix Production

2016 ◽  
Vol 198 (19) ◽  
pp. 2643-2650 ◽  
Author(s):  
Boo Shan Tseng ◽  
Charlotte D. Majerczyk ◽  
Daniel Passos da Silva ◽  
Josephine R. Chandler ◽  
E. Peter Greenberg ◽  
...  
Keyword(s):  
Quorum Sensing ◽  
Biofilm Formation ◽  
Bacterial Species ◽  
Matrix Material ◽  
Close Relative ◽  
Wild Type ◽  
Flow Conditions ◽  
Burkholderia Thailandensis ◽  
Content Type ◽  
Biofilm Development

ABSTRACTMembers of the genusBurkholderiaare known to be adept at biofilm formation, which presumably assists in the survival of these organisms in the environment and the host. Biofilm formation has been linked to quorum sensing (QS) in several bacterial species. In this study, we characterizedBurkholderia thailandensisbiofilm development under flow conditions and sought to determine whether QS contributes to this process.B. thailandensisbiofilm formation exhibited an unusual pattern: the cells formed small aggregates and then proceeded to produce mature biofilms characterized by “dome” structures filled with biofilm matrix material. We showed that this process was dependent on QS.B. thailandensishas three acyl-homoserine lactone (AHL) QS systems (QS-1, QS-2, and QS-3). An AHL-negative strain produced biofilms consisting of cell aggregates but lacking the matrix-filled dome structures. This phenotype was rescued via exogenous addition of the three AHL signals. Of the threeB. thailandensisQS systems, we show that QS-1 is required for proper biofilm development, since abtaR1mutant, which is defective in QS-1 regulation, forms biofilms without these dome structures. Furthermore, our data show that the wild-type biofilm biomass, as well as the material inside the domes, stains with a fucose-binding lectin. ThebtaR1mutant biofilms, however, are negative for fucose staining. This suggests that the QS-1 system regulates the production of a fucose-containing exopolysaccharide in wild-type biofilms. Finally, we present data showing that QS ability during biofilm development produces a biofilm that is resistant to dispersion under stress conditions.IMPORTANCEThe saprophyteBurkholderia thailandensisis a close relative of the pathogenic bacteriumBurkholderia pseudomallei, the causative agent of melioidosis, which is contracted from its environmental reservoir. Since most bacteria in the environment reside in biofilms,B. thailandensisis an ideal model organism for investigating questions inBurkholderiaphysiology. In this study, we characterizedB. thailandensisbiofilm development and sought to determine if quorum sensing (QS) contributes to this process. Our work shows thatB. thailandensisproduces biofilms with unusual dome structures under flow conditions. Our findings suggest that these dome structures are filled with a QS-regulated, fucose-containing exopolysaccharide that may be involved in the resilience ofB. thailandensisbiofilms against changes in the nutritional environment.

scholarly journals Quorum-Sensing Genes in Pseudomonas aeruginosa Biofilms: Their Role and Expression Patterns

2001 ◽  
Vol 67 (4) ◽  
pp. 1865-1873 ◽  
Author(s):  
Teresa R. De Kievit ◽  
Richard Gillis ◽  
Steve Marx ◽  
Chris Brown ◽  
Barbara H. Iglewski
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Quorum Sensing ◽  
Biofilm Formation ◽  
Fluorescent Protein ◽  
Expression Patterns ◽  
Homoserine Lactone ◽  
Lower Percentage ◽  
Spatial Studies ◽  
Green Fluorescent ◽  
Biofilm Development

ABSTRACT Acylated homoserine lactone molecules are used by a number of gram-negative bacteria to regulate cell density-dependent gene expression by a mechanism known as quorum sensing (QS). InPseudomonas aeruginosa, QS or cell-to-cell signaling controls expression of a number of virulence factors, as well as biofilm differentiation. In this study, we investigated the role played by the las and rhl QS systems during the early stages of static biofilm formation when cells are adhering to a surface and forming microcolonies. These studies revealed a marked difference in biofilm formation between the PAO1 parent and the QS mutants when glucose, but not citrate, was used as the sole carbon source. To further elucidate the contribution of lasI andrhlI to biofilm maturation, we utilized fusions to unstable green fluorescent protein in concert with confocal microscopy to perform real-time temporal and spatial studies of these genes in a flowing environment. During the course of 8-day biofilm development,lasI expression was found to progressively decrease over time. Conversely, rhlI expression remained steady throughout biofilm development but occurred in a lower percentage of cells. Spatial analysis revealed that lasI andrhlI were maximally expressed in cells located at the substratum and that expression decreased with increasing biofilm height. Because QS was shown previously to be involved in biofilm differentiation, these findings have important implications for the design of biofilm prevention and eradication strategies.

A role for rhamnolipid in biofilm dispersion

Biofilms ◽  
2004 ◽  
Vol 1 (2) ◽  
pp. 91-99 ◽  
Author(s):  
S. R. Schooling ◽  
U. K. Charaf ◽  
D. G. Allison ◽  
P. Gilbert
Keyword(s):  
Surface Tension ◽  
Quorum Sensing ◽  
Biofilm Formation ◽  
Culture Medium ◽  
High Cell Density ◽  
Culture Media ◽  
Homoserine Lactone ◽  
Wild Type ◽  
In The Wild ◽  
Biofilm Dispersion

Biofilms are often considered as localized zones of high cell density. Quorum sensing provides a means for control of population processes and has been implicated in the regulation of biofilm activities. We present a role for quorum sensing in programmed detachment and dispersal processes. Biofilms of Pseudomonas aeruginosa PAO1 and its isogenic homoserine lactone (HSL) mutant P. aeruginosa PAO-JP2 were grown in batch culture on glass substrata; differences were found in the rate and extent of formation of biofilm. Climax communities were observed for PAO1 at 24 h. These were later accompanied by foaming, a drop in the surface tension of culture media and dispersal of the biofilm, after which no subsequent biofilm accretion occurred. PAO-JP2 cultures reformed biofilm post-detachment and did not foam. Prevention of biofilm reformation in the wild type was related to some component excreted into the culture medium. Rhamnolipid, a biosurfactant regulated by quorum sensing, was detected in PAO1 cultures. When rhamnolipid was added to freshly inoculated substrata, biofilm formation was inhibited. At 20 h, PAO1 biofilms were transferred to medium with added rhamnolipid: biofilm was relatively unaffected. Biofilm events were also studied in medium supplemented with N-butyryl-L-homoserine lactone, which is involved in the regulation of rhamnolipid synthesis. Both strains exhibited similar trends of rapid biofilm formation and dramatic changes in the rate and extent of biofilm accretion. In both cases, there was premature foaming, lowered surface tension and elevated rhamnolipid levels. A role for HSLs in maintenance of biofilm and events leading to dispersion of cells is proposed. This role would encompass dispersion but not necessarily detachment of cells from biofilm and supports a new function for rhamnolipid in pathogenesis, whereby rhamnolipid would promote the dissemination of cells from a nidus of infection.

scholarly journals Quorum-Sensing Systems in the Plant Growth-Promoting Bacterium Paraburkholderia phytofirmans PsJN Exhibit Cross-Regulation and Are Involved in Biofilm Formation

2017 ◽  
Vol 30 (7) ◽  
pp. 557-565 ◽  
Author(s):  
Ana Zúñiga ◽  
Raúl A. Donoso ◽  
Daniela Ruiz ◽  
Gonzalo A. Ruz ◽  
Bernardo González
Keyword(s):  
Quorum Sensing ◽  
Biofilm Formation ◽  
Type Strain ◽  
Wild Type Strain ◽  
Homoserine Lactone ◽  
Wild Type ◽  
Transcript Levels ◽  
Sensing Systems ◽  
Plant Growth Promoting ◽  
Growth Promoting

Quorum-sensing systems play important roles in host colonization and host establishment of Burkholderiales species. Beneficial Paraburkholderia species share a conserved quorum-sensing (QS) system, designated BraI/R, that controls different phenotypes. In this context, the plant growth-promoting bacterium Paraburkholderia phytofirmans PsJN possesses two different homoserine lactone QS systems BpI.1/R.1 and BpI.2/R.2 (BraI/R-like QS system). The BpI.1/R.1 QS system was previously reported to be important to colonize and produce beneficial effects in Arabidopsis thaliana plants. Here, we analyzed the temporal variations of the QS gene transcript levels in the wild-type strain colonizing plant roots. The gene expression patterns showed relevant differences in both QS systems compared with the wild-type strain in the unplanted control treatment. The gene expression data were used to reconstruct a regulatory network model of QS systems in P. phytofirmans PsJN, using a Boolean network model. Also, we examined the phenotypic traits and transcript levels of genes involved in QS systems, using P. phytofirmans mutants in homoserine lactone synthases genes. We observed that the BpI.1/R.1 QS system regulates biofilm formation production in strain PsJN and this phenotype was associated with the lower expression of a specific extracytoplasmic function sigma factor ecf26.1 gene (implicated in biofilm formation) in the bpI.1 mutant strain.

scholarly journals Mutation of luxS Affects Biofilm Formation in Streptococcus mutans

2003 ◽  
Vol 71 (4) ◽  
pp. 1972-1979 ◽  
Author(s):  
Justin Merritt ◽  
Fengxia Qi ◽  
Steven D. Goodman ◽  
Maxwell H. Anderson ◽  
Wenyuan Shi
Keyword(s):  
Quorum Sensing ◽  
Streptococcus Mutans ◽  
Biofilm Formation ◽  
Microscopic Analysis ◽  
Homoserine Lactone ◽  
Good Evidence ◽  
Genome Project ◽  
Bacterial Biofilm ◽  
Wild Type

ABSTRACT Quorum sensing is a bacterial mechanism for regulating gene expression in response to changes in population density. Many bacteria are capable of acyl-homoserine lactone-based or peptide-based intraspecies quorum sensing and luxS-dependent interspecies quorum sensing. While there is good evidence about the involvement of intraspecies quorum sensing in bacterial biofilm, little is known about the role of luxS in biofilm formation. In this study, we report for the first time that luxS-dependent quorum sensing is involved in biofilm formation of Streptococcus mutans. S. mutans is a major cariogenic bacterium in the multispecies bacterial biofilm commonly known as dental plaque. An ortholog of luxS for S. mutans was identified using the data available in the S. mutans genome project (http://www.genome.ou.edu/smutans.html ). Using an assay developed for the detection of the LuxS-associated quorum sensing signal autoinducer 2 (AI-2), it was demonstrated that this ortholog was able to complement the luxS negative phenotype of Escherichia coli DH5α. It was also shown that AI-2 is indeed produced by S. mutans. AI-2 production is maximal during mid- to late-log growth in batch culture. Mutant strains devoid of the luxS gene were constructed and found to be defective in producing the AI-2 signal. There are also marked phenotypic differences between the wild type and the luxS mutants. Microscopic analysis of in vitro-grown biofilm structure revealed that the luxS mutant biofilms adopted a much more granular appearance, rather than the relatively smooth, confluent layer normally seen in the wild type. These results suggest that LuxS-dependent signal may play an important role in biofilm formation of S. mutans.

scholarly journals Role of Quorum Sensing and Antimicrobial Component Production by Serratia plymuthica in Formation of Biofilms, Including Mixed Biofilms with Escherichia coli

2006 ◽  
Vol 72 (11) ◽  
pp. 7294-7300 ◽  
Author(s):  
Pieter Moons ◽  
Rob Van Houdt ◽  
Abram Aertsen ◽  
Kristof Vanoirbeek ◽  
Yves Engelborghs ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Quorum Sensing ◽  
Biofilm Formation ◽  
Homoserine Lactone ◽  
Broth Culture ◽  
Confocal Laser ◽  
Wild Type ◽  
Serratia Plymuthica ◽  
E Coli

ABSTRACT We have previously characterized the N-acyl-l-homoserine lactone-based quorum-sensing system of the biofilm isolate Serratia plymuthica RVH1. Here we investigated the role of quorum sensing and of quorum-sensing-dependent production of an antimicrobial compound (AC) on biofilm formation by RVH1 and on the cocultivation of RVH1 and Escherichia coli in planktonic cultures or in biofilms. Biofilm formation of S. plymuthica was not affected by the knockout of splI or splR, the S. plymuthica homologs of the luxI or luxR quorum-sensing gene, respectively, or by the knockout of AC production. E. coli grew well in mixed broth culture with RVH1 until the latter reached 8.5 to 9.5 log CFU/ml, after which the E. coli colony counts steeply declined. In comparison, only a very small decline occurred in cocultures with the S. plymuthica AC-deficient and splI mutants. Complementation with exogenous N-hexanoyl-l-homoserine lactone rescued the wild-type phenotype of the splI mutant. The splR knockout mutant also induced a steep decline of E. coli, consistent with its proposed function as a repressor of quorum-sensing-regulated genes. The numbers of E. coli in 3-day-old mixed biofilms followed a similar pattern, being higher with S. plymuthica deficient in SplI or AC production than with wild-type S. plymuthica, the splR mutant, or the splI mutant in the presence of N-hexanoyl-l-homoserine lactone. Confocal laser scanning microscopic analysis of mixed biofilms established with strains producing different fluorescent proteins showed that E. coli microcolonies were less developed in the presence of RVH1 than in the presence of the AC-deficient mutant.

scholarly journals Assessment of Antibiofilm Potencies of Nervonic and Oleic Acid against Acinetobacter baumannii Using In Vitro and Computational Approaches

Biomedicines ◽  
2021 ◽  
Vol 9 (9) ◽  
pp. 1133
Author(s):  
Sagar Kiran Khadke ◽  
Jin-Hyung Lee ◽  
Yong-Guy Kim ◽  
Vinit Raj ◽  
Jintae Lee
Keyword(s):  
Fatty Acids ◽  
Oleic Acid ◽  
Quorum Sensing ◽  
Acinetobacter Baumannii ◽  
Biofilm Formation ◽  
Unsaturated Fatty Acids ◽  
Homoserine Lactone ◽  
Antimicrobial Treatment ◽  
Dynamic Simulations

Acinetobacter baumannii is a nosocomial pathogen, and its biofilms are tolerant to desiccation, nutrient starvation, and antimicrobial treatment on biotic and abiotic surfaces, tissues, and medical devices. Biofilm formation by A. baumannii is triggered by a quorum sensing cascade, and we hypothesized that fatty acids might inhibit its biofilm formation by interfering with quorum sensing. Initially, we investigated the antibiofilm activities of 24 fatty acids against A. baumannii ATCC 17978 and two clinical isolates. Among these fatty acids, two unsaturated fatty acids, nervonic and oleic acid, at 20 μg/mL significantly inhibited A. baumannii biofilm formation without affecting its planktonic cell growth (MICs were >500 μg/mL) and markedly decreased the motility of A. baumannii but had no toxic effect on the nematode Caenorhabditis elegans. Interestingly, molecular dynamic simulations showed that both fatty acids bind to the quorum sensing acyl homoserine lactone synthase (AbaI), and decent conformational stabilities of interactions between the fatty acids and AbaI were exhibited. Our results demonstrate that nervonic and oleic acid inhibit biofilm formation by A. baumannii strains and may be used as lead molecules for the control of persistent A. baumannii infections.

scholarly journals N-Octanoylhomoserine lactone signalling mediated by the BpsI–BpsR quorum sensing system plays a major role in biofilm formation of Burkholderia pseudomallei

Microbiology ◽  
2011 ◽  
Vol 157 (4) ◽  
pp. 1176-1186 ◽  
Author(s):  
Akshamal Mihiranga Gamage ◽  
Guanghou Shui ◽  
Markus R. Wenk ◽  
Kim Lee Chua
Keyword(s):  
Quorum Sensing ◽  
Biofilm Formation ◽  
Burkholderia Pseudomallei ◽  
Homoserine Lactone ◽  
Tandem Ms ◽  
Wild Type ◽  
Acylhomoserine Lactone ◽  
Sensing System ◽  
Sensing Systems ◽  
Quorum Sensing System

The genome of Burkholderia pseudomallei encodes three acylhomoserine lactone (AHL) quorum sensing systems, each comprising an AHL synthase and a signal receptor/regulator. The BpsI–BpsR system produces N-octanoylhomoserine lactone (C8HL) and is positively auto-regulated by its AHL product. The products of the remaining two systems have not been identified. In this study, tandem MS was used to identify and quantify the AHL species produced by three clinical B. pseudomallei isolates – KHW, K96243 and H11 – three isogenic KHW mutants that each contain a null mutation in an AHL synthase gene, and recombinant Escherichia coli heterologously expressing each of the three B. pseudomallei AHL synthase genes. BpsI synthesized predominantly C8HL, which accounted for more than 95 % of the extracellular AHLs produced in stationary-phase KHW cultures. The major products of BpsI2 and BpsI3 were N-(3-hydroxy-octanoyl)homoserine lactone (OHC8HL) and N-(3-hydroxy-decanoyl)homoserine lactone, respectively, and their corresponding transcriptional regulators, BpsR2 and BpsR3, were capable of driving reporter gene expression in the presence of these cognate lactones. Formation of biofilm by B. pseudomallei KHW was severely impaired in mutants lacking either BpsI or BpsR but could be restored to near wild-type levels by exogenous C8HL. BpsI2 was not required, and BpsI3 was partially required for biofilm formation. Unlike the bpsI mutant, biofilm formation in the bpsI3 mutant could not be restored to wild-type levels in the presence of OHC8HL, the product of BpsI3. C8HL and OHC8HL had opposite effects on biofilm formation; exogenous C8HL enhanced biofilm formation in both the bpsI3 mutant and wild-type KHW while exogenous OHC8HL suppressed the formation of biofilm in the same strains. We propose that exogenous OHC8HL antagonizes biofilm formation in B. pseudomallei, possibly by competing with endogenous C8HL for binding to BpsR.

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