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

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.

Download Full-text

Unsaturated Fatty Acids Affect Quorum Sensing Communication System and Inhibit Motility and Biofilm Formation of Acinetobacter baumannii

International Journal of Molecular Sciences ◽

10.3390/ijms19010214 ◽

2018 ◽

Vol 19 (1) ◽

pp. 214 ◽

Cited By ~ 16

Author(s):

Marion Nicol ◽

Stéphane Alexandre ◽

Jean-Baptiste Luizet ◽

Malena Skogman ◽

Thierry Jouenne ◽

...

Keyword(s):

Fatty Acids ◽

Quorum Sensing ◽

Acinetobacter Baumannii ◽

Communication System ◽

Biofilm Formation ◽

Unsaturated Fatty Acids

Download Full-text

Mutation of luxS Affects Biofilm Formation in Streptococcus mutans

Infection and Immunity ◽

10.1128/iai.71.4.1972-1979.2003 ◽

2003 ◽

Vol 71 (4) ◽

pp. 1972-1979 ◽

Cited By ~ 185

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.

Download Full-text

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

Journal of Bacteriology ◽

10.1128/jb.00635-20 ◽

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.

Download Full-text

Mechanistic analysis of a synthetic inhibitor of the Pseudomonas aeruginosa LasI quorum-sensing signal synthase

Scientific Reports ◽

10.1038/srep16569 ◽

2015 ◽

Vol 5 (1) ◽

Cited By ~ 29

Author(s):

O. Lidor ◽

A. Al-Quntar ◽

E. C. Pesci ◽

D. Steinberg

Keyword(s):

Pseudomonas Aeruginosa ◽

Quorum Sensing ◽

In Silico ◽

Biofilm Formation ◽

Homoserine Lactone ◽

Site Directed Mutagenesis ◽

Great Promise ◽

Acyl Homoserine Lactone ◽

Virulence Determinants

Abstract Pseudomonas aeruginosa is an opportunistic Gram-negative pathogen responsible for many human infections. LasI is an acyl-homoserine lactone synthase that produces a quorum-sensing (QS) signal that positively regulates numerous P. aeruginosa virulence determinants. The inhibition of the LasI protein is therefore an attractive drug target. In this study, a novel in silico to in vitro complementation was applied to screen thiazolidinedione-type compounds for their ability to inhibit biofilm formation at concentrations not affecting bacterial growth. The compound (z)-5-octylidenethiazolidine-2, 4-dione (TZD-C8) was a strong inhibitor of biofilm formation and chosen for further study. Structural exploration of in silico docking predicted that the compound had high affinity for the LasI activity pocket. The TZD-C8 compound was also predicted to create hydrogen bonds with residues Arg30 and Ile107. Site-directed mutagenesis (SDM) of these two sites demonstrated that TZD-C8 inhibition was abolished in the lasI double mutant PAO-R30D, I107S. In addition, in vitro swarming motility and quorum sensing signal production were affected by TZD-C 8, confirming this compound alters the cell to cell signalling circuitry. Overall, this novel inhibitor of P. aeruginosa quorum sensing shows great promise and validates our mechanistic approach to discovering inhibitors of LuxI-type acyl-homoserine lactone synthases.

Download Full-text

Use of Quorum Sensing Inhibition Strategies to Control Microfouling

Marine Drugs ◽

10.3390/md19020074 ◽

2021 ◽

Vol 19 (2) ◽

pp. 74

Author(s):

Andrea Muras ◽

Ana Parga ◽

Celia Mayer ◽

Ana Otero

Keyword(s):

Quorum Sensing ◽

Biofilm Formation ◽

Communication Systems ◽

Culture Medium ◽

Homoserine Lactone ◽

Bacterial Biofilm ◽

Screening Methods ◽

Time Saving ◽

Quorum Sensing Inhibition

Interfering with the quorum sensing bacterial communication systems has been proposed as a promising strategy to control bacterial biofilm formation, a key process in biofouling development. Appropriate in vitro biofilm-forming bacteria models are needed to establish screening methods for innovative anti-biofilm and anti-microfouling compounds. Four marine strains, two Pseudoalteromonas spp. and two Vibrio spp., were selected and studied with regard to their biofilm-forming capacity and sensitivity to quorum sensing (QS) inhibitors. Biofilm experiments were performed using two biofilm cultivation and quantification methods: the xCELLigence® system, which allows online monitoring of biofilm formation, and the active attachment model, which allows refreshment of the culture medium to obtain a strong biofilm that can be quantified with standard staining methods. Although all selected strains produced acyl-homoserine-lactone (AHL) QS signals, only the P. flavipulchra biofilm, measured with both quantification systems, was significantly reduced with the addition of the AHL-lactonase Aii20J without a significant effect on planktonic growth. Two-species biofilms containing P. flavipulchra were also affected by the addition of Aii20J, indicating an influence on the target bacterial strain as well as an indirect effect on the co-cultured bacterium. The use of xCELLigence® is proposed as a time-saving method to quantify biofilm formation and search for eco-friendly anti-microfouling compounds based on quorum sensing inhibition (QSI) strategies. The results obtained from these two in vitro biofilm formation methods revealed important differences in the response of biosensor bacteria to culture medium and conditions, indicating that several strains should be used simultaneously for screening purposes and the cultivation conditions should be carefully optimized for each specific purpose.

Download Full-text

Humans are more sensitive to the taste of linoleic and α-linolenic than oleic acid

AJP Gastrointestinal and Liver Physiology ◽

10.1152/ajpgi.00394.2014 ◽

2015 ◽

Vol 308 (5) ◽

pp. G442-G449 ◽

Cited By ~ 11

Author(s):

Cordelia A. Running ◽

Richard D. Mattes

Keyword(s):

Fatty Acids ◽

Oleic Acid ◽

Unsaturated Fatty Acids ◽

Nonesterified Fatty Acid ◽

Particle Sizes ◽

Nonesterified Fatty Acids ◽

Shear Rates ◽

Sensitivity Data ◽

Oral Sensitivity

Health concerns have led to recommendations to replace saturated fats with unsaturated fats. However, addition of unsaturated fatty acids may lead to changes in the way foods are perceived in the oral cavity. This study tested the taste sensitivity to and emulsion characteristics of oleic, linoleic, and α-linolenic acids. The hypothesis tested was that oral sensitivity to nonesterified fatty acids would increase with degree of unsaturation but that in vitro viscosities and particle sizes of these emulsions would not differ. Oral taste thresholds were obtained using the three-alternative, forced-choice, ascending method. Each participant was tested on each fat 7 times, for a total of 21 study visits, to account for learning effects. Viscosities were obtained for the blank solutions and all three emulsions. Results indicate lower oral thresholds to linoleic and α-linolenic than oleic acid. At higher shear rates, 5% oleic and linoleic acid were more viscous than other samples. More-dilute emulsions showed no significant differences in viscosity. Particle sizes of the emulsions increased very slightly with increasing unsaturation. Together, the emulsion characteristics and oral sensitivity data support a taste mechanism for nonesterified fatty acid detection.

Download Full-text

Phytochemical Investigation, Fatty Acid Analysis and In Vitro Membrane Stabilizing Activity of the Roots of Amaranthus spinosus L.

Dhaka University Journal of Science ◽

10.3329/dujs.v69i1.54625 ◽

2021 ◽

Vol 69 (1) ◽

pp. 59-62

Author(s):

Md Rubel Al Mamun ◽

Tasnim Ahmed ◽

Md Selim Aktar Reza ◽

Md Hasanur Rahman

Keyword(s):

Fatty Acids ◽

Oleic Acid ◽

Fatty Acid ◽

Unsaturated Fatty Acids ◽

Arachidic Acid ◽

Saturated Fatty Acids ◽

Hypotonic Solution ◽

Amaranthus Spinosus ◽

Phytochemical Investigation

Ethylacetate extract of the roots of Amaranthus spinosus L. was subjected to phytochemical investigation and three compounds stigmasterol, 1-Eicosanol and oleic acid were isolated in pure state. The n-hexane extract was analysed for fatty acid with GC-FID and four saturated fatty acids; caprylic acid, stearic acid, arachidic acid and behenic acid, and four unsaturated fatty acids; palmitoleic acid, oleic acid, linoleic acid and erucic acid were identified and quantified. Different extracts were assessed to explore their in vitro membrane stabilizing activity using standard protocol. Methanol extract of A. spinosus showed 68.13% inhibition in hypotonic solution-induced hemolysis and 74.53% inhibition in heat induced hemolysis which was the highest than its other Kupchan fractions. Acetyl salicylic acid was used as standard that showed 42.00% inhibition of hemolysis at normal condition. Dhaka Univ. J. Sci. 69(1): 59-62, 2021 (January)

Download Full-text

Protein phosphatases types 2Cα and 2Cβ in apoptosis

Biochemical Society Transactions ◽

10.1042/bst0341370 ◽

2006 ◽

Vol 34 (6) ◽

pp. 1370-1375 ◽

Cited By ~ 25

Author(s):

S. Klumpp ◽

M.-C. Thissen ◽

J. Krieglstein

Keyword(s):

Fatty Acids ◽

Oleic Acid ◽

Unsaturated Fatty Acids ◽

Initial Step ◽

Cell Types ◽

Structural Features ◽

Apoptotic Effect ◽

Endothelial Cell Death ◽

Protein Phosphatase Type

This mini-review highlights the involvement of PP2C (protein phosphatase type 2C) family members α and β in apoptosis. The activity of these isoenzymes can be stimulated by unsaturated fatty acids with special structural features, e.g. oleic acid. Those fatty acids capable of activating PP2Cα and PP2Cβ in vitro induce apoptosis in various cell types as shown here for neurons and endothelial cells. Using RNA interference to reduce the amount of PP2Cα and PP2Cβ results in cells significantly less susceptible to the apoptotic effect of oleic acid. Increased endothelial cell death is considered to be an initial step of atherogenesis. Thus activation of PP2C by physiological unbound (‘free’) unsaturated fatty acids (liberated from lipoproteins) could represent a crucial mechanism in the development of atherosclerosis.

Download Full-text

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

10.1101/2020.11.17.387936 ◽

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.

Download Full-text

Induction of Biofilm Formation in Klebsiella pneumoniae ATCC 13884 by Several Drugs: The Possible Role of Quorum Sensing Modulation

Antibiotics ◽

10.3390/antibiotics7040103 ◽

2018 ◽

Vol 7 (4) ◽

pp. 103 ◽

Cited By ~ 5

Author(s):

Elizabeth Cadavid ◽

Sara Robledo ◽

Wiston Quiñones ◽

Fernando Echeverri

Keyword(s):

Quorum Sensing ◽

Klebsiella Pneumoniae ◽

Biofilm Formation ◽

Bacterial Resistance ◽

Homoserine Lactone ◽

In Vitro Assays ◽

Bacterial Populations ◽

Other Substances ◽

Microplate Reader

Bacterial resistance is caused by several biochemical factors, the formation of biofilm being one of the main causes. This process is triggered by Quorum Sensing (QS), through the production of endogenous molecules, although other substances such as natural products can also do this. In this work, we aimed to determine whether some drugs are involved in the induction of biofilm formation in Klebsiella pneumoniae ATCC 13884, and thus, increase bacterial resistance. For this, the effect of 22 drugs on K. pneumoniae ATCC 13884 growth was determined at sub-plasmatic concentrations; the production of autoinducer lactones was established by HPLC and with a biosensor. The induction of biofilm formation was determined through crystal violet assay at 585 nm in a microplate reader and using urethral catheters. According to the in vitro assays, some drugs were found to induce biofilm formation in K. pneumoniae ATCC 13884. The effect of acetaminophen, hydrochlorothiazide, and progesterone stood out. The first drug caused several changes in the biochemistry of K. pneumoniae ATCC 13884 related to QS: high synthesis of N-hexanoyl-homoserine lactone, increasing bacterial populations by 27% and biofilm formation by 49%, and a more gentamicin resistant biofilm. Furthermore, it increased the colonization area of urethral catheters. Hydrochlorothiazide showed the biggest increase in the induction of biofilm formation of 51%, and progesterone displayed the greatest ability to provoke bacterial mass adherence but had no effects on K. pneumoniae ATCC 13884 bacterial population growth.

Download Full-text