scholarly journals Poly-N-Acetylglucosamine Expression by Wild-Type Yersinia pestis Is Maximal at Mammalian, Not Flea, Temperatures

mBio ◽  
2012 ◽  
Vol 3 (4) ◽  
Author(s):  
Pauline Yoong ◽  
Colette Cywes-Bentley ◽  
Gerald B. Pier
Keyword(s):  
Yersinia Pestis ◽  
Congo Red ◽  
Biofilm Formation ◽  
Mammalian Host ◽  
Virulence Plasmid ◽  
Insect Vector ◽  
Wild Type ◽  
Content Type ◽  
Higher Temperature ◽  
Mammalian Infection

ABSTRACTNumerous bacteria, includingYersinia pestis, express the poly-N-acetylglucosamine (PNAG) surface carbohydrate, a major component of biofilms often associated with a specific appearance of colonies on Congo red agar. Biofilm formation and PNAG synthesis byY. pestishave been reported to be maximal at 21 to 28°C or “flea temperatures,” facilitating the regurgitation ofY. pestisinto a mammalian host during feeding, but production is diminished at 37°C and thus presumed to be decreased during mammalian infection. Most studies of PNAG expression and biofilm formation byY. pestishave used a low-virulence derivative of strain KIM, designated KIM6+, that lacks the pCD1 virulence plasmid, and an isogenic mutant without the pigmentation locus, which contains the hemin storage genes that encode PNAG biosynthetic proteins. Using confocal microscopy, fluorescence-activated cell sorter analysis and growth on Congo red agar, we confirmed prior findings regarding PNAG production with the KIM6+ strain. However, we found that fully virulent wild-type (WT) strains KIM and CO92 had maximal PNAG expression at 37°C, with lower PNAG production at 28°C both in broth medium and on Congo red agar plates. Notably, the typical dark colony morphology appearing on Congo red agar was maintained at 28°C, indicating that this phenotype is not associated with PNAG expression in WTY. pestis. Extracts of WT sylvaticY. pestisstrains from the Russian Federation confirmed the maximal expression of PNAG at 37°C. PNAG production by WTY. pestisis maximal at mammalian and not insect vector temperatures, suggesting that this factor may have a role during mammalian infection.IMPORTANCEYersinia pestistransitions from low-temperature residence and replication in insect vectors to higher-temperature replication in mammalian hosts. Prior findings based primarily on an avirulent derivative of WT (wild-type) KIM, named KIM6+, showed that biofilm formation associated with synthesis of poly-N-acetylglucosamine (PNAG) is maximal at 21 to 28°C and decreased at 37°C. Biofilm formation was purported to facilitate the transmission ofY. pestisfrom fleas to mammals while having little importance in mammalian infection. Here we found that for WT strains KIM and CO92, maximal PNAG production occurs at 37°C, indicating that temperature regulation of PNAG production in WTY. pestisis not mimicked by strain KIM6+. Additionally, we found that Congo red binding does not always correlate with PNAG production, despite its widespread use as an indicator of biofilm production. Taken together, the findings show that a role for PNAG in WTY. pestisinfection should not be disregarded and warrants further study.

scholarly journals Evaluation of the Role of theopgGHOperon in Yersinia pseudotuberculosis and Its Deletion during the Emergence of Yersinia pestis

2015 ◽  
Vol 83 (9) ◽  
pp. 3638-3647 ◽  
Author(s):  
Kévin Quintard ◽  
Amélie Dewitte ◽  
Angéline Reboul ◽  
Edwige Madec ◽  
Sébastien Bontemps-Gallo ◽  
...  
Keyword(s):  
Yersinia Pestis ◽  
Cell Size ◽  
Biofilm Formation ◽  
Yersinia Pseudotuberculosis ◽  
Acyl Carrier Protein ◽  
Size Control ◽  
Growth Conditions ◽  
Mammalian Host ◽  
Dickeya Dadantii ◽  
Content Type

TheopgGHoperon encodes glucosyltransferases that synthesize osmoregulated periplasmic glucans (OPGs) from UDP-glucose, using acyl carrier protein (ACP) as a cofactor. OPGs are required for motility, biofilm formation, and virulence in various bacteria. OpgH also sequesters FtsZ in order to regulate cell size according to nutrient availability.Yersinia pestis(the agent of flea-borne plague) lost theopgGHoperon during its emergence from the enteropathogenYersinia pseudotuberculosis. When expressed in OPG-negative strains ofEscherichia coliandDickeya dadantii,opgGHfromY. pseudotuberculosisrestored OPGs synthesis, motility, and virulence. However,Y. pseudotuberculosisdid not produce OPGs (i) under various growth conditions or (ii) when overexpressing itsopgGHoperon, itsgalUFoperon (governing UDP-glucose), or theopgGHoperon or Acp fromE. coli. A ΔopgGHY. pseudotuberculosisstrain showed normal motility, biofilm formation, resistance to polymyxin and macrophages, and virulence but was smaller. Consistently,Y. pestiswas smaller thanY. pseudotuberculosiswhen cultured at ≥37°C, except when the plague bacillus expressedopgGH.Y. pestisexpressingopgGHgrew normally in serum and within macrophages and was fully virulent in mice, suggesting that small cell size was not advantageous in the mammalian host. Lastly,Y. pestisexpressingopgGHwas able to infectXenopsylla cheopisfleas normally. Our results suggest an evolutionary scenario whereby an ancestralYersiniastrain lost a factor required for OPG biosynthesis but keptopgGH(to regulate cell size). TheopgGHoperon was presumably then lost because OpgH-dependent cell size control became unnecessary.

scholarly journals Abrogation of Neuraminidase Reduces Biofilm Formation, Capsule Biosynthesis, and Virulence of Porphyromonas gingivalis

2011 ◽  
Vol 80 (1) ◽  
pp. 3-13 ◽  
Author(s):  
Chen Li ◽  
Kurniyati ◽  
Bo Hu ◽  
Jiang Bian ◽  
Jianlan Sun ◽  
...  
Keyword(s):  
Porphyromonas Gingivalis ◽  
Biofilm Formation ◽  
Adult Population ◽  
Transcriptional Analysis ◽  
Wild Type ◽  
Content Type ◽  
Multiple Organs ◽  
Biochemical Analyses

ABSTRACTThe oral bacteriumPorphyromonas gingivalisis a key etiological agent of human periodontitis, a prevalent chronic disease that affects up to 80% of the adult population worldwide.P. gingivalisexhibits neuraminidase activity. However, the enzyme responsible for this activity, its biochemical features, and its role in the physiology and virulence ofP. gingivalisremain elusive. In this report, we found thatP. gingivalisencodes a neuraminidase, PG0352 (SiaPg). Transcriptional analysis showed thatPG0352is monocistronic and is regulated by a sigma70-like promoter. Biochemical analyses demonstrated that SiaPgis an exo-α-neuraminidase that cleaves glycosidic-linked sialic acids. Cryoelectron microscopy and tomography analyses revealed that thePG0352deletion mutant (ΔPG352) failed to produce an intact capsule layer. Compared to the wild type,in vitrostudies showed that ΔPG352 formed less biofilm and was less resistant to killing by the host complement.In vivostudies showed that while the wild type caused a spreading type of infection that affected multiple organs and all infected mice were killed, ΔPG352 only caused localized infection and all animals survived. Taken together, these results demonstrate that SiaPgis an important virulence factor that contributes to the biofilm formation, capsule biosynthesis, and pathogenicity ofP. gingivalis, and it can potentially serve as a new target for developing therapeutic agents againstP. gingivalisinfection.

Two regulatory factors of Vibrio cholerae activating the mannose-sensitive haemagglutinin pilus expression is important for biofilm formation and colonization in mice

Microbiology ◽  
2021 ◽  
Vol 167 (10) ◽  
Author(s):  
Mengting Shi ◽  
Yue Zheng ◽  
Xianghong Wang ◽  
Zhengjia Wang ◽  
Menghua Yang
Keyword(s):  
Mouse Model ◽  
Vibrio Cholerae ◽  
Biofilm Formation ◽  
Type Species ◽  
Wild Type ◽  
Expression Library ◽  
Content Type ◽  
Genomic Expression ◽  
Infant Mouse ◽  
Link Type

Vibrio cholerae the causative agent of cholera, uses a large number of coordinated transcriptional regulatory events to transition from its environmental reservoir to the host intestine, which is its preferred colonization site. Transcription of the mannose-sensitive haemagglutinin pilus (MSHA), which aids the persistence of V. cholerae in aquatic environments, but causes its clearance by host immune defenses, was found to be regulated by a yet unknown mechanism during the infection cycle of V. cholerae . In this study, genomic expression library screening revealed that two regulators, VC1371 and VcRfaH, are able to positively activate the transcription of MSHA operon. VC1371 is localized and active in the cell membrane. Deletion of vc1371 or VcrfaH genes in V. cholerae resulted in less MshA protein production and less efficiency of biofilm formation compared to that in the wild-type strain. An adult mouse model showed that the mutants with vc1371 or VcrfaH deletion colonized less efficiently than the wild-type; the VcrfaH deletion mutant showed less colonization efficiency in the infant mouse model. The findings strongly suggested that the two regulators, namely VC1371 and VcRfaH, which are involved in the regulation of MSHA expression, play an important role in V. cholerae biofilm formation and colonization in mice.

scholarly journals Effect of Nitroxides on Swarming Motility and Biofilm Formation, Multicellular Behaviors in Pseudomonas aeruginosa

2013 ◽  
Vol 57 (10) ◽  
pp. 4877-4881 ◽  
Author(s):  
César de la Fuente-Núñez ◽  
Fany Reffuveille ◽  
Kathryn E. Fairfull-Smith ◽  
Robert E. W. Hancock
Keyword(s):  
Nitric Oxide ◽  
Pseudomonas Aeruginosa ◽  
Biofilm Formation ◽  
Wild Type ◽  
Planktonic Cells ◽  
Swarming Motility ◽  
Content Type ◽  
Exogenous Addition ◽  
Biofilm Dispersion ◽  
Dispersal Activity

ABSTRACTThe ability of nitric oxide (NO) to induce biofilm dispersion has been well established. Here, we investigated the effect of nitroxides (sterically hindered nitric oxide analogues) on biofilm formation and swarming motility inPseudomonas aeruginosa. A transposon mutant unable to produce nitric oxide endogenously (nirS) was deficient in swarming motility relative to the wild type and the complemented strain. Moreover, expression of thenirSgene was upregulated by 9.65-fold in wild-type swarming cells compared to planktonic cells. Wild-type swarming levels were substantially restored upon the exogenous addition of nitroxide containing compounds, a finding consistent with the hypothesis that NO is necessary for swarming motility. Here, we showed that nitroxides not only mimicked the dispersal activity of NO but also prevented biofilms from forming in flow cell chambers. In addition, anirStransposon mutant was deficient in biofilm formation relative to the wild type and the complemented strain, thus implicating NO in the formation of biofilms. Intriguingly, despite its stand-alone action in inhibiting biofilm formation and promoting dispersal, a nitroxide partially restored the ability of anirSmutant to form biofilms.

scholarly journals Motility-Independent Formation of Antibiotic-TolerantPseudomonas aeruginosaAggregates

2019 ◽  
Vol 85 (14) ◽  
Author(s):  
Sally Demirdjian ◽  
Hector Sanchez ◽  
Daniel Hopkins ◽  
Brent Berwin
Keyword(s):  
Biofilm Formation ◽  
Bacterial Pathogen ◽  
Aggregate Formation ◽  
Flagellar Motility ◽  
Wild Type ◽  
Chronic Infections ◽  
Content Type ◽  
Temporal Adaptation ◽  
Bacterial Aggregates

ABSTRACTPseudomonas aeruginosais a bacterial pathogen that causes severe chronic infections in immunocompromised individuals. This bacterium is highly adaptable to its environments, which frequently select for traits that promote bacterial persistence. A clinically significant temporal adaptation is the formation of surface- or cell-adhered bacterial biofilms that are associated with increased resistance to immune and antibiotic clearance. Extensive research has shown that bacterial flagellar motility promotes formation of such biofilms, whereupon the bacteria subsequently become nonmotile. However, recent evidence shows that antibiotic-tolerant nonattached bacterial aggregates, distinct from surface-adhered biofilms, can form, and these have been reported in the context of lung infections, otitis media, nonhealing wounds, and soft tissue fillers. It is unclear whether the same bacterial traits are required for aggregate formation as for biofilm formation. In this report, using isogenic mutants, we demonstrate thatP. aeruginosaaggregates in liquid cultures are spontaneously formed independent of bacterial flagellar motility and independent of an exogenous scaffold. This contrasts with the role of the flagellum to initiate surface-adhered biofilms. Similarly to surface-attached biofilms, these aggregates exhibit increased antibiotic tolerance compared to planktonic cultures. These findings provide key insights into the requirements for aggregate formation that contrast with those for biofilm formation and that may have relevance for the persistence and dissemination of nonmotile bacteria found within chronic clinical infections.IMPORTANCEIn this work, we have investigated the role of bacterial motility with regard to antibiotic-tolerant bacterial aggregate formation. Previous work has convincingly demonstrated thatP. aeruginosaflagellar motility promotes the formation of surface-adhered biofilms in many systems. In contrast, aggregate formation byP. aeruginosawas observed for nonmotile but not for motile cells in the presence of an exogenous scaffold. Here, we demonstrate that both wild-typeP. aeruginosaand mutants that genetically lack motility spontaneously form antibiotic-tolerant aggregates in the absence of an exogenously added scaffold. Additionally, we also demonstrate that wild-type (WT) and nonmotileP. aeruginosabacteria can coaggregate, shedding light on potential physiological interactions and heterogeneity of aggregates.

scholarly journals Targeted Disruption of the Plasmodium berghei Ctrp Gene Reveals Its Essential Role in Malaria Infection of the Vector Mosquito

1999 ◽  
Vol 190 (11) ◽  
pp. 1711-1716 ◽  
Author(s):  
Masao Yuda ◽  
Hiroshi Sakaida ◽  
Yasuo Chinzei
Keyword(s):  
Plasmodium Berghei ◽  
Malaria Infection ◽  
Molecular Mechanisms ◽  
Mammalian Host ◽  
Insect Vector ◽  
Wild Type ◽  
Mosquito Midgut ◽  
Parasite Plasmodium ◽  
Vector Mosquito ◽  
Stage 1

CTRP (circumsporozoite protein and thrombospondin-related adhesive protein [TRAP]-related protein) of the rodent malaria parasite Plasmodium berghei (PbCTRP) makes up a protein family together with other apicomplexan proteins that are specifically expressed in the host-invasive stage 1. PbCTRP is produced in the mosquito-invasive, or ookinete, stage and is a protein candidate for a role in ookinete adhesion and invasion of the mosquito midgut epithelium. To demonstrate involvement of PbCTRP in the infection of the vector, we performed targeting disruption experiments with this gene. PbCTRP disruptants showed normal exflagellation rates and development into ookinetes. However, no oocyst formation was observed in the midgut after ingestion of these parasites, suggesting complete loss of their invasion ability. On the other hand, when ingested together with wild-type parasites, disruptants were able to infect mosquitoes, indicating that the PbCTRP gene of the wild-type parasite rescued infectivity of disruptants when they heterologously mated in the mosquito midgut lumen. Our results show that PbCTRP plays a crucial role in malaria infection of the mosquito midgut and suggest that similar molecular mechanisms are used by malaria parasites to invade cells in the insect vector and the mammalian host.

scholarly journals Role of Flagellin-Homologous Proteins in Biofilm Formation by Pathogenic Vibrio Species

mBio ◽  
2019 ◽  
Vol 10 (4) ◽  
Author(s):  
You-Chul Jung ◽  
Mi-Ae Lee ◽  
Kyu-Ho Lee
Keyword(s):  
Biofilm Formation ◽  
Specific Binding ◽  
Biological Significance ◽  
Wild Type ◽  
Forming Process ◽  
Homologous Proteins ◽  
Content Type ◽  
Pathogenic Vibrio ◽  
Biofilm Matrix

ABSTRACT The pathogenic bacterium Vibrio vulnificus exhibits the ability to form biofilm, for which initiation is dependent upon swimming motility by virtue of a polar flagellum. The filament of its flagellum is composed of multiple flagellin subunits, FlaA, -B, -C, and -D. In V. vulnificus genomes, however, open reading frames (ORFs) annotated by FlaE and -F are also present. Although neither FlaE nor FlaF is involved in filament formation and cellular motility, they are well expressed and secreted to the extracellular milieu through the secretion apparatus for flagellar assembly. In the extrapolymeric matrix of V. vulnificus biofilm, significant levels of FlaEF were detected. Mutants defective in both flaE and flaF formed significantly decreased biofilms compared to the wild-type biofilm. Thus, the potential role of FlaEF during the biofilm-forming process was investigated by exogenous addition of recombinant FlaEF (rFlaEF) to the biofilm assays. The added rFlaE and rFlaF were predominantly incorporated into the biofilm matrix formed by the wild type. However, biofilms formed by a mutant defective in exopolysaccharide (EPS) biosynthesis were not affected by added FlaEF. These results raised a possibility that FlaEF specifically interact with EPS within the biofilm matrix. In vitro pulldown assays using His-tagged rFlaEF or rFlaC revealed the specific binding of EPS to rFlaEF but not to rFlaC. Taken together, our results demonstrate that V. vulnificus FlaEF, flagellin-homologous proteins (FHPs), are crucial for biofilm formation by directly interacting with the essential determinant for biofilm maturation, EPS. Further analyses performed with other pathogenic Vibrio species demonstrated both the presence of FHPs and their important role in biofilm formation. IMPORTANCE Flagellar filaments of the pathogenic Vibrio species, including V. vulnificus, V. parahaemolyticus, and V. cholerae, are composed of multiple flagellin subunits. In their genomes, however, there are higher numbers of the ORFs encoding flagellin-like proteins than the numbers of flagellin subunits required for filament assembly. Since these flagellin-homologous proteins (FHPs) are well expressed and excreted to environments via a flagellin transport channel, their extracellular role in the pathogenic Vibrio has been enigmatic. Their biological significance, which is not related with flagellar functions, has been revealed to be in maturation of biofilm structures. Among various components of the extracellular polymeric matrix produced in the V. vulnificus biofilms, the exopolysaccharides (EPS) are dominant constituents and crucial in maturation of biofilms. The enhancing role of the V. vulnificus FHPs in biofilm formation requires the presence of EPS, as indicated by highly specific interactions among two FHPs and three EPS.

scholarly journals Selective Pressure for Biofilm Formation in Bacillus subtilis: Differential Effect of Mutations in the Master Regulator SinR on Bistability

mBio ◽  
2018 ◽  
Vol 9 (5) ◽  
Author(s):  
Jan Kampf ◽  
Jan Gerwig ◽  
Kerstin Kruse ◽  
Robert Cleverley ◽  
Miriam Dormeyer ◽  
...  
Keyword(s):  
Gene Expression ◽  
Bacillus Subtilis ◽  
Biofilm Formation ◽  
Type Strain ◽  
Wild Type Strain ◽  
Selective Pressure ◽  
Wild Type ◽  
Master Regulator ◽  
Form Complex ◽  
Content Type

ABSTRACT Biofilm formation by Bacillus subtilis requires the expression of genes encoding enzymes for extracellular polysaccharide synthesis and for an amyloid-like protein. The master regulator SinR represses all the corresponding genes, and repression of these key biofilm genes is lifted when SinR interacts with its cognate antagonist proteins. The YmdB phosphodiesterase is a recently discovered factor that is involved in the control of SinR activity: cells lacking YmdB exhibit hyperactive SinR and are unable to relieve the repression of the biofilm genes. In this study, we have examined the dynamics of gene expression patterns in wild-type and ymdB mutant cells by microfluidic analysis coupled to time-lapse microscopy. Our results confirm the bistable expression pattern for motility and biofilm genes in the wild-type strain and the loss of biofilm gene expression in the mutant. Moreover, we demonstrated dynamic behavior in subpopulations of the wild-type strain that is characterized by switches in sets of the expressed genes. In order to gain further insights into the role of YmdB, we isolated a set of spontaneous suppressor mutants derived from ymdB mutants that had regained the ability to form complex colonies and biofilms. Interestingly, all of the mutations affected SinR. In some mutants, large genomic regions encompassing sinR were deleted, whereas others had alleles encoding SinR variants. Functional and biochemical studies with these SinR variants revealed how these proteins allowed biofilm gene expression in the ymdB mutant strains. IMPORTANCE Many bacteria are able to choose between two mutually exclusive lifestyles: biofilm formation and motility. In the model bacterium Bacillus subtilis, this choice is made by each individual cell rather than at the population level. The transcriptional repressor SinR is the master regulator in this decision-making process. The regulation of SinR activity involves complex control of its own expression and of its interaction with antagonist proteins. We show that the YmdB phosphodiesterase is required to allow the expression of SinR-repressed genes in a subpopulation of cells and that such subpopulations can switch between different SinR activity states. Suppressor analyses revealed that ymdB mutants readily acquire mutations affecting SinR, thus restoring biofilm formation. These findings suggest that B. subtilis cells experience selective pressure to form the extracellular matrix that is characteristic of biofilms and that YmdB is required for the homeostasis of SinR and/or its antagonists.

scholarly journals Spermidine Inversely Influences Surface Interactions and Planktonic Growth in Agrobacterium tumefaciens

2016 ◽  
Vol 198 (19) ◽  
pp. 2682-2691 ◽  
Author(s):  
Yi Wang ◽  
Sok Ho Kim ◽  
Ramya Natarajan ◽  
Jason E. Heindl ◽  
Eric L. Bruger ◽  
...  
Keyword(s):  
Agrobacterium Tumefaciens ◽  
Biofilm Formation ◽  
Direct Synthesis ◽  
Wild Type ◽  
Cyclic Diguanylate ◽  
Content Type ◽  
Exogenous Addition ◽  
In The Wild ◽  
Growth Requirement ◽  
Transposon Insertions

ABSTRACTIn bacteria, the functions of polyamines, small linear polycations, are poorly defined, but these metabolites can influence biofilm formation in several systems. Transposon insertions in an ornithine decarboxylase (odc) gene inAgrobacterium tumefaciens, predicted to direct synthesis of the polyamine putrescine from ornithine, resulted in elevated cellulose. Null mutants forodcgrew somewhat slowly in a polyamine-free medium but exhibited increased biofilm formation that was dependent on cellulose production. Spermidine is an essential metabolite inA. tumefaciensand is synthesized from putrescine inA. tumefaciensvia the stepwise actions of carboxyspermidine dehydrogenase (CASDH) and carboxyspermidine decarboxylase (CASDC). Exogenous addition of either putrescine or spermidine to theodcmutant returned biofilm formation to wild-type levels. Low levels of exogenous spermidine restored growth to CASDH and CASDC mutants, facilitating weak biofilm formation, but this was dampened with increasing concentrations. Norspermidine rescued growth for theodc, CASDH, and CASDC mutants but did not significantly affect their biofilm phenotypes, whereas in the wild type, it stimulated biofilm formation and depressed spermidine levels. Theodcmutant produced elevated levels of cyclic diguanylate monophosphate (c-di-GMP), exogenous polyamines modulated these levels, and expression of a c-di-GMP phosphodiesterase reversed the enhanced biofilm formation. Prior work revealed accumulation of the precursors putrescine and carboxyspermidine in the CASDH and CASDC mutants, respectively, but unexpectedly, both mutants accumulated homospermidine; here, we show that this requires a homospermidine synthase (hss) homologue.IMPORTANCEPolyamines are small, positively charged metabolites that are nearly ubiquitous in cellular life. They are often essential in eukaryotes and more variably in bacteria. Polyamines have been reported to influence the surface-attached biofilm formation of several bacteria. InAgrobacterium tumefaciens, mutants with diminished levels of the polyamine spermidine are stimulated for biofilm formation, and exogenous provision of spermidine decreases biofilm formation. Spermidine is also essential forA. tumefaciensgrowth, but the related polyamine norspermidine exogenously rescues growth and does not diminish biofilm formation, revealing that the growth requirement and biofilm control are separable. Polyamine control of biofilm formation appears to function via effects on the cellular second messenger cyclic diguanylate monophosphate, regulating the transition from a free-living to a surface-attached lifestyle.

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.

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