scholarly journals Vibrio fischeri Biofilm Formation Prevented by a Trio of Regulators

2018 ◽  
Vol 84 (19) ◽  
Author(s):  
Cecilia M. Thompson ◽  
Anne E. Marsden ◽  
Alice H. Tischler ◽  
Jovanka Koo ◽  
Karen L. Visick
Keyword(s):  
Biofilm Formation ◽  
Vibrio Fischeri ◽  
Negative Control ◽  
Negative Regulators ◽  
Content Type ◽  
Genetically Manipulated ◽  
Biofilm Development ◽  
Matrix Control ◽  
Symbiosis Polysaccharide

ABSTRACT Biofilms, complex communities of microorganisms surrounded by a self-produced matrix, facilitate attachment and provide protection to bacteria. A natural model used to study biofilm formation is the symbiosis between Vibrio fischeri and its host, the Hawaiian bobtail squid, Euprymna scolopes. Host-relevant biofilm formation is a tightly regulated process and is observed in vitro only with strains that have been genetically manipulated to overexpress or disrupt specific regulators, primarily two-component signaling (TCS) regulators. These regulators control biofilm formation by dictating the production of the symbiosis polysaccharide (Syp-PS), the major component of the biofilm matrix. Control occurs both at and below the level of transcription of the syp genes, which are responsible for Syp-PS production. Here, we probed the roles of the two known negative regulators of biofilm formation, BinK and SypE, by generating double mutants. We also mapped and evaluated a point mutation using natural transformation and linkage analysis. We examined traditional biofilm formation phenotypes and established a new assay for evaluating the start of biofilm formation in the form of microscopic aggregates in shaking liquid cultures, in the absence of the known biofilm-inducing signal calcium. We found that wrinkled colony formation is negatively controlled not only by BinK and SypE but also by SypF. SypF is both required for and inhibitory to biofilm formation. Together, these data reveal that these three regulators are sufficient to prevent wild-type V. fischeri from forming biofilms under these conditions. IMPORTANCE Bacterial biofilms promote attachment to a variety of surfaces and protect the constituent bacteria from environmental stresses, including antimicrobials. Understanding the mechanisms by which biofilms form will promote our ability to resolve them when they occur in the context of an infection. In this study, we found that Vibrio fischeri tightly controls biofilm formation using three negative regulators; the presence of a single one of these regulators was sufficient to prevent full biofilm development, while disruption of all three permitted robust biofilm formation. This work increases our understanding of the functions of specific regulators and demonstrates the substantial negative control that one benign microbe exerts over biofilm formation, potentially to ensure that it occurs only under the appropriate conditions.

scholarly journals Differential Gene Expression Patterns ofYersinia pestisandYersinia pseudotuberculosisduring Infection and Biofilm Formation in the Flea Digestive Tract

mSystems ◽  
2019 ◽  
Vol 4 (1) ◽  
Author(s):  
Iman Chouikha ◽  
Daniel E. Sturdevant ◽  
Clayton Jarrett ◽  
Yi-Cheng Sun ◽  
B. Joseph Hinnebusch
Keyword(s):  
Digestive Tract ◽  
Biofilm Formation ◽  
Yersinia Pseudotuberculosis ◽  
Expression Patterns ◽  
Type Vi Secretion System ◽  
Genetic Changes ◽  
Content Type ◽  
Biofilm Development

ABSTRACTYersinia pestis, the etiologic agent of plague, emerged as a fleaborne pathogen only within the last 6,000 years. Just five simple genetic changes in theYersinia pseudotuberculosisprogenitor, which served to eliminate toxicity to fleas and to enhance survival and biofilm formation in the flea digestive tract, were key to the transition to the arthropodborne transmission route. To gain a deeper understanding of the genetic basis for the development of a transmissible biofilm infection in the flea foregut, we evaluated additional gene differences and performedin vivotranscriptional profiling ofY. pestis, aY. pseudotuberculosiswild-type strain (unable to form biofilm in the flea foregut), and aY. pseudotuberculosismutant strain (able to produce foregut-blocking biofilm in fleas) recovered from fleas 1 day and 14 days after an infectious blood meal. Surprisingly, theY. pseudotuberculosismutations that increased c-di-GMP levels and enabled biofilm development in the flea did not change the expression levels of thehmsgenes responsible for the synthesis and export of the extracellular polysaccharide matrix required for mature biofilm formation. TheY. pseudotuberculosismutant uniquely expressed much higher levels ofYersiniatype VI secretion system 4 (T6SS-4) in the flea, and this locus was required for flea blockage byY. pseudotuberculosisbut not for blockage byY. pestis. Significant differences between the two species in expression of several metabolism genes, the Psa fimbrial genes, quorum sensing-related genes, transcription regulation genes, and stress response genes were evident during flea infection.IMPORTANCEY. pestisemerged as a highly virulent, arthropod-transmitted pathogen on the basis of relatively few and discrete genetic changes fromY. pseudotuberculosis. Parallel comparisons of thein vitroandin vivotranscriptomes ofY. pestisand twoY. pseudotuberculosisvariants that produce a nontransmissible infection and a transmissible infection of the flea vector, respectively, provided insights into howY. pestishas adapted to life in its flea vector and point to evolutionary changes in the regulation of metabolic and biofilm development pathways in these two closely related species.

scholarly journals Elucidating the Genetic Basis of Crystalline Biofilm Formation in Proteus mirabilis

2014 ◽  
Vol 82 (4) ◽  
pp. 1616-1626 ◽  
Author(s):  
N. Holling ◽  
D. Lednor ◽  
S. Tsang ◽  
A. Bissell ◽  
L. Campbell ◽  
...  
Keyword(s):  
Urinary Tract ◽  
Proteus Mirabilis ◽  
Biofilm Formation ◽  
Efflux Pump ◽  
Model Systems ◽  
Multidrug Efflux Pump ◽  
Gene Encoding ◽  
Content Type ◽  
Biofilm Development

ABSTRACTProteus mirabilisforms extensive crystalline biofilms on urethral catheters that occlude urine flow and frequently complicate the management of long-term-catheterized patients. Here, using random transposon mutagenesis in conjunction within vitromodels of the catheterized urinary tract, we elucidate the mechanisms underpinning the formation of crystalline biofilms byP. mirabilis. Mutants identified as defective in blockage of urethral catheters had disruptions in genes involved in nitrogen metabolism and efflux systems but were unaffected in general growth, survival in bladder model systems, or the ability to elevate urinary pH. Imaging of biofilms directly on catheter surfaces, along with quantification of levels of encrustation and biomass, confirmed that the mutants were attenuated specifically in the ability to form crystalline biofilms compared with that of the wild type. However, the biofilm-deficient phenotype of these mutants was not due to deficiencies in attachment to catheter biomaterials, and defects in later stages of biofilm development were indicated. For one blocking-deficient mutant, the disrupted gene (encoding a putative multidrug efflux pump) was also found to be associated with susceptibility to fosfomycin, and loss of this system or general inhibition of efflux pumps increased sensitivity to this antibiotic. Furthermore, homologues of this system were found to be widely distributed among other common pathogens of the catheterized urinary tract. Overall, our findings provide fundamental new insight into crystalline biofilm formation byP. mirabilis, including the link between biofilm formation and antibiotic resistance in this organism, and indicate a potential role for efflux pump inhibitors in the treatment or prevention ofP. mirabiliscrystalline biofilms.

scholarly journals Plasticity of Candida albicans Biofilms

2016 ◽  
Vol 80 (3) ◽  
pp. 565-595 ◽  
Author(s):  
David R. Soll ◽  
Karla J. Daniels
Keyword(s):  
Extracellular Matrix ◽  
Candida Albicans ◽  
Fungal Pathogen ◽  
Biofilm Formation ◽  
Strain Differences ◽  
Type Locus ◽  
Content Type ◽  
Biofilm Development ◽  
Candida Albicans Biofilms

SUMMARYCandida albicans, the most pervasive fungal pathogen that colonizes humans, forms biofilms that are architecturally complex. They consist of a basal yeast cell polylayer and an upper region of hyphae encapsulated in extracellular matrix. However, biofilms formedin vitrovary as a result of the different conditions employed in models, the methods used to assess biofilm formation, strain differences, and, in a most dramatic fashion, the configuration of the mating type locus (MTL). Therefore, integrating data from different studies can lead to problems of interpretation if such variability is not taken into account. Here we review the conditions and factors that cause biofilm variation, with the goal of engendering awareness that more attention must be paid to the strains employed, the methods used to assess biofilm development, every aspect of the model employed, and the configuration of theMTLlocus. We end by posing a set of questions that may be asked in comparing the results of different studies and developing protocols for new ones. This review should engender the notion that not all biofilms are created equal.

scholarly journals A Survival Strategy for Pseudomonas aeruginosa That Uses Exopolysaccharides To Sequester and Store Iron To Stimulate Psl-Dependent Biofilm Formation

2016 ◽  
Vol 82 (21) ◽  
pp. 6403-6413 ◽  
Author(s):  
Shan Yu ◽  
Qing Wei ◽  
Tianhu Zhao ◽  
Yuan Guo ◽  
Luyan Z. Ma
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Biofilm Formation ◽  
Iron Concentration ◽  
Survival Strategy ◽  
Iron Storage ◽  
Content Type ◽  
High Level ◽  
Biofilm Development ◽  
Biofilm Matrix

ABSTRACTExopolysaccharide Psl is a critical biofilm matrix component inPseudomonas aeruginosa, which forms a fiber-like matrix to enmesh bacterial communities. Iron is important forP. aeruginosabiofilm development, yet it is not clearly understood how iron contributes to biofilm development. Here, we showed that iron promoted biofilm formation via elevating Psl production inP. aeruginosa. The high level of iron stimulated the synthesis of Psl by reducing rhamnolipid biosynthesis and inhibiting the expression of AmrZ, a repressor ofpslgenes. Iron-stimulated Psl biosynthesis and biofilm formation held true in mucoidP. aeruginosastrains. Subsequent experiments indicated that iron bound with Pslin vitroand in biofilms, which suggested that Psl fibers functioned as an iron storage channel inP. aeruginosabiofilms. Moreover, among three matrix exopolysaccharides ofP. aeruginosa, Psl is the only exopolysaccharide that can bind with both ferrous and ferric ion, yet with higher affinity for ferrous iron. Our data suggest a survival strategy ofP. aeruginosathat uses exopolysaccharide to sequester and store iron to stimulate Psl-dependent biofilm formation.IMPORTANCEPseudomonas aeruginosais an environmental microorganism which is also an opportunistic pathogen that can cause severe infections in immunocompromised individuals. It is the predominant airway pathogen causing morbidity and mortality in individuals affected by the genetic disease cystic fibrosis (CF). Increased airway iron and biofilm formation have been proposed to be the potential factors involved in the persistence ofP. aeruginosain CF patients. Here, we showed that a high level of iron enhanced the production of the key biofilm matrix exopolysaccharide Psl to stimulate Psl-dependent biofilm formation. Our results not only make the link between biofilm formation and iron concentration in CF, but also could guide the administration or use of iron chelators to interfere with biofilm formation inP. aeruginosain CF patients. Furthermore, our data also imply a survival strategy ofP. aeruginosaunder high-iron environmental conditions.

scholarly journals Expression ofUME6, a Key Regulator of Candida albicans Hyphal Development, Enhances Biofilm Formation via Hgc1- and Sun41-Dependent Mechanisms

2012 ◽  
Vol 12 (2) ◽  
pp. 224-232 ◽  
Author(s):  
Mohua Banerjee ◽  
Priya Uppuluri ◽  
Xiang R. Zhao ◽  
Patricia L. Carlisle ◽  
Geethanjali Vipulanandan ◽  
...  
Keyword(s):  
Candida Albicans ◽  
Biofilm Formation ◽  
Transcriptional Regulator ◽  
Three Dimensional Model ◽  
Content Type ◽  
Hyphal Development ◽  
Functional Relationships ◽  
High Level ◽  
Biofilm Development

ABSTRACTBiofilm formation is associated with the ability ofCandida albicans, the major human fungal pathogen, to resist antifungal therapies and grow on tissues, catheters, and medical devices. In order to better understand the relationship betweenC. albicansmorphology and biofilm formation, we examined biofilms generated in response to expression ofUME6, a key filament-specific transcriptional regulator. AsUME6levels rise,C. albicanscells are known to transition from yeast to hyphae, and we also observed a corresponding increase in the level of biofilm formationin vitro. In addition to forming a biofilm, we observed that aC. albicansstrain expressing constitutive high levels ofUME6promoted tissue invasion in a reconstituted human three-dimensional model of oropharyngeal candidiasis. Confocal microscopy indicated that both the top and bottom layers of the biofilm generated upon high-level constitutiveUME6expression consist primarily of hyphal cells.UME6-driven biofilm formation was reduced upon deletion of Hgc1, a cyclin-related protein important for hyphal development, as well as Sun41, a putative cell wall glycosidase. Constitutive high-levelUME6expression was also able to completely bypass both the filamentation and biofilm defects of a strain deleted for Efg1, a key transcriptional regulator of these processes. Finally, we show that both Sun41 and Efg1 affect the ability ofUME6to induce certain filament-specific transcripts. Overall, these findings indicate a strong correlation between increasedC. albicanshyphal growth and enhanced biofilm formation and also suggest functional relationships betweenUME6and other regulators of biofilm development.

scholarly journals Discovery of Calcium as a Biofilm-Promoting Signal for Vibrio fischeri Reveals New Phenotypes and Underlying Regulatory Complexity

2018 ◽  
Vol 200 (15) ◽  
Author(s):  
Alice H. Tischler ◽  
Louise Lie ◽  
Cecilia M. Thompson ◽  
Karen L. Visick
Keyword(s):  
Biofilm Formation ◽  
Vibrio Fischeri ◽  
Response Regulator ◽  
Negative Regulator ◽  
Regulatory Control ◽  
Cellulose Synthesis ◽  
Sensor Kinase ◽  
Content Type ◽  
First Time ◽  
Symbiosis Polysaccharide

ABSTRACT Vibrio fischeri uses biofilm formation to promote symbiotic colonization of its squid host, Euprymna scolopes. Control over biofilm formation is exerted at the level of transcription of the symbiosis polysaccharide (syp) locus by a complex set of two-component regulators. Biofilm formation can be induced by overproduction of the sensor kinase RscS, which requires the activities of the hybrid sensor kinase SypF and the response regulator SypG and is negatively regulated by the sensor kinase BinK. Here, we identify calcium as a signal that promotes biofilm formation by biofilm-competent strains under conditions in which biofilms are not typically observed (growth with shaking). This was true for RscS-overproducing cells as well as for strains in which only the negative regulator binK was deleted. The latter results provided, for the first time, an opportunity to induce and evaluate biofilm formation without regulator overexpression. Using these conditions, we determined that calcium induces both syp-dependent and bacterial cellulose synthesis (bcs)-dependent biofilms at the level of transcription of these loci. The calcium-induced biofilms were dependent on SypF, but SypF's Hpt domain was sufficient for biofilm formation. These data suggested the involvement of another sensor kinase(s) and led to the discovery that both RscS and a previously uncharacterized sensor kinase, HahK, functioned in this pathway. Together, the data presented here reveal both a new signal and biofilm phenotype produced by V. fischeri cells, the coordinate production of two polysaccharides involved in distinct biofilm behaviors, and a new regulator that contributes to control over these processes. IMPORTANCE Biofilms, or communities of surface-attached microorganisms adherent via a matrix that typically includes polysaccharides, are highly resistant to environmental stresses and are thus problematic in the clinic and important to study. Vibrio fischeri forms biofilms to colonize its symbiotic host, making this organism useful for studying biofilms. Biofilm formation depends on the syp polysaccharide locus and its regulators. Here, we identify a signal, calcium, that induces both SYP-PS and cellulose-dependent biofilms. We also identify a new syp regulator, the sensor kinase HahK, and discover a mutant phenotype for the sensor kinase RscS. This work thus reveals a specific biofilm-inducing signal that coordinately controls two polysaccharides, identifies a new regulator, and clarifies the regulatory control over biofilm formation by V. fischeri.

scholarly journals In VitroAnalyses of the Effects of Heparin and Parabens on Candida albicans Biofilms and Planktonic Cells

2011 ◽  
Vol 56 (1) ◽  
pp. 148-153 ◽  
Author(s):  
Marisa H. Miceli ◽  
Stella M. Bernardo ◽  
T. S. Neil Ku ◽  
Carla Walraven ◽  
Samuel A. Lee
Keyword(s):  
Candida Albicans ◽  
Metabolic Activity ◽  
Biofilm Formation ◽  
High Dose ◽  
Dependent Manner ◽  
Planktonic Cells ◽  
Content Type ◽  
Heparin Sodium ◽  
The Individual

ABSTRACTInfections and thromboses are the most common complications associated with central venous catheters. Suggested strategies for prevention and management of these complications include the use of heparin-coated catheters, heparin locks, and antimicrobial lock therapy. However, the effects of heparin onCandida albicansbiofilms and planktonic cells have not been previously studied. Therefore, we sought to determine thein vitroeffect of a heparin sodium preparation (HP) on biofilms and planktonic cells ofC. albicans. Because HP contains two preservatives, methyl paraben (MP) and propyl paraben (PP), these compounds and heparin sodium without preservatives (Pure-H) were also tested individually. The metabolic activity of the mature biofilm after treatment was assessed using XTT [2,3-bis-(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide] reduction and microscopy. Pure-H, MP, and PP caused up to 75, 85, and 60% reductions of metabolic activity of the mature preformedC. albicansbiofilms, respectively. Maximal efficacy against the mature biofilm was observed with HP (up to 90%) compared to the individual compounds (P< 0.0001). Pure-H, MP, and PP each inhibitedC. albicansbiofilm formation up to 90%. A complete inhibition of biofilm formation was observed with HP at 5,000 U/ml and higher. When tested against planktonic cells, each compound inhibited growth in a dose-dependent manner. These data indicated that HP, MP, PP, and Pure-H havein vitroantifungal activity againstC. albicansmature biofilms, formation of biofilms, and planktonic cells. Investigation of high-dose heparin-based strategies (e.g., heparin locks) in combination with traditional antifungal agents for the treatment and/or prevention ofC. albicansbiofilms is warranted.

scholarly journals A Single B-Repeat of Staphylococcus epidermidis Accumulation-Associated Protein Induces Protective Immune Responses in an Experimental Biomaterial-Associated Infection Mouse Model

2014 ◽  
Vol 21 (9) ◽  
pp. 1206-1214 ◽  
Author(s):  
Lin Yan ◽  
Lei Zhang ◽  
Hongyan Ma ◽  
David Chiu ◽  
James D. Bryers
Keyword(s):  
Staphylococcus Epidermidis ◽  
Biofilm Formation ◽  
Porous Scaffold ◽  
The United States ◽  
Protein Vaccine ◽  
Weight Changes ◽  
Biofilm Inhibition ◽  
Content Type ◽  
Accumulation Associated Protein

ABSTRACTNosocomial infections are the fourth leading cause of morbidity and mortality in the United States, resulting in 2 million infections and ∼100,000 deaths each year. More than 60% of these infections are associated with some type of biomedical device.Staphylococcus epidermidisis a commensal bacterium of the human skin and is the most common nosocomial pathogen infecting implanted medical devices, especially those in the cardiovasculature.S. epidermidisantibiotic resistance and biofilm formation on inert surfaces make these infections hard to treat. Accumulation-associated protein (Aap), a cell wall-anchored protein ofS. epidermidis, is considered one of the most important proteins involved in the formation ofS. epidermidisbiofilm. A small recombinant protein vaccine comprising a single B-repeat domain (Brpt1.0) ofS. epidermidisRP62A Aap was developed, and the vaccine's efficacy was evaluatedin vitrowith a biofilm inhibition assay andin vivoin a murine model of biomaterial-associated infection. A high IgG antibody response againstS. epidermidisRP62A was detected in the sera of the mice after two subcutaneous immunizations with Brpt1.0 coadministered with Freund's adjuvant. Sera from Brpt1.0-immunized mice inhibitedin vitroS. epidermidisRP62A biofilm formation in a dose-dependent pattern. After receiving two immunizations, each mouse was surgically implanted with a porous scaffold disk containing 5 × 106CFU ofS. epidermidisRP62A. Weight changes, inflammatory markers, and histological assay results after challenge withS. epidermidisindicated that the mice immunized with Brpt1.0 exhibited significantly higher resistance toS. epidermidisRP62A implant infection than the control mice. Day 8 postchallenge, there was a significantly lower number of bacteria in scaffold sections and surrounding tissues and a lower residual inflammatory response to the infected scaffold disks for the Brpt1.0-immunized mice than for of the ovalbumin (Ova)-immunized mice.

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.

scholarly journals Bacterial lipopolysaccharides variably modulate in vitro biofilm formation of Candida species

2010 ◽  
Vol 59 (10) ◽  
pp. 1225-1234 ◽  
Author(s):  
H. M. H. N. Bandara ◽  
O. L. T. Lam ◽  
R. M. Watt ◽  
L. J. Jin ◽  
L. P. Samaranayake
Keyword(s):  
Biofilm Formation ◽  
Laser Scanning ◽  
Significant Inhibition ◽  
Laser Scanning Microscopy ◽  
Confocal Laser ◽  
Dependent Manner ◽  
Bacterial Lipopolysaccharides ◽  
Species Specific ◽  
Biofilm Development

The objective of this study was to evaluate the effect of the bacterial endotoxin LPS on Candida biofilm formation in vitro. The effect of the LPS of Pseudomonas aeruginosa, Klebsiella pneumoniae, Serratia marcescens and Salmonella typhimurium on six different species of Candida, comprising Candida albicans ATCC 90028, Candida glabrata ATCC 90030, Candida krusei ATCC 6258, Candida tropicalis ATCC 13803, Candida parapsilosis ATCC 22019 and Candida dubliniensis MYA 646, was studied using a standard biofilm assay. The metabolic activity of in vitro Candida biofilms treated with LPS at 90 min, 24 h and 48 h was quantified by XTT reduction assay. Viable biofilm-forming cells were qualitatively analysed using confocal laser scanning microscopy (CLSM), while scanning electron microscopy (SEM) was employed to visualize the biofilm structure. Initially, adhesion of C. albicans was significantly stimulated by Pseudomonas and Klebsiella LPS. A significant inhibition of Candida adhesion was noted for the following combinations: C. glabrata with Pseudomonas LPS, C. tropicalis with Serratia LPS, and C. glabrata, C. parapsilosis or C. dubliniensis with Salmonella LPS (P<0.05). After 24 h of incubation, a significant stimulation of initial colonization was noted for the following combinations: C. albicans/C. glabrata with Klebsiella LPS, C. glabrata/C. tropicalis/C. krusei with Salmonella LPS. In contrast, a significant inhibition of biofilm formation was observed in C. glabrata/C. dubliniensis/C. krusei with Pseudomonas LPS, C. krusei with Serratia LPS, C. dubliniensis with Klebsiella LPS and C. parapsilosis/C. dubliniensis /C. krusei with Salmonella LPS (P<0.05). On further incubation for 48 h, a significant enhancement of biofilm maturation was noted for the following combinations: C. glabrata/C. tropicalis with Serratia LPS, C. dubliniensis with Klebsiella LPS and C. glabrata with Salmonella LPS, and a significant retardation was noted for C. parapsilosis/C. dubliniensis/C. krusei with Pseudomonas LPS, C. tropicalis with Serratia LPS, C. glabrata/C. parapsilosis/C. dubliniensis with Klebsiella LPS and C. dubliniensis with Salmonella LPS (P<0.05). These findings were confirmed by SEM and CLSM analyses. In general, the inhibition of the biofilm development of LPS-treated Candida spp. was accompanied by a scanty architecture with a reduced numbers of cells compared with the profuse and densely colonized control biofilms. These data are indicative that bacterial LPSs modulate in vitro Candida biofilm formation in a species-specific and time-dependent manner. The clinical and the biological relevance of these findings have yet to be explored.

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