The impact of the competence quorum sensing system on <Emphasis Type="Italic">Streptococcus pneumoniae</Emphasis>biofilms varies depending on the experimental model

Background  

Different models for biofilm in Streptococcus pneumoniae have been described in literature. To permit comparison of experimental data, we characterised the impact of the pneumococcal quorum-sensing competence system on biofilm formation in three models. For this scope, we used two microtiter and one continuous culture biofilm system.     

Global screening of potential <Emphasis Type="Italic">Candida albicans</Emphasis> biofilm-related transcription factors via network comparison

Background  

Candida albicans is a commonly encountered fungal pathogen in humans. The formation of biofilm is a major virulence factor in C. albicans pathogenesis and is related to antidrug resistance of this organism. Although many factors affecting biofilm have been analyzed, molecular mechanisms that regulate biofilm formation still await to be elucidated.     

Effects of extracellular DNA and DNA‐binding protein on the development of a Streptococcus intermedius biofilm

Aims

The aim of this study was to clarify the effects of homologous and heterologous extracellular DNAs (eDNAs) and histone‐like DNA‐binding protein (HLP) on Streptococcus intermedius biofilm development and rigidity.

Methods and Results

Formed biofilm mass was measured with 0·1% crystal violet staining method and observed with a scanning electron microscope. The localizations of eDNA and extracellular HLP (eHLP) in formed biofilm were detected by staining with 7‐hydoxyl‐9H‐(1,3‐dichloro‐9,9‐dimethylacridin‐2‐one) and anti‐HLP antibody without fixation, respectively. DNase I treatment (200 U ml^?1) markedly decreased biofilm formation and cell density in biofilms. Colocalization of eHLP and eDNA in biofilm was confirmed. The addition of eDNA (up to 1 μg ml^?1) purified from Strep. intermedius, other Gram‐positive bacteria, Gram‐negative bacteria, or human KB cells into the Strep. intermedius culture increased the biofilm mass of all tested strains of Strep. intermedius, wild‐type, HLP‐downregulated strain and control strains. In contrast, the addition of eDNA (>1 μg ml^?1) decreased the biofilm mass of all Strep. intermedius strains.

Conclusions

These findings demonstrated that eDNA and eHLP play crucial roles in biofilm development and its rigidity.

Significance and Impact of the Study

eDNA‐ and HLP‐targeting strategies may be applicable to novel treatments for bacterial biofilm‐related infectious diseases.     

A three-phase <Emphasis Type="Italic">in-vitro</Emphasis> system for studying <Emphasis Type="Italic">Pseudomonas aeruginosa</Emphasis> adhesion and biofilm formation upon hydrogel contact lenses

Background  

Pseudomonas aeruginosa is commonly associated with contact lens (CL) -related eye infections, for which bacterial adhesion and biofilm formation upon hydrogel CLs is a specific risk factor. Whilst P. aeruginosa has been widely used as a model organism for initial biofilm formation on CLs, in-vitro models that closely reproduce in-vivo conditions have rarely been presented.     

DNA-microarrays identification of <Emphasis Type="Italic">Streptococcus mutans</Emphasis> genes associated with biofilm thickness

Background  

A biofilm is a complex community of microorganisms that develop on surfaces in diverse environments. The thickness of the biofilm plays a crucial role in the physiology of the immobilized bacteria. The most cariogenic bacteria, mutans streptococci, are common inhabitants of a dental biofilm community. In this study, DNA-microarray analysis was used to identify differentially expressed genes associated with the thickness of S. mutans biofilms.     

Impact of the <Emphasis Type="Italic">Staphylococcus epidermidis</Emphasis> LytSR two-component regulatory system on murein hydrolase activity,pyruvate utilization and global transcriptional profile

Background  

Staphylococcus epidermidis has emerged as one of the most important nosocomial pathogens, mainly because of its ability to colonize implanted biomaterials by forming a biofilm. Extensive studies are focused on the molecular mechanisms involved in biofilm formation. The LytSR two-component regulatory system regulates autolysis and biofilm formation in Staphylococcus aureus. However, the role of LytSR played in S. epidermidis remained unknown.     

Pleurotus ostreatus biofilm‐forming ability and ultrastructure are significantly influenced by growth medium and support type

Aims

To investigate the effect of support and growth medium (GM) on Pleurotus ostreatus biofilm production, specific metabolic activity (SMA) and ultrastructure.

Methods and Results

Biofilms were developed on membranes covering a broad range of surface properties and, due to the applicative implications of mixed biofilms, on standard bacterial GM in stationary and shaken culture. Hydrophilic (glass fibre, Duran glass and hydroxyapatite) and mild hydrophobic (polyurethane, stainless steel, polycarbonate, nylon) supports were more adequate for biofilm attachment than the hydrophobic Teflon. Among the GM, sucrose–asparagine (SA) was more conducive to biofilm production than Luria–Bertani and M9. GM was more influential than support type on biofilm ultrastructure, and a high compactness was evident in biofilms developed on SA. Biofilms on Duran glass were more efficient than planktonic cultures in olive‐mill wastewater treatment.

Conclusions

The main effects of support and GM variables and their binary interactions on both biofilm production and SMA were all highly significant (P < 0·001): thus, the magnitude of the effect of each variable strongly depended on the level of the other one.

Significance and Impact of the Study

There is a lack of basic information regarding physiology and ultrastructure of P. ostreatus biofilms. To our knowledge, this is the first attempt to fill this gap, thus representing a basis for future studies.     

<Emphasis Type="Italic">Pseudomonas aeruginosa</Emphasis> Cystic Fibrosis isolates of similar RAPD genotype exhibit diversity in biofilm forming ability <Emphasis Type="Italic">in vitro</Emphasis>

Background  

Pseudomonas aeruginosa is considered to grow in a biofilm in cystic fibrosis (CF) chronic lung infections. Bacterial cell motility is one of the main factors that have been connected with P. aeruginosa adherence to both biotic and abiotic surfaces. In this investigation, we employed molecular and microscopic methods to determine the presence or absence of motility in P. aeruginosa CF isolates, and statistically correlated this with their biofilm forming ability in vitro.     

Identification of critical residues in Gap3 of <Emphasis Type="Italic">Streptococcus parasanguinis</Emphasis> involved in Fap1 glycosylation,fimbrial formation and <Emphasis Type="Italic">in vitro</Emphasis>adhesion

Background  

Streptococcus parasanguinis is a primary colonizer of human tooth surfaces and plays an important role in dental plaque formation. Bacterial adhesion and biofilm formation are mediated by long peritrichous fimbriae that are composed of a 200 kDa serine rich glycoprotein named Fap1 (fimbriae-associated protein). Glycosylation and biogenesis of Fap1 are modulated by a gene cluster downstream of the fap1 locus. A gene encoding a glycosylation-associated protein, Gap3, was found to be important for Fap1 glycosylation, long fimbrial formation and Fap1-mediated biofilm formation.     

Genetic adaptation of <Emphasis Type="Italic">Streptococcus mutans</Emphasis> during biofilm formation on different types of surfaces

Background  

Adhesion and successful colonization of bacteria onto solid surfaces play a key role in biofilm formation. The initial adhesion and the colonization of bacteria may differ between the various types of surfaces found in oral cavity. Therefore, it is conceivable that diverse biofilms are developed on those various surfaces. The aim of the study was to investigate the molecular modifications occurring during in vitro biofilm development of Streptococcus mutans UA159 on several different dental surfaces.     

N-acetylcysteine inhibit biofilms produced by <Emphasis Type="Italic">Pseudomonas aeruginosa</Emphasis>

Background  

Pseudomonas aeruginosa is a common pathogen in chronic respiratory tract infections. It typically makes a biofilm, which makes treatment of these infections difficult. In this study, we investigated the inhibitory effects of N-acetylcysteine (NAC) on biofilms produced by P. aeruginosa.     

Pellicle formation in <Emphasis Type="Italic">Shewanella oneidensis</Emphasis>

Background  

Although solid surface-associated biofilm development of S. oneidensis has been extensively studied in recent years, pellicles formed at the air-liquid interface are largely overlooked. The goal of this work was to understand basic requirements and mechanism of pellicle formation in S. oneidensis.     

Species specificity,surface exposure,protein expression,immunogenicity, and participation in biofilm formation of <Emphasis Type="Italic">Porphyromonas gingivalis</Emphasis> HmuY

Background  

Porphyromonas gingivalis is a major etiological agent of chronic periodontitis. The aim of this study was to examine the species specificity, surface exposure, protein expression, immunogenicity, and participation in biofilm formation of the P. gingivalis heme-binding protein HmuY.     

The small regulatory RNA molecule MicA is involved in <Emphasis Type="Italic">Salmonella enterica</Emphasis> serovar Typhimurium biofilm formation

Background  

LuxS is the synthase enzyme of the quorum sensing signal AI-2. In Salmonella Typhimurium, it was previously shown that a luxS deletion mutant is impaired in biofilm formation. However, this phenotype could not be complemented by extracellular addition of quorum sensing signal molecules.     

Robustness analysis of culturing perturbations on <Emphasis Type="Italic">Escherichia coli</Emphasis> colony biofilm beta-lactam and aminoglycoside antibiotic tolerance

Background  

Biofilms are ubiquitous. For instance, the majority of medical infections are thought to involve biofilms. However even after decades of investigation, the in vivo efficacy of many antimicrobial strategies is still debated suggesting there is a need for better understanding of biofilm antimicrobial tolerances. The current study's goal is to characterize the robustness of biofilm antibiotic tolerance to medically and industrially relevant culturing perturbations. By definition, robust systems will return similar, predictable responses when perturbed while non-robust systems will return very different and potentially unpredictable responses. The predictability of an antibiotic tolerance response is essential to developing, testing, and employing antimicrobial strategies.     

Roles of curli,cellulose and BapA in <Emphasis Type="Italic">Salmonella</Emphasis> biofilm morphology studied by atomic force microscopy

Background  

Curli, cellulose and the cell surface protein BapA are matrix components in Salmonella biofilms. In this study we have investigated the roles of these components for the morphology of bacteria grown as colonies on agar plates and within a biofilm on submerged mica surfaces by applying atomic force microscopy (AFM) and light microscopy.     

Probiotic‐mediated competition,exclusion and displacement in biofilm formation by food‐borne pathogens

The objective of this study was to examine the inhibitory effect of probiotic strains on pathogenic biofilm formation in terms of competition, exclusion and displacement. Probiotic strains (Lactobacillus acidophilus KACC 12419, Lact. casei KACC 12413, Lact. paracasei KACC 12427 and Lact. rhamnosus KACC 11953) and pathogens (Salmonella Typhimurium KCCM 40253 and Listeria monocytogenes KACC 12671) were used to evaluate the auto‐aggregation, hydrophobicity and biofilm formation inhibition. The highest auto‐aggregation abilities were observed in Lact. rhamnosus (17·5%), Lact. casei (17·2%) and Lact. acidophilus (15·1%). Salm. Typhimurium had the highest affinity to xylene, showing the hydrophobicity of 53·7%. The numbers of L. monocytogenes biofilm cells during the competition, exclusion and displacement assays were effectively reduced by more than 3 log when co‐cultured with Lact. paracasei and Lact. rhamnosus. The results suggest that probiotic strains can be used as alternative way to effectively reduce the biofilm formation in pathogenic bacteria through competition, exclusion and displacement.

Significance and Impact of the Study

This study provides new insight into biofilm control strategy based on probiotic approach. Probiotic strains effectively inhibited the biofilm formation of Listeria monocytogenes through the mechanisms of competition, exclusion and displacement. These findings contribute to better understand the probiotic‐mediated competition, exclusion and displacement in biofilm formation by pathogens.     

Role of type 1 and type 3 fimbriae in <Emphasis Type="Italic">Klebsiella pneumoniae</Emphasis> biofilm formation

Background  

Klebsiella pneumoniae is an important gram-negative opportunistic pathogen causing primarily urinary tract infections, respiratory infections, and bacteraemia. The ability of bacteria to form biofilms on medical devices, e.g. catheters, has a major role in development of many nosocomial infections. Most clinical K. pneumoniae isolates express two types of fimbrial adhesins, type 1 fimbriae and type 3 fimbriae. In this study, we characterized the role of type 1 and type 3 fimbriae in K. pneumoniae biofilm formation.     

Deletion of the glycosyltransferase <Emphasis Type="Italic">bgsB of Enterococcus faecalis</Emphasis>leads to a complete loss of glycolipids from the cell membrane and to impaired biofilm formation

Background  

Deletion of the glycosyltransferase bgsA in Enterococcus faecalis leads to loss of diglucosyldiacylglycerol from the cell membrane and accumulation of its precursor monoglucosyldiacylglycerol, associated with impaired biofilm formation and reduced virulence in vivo. Here we analyzed the function of a putative glucosyltransferase EF2890 designated biofilm-associated glycolipid synthesis B (bgsB) immediately downstream of bgsA.     

Real-time PCR expression profiling of genes encoding potential virulence factors in <Emphasis Type="Italic">Candida albicans</Emphasis> biofilms: identification of model-dependent and -independent gene expression

Background  

Candida albicans infections are often associated with biofilm formation. Previous work demonstrated that the expression of HWP1 (hyphal wall protein) and of genes belonging to the ALS (agglutinin-like sequence), SAP (secreted aspartyl protease), PLB (phospholipase B) and LIP (lipase) gene families is associated with biofilm growth on mucosal surfaces. We investigated using real-time PCR whether genes encoding potential virulence factors are also highly expressed in biofilms associated with abiotic surfaces. For this, C. albicans biofilms were grown on silicone in microtiter plates (MTP) or in the Centres for Disease Control (CDC) reactor, on polyurethane in an in vivo subcutaneous catheter rat (SCR) model, and on mucosal surfaces in the reconstituted human epithelium (RHE) model.