Exopolysaccharide Matrix Research Articles

Structural basis for synthase activation and cellulose modification in the E. coli Type II Bcs secretion system

Bacterial cellulosic polymers constitute a prevalent class of biofilm matrix exopolysaccharides that are synthesized by several types of bacterial cellulose secretion (Bcs) systems, which include conserved cyclic diguanylate (c-di-GMP)-dependent cellulose synthase modules together with diverse accessory subunits. In E. coli, the biogenesis of phosphoethanolamine (pEtN)-modified cellulose relies on the BcsRQABEFG macrocomplex, encompassing inner-membrane and cytosolic subunits, and an outer membrane porin, BcsC. Here, we use cryogenic electron microscopy to shed light on the molecular mechanisms of BcsA-dependent recruitment and stabilization of a trimeric BcsG pEtN-transferase for polymer modification, and a dimeric BcsF-dependent recruitment of an otherwise cytosolic BcsE2R2Q2 regulatory complex. We further demonstrate that BcsE, a secondary c-di-GMP sensor, can remain dinucleotide-bound and retain the essential-for-secretion BcsRQ partners onto the synthase even in the absence of direct c-di-GMP-synthase complexation, likely lowering the threshold for c-di-GMP-dependent synthase activation. Such activation-by-proxy mechanism could allow Bcs secretion system activity even in the absence of substantial intracellular c-di-GMP increase, and is reminiscent of other widespread synthase-dependent polysaccharide secretion systems where dinucleotide sensing and/or synthase stabilization are carried out by key co-polymerase subunits.

Effect of zinc oxide-eugenol endodontic paste on planktonic aggregates and biofilm of Enterococcus faecalis - An atomic force microscopy evaluation

ObjectiveThis work aimed to evaluate the in vitro effect of zinc oxide-eugenol paste (ZOE) on planktonic aggregates (EfPA) and biofilm (EfBio) of Enterococcus faecalis, focusing on their morphological aspects observed and analyzed using atomic force microscopy (AFM). DesignThe eugenol and paste were characterized by Gas Chromatography coupled with Mass Spectrometry (GC-MS) and Fourier Transform Infrared Spectroscopy (FTIR), respectively. The effect of ZOE on EfPA and EfBio was evaluated by a direct-contact test through colony counting and crystal violet staining protocol. AFM images of untreated and treated EfPA and EfBio growth on bovine dentin were obtained to analyze the morphological damage caused by the treatments. ResultsThe characterization showed high purity in the eugenol composition and chemical interaction between the components of the paste. A bactericidal effect on aggregates was observed after 6 h of exposure, and on biofilm after 24 h of treatment (p < 0.001). A disruptive effect on the biofilm was also evident. AFM images revealed the formation of EfPA, with a notable presence of an exopolysaccharide matrix. After 6 h of ZOE treatment, there was a significant increase in the size and surface roughness profile of treated cells (p < 0.05). Loss of typical cell morphology was observed after 24 h. The effect on the biofilm showed a tendency towards a less condensed biofilm pattern in the treated group, with no differences in surface roughness. ConclusionZOE presents bactericidal action on EfPA and EfBio, promoting significant morphological changes after treatment, especially in the aggregates.

BBSdb, an open resource for bacterial biofilm-associated proteins.

Bacterial biofilms are organized heterogeneous assemblages of microbial cells encased within a self-produced matrix of exopolysaccharides, extracellular DNA and proteins. Over the last decade, more and more biofilm-associated proteins have been discovered and investigated. Furthermore, omics techniques such as transcriptomes, proteomes also play important roles in identifying new biofilm-associated genes or proteins. However, those important data have been uploaded separately to various databases, which creates obstacles for biofilm researchers to have a comprehensive access to these data. In this work, we constructed BBSdb, a state-of-the-art open resource of bacterial biofilm-associated protein. It includes 48 different bacteria species, 105 transcriptome datasets, 21 proteome datasets, 1205 experimental samples, 57,823 differentially expressed genes (DEGs), 13,605 differentially expressed proteins (DEPs), 1,930 'Top 5% differentially expressed genes', 444 'Threshold-based DEGs' and a predictor for prediction of biofilm-associated protein. In addition, 1,781 biofilm-associated proteins, including annotation and sequences, were extracted from 942 articles and public databases via text-mining analysis. We used E. coli as an example to represent how to explore potential biofilm-associated proteins in bacteria. We believe that this study will be of broad interest to researchers in field of bacteria, especially biofilms, which are involved in bacterial growth, pathogenicity, and drug resistance. Availability and implementation: The BBSdb is freely available at http://124.222.145.44/#!/.

Fourfold increase in photocurrent generation of Synechocystis sp. PCC 6803 by exopolysaccharide deprivation

Photosynthetic microorganisms, including algae and cyanobacteria, export electrons in a light-stimulated phenomenon called ‘exoelectrogenesis’. However, the route(s) by which electrons reach an external electrode from the cell remain(s) unclear. For the model cyanobacterium Synechocystis sp. PCC 6803, it has been established that electron transfer does not depend on direct extracellular electron transfer by type IV pili. However, the role of the exopolysaccharide matrix in which cells are embedded has not been investigated. We show that a Synechocystis mutant with substantially reduced exopolysaccharide production has a four-fold greater photocurrent than wild-type cells. This increase is due in part to increased adhesion of exopolysaccharide-deficient cells to electrodes. Stirred system experiments reveal that a substantial portion of the photocurrent depends on an endogenous diffusible electron mediator, supporting indirect extracellular electron transfer as the bioelectrochemical mechanism of exoelectrogenesis. These findings will be important in harnessing exoelectrogenesis for sustainable electricity generation in biophotovoltaic devices.

Comparative analysis of commercial cleaning and disinfection formulations and protocols for effective eradication of biofilms formed by a Pseudomonas fluorescens strain isolated from a poultry meat plant

Pseudomonas spp. is the main genus of spoilage bacteria for meat stored under aerobic chilling conditions. Given their ability to adapt to various environmental conditions and to form biofilms, they are common among residential microbiota in the food industry. Biofilms are complex, structured microbial communities encased in a self-produced exopolysaccharide matrix. Resident biofilm bacteria show increased resistance against disinfectants and dynamic or hostile environments, and are therefore a persistent source of food contamination. Hence, there is a need to design and implement control strategies that are effective against biofilms in the food industry. In this study, we tested a series of commercial cleaning and disinfection agents applied by immersion or aerosolization against robust biofilms of a Pseudomonas fluorescens strain isolated from a poultry meat plant by comparing the sessile cell counts before and after the procedure. The single application of a) an alkaline or an enzymatic detergent, b) a disinfectant based on peracetic acid and hydrogen peroxide, or c) a detergent-disinfectant based on tertiary alkylamines or sodium hypochlorite, failed to completely eradicate the biofilm. However, two-step cleaning and disinfection procedures involving the application of a detergent (either alkaline or enzymatic at 50 °C) followed by the application of the disinfectant based on peracetic acid and hydrogen peroxide at the manufacturer's recommended concentrations did result in the complete eradication (p ≤ 0.05) of the robust biofilm. In addition, cleaning and disinfection procedures applied by aerosolization showed a notable efficacy (p ≤ 0.05) against surface-dried cells and sessile cells of P. fluorescens. Therefore, this approach could be regarded as a potentially viable alternative to commonly applied immersion techniques.

Biofilm Disruption and Virulence Attenuation Effects of Essential Oil From Endemic Algerian Cistus munbyi (Cistaceae) Against Clinical Strains of Pseudomonas aeruginosa

Background: Pseudomonas aeruginosa is an opportunistic, resistant and highly pathogenic bacteria, responsible for severe nosocomial infections in humans. There is need to search new antimicrobials to target P. aeruginosa strains. Cistus munbyi is used in traditional medicine to manage infections. Objectives: This work aims to investigate the antimicrobial, antibiofilm and other antivirulence effects of essential oil from C. munbyi against P. aeruginosa. Materials and methods: Essential oil (EO) was prepared by hydro-distillation from C. munbyi, characterized by GC–MS and evaluated for its antimicrobial, antibiofilm and anti-virulence effects against clinical isolates of P. aeruginosa. Results: 100% of compounds were identified with Terpinen-4-ol (33.20%), Sabinene (13.20%), α-Thujene (11.30%), and p-Cymene (9.94%) being the major constituents. The EO had good antimicrobial activity determined by diameters of inhibition zones and broth dilution. At minimal inhibitory concentration (MIC), the EO eliminated more that 70% of young biofilms in 19 strains out of 24 tested strains while at 2MIC, only one strain had biofilm inhibition below 70%. The EO eliminated more than 50% of mature biofilms in 13 strains out of 24 tested. Biofilm disruption was concentration-dependent at sub-MIC and indicated good potential of C. munbyi EO as P. aeruginosa antibiofilm agent. Scanning electron microscopy (SEM) images revealed that untreated colonies had a well-developed biofilm while there was significant reduction of biofilms with distorted architecture and cell shrinkage upon treatment with EO. The C. munbyi EO at MIC and sub-MIC was able to reduce quorum-sensing (QS) virulence factors such as pyocyanin production, exopolysaccharides matrix and elastase secretion. Significant QS revealed by reduction of violacein in C. violaceum (CV12472 and CV026) was observed. Conclusion: The overall results show good anti-pseudomonal effects of C. munbyi EO which makes it a potential agent to reduce the spread of infections and resistance to antibiotics from P. aeruginosa strains.

Scanning electron microscopic features of lacrimal drainage silastic stents: Comparison of various Crawford and large-diameter stents

Purpose This study aimed to examine the differences in the biofilms and physical deposits on Crawford stents compared to large-diameter stents. Methods A prospective interventional study was performed on a series of patients undergoing external or endoscopic dacryocystorhinostomy (DCR) and endoluminal lacrimal duct recanalization (ELDR) with either Crawford or large-diameter stents. All the Crawford stents were retrieved at six weeks and the large-diameter ones at eight weeks following the surgical intervention. There was no evidence of post-operative infection in any of the patients. Following extubation, standard protocols of scanning electron microscopy were used to assess the biofilms and physical deposits on the stents. Results A total of 15 stents were studied. Of these, twelve were Crawford, and three were large-diameter stents. The Crawford stents were from two different manufacturers. All the stents demonstrated evidence of biofilm formation and physical deposits. The Crawford stents showed thin biofilms and sparse physical deposits, but there were no demonstrable differences amongst stents from different manufacturers. However, the deposits and biofilms were thicker and more extensive in the large-diameter stents than the Crawford ones. The biofilms from all stents showed the presence of polymicrobial communities within the exopolysaccharide matrix. Conclusions The present study found differences in biofilms and physical deposits between Crawford and large-diameter stents. These differences can be partly explained by stent duration, size, and their tissue interactions.

Challenges and opportunities in elucidating the structures of biofilm exopolysaccharides: A case study of the Pseudomonas aeruginosa exopolysaccharide called Pel.

Biofilm formation protects bacteria from antibiotic treatment and host immune responses, making biofilm infections difficult to treat. Within biofilms, bacterial cells are entangled in a self-produced extracellular matrix that typically includes exopolysaccharides. Molecular-level descriptions of biofilm matrix components, especially exopolysaccharides, have been challenging to attain due to their complex nature and lack of solubility and crystallinity. Solid-state nuclear magnetic resonance (NMR) has emerged as a key tool to determine the structure of biofilm matrix exopolysaccharides without degradative sample preparation. In this review, we discuss challenges of studying biofilm matrix exopolysaccharides and opportunities to develop solid-state NMR approaches to study these generally intractable materials. We specifically highlight investigations of the exopolysaccharide called Pel made by the opportunistic pathogen, Pseudomonas aeruginosa. We provide a roadmap for determining exopolysaccharide structure and discuss future opportunities to study such systems using solid-state NMR. The strategies discussed for elucidating biofilm exopolysaccharide structure should be broadly applicable to studying the structures of other glycans.

Dual-Species Biofilms: Biomass, Viable Cell Ratio/Cross-Species Interactions, Conjugative Transfer.

Biofilms as a form of adaptation are beneficial for bacterial survival and may be hot spots for horizontal gene transfer, including conjugation. The aim of this research was to characterize the biofilm biomass, viable cell ratios and conjugative transfer of the pOX38 plasmid, an F-plasmid derivative, from the Escherichia coli N4i pOX38 strain (donor) into a uropathogenic E. coli DL82 strain (recipient) within dual-species biofilms with one of the following opportunistic pathogenic bacteria: Klebsiella pneumoniae, Enterococcus faecalis or Pseudomonas aeruginosa. Dual-species biofilms of E. coli with K. pneumoniae or P. aeruginosa but not E. faecalis were more massive and possessed more exopolysaccharide matrix compared to single-species biofilms of donor and recipient cells. Correlation between biofilm biomass and exopolysaccharide matrix was rs = 0.888 in dual-species biofilms. In dual-species biofilm with E. faecalis the proportion of E. coli was the highest, while in the biofilm with P. aeruginosa and K. pneumoniae, the E. coli was less abundant. The conjugative frequencies of plasmid transfer in dual-species biofilms of E. coli with E. faecalis and P. aeruginosa were reduced. A decrease in conjugative frequency was also observed when cell-free supernatants (CFSs) of E. faecalis and P. aeruginosa were added to the E. coli conjugation mixture. Further, the activity of the autoinducer AI-2 in the CFSs of the E. coli conjugation mixture was reduced when bacteria or CFSs of E. faecalis and P. aeruginosa were added to the E. coli conjugation mixture. Hence, the intercellular and interspecies interactions in dual-species biofilms depend on the partners involved.

Dual functions: A coumarin-chalcone conjugate inhibits cyclic-di-GMP and quorum-sensing signaling to reduce biofilm formation and virulence of pathogens.

Antibiotic resistance or tolerance of pathogens is one of the most serious global public health threats. Bacteria in biofilms show extreme tolerance to almost all antibiotic classes. Thus, use of antibiofilm drugs without bacterial-killing effects is one of the strategies to combat antibiotic tolerance. In this study, we discovered a coumarin-chalcone conjugate C9, which can inhibit the biofilm formation of three common pathogens that cause nosocomial infections, namely, Pseudomonas aeruginosa, Staphylococcus aureus, and Escherichia coli, with the best antibiofilm activity against P. aeruginosa. Further investigations indicate that C9 decreases the synthesis of the key biofilm matrix exopolysaccharide Psl and bacterial second messenger cyclic-di-GMP. Meanwhile, C9 can interfere with the regulation of the quorum sensing (QS) system to reduce the virulence of P. aeruginosa. C9 treatment enhances the sensitivity of biofilm to several antibiotics and reduces the survival rate of P. aeruginosa under starvation or oxidative stress conditions, indicating its excellent potential for use as an antibiofilm-forming and anti-QS drug.

Pseudomonas aeruginosa biofilm formation and its resistance to beta-lactam antibiotics

ABSTRACT Introduction: An opportunistic pathogen, Pseudomonas aeruginosa is a Gram-negative bacteria that causes acute and chronic human infections. By adhering to appropriate surfaces and creating a biofilm matrix, Pseudomonas aeruginosa has a high-resistance structure. Due to biofilm resistance mechanisms, this bacterial biofilm may increase natural antibiotic resistance. Antibiotics have difficulty penetrating the exopolysaccharide matrix that makes up the biofilm structure (Psl, Pe, alginate, and eDNA). Alginate is involved in generating mucus, and Psl and Pel components are implicated in biofilm development and antibiotic resistance. Due to the connection between biofilm production and antibiotic resistance, Pseudomonas aeruginosa involves mechanisms of beta-lactam antibiotic resistance. Objective: On this basis, learning more about the connection between Pseudomonas aeruginosa bacteria's ability to form biofilms and their resistance to beta-lactam antibiotics is essential. Methods: We use literature methods from various literature on the biofilm formation of P. aeruginosa and its resistance to beta-lactam antibiotics, including research papers and studies with no restrictions types of studies included in this article. Discussion: Pseudomonas aeruginosa has intrinsic and adaptive antibiotic resistance mechanisms. Decreased membrane permeability, the production of enzymes resistant to antibiotics, chromosomal changes, and horizontal gene transfer from other bacteria contribute to antimicrobial resistance. Beta-lactam antibiotic resistance mechanisms are known to be developed by Pseudomonas aeruginosa. The resistance characteristics of Pseudomonas aeruginosa may change phenotypically due to biofilm development. This article will be helpful in future research on Pseudomonas aeruginosa therapy and medication.

Defining early steps in Bacillus subtilis biofilm biosynthesis.

Biofilms are the communal way of life that microbes adopt to increase survival. Key to our ability to systematically promote or ablate biofilm formation is a detailed understanding of the biofilm matrix macromolecules. Here, we identify the first two essential steps in the Bacillus subtilis biofilm matrix exopolysaccharide (EPS) synthesis pathway. Together, our studies and approaches provide the foundation for the sequential characterization of the steps in EPS biosynthesis, using prior steps to enable chemoenzymatic synthesis of the undecaprenyl diphosphate-linked glycan substrates.

A comparative approach on the spray and freeze drying of probiotic and Gamma-aminobutyric acid as a single entity: Characterization and evaluation of stability in simulated gastrointestinal conditions

To promote the adequate supplementation of probiotics and bioactives in food formulations, this study aimed to develop synbiotic co-microcapsules containing probiotic strain Lactococcus lactis SKL 13 and bioactive compound, namely γ-Aminobutyric acid (GABA), using spray (at the air inlet and outlet temperatures of 110 ± 2 °C and 50 ± 5 °C, respectively, with a feed flow rate of 2.5 mL min−1) and freeze-drying (at - 40 °C temperature, 1 mbar pressure for 12 h) in a ternary exopolysaccharide (such as maltodextrin, dextran, and inulin in a combination of 8.41, 4.59, and 0.40 g/100 mL, respectively) matrix. The freeze-drying resulted in higher probiotic and GABA encapsulation efficiencies of 95.08 and 90.04%, respectively, than spray drying (probiotics: 93.12% and GABA: 83.46%). The absence of diffraction peaks indicated an amorphous metastable state of microcapsules. Only ∼1% reduction in probiotic count and ∼5% decrease in GABA content were observed in dried capsules after 60 days of storage as well as both the powders showed non-significant (p > 0.05) reduction in probiotic count (2.9 and 1.35 log CFU/mL in intestinal and gastric conditions, respectively) and 80% release of GABA after 240 min of simulated gastrointestinal conditions. The Fourier-transform infrared (FTIR) and scanning electron microscopy (SEM) results further confirmed the proper embedding of probiotics and GABA in the dried microcapsules. The lower moisture content (4.15%), good flowability and higher thermal decomposition peaks at an elevated temperature of 308 °C exhibited by spray-dried powder compared to freeze-dried particles indicated their greater potentiality for high-temperature food applications.

Microbial Biofilm: A Review on Formation, Infection, Antibiotic Resistance, Control Measures, and Innovative Treatment.

Biofilm is complex and consists of bacterial colonies that reside in an exopolysaccharide matrix that attaches to foreign surfaces in a living organism. Biofilm frequently leads to nosocomial, chronic infections in clinical settings. Since the bacteria in the biofilm have developed antibiotic resistance, using antibiotics alone to treat infections brought on by biofilm is ineffective. This review provides a succinct summary of the theories behind the composition of, formation of, and drug-resistant infections attributed to biofilm and cutting-edge curative approaches to counteract and treat biofilm. The high frequency of medical device-induced infections due to biofilm warrants the application of innovative technologies to manage the complexities presented by biofilm.

Iranian traditional kefir beverage: isolation and identification of beneficial microorganisms and evaluation of antimicrobial activity against food-borne pathogens

Purpose Kefir is a traditional fermented dairy beverage that has numerous health benefits due to the presence of bacteria and yeasts in an exopolysaccharide matrix. This study aims to isolate and identify beneficial microorganisms and evaluate the antimicrobial activity of kefir beverage against two important food-borne pathogens including Salmonella Typhimurium and Listeria monocytogenes. Design/methodology/approach Microorganisms were identified by the polymerase chain reaction with specific primers, and antimicrobial activity was evaluated by the disk diffusion method. Findings The following microorganisms were identified as natural inhabitants of the kefir grains: Leuconostoc lactis, Lactococcus lactis subspecies lactis, Streptococcus cremoris, Enterococcus faecalis, Enterococcus faecium, Lactobacillus helveticus, Leuconostoc mesenteroides, Lactobacillus fermentum, Lactobacillus reuteri, Lactobacillus plantarum, Lactobacillus casei, Bifidobacterium langum, Saccharomyces cerevisiae and Pichia fermentas. Also, the results obtained from the disk diffusion method showed the inhibitory effect of kefir milk on Salmonella Typhimurium and Listeria monocytogenes with an inhibitory average diameter of 8.3 ± 4–9.1 ± 2.8 and 3.4 ± 3–6.6 ± 3 mm, respectively. Originality/value The results of this study showed that Iranian traditional kefir beverage contained different species of lactic acid bacteria and yeasts and has antimicrobial activity against two important food-borne pathogens, Salmonella Typhimurium and Listeria monocytogenes, which the highest inhibitory effect was observed against Salmonella Typhimurium.

Vibrio cholerae biofilms use modular adhesins with glycan-targeting and nonspecific surface binding domains for colonization

Bacterial biofilms are formed on environmental surfaces and host tissues, and facilitate host colonization and antibiotic resistance by human pathogens. Bacteria often express multiple adhesive proteins (adhesins), but it is often unclear whether adhesins have specialized or redundant roles. Here, we show how the model biofilm-forming organism Vibrio cholerae uses two adhesins with overlapping but distinct functions to achieve robust adhesion to diverse surfaces. Both biofilm-specific adhesins Bap1 and RbmC function as a “double-sided tape”: they share a β-propeller domain that binds to the biofilm matrix exopolysaccharide, but have distinct environment-facing domains. Bap1 adheres to lipids and abiotic surfaces, while RbmC mainly mediates binding to host surfaces. Furthermore, both adhesins contribute to adhesion in an enteroid monolayer colonization model. We expect that similar modular domains may be utilized by other pathogens, and this line of research can potentially lead to new biofilm-removal strategies and biofilm-inspired adhesives.

Biogenic silver nanoparticles (AgNPs) from Tinosporacordifolia leaves: An effective antibiofilm agent against Staphylococcus aureus ATCC 23235.

Medicinal plants are long known for their therapeutic applications. Tinospora cordifolia (commonly called gulancha or heart-leaved moonseed plant), a herbaceous creeper widely has been found to have antimicrobial, anti-inflammatory, anti-diabetic, and anti-cancer properties. However, there remains a dearth of reports regarding its antibiofilm activities. In the present study, the anti-biofilm activities of phytoextractof T. cordifolia and the silver nanoparticles made from this phytoextract were tested against the biofilm of S.taphylococcus aureus, one of the major nosocomial infection-producing bacteria taking tetracycline antibiotic as control. Both phytoextract from the leaves of T. cordifolia, and the biogenic AgNPs from the leaf extract of T. cordifolia, were found successful in reducing the biofilm of Staphylococcus aureus. The biogenic AgNPs formed were characterized by UV- Vis spectroscopy, Field emission Scanning Electron Microscopy (FE- SEM), and Dynamic light scattering (DLS) technique. FE- SEM images showed that the AgNPs were of size ranging between 30 and 50nm and were stable in nature, as depicted by the zeta potential analyzer. MIC values for phytoextract and AgNPs were found to be 180mg/mL and 150μg/mL against S. aureusrespectively. The antibiofilm properties of the AgNPs and phytoextract were analyzed using the CV assay and MTT assay for determining the reduction of biofilms. Reduction in viability count and revival of the S. aureus ATCC 23235 biofilm cells were analyzed followed by the enfeeblement of the EPS matrix to quantify the reduction in the contents of carbohydrates, proteins and eDNA. The SEM analyses clearly indicated that although the phytoextracts could destroy the biofilm network of S. aureuscells yet the biogenicallysynthesizedAgNPs were more effective in biofilm disruption. Fourier Transformed Infrared Radiations (FT- IR) analyses revealed that the AgNPs could bring about more exopolysaccharide (EPS) destruction in comparison to the phytoextract. The antibiofilm activities of AgNPs made from the phytoextract were found to be much more effective than the non-conjugated phytoextract, indicating the future prospect of using such particles for combatting biofilm-mediated infections caused by S aureus.

Antibiofilm formation activities of ethanol extracts from Curcuma domestica rhizome against bacteria resistant Pseudomonas aeruginosa

The Biofilm P.aeruginosa communities are characterized by close juxtaposition of bacterial cells and the presence of an exopolysaccharide matrix that surrounds the bacterial population. Many reports have postulated that the exopolysaccharide matrix provides an effective barrier that restricts penetration of chemically reactive biocides, cationic antibiotics and antimicrobial peptides. This study aims to antibiofilm formation activities of ethanol extract from Curcuma domestica against Pseudomonas aeruginosa resistant bacteria. These antibiofilm formation was determined using a modified-method of microdilution assay. Ethanol extract of C. domestica strong activity against P.aeruginosa with Anti-biofilm activity was observed through biofilm inhibition and degradation activities, determined by Cristal Violet assay. Data were analyzed using ANOVA test and Tukey HSD post hoc test. The significant inhibition of P.aeruginosa the biofilm degradation was obtained at a concentration of 31.2 µg/ml until 250 µg/ml. The ethanol extract of C. domestica have potency as alternative antibiofilm formation against selected bacteria resistant.

The Determination, Monitoring, Molecular Mechanisms and Formation of Biofilm in E. coli.

Biofilms are cell assemblies embedded in an exopolysaccharide matrix formed by microorganisms of a single or many different species. This matrix in which they are embedded protects the bacteria from external influences and antimicrobial effects. The biofilm structure that microorganisms form to protect themselves from harsh environmental conditions and survive is found in nature in many different environments. These environments where biofilm formation occurs have in common that they are in contact with fluids. The gene expression of bacteria in complex biofilm differs from that of bacteria in the planktonic state. The differences in biofilm cell expression are one of the effects of community life. Means of quorum sensing, bacteria can act in coordination with each other. At the same time, while biofilm formation provides many benefits to bacteria, it has positive and negative effects in many different areas. Depending on where they occur, biofilms can cause serious health problems, contamination risks, corrosion, and heat and efficiency losses. However, they can also be used in water treatment plants, bioremediation, and energy production with microbial fuel cells. In this review, the basic steps of biofilm formation and biofilm regulation in the model organism Escherichia coli were discussed. Finally, the methods by which biofilm formation can be detected and monitored were briefly discussed.

Characterization of kefir yeasts with antifungal capacity against Aspergillus species.

Kefir is a fermented probiotic drink obtained by placing kefir granules in a suitable substrate. The kefir granules are a consortium of bacteria and yeasts embedded in a exopolysaccharide matrix. The aim of this research was the isolation and identification of yeasts from kefir of different origin, the evaluation of their antifungal capacity against Aspergillus spp., and the characterization of virulence related traits. Using RFLP of ITS1/ITS4 region, D1/D2 region sequencing, and RAPD techniques, 20 kefir isolates were identified as Geotrichum candidum, Pichia kudriavzevii, Pichia membranifaciens, Saccharomyces cerevisiae, and Candida ethanolica. Their antifungal capacity was evaluated by their conidia germination reduction, which allowed the selection of eight isolates with high to moderate conidia germination reduction against Aspergillus flavus and Aspergillus parasiticus. Furthermore, these selected isolates showed growth inhibition on contact in the dual culture assay for both Aspergillus species and 3 of them-belonging to S. cerevisiae and P. kudriavzevii species-generated volatile organic compounds which significantly affected the growth of both fungi. For the evaluation of virulence-related traits, growth at high temperatures, enzymatic activities, and the adhesion to Caco-2 cells were analyzed. The isolates did not present more than one positive virulence-related trait simultaneously. In particular, it is important to highlight that the adhesion capacity to the model of intestinal barrier was extremely low for all of them. According to the results obtained, further studies would be of interest for the possible use of these promising yeasts as biocontrol agents against fungi in food.