Giving structure to the biofilm matrix:an overview of individual strategies and emerging common themes

Biofilms are communities of microbial cells that underpin diverse processes including sewage bioremediation, plant growth promotion, chronic infections and industrial biofouling. The cells resident in the biofilm are encased within a self-produced exopolymeric matrix that commonly comprises lipids, proteins that frequently exhibit amyloid-like properties, eDNA and exopolysaccharides. This matrix fulfils a variety of functions for the community, from providing structural rigidity and protection from the external environment to controlling gene regulation and nutrient adsorption. Critical to the development of novel strategies to control biofilm infections, or the capability to capitalize on the power of biofilm formation for industrial and biotechnological uses, is an in-depth knowledge of the biofilm matrix. This is with respect to the structure of the individual components, the nature of the interactions between the molecules and the three-dimensional spatial organization. We highlight recent advances in the understanding of the structural and functional role that carbohydrates and proteins play within the biofilm matrix to provide three-dimensional architectural integrity and functionality to the biofilm community. We highlight, where relevant, experimental techniques that are allowing the boundaries of our understanding of the biofilm matrix to be extended using Escherichia coli, Staphylococcus aureus, Vibrio cholerae, and Bacillus subtilis as exemplars

High mannose-specific lectin Msl mediates key interactions of the vaginal Lactobacillus plantarum isolate CMPG5300

To characterize the interaction potential of the human vaginal isolate Lactobacillus plantarum CMPG5300, its genome was mined for genes encoding lectin-like proteins. cmpg5300.05_29 was identified as the gene encoding a putative mannose-binding lectin. Phenotypic analysis of a gene knock-out mutant of cmpg5300.05_29 showed that expression of this gene is important for auto-aggregation, adhesion to the vaginal epithelial cells, biofilm formation and binding to mannosylated glycans. Purification of the predicted lectin domain of Cmpg5300.05_29 and characterization of its sugar binding capacity confirmed the specificity of the lectin for high-mannose glycans. Therefore, we renamed Cmpg5300.05_29 as a mannose-specific lectin (Msl). The purified lectin domain of Msl could efficiently bind to HIV-1 glycoprotein gp120 and Candida albicans, and showed an inhibitory activity against biofilm formation of uropathogenic Escherichia coli, Staphylococcus aureus and Salmonella Typhimurium. Thus, using a combination of molecular lectin characterization and functional assays, we could show that lectin-sugar interactions play a key role in host and pathogen interactions of a prototype isolate of the vaginal Lactobacillus microbiota

Inhibition of bacterial adhesion by epigallocatechin gallate attached polymeric membranes

Microbial adhesion and formation of biofilms cause a serious problem in several areas including but not limited to food spoilage, industrial corrosion and nosocomial infections. These microbial biofilms pose a serious threat to human health since microbial communities in the biofilm matrix are protected with exopolymeric substances and difficult to eradicate with antibiotics. Hence, the prevention of microbial adhesion followed by biofilm formation is one of the promising strategies to prevent these consequences. The attachment of antimicrobial agents, coatings of nanomaterials and synthesis of hybrid materials are widely used approach to develop surfaces having potential to hinder bacterial adhesion and biofilm formation. In this study, epigallocatechin gallate (EGCG) is attached on p(HEMA-co-GMA) membranes to prevent the bacterial colonization. The attachment of EGCG to membranes was proved by Fourier-transform infrared spectroscopy (FT-IR). The synthesized membrane showed porous structure (SEM), and desirable swelling degree, which are ideal when it comes to the application in biotechnology and biomedicine. Furthermore, EGCG attached membrane showed significant potential to prevent the microbial colonization on the surface. The obtained results suggest that EGCG attached polymer could be used as an alternative approach to prevent the microbial colonization on the biomedical surfaces, food processing equipment as well as development of microbial resistant food packaging systems

Signals, Regulatory Networks, And Materials That Build And Break Bacterial Biofilms

No Abstract Availabl

Antibiofilm and antimicrobial-enhancing activity of Chelidonium majus and Corydalis cheilanthifolia extracts against multidrug-resistant Helicobacter pylori

Helicobacter pylori is a Gram-negative bacterium that colonizes the stomach of about 60% of people worldwide. The search for new drugs with activity against H. pylori is now a hotspot in the effective and safe control of this bacterium. Therefore, the aim of this research was to determine the antibacterial activity of extracts from selected plants of the Papaveraceae family against planktonic and biofilm forms of the multidrug-resistant clinical strain of H. pylori using a broad spectrum of analytical in vitro methods. It was revealed that among the tested extracts, those obtained from Corydalis cheilanthifolia and Chelidonium majus were the most active, with minimal inhibitory concentrations (MICs) of 64 µg/mL and 128 µg/mL, respectively. High concentrations of both extracts showed cytotoxicity against cell lines of human hepatic origin. Therefore, we attempted to lower their MICs through the use of a synergistic combination with synthetic antimicrobials as well as by applying cellulose as a drug carrier. Using checkerboard assays, we determined that both extracts presented synergistic interactions with amoxicillin (AMX) and 3-bromopyruvate (3-BP) (FICI = 0.5) and additive relationships with sertraline (SER) (FICI = 0.75). The antibiofilm activity of extracts and their combinations with AMX, 3-BP, or SER, was analyzed by two methods, i.e., the microcapillary overgrowth under flow conditions (the Bioflux system) and assessment of the viability of lawn biofilms after exposure to drugs released from bacterial cellulose (BC) carriers. Using both methods, we observed a several-fold decrease in the level of H. pylori biofilm, indicating the ability of the tested compounds to eradicate the microbial biofilm. The obtained results indicate that application of plant-derived extracts from the Papaveraceae family combined with synthetic antimicrobials, absorbed into organic BC carrier, may be considered a promising way of fighting biofilm-forming H. pylori

Sustainable use of marine biodiversity as source of novel anti-biofilm agents in industrial and clinical settings

Amongst marine bacteria, cold-adapted microorganisms represent an untapped reservoir of biodiversity endowed with an interesting chemical repertoire able to synthesize a broad range of potentially valuable bioactive compounds, including antimicrobial activity. The rapid emergence of resistant bacteria is occurring worldwide, endangering the efficacy of antibiotics. One of the main causes of antibiotic resistance is the capability of microorganisms to associate into communities of cells called biofilms. These complex structures provide protection from potential stressors, including the lack of water, high or low pH, or the presence of substances toxic to microorganisms such as antibiotics, antimicrobials or heavy metals. Therefore, coordinated efforts to implement the arsenal of novel anti-infective treatments are greatly needed. In this contest, my PhD project aimed to the sustainable exploitation of Polar marine biodiversity in an attempt to find viable sources of novel anti-biofilm agents, in particular acting against Staphylococcus epidermidis, one of the most common causes of infections associated with medical devices. In detail, during the first part of my project, I focused on the study of the Antarctic marine bacterium Pseudoalteromonas haloplanktis TAC125 and of its ability to produce anti-biofilm molecules, then, on the purification, identification and characterization of the active molecule produced. By setting up of a strategy for the large scale biofilm cultivation of the Antarctic bacterium, the production yield of P. haloplanktis TAC125 anti-biofilm agent was improved, so as to allow the purification and the identification of the active molecule, the pentadecanal. However, as the pentadecanal is a chemically reactive agent, it could easily undergo oxidation reactions, therefore it could not be suitable for all possible anti-biofilm strategies. Therefore, some chemical analogues were synthesized and characterized for their anti-biofilm activity and their possible use in combination with antibiotics were investigated. Then, as a possible clinical application, an anti-biofilm coating system, active against S. epidermidis, was developed, by physical adsorption of pentadecanal and its analogues on polydimethylsiloxane (PDMS), a silicon-based material commonly used for the manufacturing of medical devices. Finally, some physiological studies were dedicated to P. haloplanktis TAC125 biofilm formation in relation with environmental adaptations, with the purpose to explore the potentiality of P. haloplanktis TAC125 in biotechnological field. In the second part of my PhD project, given their only partially explored potential, I have also studied other Polar bacteria belonging to different genera, looking for novel anti-biofilm agents against S. epidermidis. Through the screening of small metabolites and proteins/peptides libraries designed starting from planktonic cultures of Polar bacteria, some promising producer strains were identified and their anti-biofilm activities were characterized. Preliminary purification protocols were set up for each kind of molecules, according to their physico-chemical characteristics. Further studies are still ongoing to identify the structure of the active molecules

Bacterial nanocellulose enables auxetic supporting implants

Owing to its purity and exceptional mechanical performance, bacterial nanocellulose (BNC) is well suited for tissue engineering applications. BNC assembles as a network that features similarities with the extracellular matrix (ECM) while exhibiting excellent integrity in the wet state, suitable for suturing and sterilization. The development of complex 3D forms is shown by taking advantage of the aerobic process involved in the biogenesis of BNC at the air/culture medium interphase. Hence, solid supports are used to guide the formation of BNC biofilms that easily form auxetic structures. Such biomaterials are demonstrated as implantable meshes with prescribed opening size and infill density. The measured mechanical strength is easily adjustable (48-456 MPa tensile strength) while ensuring shape stability (>87% shape retention after 100 burst loading/unloading cycles). We further study the cytotoxicity, monocyte/macrophage pro-inflammatory activation, and phenotype to demonstrate the prospective use of BNC as supportive implants with long-term comfort and minimal biomaterial fatigue.Peer reviewe

Enterobacter Sakazakii Growth Profile and Tolerance to Chlorine Sanitizers

Enterobacter sakazakii is considered an emerging opportunistic pathogen associated with sporadic life-threatening bacterial infections in neonates linked to the compsumption of contaminated infant formula [Stoll et al., 2004]. In 2001 a neonate fatal infection associated with the presence of E. sakazakii in infant formula occurred in the neonatal intensive care unit (NICU) of the University of Tennessee Hospital [Himelright et al., 2002], as a result of this outbreak, the hospital made several policy changes and requested the Food Safety Center of Excellence of University of Tennessee to analyze the growth pattern of this microorganism at the conditions maintained in the hospital. The objective of this study was to analize E. sakazakii growth profile during preparation and administration of formula, as well as E. sakazakii tolerance to chlorine sanitizers widely used in hospital settings.Our results showed that if the starting temperature of the formula at the time of administration was 6 oC, the formula reached 25 oC in a period of four hours. Once contaminated formula reach 25 oC the generation times can decrease to less than one hour. We also noted that cells organized in colonies or in contact with solid surfaces had a higher resistance to chlorine sanitizers than those of planktonic cells, this phenomena could be explained by the expression of genes triggered by the physical contact between cell and surface