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Abstract The biofilm matrix is a fortress; sheltering bacteria in a protective and nourishing barrier that allows for growth and adaptation to various surroundings. A variety of different components are found within the matrix including water, lipids, proteins, extracellular DNA, RNA, membrane vesicles, phages, and exopolysaccharides. As part of its biofilm matrix, Pseudomonas aeruginosa is genetically capable of producing three chemically distinct exopolysaccharides – alginate, Pel, and Psl – each of which has a distinct role in biofilm formation and immune evasion during infection. The polymers are produced by highly conserved mechanisms of secretion, involving many proteins that span both the inner and outer bacterial membranes. Experimentally determined structures, predictive modelling of proteins whose structures are yet to be solved, and structural homology comparisons give us insight into the molecular mechanisms of these secretion systems, from polymer synthesis to modification and export. Here, we review recent advances that enhance our understanding of P. aeruginosa multiprotein exopolysaccharide biosynthetic complexes, and how the glycoside hydrolases/lyases within these systems have been commandeered for antimicrobial applications. This comprehensive review highlights recent advances in the field of Pseudomonas aeruginosa biofilm exopolysaccharide biosynthesis and discusses the potential use of glycoside hydrolases for antibiofilm therapies.

Bacteria produce various polysaccharides with important biological functions and biotechnological applications. Polysaccharide synthesis is energy-costly and requires substrates that are in limited supply, raising the question of how bacteria regulate these pathways. Here, we explored the regulation of exopolysaccharide biosynthesis in Myxococcus xanthus . We demonstrate that the phosphorylated single-domain response regulator EpsW activates exopolysaccharide biosynthesis at the post-translational level by stimulating the activity of the phosphoglycosyl transferase EpsZ. By interacting with EpsZ, phosphorylated EpsW facilitates the formation of the active, dimeric conformation of EpsZ, thereby activating exopolysaccharide biosynthesis at its initial step. We propose that this previously unrecognized regulatory mechanism is broadly conserved, not only in myxobacteria but also beyond.

Bacterial biofilms are aggregation or collection of different bacterial cells which are covered by self-produced extracellular matrix and are attached to a substratum. Generally, under stress or in unfavorable conditions, free planktonic bacteria transform themselves into bacterial biofilms and become sessile. Involvement of quorum sensing and efflux pumps in antibiotic resistance in association with exopolysaccharides. Also, strategies to overcome or attack biofilms are provided.

Exopolysaccharide (EPS) show remarkable properties in various food applications. In this review paper, EPS composition, structural characterization, biosynthesis pathways, and recent advancements in the context of application of EPS-producing Lactobacillus spp. in different food industries are discussed. Various chemical and physical properties of Lactobacillus EPS, such as the structural, rheological, and shelf-life enhancement of different food products, are mentioned. Moreover, EPSs play a characteristic role in starter culture techniques, yogurt production, immunomodulation, and potential prebiotics. It has been seen that the wastes of fermented and non-fermented products are used as biological food for EPS extraction. The main capabilities of probiotics are the use of EPS for technological properties such as texture and flavor enhancement, juiciness, and water holding capacities of specific food products. For these reasons, EPSs are used in functional and fermented food products to enhance the healthy activity of the human digestive system as well as for the benefit of the food industry to lower product damage and increase consumer demand. Additionally, some pseudocereals such as amaranth and quinoa that produce EPS also play an important role in improving the organoleptic properties of food-grade products. In conclusion, more attention should be given to sustainable extraction techniques of LAB EPS to enhance structural and functional use in the developmental process of food products to meet consumer preferences.

Biofilms are complex microbial communities in which planktonic and dormant bacteria are enveloped in extracellular polymeric substances (EPS) such as exopolysaccharides, proteins, lipids, and DNA. These multicellular structures present resistance to conventional antimicrobial treatments, including antibiotics. The formation of biofilms raises considerable concern in healthcare settings, biofilms can exacerbate infections in patients and compromise the integrity of medical devices employed during treatment. Similarly, certain bacterial species contribute to bulking, foaming, and biofilm development in water environments such as wastewater treatment plants, water reservoirs, and aquaculture facilities. Additionally, food production facilities provide ideal conditions for establishing bacterial biofilms, which can serve as reservoirs for foodborne pathogens. Efforts to combat antibiotic resistance involve exploring various strategies, including bacteriophage therapy. Research has been conducted on the effects of phages and their individual proteins to assess their potential for biofilm removal. However, challenges persist, prompting the examination of refined approaches such as drug-phage combination therapies, phage cocktails, and genetically modified phages for clinical applications. This review aims to highlight the progress regarding bacteriophage-based approaches for biofilm eradication in different settings.

Abiotic stresses arising from climate change negates crop growth and yield, leading to food insecurity. Drought causes oxidative stress on plants, arising from excessive production of reactive oxygen species (ROS) due to inadequate CO2, which disrupts the photosynthetic machinery of plants. The use of conventional methods for the development of drought-tolerant crops is time-consuming, and the full adoption of modern biotechnology for crop enhancement is still regarded with prudence. Plant growth-promoting rhizobacteria (PGPR) could be used as an inexpensive and environmentally friendly approach for enhancing crop growth under environmental stress. The various direct and indirect mechanisms used for plant growth enhancement by PGPR were discussed. Synthesis of 1-aminocyclopropane−1-carboxylate (ACC) deaminase enhances plant nutrient uptake by breaking down plant ACC, thereby preventing ethylene accumulation, and enable plants to tolerate water stress. The exopolysaccharides produced also improves the ability of the soil to withhold water. PGPR enhances osmolyte production, which is effective in reducing the detrimental effects of ROS. Multifaceted PGPRs are potential candidates for biofertilizer production to lessen the detrimental effects of drought stress on crops cultivated in arid regions. This review proffered ways of augmenting their efficacy as bio-inoculants under field conditions and highlighted future prospects for sustainable agricultural productivity.

This study was designed to explore the different intestinal barrier repair mechanisms of Bifidobacterium breve (B. breve) H4-2 and H9-3 with different exopolysaccharide (EPS) production in mice with colitis. The lipopolysaccharide (LPS)-induced IEC-6 cell inflammation model and dextran sulphate sodium (DSS)-induced mice colitis model were used. Histopathological changes, epithelial barrier integrity, short-chain fatty acid (SCFA) content, cytokine levels, NF-κB expression level, and intestinal flora were analyzed to evaluate the role of B. breve in alleviating colitis. Cell experiments indicated that both B. breve strains could regulate cytokine levels. In vivo experiments confirmed that oral administration of B. breve H4-2 and B. breve H9-3 significantly increased the expression of mucin, occludin, claudin-1, ZO-1, decreased the levels of IL-6, TNF-α, IL-1β and increased IL-10. Both strains of B. breve also inhibited the expression of the NF-κB signaling pathway. Moreover, B. breve H4-2 and H9-3 intervention significantly increased the levels of SCFAs, reduced the abundance of Proteobacteria and Bacteroidea, and increased the abundance of Muribaculaceae. These results demonstrate that EPS-producing B. breve strains H4-2 and H9-3 can regulate the physical, immune, and microbial barrier to repair the intestinal damage caused by DSS in mice. Of the two strains, H4-2 had a higher EPS output and was more effective at repair than H9-3. These results will provide insights useful for clinical applications and the development of probiotic products for the treatment of colitis.

Exopolysaccharides (EPSs) are an important class of biopolymers with great ecological importance. In natural environments, they are a common feature of microbial biofilms, where they play key protective and structural roles. As the primary colonizers of constrained environments, such as desert soils and lithic and exposed substrates, cyanobacteria are the first contributors to the synthesis of the EPSs constituting the extracellular polymeric matrix that favors the formation of microbial associations with varying levels of complexity called biofilms. Cyanobacterial colonization represents the first step for the formation of biofilms with different levels of complexity. In all of the possible systems in which cyanobacteria are involved, the synthesis of EPSs contributes a structurally-stable and hydrated microenvironment, as well as chemical/physical protection against biotic and abiotic stress factors. Notwithstanding the important roles of cyanobacterial EPSs, many aspects related to their roles and the relative elicited biotic and abiotic factors have still to be clarified. The aim of this survey is to outline the state-of-the-art of the importance of the cyanobacterial EPS excretion, both for the producing cells and for the microbial associations in which cyanobacteria are a key component.

Background Bacterial biofilms are surface-adherent microbial communities in which individual cells are surrounded by a self-produced extracellular matrix of polysaccharides, extracellular DNA (eDNA) and proteins. Interactions among matrix components within biofilms are responsible for creating an adaptable structure during biofilm development. However, it is unclear how the interactions among matrix components contribute to the construction of the three-dimensional (3D) biofilm architecture. Results DNase I treatment significantly inhibited Bacillus subtilis biofilm formation in the early phases of biofilm development. Confocal laser scanning microscopy (CLSM) and image analysis revealed that eDNA was cooperative with exopolysaccharide (EPS) in the early stages of B. subtilis biofilm development, while EPS played a major structural role in the later stages. In addition, deletion of the EPS production gene epsG in B. subtilis SBE1 resulted in loss of the interaction between EPS and eDNA and reduced the biofilm biomass in pellicles at the air-liquid interface. The physical interaction between these two essential biofilm matrix components was confirmed by isothermal titration calorimetry (ITC). Conclusions Biofilm 3D structures become interconnected through surrounding eDNA and EPS. eDNA interacts with EPS in the early phases of biofilm development, while EPS mainly participates in the maturation of biofilms. The findings of this study provide a better understanding of the role of the interaction between eDNA and EPS in shaping the biofilm 3D matrix structure and biofilm formation.

Microalgae of the genus Porphyridium show great potential for large-scale commercial cultivation, as they accumulate large quantities of B-phycoerythrin (B-PE), long chain polyunsaturated fatty acids (LC-PUFAs) and exopolysaccharide (EPS). The present study aimed to adjust culture nitrogen concentrations to produce Porphyridium biomass rich in B-PE, LC-PUFAs and EPS. Porphyridium purpureum SCS-02 was cultured in ASW culture medium with low nitrogen supply (LN, 3.5 mM), medium nitrogen supply (MN, 5.9 mM) or high nitrogen supply (HN, 17.6 mM). HN significantly enhanced the accumulation of biomass, intracellular protein, B-PE and eicosapentaenoic acid. LN increased the intracellular carbohydrate and arachidonic acid content, and promoted the secretion of EPS. The total lipids content was almost unaffected by nitrogen concentration. Based on these results, a semi-continuous two-step process was proposed, which included the production of biomass rich in B-PE and LC-PUFAs with sufficient nitrogen, and induced EPS excretion with limited nitrogen and strong light.