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Salmonella enterica serovar Rissen ( S. Rissen) is an emerging causative agent of foodborne diseases. The current emergence of antibiotic resistance makes necessary alternative therapeutic strategies. In this study, we investigated the potential of a phage-resistant strain of S. Rissen (R R ) as a tool for developing an effective lipopolysaccharide (LPS)-based vaccine. The LPS O-antigen is known to play critical roles in protective immunity against Salmonella . However, the high toxicity of the LPS lipid A moiety limits its use in vaccines. Here, we demonstrated that the acquisition of bacteriophage resistance by S. Rissen leads to structural modifications in the LPS structure. Using NMR and mass spectrometry, we characterized the LPS from phage-resistant strains as a smooth variant bearing under-acylated Lipid A portions (penta- and tetra-acylated forms). We then combined RT-qPCR and NMR-based metabolomics to explore the effects of phage resistance and LPS modification on bacterial fitness and virulence. Finally, we conducted in vivo studies to determine whether lysogeny-induced remodeling of LPS affects the host immune response. Results revealed that the under-acylated variant of LPS from R R attenuates the inflammatory response in BALB/c mice, while eliciting a specific antibody response that protects against S. Rissen (R W ) infection. In conclusion, our findings suggest that phage resistance, through lipid A modification, may offer a novel strategy for reducing LPS toxicity, highlighting its potential as a promising biological approach for developing LPS-based vaccines against Salmonella infections., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Cuomo, Medaglia, Casillo, Gentile, Fruggiero, Corsaro and Capparelli.)

Microbial biofilm formation on medical devices paves the way for device-associated infections. Staphylococcus epidermidis is one of the most common strains involved in such infections as it is able to colonize numerous devices, such as intravenous catheters, prosthetic joints, and heart valves. We previously reported the antibiofilm activity against S. epidermidis of pentadecanoic acid (PDA) deposited by drop-casting on the silicon-based polymer poly(dimethyl)siloxane (PDMS). This material exerted an antibiofilm activity by releasing PDA; however, a toxic effect on bacterial cells was observed, which could potentially favor the emergence of resistant strains. To develop a PDA-functionalized material for medical use and overcome the problem of toxicity, we produced PDA-doped PDMS by either spray-coating or PDA incorporation during PDMS polymerization. Furthermore, we created a strategy to assess the kinetics of PDA release using ADIFAB, a very sensitive free fatty acids fluorescent probe. Spray-coating resulted in the most promising strategy as the concentration of released PDA was in the range 0.8-1.5 μM over 21 days, ensuring long-term effectiveness of the antibiofilm molecule. Moreover, the new coated material resulted biocompatible when tested on immortalized human keratinocytes. Our results indicate that PDA spray-coated PDMS is a promising material for the production of medical devices endowed with antibiofilm activity.

Mixtures containing β-glucans were extracted from barley, under both mild and high alkaline conditions, to prepare biodegradable films (MA and HA, respectively), as natural dressings with intrinsic therapeutic properties. An in-depth characterization was performed to evaluate the impact of mild and high alkaline conditions on chemical, physicochemical, and biological features for potential use in wound treatments. Both MA and HA films exhibited a good ability to absorb water and simulate wound fluid, which helps maintain optimal tissue hydration. Moreover, their oxygen permeability (147.6 and 16.4 cm 3  × μm/m 2  × 24 h × Pa × 10 7 , respectively) appeared adequate for the intended application. Biocompatibility tests showed that the films do not harm human dermal fibroblasts. Impressively, they promote cell attachment and growth, with MA having a stronger effect due to its higher β-glucan content. Furthermore, MA films can modulate macrophage behaviour in an inflamed microenvironment, reducing oxidative stress and pro-inflammatory cytokines, while simultaneously increasing levels of anti-inflammatory cytokines. In a scratch test, HA films allowed for faster fibroblast migration within the first 16 h compared to MA. Overall, this study demonstrates that developing β-glucan based films from barley, through a sustainable and cost-effective process, holds great promise for skin applications. These films exhibit significant potential to promote wound healing and modulate inflammation., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier B.V.)

In marine ecosystems, communication among microorganisms is crucial since the distance is significant if considered on a microbial scale. One of the ways to reduce this gap is through the production of extracellular vesicles, which can transport molecules to guarantee nutrients to the cells. Marine bacteria release extracellular vesicles (EVs), small membrane-bound structures of 40 nm to 1 µm diameter, into their surrounding environment. The vesicles contain various cellular compounds, including lipids, proteins, nucleic acids, and glycans. EVs may contribute to dissolved organic carbon, thus facilitating heterotroph growth. This review will focus on marine bacterial EVs, analyzing their structure, composition, functions, and applications.

Introduction: B. animalis subsp. lactis HN019 is a commercially available well-characterized probiotic with documented effects on human health, such as the ability to enhance the immune function and to balance the intestinal microbiome. Therefore, optimizing the manufacturing process to improve sustainability, increasing biomass yields and viability, and avoiding animal -derived nutrients in the medium to meet vegan consumer's needs, is currently of interest. Besides the established use of live probiotic cells, alternative supplements indicated as postbiotics, like non-viable cells and/or probiotics derived bioactive molecules might be considered as potential next generation biotherapeutics. In fact, advantages of postbiotics include fewer technological limitations, such as easier production processes and scale-up, and even higher specificity. Methods: In this work, medium design together with different fermentation strategies such as batch, fed-batch and in situ product removal on lab-scale bioreactors were combined. Medium pretreatment by ultrafiltration and protease digestion was performed to reduce polysaccharidic contaminants and facilitate the purification of secreted exopolysaccharides (EPS). The latter were isolated from the fermentation broth and characterized through NMR, GC-MS and SEC-TDA analyses. The expression of TLR-4, NF-kb and IL-6 in LPS challenged differentiated CaCo-2 cells treated with EPS, live and heat-killed B. lactis cells/broth, was evaluated in vitro by western blotting and ELISA. Zonulin was also assessed by immunofluorescence assays. Results and Discussion: The titer of viable B. lactis HN019 was increased up to 2.9 ± 0.1 x 10 10 on an animal-free semidefined medium by applying an ISPR fermentation strategy. Medium pre-treatment and a simple downstream procedure enriched the representativity of the EPS recovered (87%), the composition of which revealed the presence of mannuronic acid among other sugars typically present in polysaccharides produced by bifidobacteria. The isolated EPS, live cells and whole heat inactivated broth were compared for the first up to date for their immunomodulatory and anti-inflammatory properties and for their ability to promote intestinal barrier integrity. Interestingly, EPS and live cells samples demonstrated immune-stimulating properties by downregulating the expression of TLR-4 and NF-kb, and the ability to promote restoring the integrity of the intestinal barrier by up-regulating the expression of zonulin, one of the tight junctions forming proteins. Postbiotics in the form of heat killed broth only reduced NF-kb expression, whereas they did not seem effective in the other tested conditions., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. The author(s) declared that they were an editorial board member of Frontiers, at the time of submission. This had no impact on the peer review process and the final decision., (Copyright © 2024 D’ambrosio, Dabous, Sadiq, Casillo, Schiraldi, Cassese, Bedini, Corsaro and Cimini.)

Shewanella vesiculosa HM13 is a Gram-negative bacterium able to produce a large amount of extracellular membrane vesicles. These nanoparticles carry a major protein P49, the loading of which seems to be influenced by the glycans decorating the membrane. Here we report the structural characterization, using chemical analyses and NMR spectroscopy, of the capsular polysaccharides isolated from the nfnB-mutant strain of S. vesiculosa HM13, which is unable to load P49 on the membrane vesicles. In addition to the polysaccharide corona isolated and characterized from the parental strain, the nfnB-mutant strain released another polysaccharide composed of disaccharide repeating units having the following structure. →4)-β-D-Glc-(1 → 3)-β-D-GlcNAc-(1→., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests:Maria Michela Corsaro reports financial support was provided by Italian Ministry of University and Research, PNRR. If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier Ltd.)

Pseudomonas strain 2ASCA isolated in subarctic Québec, Canada, produced a cell membrane bound levan-type exopolymer (yield 1.17 g/L), after incubation in growth media containing 6 % sucrose (w/v) at temperature of 15 °C for 96 h. The objective of this study was to optimize levan production by varying the growth parameters. Moreover, the polymer's chemical characterization has been studied with the aim of increasing knowledge and leading to future applications in many fields, including heavy metal remediation. Higher levan yields (7.37 g/L) were reached by setting up microbial fermentation conditions based on the re-use of the molasses obtained from sugar beet processing. Spectroscopy analyses confirmed the levan-type nature of the exopolymer released by strain 2ASCA, consisting of a β-(2,6)-linked fructose repeating unit. Gel permeation chromatography revealed that the polymer has a molecular weight of 13 MDa. Scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS) showed that the levan sequestered with a strong affinity Cr(III), which has never been previously reported, highlighting an interesting biosorption potential. In addition, SEM analysis revealed the formation of nanoparticles in acidified water solution., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier B.V. All rights reserved.)

The opportunistic human fungal pathogen Candida albicans produces and releases into the surrounding medium extracellular vesicles (EVs), which are involved in some processes as communication between fungal cells and host-pathogen interactions during infection. Here, we have conducted the isolation of EVs produced by a clinical isolate of C. albicans during biofilm formation and proved their effect towards the ability of the Gram-negative bacterial pathogen Klebsiella pneumoniae to adhere to HaCaT cells and form a biofilm in vitro. The results represent the first evidence of an antagonistic action of fungal EVs against bacteria.

This study investigated the antibiofilm activity of water-soluble extracts obtained under different pH conditions from Cannabis sativa seeds and from previously defatted seeds. The chemical composition of the extracts, determined through GC-MS and NMR, revealed complex mixtures of fatty acids, monosaccharides, amino acids and glycerol in ratios depending on extraction pH. In particular, the extract obtained at pH 7 from defatted seeds (Ex7d) contained a larger variety of sugars compared to the others. Saturated and unsaturated fatty acids were found in all of the analysed extracts, but linoleic acid (C18:2) was detected only in the extracts obtained at pH 7 and pH 10. The extracts did not show cytotoxicity to HaCaT cells and significantly inhibited the formation of Staphylococcus epidermidis biofilms. The exception was the extract obtained at pH 10, which appeared to be less active. Ex7d showed the highest antibiofilm activity, i.e., around 90%. Ex7d was further fractionated by HPLC, and the antibiofilm activity of all fractions was evaluated. The 2D-NMR analysis highlighted that the most active fraction was largely composed of glycerolipids. This evidence suggested that these molecules are probably responsible for the observed antibiofilm effect but does not exclude a possible synergistic contribution by the other components.

Here, an unprecedented biorefinery approach has been designed to recover high-added value bioproducts starting from the culture of Porphyridium cruentum . This unicellular marine red alga can secrete and accumulate high-value compounds that can find applications in a wide variety of industrial fields. 300 ± 67 mg/L of exopolysaccharides were obtained from cell culture medium; phycoerythrin was efficiently extracted (40% of total extract) and isolated by single chromatography, with a purity grade that allowed the crystal structure determination at 1.60 Å; a twofold increase in β-carotene yield was obtained from the residual biomass; the final residual biomass was found to be enriched in saturated fatty acids. Thus, for the first time, a complete exploitation of P. cruentum culture was set up., Competing Interests: The authors declare no competing financial interest., (© 2022 The Authors. Published by American Chemical Society.)

Bacterial extracellular membrane vesicles (EMVs) play an active role in many physiological and pathogenic processes. Here, we report the identification and the detailed structural characterization of the capsular polysaccharide from both cells and EMVs from Shewanella vesiculosa by NMR and chemical analysis. The polysaccharide consists of a pentasaccharide repeating unit containing neutral monosaccharides together with amino sugars, of which one has never been isolated from a natural source. The adhesion ability of the polymer both on synthetic surfaces, such as polystyrene nanoparticles and on vesicles with a bilayer mimicking the bacterial membrane in the presence and absence of lipopolysaccharide was investigated. In both cases, a "CPS-corona" that could be the first stage of biofilm formation was observed. The polymer also activates Caspases on colon cancer cells, making S. vesiculosa EMVs as natural nanocarriers for drug delivery., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

The development of new approaches to prevent microbial surface adhesion and biofilm formation is an emerging need following the growing understanding of the impact of biofilm-related infections on human health. Staphylococcus epidermidis , with its ability to form biofilm and colonize biomaterials, represents the most frequent causative agent involved in infections of medical devices. In the research of new anti-biofilm agents against S. epidermidis biofilm, Antarctic marine bacteria represent an untapped reservoir of biodiversity. In the present study, the attention was focused on Psychrobacter sp . TAE2020, an Antarctic marine bacterium that produces molecules able to impair the initial attachment of S. epidermidis strains to the polystyrene surface. The setup of suitable purification protocols allowed the identification by NMR spectroscopy and LC-MS/MS analysis of a protein-polysaccharide complex named CATASAN. This complex proved to be a very effective anti-biofilm agent. Indeed, it not only interferes with cell surface attachment, but also prevents biofilm formation and affects the mature biofilm matrix structure of S. epidermidis . Moreover, CATASAN is endowed with a good emulsification activity in a wide range of pH and temperature. Therefore, its use can be easily extended to different biotechnological applications.

Several Levilactobacillus brevis strains have the potential to be used as probiotics since they provide health benefits due to the interaction of live cells, and of their secreted products, with the host (tissues). Therefore, the development of simple fermentation processes that improve cell viability to reduce industrial production costs, and at the same time the characterization and biological evaluation of cell-free postbiotics that can further promote application, are of great interest. In the present study, small scale batch fermentations on semi defined media, deprived of animal derived raw materials, were used to optimize growth of L. brevis SP48, reaching 1.2 ± 0.4 × 10 10  CFU/ml of viable cells after 16 h of growth. Displacement, competition, and inhibition assays compared the effect, on Helicobacter pylori , of L. brevis cells to that of its partially purified potentially postbiotic fraction rich in exopolysaccharides and proteins. The expression of pro and anti-inflammatory biochemical markers indicated that both samples activated antimicrobial defenses and innate immunity in a gastric model. Moreover, these compounds also acted as modulators of the inflammatory response in a gut in vitro model. These data demonstrate that the high molecular weight compounds secreted by L. brevis SP48 can contrast H. pylori and reduce inflammation related to intestinal bowel disease, potentially overcoming issues related to the preservation of probiotic viability., Competing Interests: AMG is employed by the company R&D—IBSA Farmaceutici Italia. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Cimini, D’ambrosio, Stellavato, Fusco, Corsaro, Dabous, Casillo, Donnarumma, Giori and Schiraldi.)

Probiotics are living microorganisms that give beneficial health effects while consumed, and each strain possesses diverse and unique properties and also different technological characteristics that affect its ability to be produced at large scale. Limosilactobacillus fermentum is a widely studied member of probiotics, however, few data are available on the development of fermentation and downstream processes for the production of viable biomasses for potential industrial applications. In the present study a novel L. fermentum strain was isolated from buffalo milk and used as test example for biotechnological process development. The strain was able to produce up to 10 9 CFU/mL on a (glucose based) semi-defined medium deprived of animal-derived raw materials up to the pilot scale (150 L), demonstrating improved results compared to commonly used, although industrially not suitable, media rich of casein and beef extract. The study of strain behavior in batch experiments indicated that the highest concentration of viable cells was reached after only 8 h of growth, greatly shortening the process. Moreover, initial concentrations of glucose in the medium above 30 g/L, if not supported by higher nitrogen concentrations, reduced the yield of biomass and increased production of heterolactic fermentation by-products. Biomass concentration via microfiltration on hollow fibers, and subsequent spray-drying allowed to recover about 5.7 × 10 10 CFU/g powder of viable cells, indicating strain resistance to harsh processing conditions. Overall, these data demonstrate the possibility to obtain and maintain adequate levels of viable L. fermentum cells by using a simple approach that is potentially suitable for industrial development. Moreover, since often exopolysaccharides produced by lactobacilli contribute to the strain's functionality, a partial characterization of the EPS produced by the newly identified L. fermentum strain was carried out. Finally, the effect of L. fermentum versus H. pylori in a gastric epithelial cell model was evaluated demonstrating its ability to stimulate the response of the immune system and displace the infective agent., Competing Interests: The authors declare non conflict of interest., (© 2022 The Authors. Published by Elsevier B.V.)

Colwellia psychrerythraea 34H is a marine Gram-negative psychrophile; it was isolated from Arctic marine sediments, but it is considered cosmopolitan in cold environments. This microorganism is considered a model to study adaptive strategies to sub-zero temperatures, and its lifestyle has been the object of numerous studies. In the last few years, we focused our studies on the glycoconjugates produced by C. psychrerythraea 34H at 4°C, resulting in the isolation and characterization of very interesting molecules. It produces an unusual lipooligosaccharide molecule and both capsular and medium released polysaccharides. In this study, we described the response of these glycoconjugates in terms of production and chemical structure produced by C. psychrerythraea 34H grown in planktonic conditions at -2, 4, and 8°C. The glycopolymers have been detected by chemical methods and spectroscopic analyses. Moreover, the glycopolymer content of the biofilm matrix of C. psychrerythraea 34H has been evaluated, through confocal microscopy and glycosyl analysis. The results highlighted that C. psychrerythraea 34H adjusts both the production and the typology of its glyconjugates in response to temperature fluctuations., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Casillo, D’Angelo, Parrilli, Tutino and Corsaro.)

Among the widespread malignancies colorectal cancer is the most lethal. Treatments of this malignant tumor include surgery for lesions and metastases, radiotherapy, immunotherapy, and chemotherapy. Nevertheless, novel therapies to reduce morbidity and mortality are demanding. Natural products, such as polysaccharides, can be a valuable alternative to sometimes very toxic chemotherapeutical agents, also because they are biocompatible and biodegradable biomaterials. Microbial polysaccharides have been demonstrated to fulfill this requirement. In this paper, the results about the structure and the activity of a capsular polysaccharide isolated from the psychrotroph Pseudoalteromonas nigrifaciens Sq02-Rif r , newly isolated from the fish intestine, have been described. The characterization has been obtained by spectroscopic and chemical methods, and it is supported by the bioinformatic analysis. The polymer activates Caspases 3 and 9 on colon cancer cells CaCo-2 and HCT-116, indicating a promising antitumor effect, and suggesting a potential capacity of CPS to induce apoptosis., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Aeromonas species are found in the aquatic environment, drinking water, bottled mineral water, and different types of foods, such as meat, fish, seafood, or vegetables. Some of these species are primary or opportunistic pathogens for invertebrates and vertebrates, including humans. Among the pathogenic factors associated with these species, there are the lipopolysaccharides (LPSs). LPSs are the major components of the external leaflet of Gram-negative bacterial outer membrane. LPS is a glycoconjugate, generally composed of three portions: lipid A, core oligosaccharide, and O-specific polysaccharide or O-antigen. The latter, which may be present (smooth LPS) or not (rough LPS), is the most exposed part of the LPS and is involved in the pathogenicity by protecting infecting bacteria from serum complement killing and phagocytosis. The O-antigen is a polymer of repeating oligosaccharide units with high structural variability, particularly the terminal sugar, that confers the immunological specificity to the O-antigen. In this study, we established the structure of the O-chain repeating unit of the LPS from Aeromonas bivalvium strain 868 E T (=CECT 7113 T = LMG 23376 T ), a mesophilic bacterium isolated from cockles ( Cardium sp.) and obtained from a retail market in Barcelona (Spain), whose biosynthesis core LPS cluster does not contain the waaE gene as most of Aeromonas species. After mild acid hydrolysis, the lipid A was removed by centrifugation and the obtained polysaccharide was fully characterized by chemical analysis and NMR spectroscopy. The polymer consists of a heptasaccharide repeating unit containing D-GalNAc, L-Rha, D-GlcNAc, and D-FucNAc residues.

Lipopolysaccharides (LPS) are surface glycoconjugates embedded in the external leaflet of the outer membrane (OM) of the Gram-negative bacteria. They consist of three regions: lipid A, core oligosaccharide (OS), and O-specific polysaccharide or O-antigen. Lipid A is the glycolipid endotoxin domain that anchors the LPS molecule to the OM, and therefore, its chemical structure is crucial in the maintenance of membrane integrity in the Gram-negative bacteria. In this paper, we reported the characterization of the lipid A and OS structures from Pseudoalteromonas nigrifaciens Sq02-Rif r , which is a psychrotrophic Gram-negative bacterium isolated from the intestine of Seriola quinqueradiata . The immunomodulatory activity of both LPS and lipid A was also examined.

The ability to form biofilms is a common feature of microorganisms, which can colonize a variety of surfaces, such as host tissues and medical devices, resulting in infections highly resistant to conventional drugs. This aspect is particularly critical in polymicrobial biofilms involving both fungi and bacteria, therefore, to eradicate such severe infections, new and effective anti-biofilm strategies are needed. The efficacy of pentadecanal and pentadecanoic acid as anti-biofilm agents has been recently reported against different bacterial strains. Their chemical similarity with diffusible signal factors (DSFs), plus the already known ability of fatty acids to act as anti-biofilm agents, suggested to explore their use against Candida albicans and Klebsiella pneumoniae mixed biofilm. In this work, we demonstrated the ability of both molecules to prevent the formation and destabilize the structure of the dual-species biofilm. Moreover, the pentadecanoic acid anti-biofilm coating, previously developed through the adsorption of the fatty acid on polydimethylsiloxane (PDMS), was proved to prevent the polymicrobial biofilm formation in dynamic conditions by confocal laser scanning microscopy analysis. Finally, the evaluation of the expression levels of some biofilm-related genes of C. albicans and K. pneumoniae treated with pentadecanoic acid provided some insights into the molecular mechanisms underpinning its anti-biofilm effect., Competing Interests: Declaration of competing interest All authors declare that they have no conflict of interest., (Copyright © 2021 The Author(s). Published by Elsevier Masson SAS.. All rights reserved.)

One of the major issues for the microbial production of polyhydroxyalkanoates (PHA) is to secure renewable, non-food biomass feedstocks to feed the fermentation process. Inulin, a polydisperse fructan that accumulates as reserve polysaccharide in the roots of several low-requirement crops, has the potential to face this challenge. In this work, a "substrate facilitator" microbial consortium was designed to address PHA production using inulin as feedstock. A microbial collection of Bacillus species was screened for efficient inulinase producer and the genome of the selected strain, RHF15, identified as Bacillus gibsonii, was analysed unravelling its wide catabolic potential. RHF15 was co-cultured with Cupriavidus necator, an established PHA producer, lacking the ability to metabolize inulin. A Central Composite Rotary Design (CCRD) was applied to optimise PHA synthesis from inulin by the designed artificial microbial consortium, assessing the impact of species inoculum ratio and inulin and N-source concentrations. In the optimized conditions, a maximum of 1.9 g L -1 of Polyhydroxybutyrate (PHB), corresponding to ~80% (g polymer /g CDW ) polymer content was achieved. The investigated approach represents an effective process optimization method, potentially applicable to the production of PHA from other complex C- sources., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Pseudomonas aeruginosa is an opportunistic pathogen often involved in airway infections of cystic fibrosis (CF) patients. Its pathogenicity is related to several virulence factors, such as biofilm formation, motility and production of toxins and proteases. The expression of these virulence factors is controlled by quorum sensing (QS). Thus, QS inhibition is considered a novel strategy for the development of antipathogenic compounds acting on specific bacterial virulence programs without affecting bacterial vitality. In this context, cold-adapted marine bacteria living in polar regions represent an untapped reservoir of biodiversity endowed with an interesting chemical repertoire. In this paper, we investigated the biological activity of a supernatant derived from a novel Antarctic bacterium (SN_TAE2020) against specific virulence factors produced by P. aeruginosa strains isolated from FC patients. Our results clearly show a reduction in pyocyanin and protease production in the presence of SN_TAE2020. Finally, SN_TAE2020 was also able to strongly affect swarming and swimming motility for almost all tested strains. Furthermore, the effect of SN_TAE2020 was investigated on biofilm growth and texture, captured by SEM analysis. In consideration of the novel results obtained on clinical strains, polar bacteria might represent potential candidates for the discovery of new compounds limiting P. aeruginosa virulence in CF patients.

Extracellular polysaccharides are widely produced by bacteria, yeasts, and algae. These polymers are involved in several biological functions, such as bacteria adhesion to surface and biofilm formation, ion sequestering, protection from desiccation, and cryoprotection. The chemical characterization of these polymers is the starting point for obtaining relationships between their structures and their various functions. While this fundamental correlation is well reported and studied for the proteins, for the polysaccharides, this relationship is less intuitive. In this paper, we elucidate the chemical structure and conformational studies of a mannan exopolysaccharide from the permafrost isolated bacterium Psychrobacter arcticus strain 273-4. The mannan from the cold-adapted bacterium was compared with its dephosphorylated derivative and the commercial product from Saccharomyces cerevisiae . Starting from the chemical structure, we explored a new approach to deepen the study of the structure/activity relationship. A pool of physicochemical techniques, ranging from small-angle neutron scattering (SANS) and dynamic and static light scattering (DLS and SLS, respectively) to circular dichroism (CD) and cryo-transmission electron microscopy (cryo-TEM), have been used. Finally, the ice recrystallization inhibition activity of the polysaccharides was explored. The experimental evidence suggests that the mannan exopolysaccharide from P. arcticus bacterium has an efficient interaction with the water molecules, and it is structurally characterized by rigid-rod regions assuming a 14-helix-type conformation.

EPS-BMS, is to our knowledge, the first high molecular weight exopolysaccharide from potential probiotic Leuconostoc citreum-BMS strain that consists on a mixture of α-(1,6)-dextran branched at the third position and β-(2,6)-levan. This sample exhibited interesting rheological and emulsifying properties under different conditions. Steady shear experiments proved that EPS-BMS had a pseudoplastic behavior without thixotropic properties. Interestingly, pseudoplasticity was maintained even under stress conditions of temperature, pH and salts, which could provide some sensory properties for food products such as mouth feel. Dynamic oscillatory measurements reflected a liquid-like behavior of the sample regardless of the studied EPS concentration, pH, temperature and ionic force. Results related to the emulsifying as well as interfacial properties showed that EPS-BMS had great potential to be applied as emulsifier and/or emulsion stabilizer in both neutral and acidic conditions. Based on the properties reported in this work, EPS-BMS could be potentially applied in the food industry., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Xanthomonas campestris pv. campestris is known as the causative agent of black rot disease, which attacks mainly crucifers, severely lowering their global productivity. One of the main virulence factors of this pathogen is its capability to penetrate and form biofilm structures in the xylem vessels. The discovery of novel approaches to crop disease management is urgent and a possible treatment could be aimed at the eradication of biofilm, although anti-biofilm approaches in agricultural microbiology are still rare. Considering the multifactorial nature of biofilm, an effective approach against Xanthomonas campestris implies the use of a multi-targeted or combinatorial strategy. In this paper, an anti-biofilm strategy based on the use of fatty acids and the bacteriophage (Xccφ1)-hydroxyapatite complex was optimized against Xanthomonas campestris mature biofilm. The synergic action of these elements was demonstrated and the efficient removal of Xanthomonas campestris mature biofilm was also proven in a flow cell system, making the proposed approach an effective solution to enhance plant survival in Xanthomonas campestris infections. Moreover, the molecular mechanisms responsible for the efficacy of the proposed treatment were explored.

Functional foods and nutraceuticals frequently contain viable probiotic strains that, at certain titers, are considered to be responsible of beneficial effects on health. Recently, it was observed that secreted metabolites might play a key role in this respect, especially in immunomodulation. Exopolysaccharides produced by probiotics, for example, are used in the food, pharmaceutical, and biomedical fields, due to their unique properties. Lactobacillus brevis CD2 demonstrated the ability to inhibit oral pathogens causing mucositis and periodontal inflammation and to reduce Helycobacter pylori infections. Due to the lack of literature, for this strain, on the development of fermentation processes that can increase the titer of viable cells and associated metabolites to industrially attractive levels, different batch and fed-batch strategies were investigated in the present study. In particular, aeration was shown to improve the growth rate and the yields of lactic acid and biomass in batch cultures. The use of an exponential feeding profile in fed-batch experiments allowed to produce 9.3 ± 0.45 × 10 9  CFU/mL in 42 h of growth, corresponding to a 20-fold increase of viable cells compared with that obtained in aerated batch processes; moreover, also increased titers of exopolysaccharides and lactic acid (260 and 150%, respectively) were observed. A purification process based on ultrafiltration, charcoal treatment, and solvent precipitation was applied to partially purify secreted metabolites and separate them into two molecular weight fractions (above and below 10 kDa). Both fractions inhibited growth of the known gut pathogen, Salmonella typhimurium, demonstrating that lactic acid plays a major role in pathogen growth inhibition, which is however further enhanced by the presence of Lact. brevis CD2 exopolysaccharides. Finally, the EPS produced from Lact. brevis CD2 was characterized by NMR for the first time up to date.

Pseudomonas ANT_J38B is a Gram-negative bacterium isolated from an Antarctic island. LPS was extracted using the phenol/chloroform/petroleum ether method. A mild acid hydrolysis followed by a gel filtration purification afforded the O-chain. The polysaccharide was characterized by means of chemical analyses and NMR spectroscopy. The O-chain displays a disaccharide repeating unit with the following backbone: →4)-α-l-GulpNAc3OAcAN-(1 →3)-β-d-QuipNAc-(1→ ., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Based on Plackett-Burman design, steepest ascent method, and Box-Behnken design, statistical optimization for B. subtilis AF17 for levan production was carried out. Sucrose, tryptone and initial pH were found to be the most significant parameter (P < 0.05) for levan production. Result showed that the optimum condition was sucrose 162.5 g/L, tryptone 10 g/L, initial pH 7 and maximum yield was 7.9 ± 0.18 g/L in 72 h fermentation. Purified levan was characterized using various physicochemical techniques such as GC-MS, 1 H NMR, 13 C NMR spectroscopy and SEC/TDA. Based on this data, the structure of levan was independent of initial culture conditions. The biomedical potential of the isolated Bacillus subtilis A17 levan for its angiotensin-I converting enzyme (ACE) inhibition activities was exploited in vitro. Interestingly, levan possessed an important angiotensin I converting enzyme (ACE) inhibitory 81.1 ± 4.1% at 4 mg/mL. The overall, data suggested that levan presents a promising natural source of antihypertensive agents., Competing Interests: Declaration of competing interest The authors have no conflict of interest to declare., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Bacterial extracellular membrane vesicles (EMVs) are membrane-bound particles released during cell growth by a variety of microorganisms, among which are cold-adapted bacteria. Shewanella vesiculosa HM13, a cold-adapted Gram-negative bacterium isolated from the intestine of a horse mackerel, is able to produce a large amount of EMVs. S. vesiculosa HM13 has been found to include a cargo protein, P49, in the EMVs, but the entire mechanism in which P49 is preferentially included in the vesicles has still not been completely deciphered. Given these premises, and since the structural study of the components of the EMVs is crucial for deciphering the P49 transport mechanism, in this study the complete characterization of the lipooligosaccharide (LOS) isolated from the cells and from the EMVs of S. vesiculosa HM13 grown at 18 °C is reported. Both lipid A and core oligosaccharide have been characterized by chemical and spectroscopic methods., Competing Interests: The authors declare no conflicts of interest.