Multitasking functions of bacterial extracellular DNA in biofilms.

Bacterial biofilms are intricate ecosystems of microbial communities that adhere to various surfaces and are enveloped by an extracellular matrix composed of polymeric substances. Within the context of bacterial biofilms, extracellular DNA (eDNA) originates from cell lysis or is actively secreted, where it exerts a significant influence on the formation, stability, and resistance of biofilms to environmental stressors. The exploration of eDNA within bacterial biofilms holds paramount importance in research, with far-reaching implications for both human health and the environment. An enhanced understanding of the functions of eDNA in biofilm formation and antibiotic resistance could inspire the development of strategies to combat biofilm-related infections and improve the management of antibiotic resistance. This comprehensive review encapsulates the latest discoveries concerning eDNA, encompassing its origins, functions within bacterial biofilms, and significance in bacterial pathogenesis.

EDTA-enhanced alkaline anaerobic fermentation of landfill leachate-derived waste activated sludge for short-chain fatty acids production: Metals chelation and EPSs destruction.

Alkaline anaerobic fermentation (AAF) of waste activated sludge (WAS) has been demonstrated to be promising for short-chain fatty acids (SCFAs) recovery. However, high-strength metals and EPSs in the landfill leachate-derived WAS (LL-WAS) would stabilize its structure, suppressing AAF performance. To improve sludge solubilization and SCFAs production, AAF was coupled with EDTA addition for LL-WAS treatment. The results show that sludge solubilization at AAF-EDTA was promoted by 62.8% than AAF, releasing 21.8% more soluble COD. The maximal SCFAs production of 477.4 mg COD/g VSS was thus achieved, i.e., 1.21 and 6.13 times those at AAF and the control, respectively. SCFAs composition was also improved with more acetic and propionic acids (80.8% versus 64.3%). Metals bridging EPSs were chelated by EDTA, which significantly dissolved metals from sludge matrix (e.g., 23.28 times higher soluble Ca than AAF). EPSs tightly bound with microbial cells were thus destructed (e.g., 4.72 times more protein release than alkaline treatment), causing an easier sludge disruption and subsequently a higher SCFAs production by hydroxide ions. These findings suggest an effective EDTA-supported AAF for metals and EPSs-rich WAS to recover carbon source.

The roles of extracellular polymeric substances of Pandoraea sp. XY-2 in the removal of tetracycline.

In this study, the roles of extracellular polymeric substances (EPSs) excreted by Pandoraea sp. XY-2 in the removal of tetracycline (TC) were investigated. In the early stage, TC in the solution was mainly removed by the adsorption of EPSs, which accounted for 20% of TC. Thereafter, large amount of TC was transported into the intracellular and biodegraded. EPSs was extracted and the contents of polyprotein and polysaccharides reached their maximum values (30.84 mg/g and 11.15 mg/g) in the first four days. Fourier transform infrared spectroscopy analysis revealed that hydroxyl, methylidyne, methylene and amide I groups in EPSs participated in the adsorption of TC. Furthermore, three-dimensional excitation-emission matrix fluorescence spectroscopy analysis revealed that TC caused the quenching of EPSs fluorescent groups. The quenching mechanism was attributed to static quenching and protein-like substances in EPSs from Pandoraea sp. XY-2 dominated the TC adsorption process. Bioinformatic analysis of Pandoraea sp. XY-2 genome identified multiple genes involved in exopolysaccharide synthesis and EPSs formation. The insights gained in this study might provide a better understanding about the adsorption process of EPSs in tetracycline-contaminated environment.

Optimization of Biosynthesis Conditions for the Production of Exopolysaccharides by Lactobacillus plantarum SP8 and the Exopolysaccharides Antioxidant Activity Test.

Lactobacillus plantarum SP8, isolated from traditional Chinese pickle juice, was utilized for the production of exopolysaccharides (EPSs), but the EPS yield was low under normal MRS medium. The single factor experiment and response surface methodology were used to optimize the medium components and culture conditions and the optimal conditions for EPS production were successfully obtained. Results showed that the optimum condition was glucose 22 g/L, yeast extract 30 g/L, fermentation temperature 35.6 °C, fermentation time 22 h and the theoretical EPS yield was 282.494 mg/L. The results were similar to the actual yield, 280.105 mg/L. By optimizing the culture conditions, the yield of L. plantarum SP8 EPS was improved by nearly 19 times. In the gas chromatography analysis, it was found that L. plantarum SP8 EPS consisted of d-rhamnose, arabinose, galactose, and d-acetylglucosamine, but glucose was not included, which was quite different from the reported heteropolysaccharide component of Lactobacillus. Furthermore, the antioxidant activity of L. plantarum SP8 EPS was evaluated with the in vitro scavenging abilities on DPPH·, O 2 - and ·OH. The in vitro antioxidant activity study indicated that L. plantarum SP8 EPS possessed certain antioxidant activity. All results demonstrated the potential of L. plantarum SP8 in the food and dairy industry.

Newly isolated marine bacterial exopolysaccharides enhance antitumor activity in HepG2 cells via affecting key apoptotic factors and activating toll like receptors.

Hepatocellular carcinoma (HCC) was accompanied by high incidence of morbidity and mortality worldwide. Apoptosis is a vital biological process playing a critical role in cancer. Besides, toll like receptors were reported to regulator the innate immune response against cancer development. Exopolysaccharides (EPSs) derived from marine bacteria were reported to have a potential biological importance. This work aimed to elucidate the antitumor effects of newly isolated EPSs against HepG2 cells. Moreover, their effects on some apoptotic markers and TLRs were followed. Isolated EPSs were tested for their cytotoxic effects in a previous study and the most promising; MSA1, E4, MGA2, SGA3, and NRC7 EPSs were subjected to molecular analysis to investigate their pro-apoptotic effects, in addition to their effects on TLR2 and TLR-9 using quantitative real time RT-PCR. And the most cytotoxic and pro-apoptotic EPS; MSA1 were subjected to antibody array analysis to investigate a panel of 43 apoptotic proteins. All isolated EPSs produced a positive role in regulating the apoptotic gene and increasing the TLRs expression in different manners. However, the most promising EPS was MSA1. It showed pro-apoptotic effects on gene and protein levels, besides its up-regulation of TLRs.

Quorum sensing: an emerging link between temperature and membrane biofouling in membrane bioreactors.

Lab-scale membrane bioreactors (MBRs) were investigated at 12, 18, and 25 °C to identify the correlation between quorum sensing (QS) and biofouling at different temperatures. The lower the reactor temperature, the more severe the membrane biofouling measured in terms of the transmembrane pressure (TMP) during filtration. More extracellular polymeric substances (EPSs) that cause biofouling were produced at 18 °C than at 25 °C, particularly polysaccharides, closely associated with QS via the production of N-acyl homoserine lactone (AHL). However, at 12 °C, AHL production decreased, but the release of EPSs due to deflocculation increased the soluble EPS concentration. To confirm the temperature effect related to QS, bacteria producing AHL were isolated from MBR sludge and identified as Aeromonas sp., Leclercia sp., and Enterobacter sp. through a 16S rDNA sequencing analysis. Batch assays at 18 and 25 °C showed that there was a positive correlation between QS through AHL and biofilm formation in that temperature range.

Agent-Based Recovery Model for Seismic Resilience Evaluation of Electrified Communities.

In this article, an agent-based framework to quantify the seismic resilience of an electric power supply system (EPSS) and the community it serves is presented. Within the framework, the loss and restoration of the EPSS power generation and delivery capacity and of the power demand from the served community are used to assess the electric power deficit during the damage absorption and recovery processes. Damage to the components of the EPSS and of the community-built environment is evaluated using the seismic fragility functions. The restoration of the community electric power demand is evaluated using the seismic recovery functions. However, the postearthquake EPSS recovery process is modeled using an agent-based model with two agents, the EPSS Operator and the Community Administrator. The resilience of the EPSS-community system is quantified using direct, EPSS-related, societal, and community-related indicators. Parametric studies are carried out to quantify the influence of different seismic hazard scenarios, agent characteristics, and power dispatch strategies on the EPSS-community seismic resilience. The use of the agent-based modeling framework enabled a rational formulation of the postearthquake recovery phase and highlighted the interaction between the EPSS and the community in the recovery process not quantified in resilience models developed to date. Furthermore, it shows that the resilience of different community sectors can be enhanced by different power dispatch strategies. The proposed agent-based EPSS-community system resilience quantification framework can be used to develop better community and infrastructure system risk governance policies.

Angle Sensor Module for Vehicle Steering Device Based on Multi-Track Impulse Ring.

In step with the development of Industry 4.0, research on automatic operation technology and components related to automobiles is continuously being conducted. In particular, the torque angle sensor (TAS) module of the steering wheel system is considered to be a core technology owing to its precise angle, torque sensing, and high-speed signal processing. In the case of conventional TAS modules, in addition to the complicated gear structure, there is an error in angle detection due to the backlash between the main and sub-gear. In this paper, we propose a multi-track encoder-based vehicle steering system, which is incorporated with a TAS module structure that minimizes the number of components and the angle detection error of the module compared with existing TAS modules. We also fabricated and tested an angle detection signal processing board and evaluated it on a test stand. As a result, we could confirm its excellent performance of an average deviation of 0.4° and applicability to actual vehicles by evaluating its electromagnetic interference (EMI) environmental reliability. The ultimate goal of the TAS module is to detect the target steering angle with minimal computation by the steering or main electronic control unit (ECU) to meet the needs of the rapidly growing vehicle technology. The verified angle detection module can be applied to an actual steering system in accordance with the mentioned technical requirements.

Auto-aggregation properties of a novel aerobic denitrifier Enterobacter sp. strain FL.

Enterobacter sp. strain FL was newly isolated from activated sludge and exhibited significant capability of auto-aggregation as well as aerobic denitrification. The removal efficiencies of NO3--N, total nitrogen (TN), and TOC by strain FL in batch culture reached 94.6, 63.9, and 72.5% in 24 h, respectively. The production of N2O and N2 in the presence of oxygen demonstrated the occurrence of aerobic denitrification. The auto-aggregation index of strain FL reached 54.3%, suggesting a high tendency that the cells would agglomerate into aggregates. The production of extracellular polymeric substances (EPSs), which were mainly composed of proteins followed by polysaccharides, was considered to be related to the cell aggregation according to Fourier transform infrared (FT-IR) and confocal laser scanning microscopy (CLSM). The proteins in EPS were evenly and tightly combined to cells and altered the protein secondary structures of cell surface from random coils to ß-sheets and three-turn helices. The alteration of protein secondary structures of cell surface caused by the proteins in EPS might play a dominant role in the auto-aggregation of strain FL. To further assess the feasibility of strain FL for synthetic wastewater treatment, a sequencing batch reactor (SBR), solely inoculated with strain FL, was conducted. During the 16 running cycles, the removal efficiency of NO3--N was 90.2-99.7% and the auto-aggregation index was stabilized at 35.0-41.5%. The EPS promoted the biomass of strain FL to aggregate in the SBR.

Fate of aerobic granular sludge in the long-term: The role of EPSs on the clogging of granular sludge porosity.

This work aims to investigate the stability of aerobic granular sludge in the long term, focusing on the clogging of the granular sludge porosity exerted by the extracellular polymeric substances (EPSs). The effects of different cycle lengths (short and long-term cycle) on the granular sludge stability were investigated. Results obtained outlined that during the short duration cycle, the formation and breakage of the aerobic granules were continuously observed. During this period, the excess of EPS production contributed to the clogging of the granules porosity, causing their breakage in the long run. During the long-duration cycle, the extended famine period entailed a greater EPSs consumption by bacteria, thus limiting the clogging of the porosity, and allowed obtaining stable aerobic granules. Reported results demonstrated that an excess in EPSs content could be detrimental to the stability of aerobic granular sludge in the long-term.

Effects of combined oleic acid and fluoride at sub-MIC levels on EPS formation and viability of Streptococcus mutans UA159 biofilms.

Despite the widespread use of fluoride, dental caries, a biofilm-related disease, remains an important health problem. This study investigated whether oleic acid, a monounsaturated fatty acid, can enhance the effect of fluoride on extracellular polysaccharide (EPS) formation by Streptococcus mutans UA159 biofilms at sub-minimum inhibitory concentration levels, via microbiological and biochemical methods, confocal fluorescence microscopy, and real-time PCR. The combination of oleic acid with fluoride inhibited EPS formation more strongly than did fluoride or oleic acid alone. The superior inhibition of EPS formation was due to the combination of the inhibitory effects of oleic acid and fluoride against glucosyltransferases (GTFs) and GTF-related gene (gtfB, gtfC, and gtfD) expression, respectively. In addition, the combination of oleic acid with fluoride altered the bacterial biovolume of the biofilms without bactericidal activity. These results suggest that oleic acid may be useful for enhancing fluoride inhibition of EPS formation by S. mutans biofilms, without killing the bacterium.

Characterization and antioxidant properties of three exopolysaccharides produced by the Cyclocarya paliurus endophytic fungus.

In recent years, the considerable potential of endophytic bacteria and fungi as prolific producers of exopolysaccharides (EPSs) have attracted interest. In this study, 56 endophytes were isolated from Cyclocarya paliurus, and the secondary metabolites of EPSs were extracted from Monascus purpureus, Penicillium citrinum and Aspergillus versicolor, screened, and named MPE, PCE and AVE, respectively. In this work, the physicochemical properties and antioxidant activities of three EPSs, their cell proliferation activity on IEC-6 and RAW264.7 were investigated. The three EPSs were mainly composed of neutral sugar and differ in microstructure. However, MPE had a loose structure, and PCE exhibited a dense and sheet-like structure. In addition, the three EPSs performed ordinary antioxidant activity in vitro but showed excellent cell proliferation activity on IEC-6 and RAW264.7. The cell proliferation activity of PCE was 1.4-fold that of the controls at a concentration of 800 µg/mL on IEC-6, and MPE exhibited 1.3-fold increase on RAW264.7. This study provided scientific evidence and insights into the application of endophytes as a novel plant resource possessing huge application potential.

Production of exopolysaccharides from Bacillus licheniformis, a thermophilic bacteria from hot spring of Jharkhand.

Thermophiles are the microorganisms which thrive under extreme conditions such as high temperature, making them significant for scientific interest. This study provides information based on isolation of thermophilic strain from Surajkund and Ramkund, hot spring of Jharkhand at 50, 60 and 70 °C. Two of the best isolates were used for the extraction of exopolysaccharides. Additionally, the lyophilized product obtained was further analyzed for protein and total sugar estimation. The FTIR analysis revealed the presence of different functional groups such as hydroxyl, C-H stretching, vibration of aliphatic CH2 and glycosidic linkage, thus proving the product obtained from bacteria was an exopolysaccharides The FESEM analysis of exopolysaccharides show varying surface morphology that is from porous to globular structure. Based on 16S rRNA sequences, the isolates from Surajkund (ON795919) and Ramkund (ON795916) were different strains of Bacillus licheniformis. This is the first report on exopolysaccharide secreting thermophilic strain from these hot springs.

Reuterin, Phenyllactic Acid, and Exopolysaccharides as Main Antifungal Molecules Produced by Lactic Acid Bacteria: A Scoping Review.

The primary goal of this scoping review is to collect, analyze, and critically describe information regarding the role of the main compounds (reuterin, phenyllactic acid, and exopolysaccharides) produced by LAB that possess antifungal properties and provide some suggestions for further research. The use of lactic acid bacteria (LAB) to mitigate spoilage and extend the shelf life of foodstuffs has a long history. Recently, there has been a growing interest in the unique properties of these additions to the foodstuffs in which they are applied. In recent studies regarding biopreservation, significant attention has been given to the role of these microorganisms and their metabolites. This fascinating recent discipline aims not only to replace traditional preservation systems, but also to improve the overall quality of the final product. The biologically active by-products produced by lactic acid bacteria are synthesized under certain conditions (time, temperature, aerobiosis, acidity, water activity, etc.), which can be enacted through one of the oldest approaches to food processing: fermentation (commonly used in the dairy and bakery sectors). This study also delves into the biosynthetic pathways through which they are synthesized, with a particular emphasis on what is known about the mechanisms of action against molds in relation to the type of food.

Microbial exopolysaccharides in the biomedical and pharmaceutical industries.

The most significant and renewable class of polymeric materials are extracellular exopolysaccharides (EPSs) produced by microorganisms. Because of their diverse chemical and structural makeup, EPSs play a variety of functions in a variety of industries, including the agricultural industry, dairy industry, biofilms, cosmetics, and others, demonstrating their biotechnological significance. EPSs are typically utilized in high-value applications, and current research has focused heavily on them because of their biocompatibility, biodegradability, and compatibility with both people and the environment. Due to their high production costs, only a few microbial EPSs have been commercially successful. The emergence of financial barriers and the growing significance of microbial EPSs in industrial and medical biotechnology has increased interest in exopolysaccharides. Since exopolysaccharides can be altered in a variety of ways, their use is expected to increase across a wide range of industries in the coming years. This review introduces some significant EPSs and their composites while concentrating on their biomedical uses.

Screening of exopolysaccharide-producing Enterobacter aerogenes NJ1023 and its cadaverine biosynthesis promotion.

Enterobacter aerogenes, the gram-negative bacteria belonging to the family Enterobacteriaceae, lacks the ability to synthesize chemicals. However, in this study, a strain of Enterobacter aerogenes NJ1023 screened from the soil containing petrochemicals was found to be capable of producing extracellular polysaccharides (EPSs). After purification of the polysaccharide, the chemical composition and physicochemical properties of the polysaccharide were analyzed by UV-Vis spectra, FTIR spectroscopy and GC-MS, etc. The results showed that: The molecular weight of the polysaccharide produced by this strain was only 2.7×103 Da, which was lower than that reported in other polysaccharides from the same genus. The polysaccharide produced by E. aerogenes NJ1023 mainly comprised xylose, glucose, galactose, and N-acetylglucosamine with a molar ratio of 0.27: 4.52: 1.74: 0.2, which differed from those reported from the same genus. The results demonstrated that lower incubation temperatures and shaking speeds were more favorable for EPSs synthesis, while higher incubation temperatures and shaking speeds favored cell growth. Additionally, the EPSs produced by E. aerogenes NJ1023 significantly protected the Escherichia coli cells against cadaverine stress. Overall, the discovery of EPSs produced by E. aerogenes increased the diversity of bacterial polysaccharides and broadened the potential applications of this species.

Exploring Extremophiles from Bulgaria: Biodiversity, Biopolymer Synthesis, Functional Properties, Applications.

Bulgaria stands out as a country rich in diverse extreme environments, boasting a remarkable abundance of mineral hot waters, which positions it as the second-largest source of such natural resources in Europe. Notably, several thermal and coastal solar salterns within its territory serve as thriving habitats for thermophilic and halophilic microorganisms, which offer promising bioactive compounds, including exopolysaccharides (EPSs). Multiple thermophilic EPS producers were isolated, along with a selection from several saltern environments, revealing an impressive taxonomic and bacterial diversity. Four isolates from three different thermophilic species, Geobacillus tepidamans V264, Aeribacillus pallidus 418, Brevibacillus thermoruber 423, and Brevibacillus thermoruber 438, along with the halophilic strain Chromohalobacter canadensis 28, emerged as promising candidates for further exploration. Optimization of cultivation media and conditions was conducted for each EPS producer. Additionally, investigations into the influence of aeration and stirring in laboratory bioreactors provided valuable insights into growth dynamics and polymer synthesis. The synthesized biopolymers showed excellent emulsifying properties, emulsion stability, and synergistic interaction with other hydrocolloids. Demonstrated biological activities and functional properties pave the way for potential future applications in diverse fields, with particular emphasis on cosmetics and medicine. The remarkable versatility and efficacy of biopolymers offer opportunities for innovation and development in different industrial sectors.

Nitrogen concentration acting as an environmental signal regulates cyanobacterial EPS excretion.

As an important carbon (C) storage in biological soil crusts (BSCs), exopolysaccharides (EPSs) are not only a part of the desert C cycle, but also the key materials for cyanobacteria to resist desert stress. In this study, the influence of initial N concentrations (10, 25 and 50 mg L-1 designated as N10, N25 and N50 respectively) on Microcoleus vaginatusis growth and the excretion of EPSs including RPS (released exopolysaccharides) and CPS (capsule exopolysaccharides) were evaluated at different growth periods. In logarithmic period, higher ratio of biomass to EPSs indicated by (DW-CPS)/EPSs was observed in the N50 group with the highest N concentration (about 40 mg L-1) in the medium, while no difference was observed among the three groups in stationary period when the N concentrations of medium were lower than 25 mg L-1. The CPS/RPS showed similar results with (DW-CPS)/EPSs, and stayed higher than 1 in each group. Notably, obvious difference displayed in the monosaccharidic composition and morphologies between CPS and RPS, but not the N levels. The changes of C/N in cells at different growth period indicate that the excretion of EPSs, a mechanism that maintains the balance of cell C/N ratio, only works when the N in the environment is sufficient. Our results showed that, as the raw material and environmental signal, environmental N concentration regulates the elements (C and N) percentage of cyanobacterial cells and its EPSs excretion pattern, but not the monosaccharidic composition or the morphologies. These results also implied that, as the essential self-protecting materials, more EPSs with higher proportion of CPS would be excreted to response the low N environment.

Extracellular DNA: A Critical Aspect of Marine Biofilms.

Multispecies biofilms represent a pervasive threat to marine-based industry, resulting in USD billions in annual losses through biofouling and microbiologically influenced corrosion (MIC). Biocides, the primary line of defence against marine biofilms, now face efficacy and toxicity challenges as chemical tolerance by microorganisms increases. A lack of fundamental understanding of species and EPS composition in marine biofilms remains a bottleneck for the development of effective, target-specific biocides with lower environmental impact. In the present study, marine biofilms are developed on steel with three bacterial isolates to evaluate the composition of the EPSs (extracellular polymeric substances) and population dynamics. Confocal laser scanning microscopy, scanning electron microscopy, and fluorimetry revealed that extracellular DNA (eDNA) was a critical structural component of the biofilms. Parallel population analysis indicated that all three strains were active members of the biofilm community. However, eDNA composition did not correlate with strain abundance or activity. The results of the EPS composition analysis and population analysis reveal that biofilms in marine conditions can be stable, well-defined communities, with enabling populations that shape the EPSs. Under marine conditions, eDNA is a critical EPS component of the biofilm and represents a promising target for the enhancement of biocide specificity against these populations.

Two (p)ppGpp Synthetase Genes, relA and spoT, Are Involved in Regulating Cell Motility, Exopolysaccharides Production, and Biofilm Formation of Vibrio alginolyticus.

The stringent response mediated by the signal molecule (p)ppGpp is involved in response to multiple environmental stresses and control of various physiological processes. Studies have revealed that (p)ppGpp strongly affects the formation and maintenance of several bacterial biofilms. However, the specific regulatory roles of (p)ppGpp in biofilms, especially in the expression of genes related to cell motility and exopolysaccharides (EPSs) production, remain poorly understood. We recently reported two (p)ppGpp synthetase genes relA and spoT from the epizootic pathogen Vibrio alginolyticus. Herein, we found that the (p)ppGpp synthetase genes of V. alginolyticus contributed to biofilm formation at low cell density and biofilm detachment at high cell density, respectively, in polystyrene microtiter plates. Quantitative reverse transcription PCR (qRT-PCR) analysis revealed that the expression levels of both EPSs and motility associated genes were consistent with the development of biofilms. Besides, the (p)ppGpp synthetase gene spoT was found to be closely involved in the regulation of flagellum, smooth/translucent colony morphology and spotty pellicle at the air-liquid interface. Interestingly, pleiotropic phenotypes of ΔrelAΔspoT were similar to that of the rpoN (σ54) deletion mutant. Meanwhile, the absence of (p)ppGpp synthetase genes significantly reduced the expression levels of rpoN at low cell density, suggesting that (p)ppGpp may mediate the formation via positively affecting the alternative sigma factor RpoN. These findings allow us to propose (p)ppGpp as a crucial regulator for biofilm development in V. alginolyticus, in view of the regulatory roles of relA and spoT in cell motility and EPSs production.