A biofilm is an assemblage of microbial cells attached to a surface and encapsulated in an extracellular polymeric substance (EPS) matrix. The formation of a biofilm is one of the important ...mechanisms of bacterial resistance, which not only leads to hard-to-control bacterial infections in humans and animals but also enables bacteria to be a major problem in various fields, such as food processing, wastewater treatment and metalworking. Quorum sensing (QS) is a bacterial cell-to-cell communication process that depends on the bacterial population density and is mediated by small diffusible signaling molecules called autoinducers (AIs). Bacteria use QS to regulate diverse arrays of functions, including virulence and biofilm formation. Therefore, the interference with QS by using QS inhibiting agents, including QS inhibitors (QSIs) and quorum quenching (QQ) enzymes, to reduce or even completely repress the biofilm formation of pathogenic bacteria appears to be a promising approach to control bacterial infections. In this review, we summarize the mechanisms of QS-regulating biofilm formation and QS-inhibiting agents that control bacterial biofilm formation, strategies for the discovery of new QS inhibiting agents, and the current applications of QS-inhibiting agents in several fields to provide insight into the development of effective drugs to control pathogenic bacteria.
Lacticaseibacillusparacasei is commonly present in the gut flora of healthy individuals and in various fermented foods, such as yogurt, and other dairy items. This strain is frequently incorporated ...into dietary supplements and functional foods. In this study, L.paracasei B31-2 was isolated from local yogurt, and its probiotic, anti-microbial, anti-biofilm, and safety properties were investigated. The L.paracasei B31-2 exhibited robust resilience to acidic conditions, bile salts, and the challenges of the gastrointestinal environment. Its cell surface hydrophobicity measured at 55.42%, along with notable co-aggregation (25.80%), auto-aggregation (42.50%), and adhesion capacity (12.60%). Moreover, L.paracasei B31-2 did not exhibit any hemolytic/DNase effect and did not generate biogenic amines. The strain exhibited varying susceptibility levels, with the highest susceptibility to nitrofurantoin (27.50 mm) and the lowest to ampicillin (13.60 mm). Treatment with cell-free supernatants of L.paracasei B31-2 resulted in a reduction of biofilm formation by Listeriamonocytogenes. The second section of this study evaluated the Gaussian Process Regression (GPR) model for predicting probiotic viability. The results demonstrated that the GPR model could predict probiotic viability with high accuracy. The findings suggest that L.paracasei B31-2 has promising potential for health-improving purposes, potentially offering protective effects against specific pathogens and contributing to gastrointestinal health.
•The minimum inhibitory concentration for Listeriamonocytogenes was equal to 15.62 mg/mL.•The Lacticaseibacillusparacasei B31-2 inhibited the development of L.monocytogenes biofilm.•The Gaussian Process Regression model could predict probiotic viability with high accuracy.
One of the emerging conundrums of Campylobacter food-borne illness is the bacterial ability to survive stressful environmental conditions. We evaluated the heterogeneity among 90 C. jejuni and 21 C. ...coli isolates from different sources in Egypt with respect to biofilm formation capabilities (under microaerobic and aerobic atmosphere) and resistance to a range of stressors encountered along the food chain (aerobic stress, refrigeration, freeze-thaw, heat, peracetic acid, and osmotic stress). High prevalence (63%) of hyper-aerotolerant (HAT) isolates was observed, exhibiting also a significantly high tolerance to heat, osmotic stress, refrigeration, and freeze-thaw stress, coupled with high biofilm formation ability which was clearly enhanced under aerobic conditions, suggesting a potential link between stress adaptation and biofilm formation. Most HAT multi-stress resistant and strong biofilm producing C. jejuni isolates belonged to host generalist clonal complexes (ST-21, ST-45, ST-48 and ST-206). These findings highlight the potential role of oxidative stress response systems in providing cross-protection (resistance to other multiple stress conditions) and enhancing biofilm formation in Campylobacter and suggest that selective pressures encountered in hostile environments have shaped the epidemiology of C. jejuni in Egypt by selecting the transmission of highly adapted isolates, thus promoting the colonization of multiple host species by important disease-causing lineages.
•Oxidative stress defense responses in Campylobacter are associated with enhanced biofilm formation capabilities.•Host generalist lineages are better equipped to withstand hostile environmental conditions favoring zoonotic transmission.•Multi-stress adapted Campylobacter isolates challenges efforts made to eliminate this foodborne pathogen from the food chain.
Dental caries is one of the most prevalent and costly biofilm-associated infectious diseases affecting most of the world's population. In particular, dental caries is driven by dysbiosis of the ...dental biofilm adherent to the enamel surface. Specific types of acid-producing bacteria, especially Streptococcus mutans, colonize the dental surface and cause damage to the hard tooth structure in the presence of fermentable carbohydrates. Streptococcus mutans has been established as the major cariogenic pathogen responsible for human dental caries, with a high ability to form biofilms. The exopolysaccharide (EPS) matrix, mainly contributed by S. mutans, has been considered as a virulence determinant of cariogenic biofilm. As EPS is an important virulence factor, targeting EPS metabolism could be useful in preventing cariogenic biofilm formation. This review summarizes plausible strategies targeting S. mutans biofilms by degrading EPS structure, inhibiting EPS production, and disturbing the EPS metabolism-related gene expression and regulatory systems.
Heavy metals bring long-term hazardous consequences and pose a serious threat to all life forms. Being non-biodegradable, they can remain in the food webs for a long period of time. Metal ions are ...essential for life and indispensable for almost all aspects of metabolism but can be toxic beyond threshold level to all living beings including microbes. Heavy metals are generally present in the environment, but many geogenic and anthropogenic activities has led to excess metal ion accumulation in the environment. To survive in harsh metal contaminated environments, bacteria have certain resistance mechanisms to metabolize and transform heavy metals into less hazardous forms. This also gives rise to different species of heavy metal resistant bacteria. Herein, we have tried to incorporate the different aspects of heavy metal toxicity in bacteria and provide an up-to-date and across-the-board review. The various aspects of heavy metal biology of bacteria encompassed in this review includes the biological notion of heavy metals, toxic effect of heavy metals on bacteria, the factors regulating bacterial heavy metal resistance, the diverse mechanisms governing bacterial heavy metal resistance, bacterial responses to heavy metal stress, and a brief overview of gene regulation under heavy metal stress.
This study assesses the improvement in nitrogen and phosphorus removal from wastewater achieved through the integration of zeolite and attapulgite carrier materials into the activated sludge (AS) ...process. It was found that the addition of these materials significantly enhanced the processing performance of the reactor. Specifically, the use of zeolite and attapulgite powders increased sludge particle sizes to averages of 231.56 μm and 219.62 μm, respectively. This facilitated micro-granule formation, substantially improving the settling characteristics of the sludge and boosting the activity and proliferation of essential microbes. Illumina MiSeq sequencing demonstrated significant accumulations of DGAOs (Candidatus_Competibacter) and DPAOs (Candidatus_Accumulibacter). Furthermore, these carriers augmented the protein content in extracellular polymers, enhancing the hydrophobicity of the sludge and promoting aggregation. Comparative analysis based on the extended Derjaguin, Landau, Verwey, and Overbeek (DLVO) theory indicated a preferential adhesion affinity of sludge for zeolite compared to attapulgite, attributed primarily to Lewis acid-base and electric double-layer interactions. These findings underscore zeolite's enhanced efficacy in biomass fixation and suggest significant potential for the technological advancement of wastewater treatment plants.
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•Integrating powder carriers into activated sludge enhances the removal of N and P.•The extended DLVO theory was applied to describe the sludge aggregation properties.•Powder carriers have high biomass immobilizatsion ability.•The system was overwhelmingly dominated by Candidatus_Competibacter (10.46–13.18 %).
Legume-rhizobial symbiosis plays an important role in agriculture and ecological restoration. This process occurs within special new structures, called nodules, formed mainly on legume roots. Soil ...bacteria, commonly known as rhizobia, fix atmospheric dinitrogen, converting it into a form that can be assimilated by plants. Various environmental factors, including a low temperature, have an impact on the symbiotic efficiency. Nevertheless, the effect of temperature on the phenotypic and symbiotic traits of rhizobia has not been determined in detail to date. Therefore, in this study, the influence of temperature on different cell surface and symbiotic properties of rhizobia was estimated. In total, 31 Rhizobium leguminosarum sv. trifolii strains isolated from root nodules of red clover plants growing in the subpolar and temperate climate regions, which essentially differ in year and day temperature profiles, were chosen for this analysis. Our results showed that temperature has a significant effect on several surface properties of rhizobial cells, such as hydrophobicity, aggregation, and motility. Low temperature also stimulated EPS synthesis and biofilm formation in R. leguminosarum sv. trifolii. This extracellular polysaccharide is known to play an important protective role against different environmental stresses. The strains produced large amounts of EPS under tested temperature conditions that facilitated adherence of rhizobial cells to different surfaces. The high adaptability of these strains to cold stress was also confirmed during symbiosis. Irrespective of their climatic origin, the strains proved to be highly effective in attachment to legume roots and were efficient microsymbionts of clover plants. However, some diversity in the response to low temperature stress was found among the strains. Among them, M16 and R137 proved to be highly competitive and efficient in nodule occupancy and biomass production; thus, they can be potential yield-enhancing inoculants of legumes.
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•Low temperature stimulated EPS synthesis and biofilm formation by R. leguminosarum sv. trifolii strains.•Temperature significantly influenced hydrophobicity, aggregation, and motility of rhizobial cells.•The strains from two subpolar and temperate climate regions exhibited diversity in cell surface and symbiotic properties.•The strains were effective in attachment to abiotic and biotic surfaces and were efficient microsymbionts of clover plants.•M16 and R137 were highly efficient in nodule occupancy and clover production, being potential yield-enhancing inoculants.
Organosulfur compounds are prevalent in wastewater, presenting challenges for biodegradation, particularly in low-carbon environments. Supplementing additional carbon sources not only provides ...essential nutrients for microbial growth but also serves as regulators, influencing adaptive changes in biofilm and enhancing the survival of microorganisms in organosulfur-induced stress bioreactors. This study aims to elucidate the biodegradation of organosulfur under varying carbon source levels, placing specific emphasis on functional bacteria and metabolic processes. It has been observed that higher levels of carbon supplementation led to significantly improved total sulfur (TS) removal efficiencies, exceeding 83 %, and achieve a high organosulfur CH3SH removal efficiency of ~100 %. However, in the reactor with no external carbon source added, the oxidation end-product SO42− accumulated significantly, surpassing 120 mEq/m2-day. Furthermore, the TB-EPS concentration consistently increasedwith the ascending glucose concentration. The analysis of bacterial community reveals the enrichment of functional bacteria involved in sulfur metabolism and biofilm formation (e.g. Ferruginibacter, Rhodopeudomonas, Gordonia, and Thiobacillus). Correspondingly, the gene expressions related to the pathway of organosulfur to SO42− were notably enhanced (e.g. MTO increased by 27.7 %). In contrast, extra carbon source facilitated the transfer of organosulfur into amino acids in sulfur metabolism and promoted assimilation. These metabolic insights, coupled with kinetic transformation results, further validate distinct sulfur pathways under different carbon source conditions. The intricate interplay between bacteria growth regulation, pollutant biodegradation, and microbial metabolites underscores a complex network relationship that significantly contributes to efficient operation of bioreactors.
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•Extra carbon source promoted organosulfur utilization and assimilation.•Extra carbon source regulated the biofilm formation and adaptive evolution.•Extra carbon source shifted the absolute abundances of functional bacteria and genes.•Extra carbon source mediated the organosulfur metabolic process.
Nitrogen- and phosphorus-doped, ordered mesoporous carbon (NPOMC) is a novel metal-free cathode catalyst for the oxygen reduction reaction (ORR). The electrochemical performance of NPOMC is compared ...with that of a Pt/C catalyst for the ORR in two different type microbial fuel cell (MFC) configurations: single-chamber MFC (SMFC) without an ion exchange membrane, and two-chamber MFC (TMFC) with an ion exchange membrane. The NPOMC shows approximately 60–75% of the ORR activity observed with the Pt/C catalyst in an ion exchange membrane implementing TMFC (OCV 0.42 V and power density of 245.8 mW m−2). In contrast, the membrane-less SMFC produces approximately 30% of the ORR activity of Pt/C (154.0 mW m−2). The mesoporous catalyst with NPOMC shows not only higher electrochemical charge transfer performance, but also improves electrical capacitance due to the larger surface area and morphology of the mesoporous structure. Biofilm formation on mesoporous NPOMC reduces the ORR activity in the SMFC significantly, whereas the decrease is less severe in the TMFC because of the ion exchange membrane. The material cost of the NPOMC is estimated to be approximately 5% of the cost of Pt/C. Therefore, NPOMC is a cost-effective alternative catalyst for MFC applications.
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•Nitrogen- and phosphorus-doped ordered mesoporous carbon (NPOMC) was developed.•The performance of NPOMC was compared in different types of MFC configurations.•Metal-free NPOMC produced approximately 75% of the ORR activity compared to Pt/C.•Biofilm formation on the NPOMC surface may hinder the ORR activity during operation.•NPOMC is a cost effective alternative catalyst for the MFC cathode.
is well adapted to hospital environments, and the persistence of its chronic infections is mainly due to its ability to form biofilms resistant to conventional antibiotics and host immune systems. ...Hence, the inhibitions of biofilm formation and virulence characteristics provide other means of addressing infections. In this study, the antibiofilm activities of twelve flavonoids were initially investigated. Three most active flavonoids, namely, fisetin, phloretin, and curcumin, dose-dependently inhibited biofilm formation by a reference
strain and by several clinical isolates, including four multidrug-resistant isolates. Furthermore, the antibiofilm activity of curcumin (the most active flavonoid) was greater than that of the well-known biofilm inhibitor gallium nitrate. Curcumin inhibited pellicle formation and the surface motility of
. Interestingly, curcumin also showed antibiofilm activity against
and mixed cultures of
and
.
molecular docking of the biofilm response regulator BfmR showed that the binding efficacy of flavonoids with BfmR was correlated with antibiofilm efficacy. In addition, curcumin treatment diminished
virulence in an
model without cytotoxicity. The study shows curcumin and other flavonoids have potential for controlling biofilm formation by and the virulence of
.
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