Broad-spectrum biofilm inhibition by a secreted bacterial polysaccharide

Escherichia coli exopolysaccharides disrupt Pseudomonas aeruginosa biofilm and increase its antibiotic susceptibility

Pseudomonas aeruginosa (P. aeruginosa) is a major pathogen that causes infectious diseases. It has high tendency to form biofilms, resulting in the failure of traditional antibiotic therapies. Inspired by the phenomenon that co-culture of Escherichia coli (E. coli) and P. aeruginosa leads to a biofilm reduction, we reveal that E. coli exopolysaccharides (EPS) can disrupt P. aeruginosa biofilm and increase its antibiotic susceptibility. The results show that E. coli EPS effectively inhibit biofilm formation and disrupt mature biofilms in P. aeruginosa, Staphylococcus aureus, and E. coli itself. The maximal inhibition and disruption rates against P. aeruginosa biofilm are 40% and 47%, respectively. Based on the biofilm-disrupting ability of E. coli EPS, we develop an E. coli EPS/antibiotic combining strategy for the treatment of P. aeruginosa biofilms. The combination with E. coli EPS increases the antibacterial efficiency of tobramycin against P. aeruginosa biofilms in vitro and in vivo. This study provides a promising strategy for treating biofilm infections. STATEMENT OF SIGNIFICANCE: Biofilm formation is a leading cause of chronic infections. It blocks antibiotics, increases antibiotic-tolerance, and aids in immune evasion, thus representing a great challenge in clinic. This study proposes a promising approach to combat pathogenic Pseudomonas aeruginosa (P. aeruginosa) biofilms by combining Escherichia coli exopolysaccharides with antibiotics. This strategy shows high efficiency in different P. aeruginosa stains, including two laboratory strains, PAO1 and ATCC 10145, as well as a clinically acquired carbapenem-resistant strain. In addition, in vivo experiments have shown that this approach is effective against implanted P. aeruginosa biofilms and can prevent systemic inflammation in mice. This strategy offers new possibilities to address the clinical failure of conventional antibiotic therapies for microbial biofilms.

Glyphosate effects on growth and biofilm formation in bee gut symbionts and diverse associated bacteria

Biofilm formation is a common adaptation enabling bacteria to thrive in various environments and withstand external pressures. In the context of host-microbe interactions, biofilms play vital roles in establishing microbiomes associated with animals and plants and are used by opportunistic microbes to facilitate survival within hosts. Investigating biofilm dynamics, composition, and responses to environmental stressors is crucial for understanding microbial community assembly and biofilm regulation in health and disease. In this study, we explore in vivo colonization and in vitro biofilm formation abilities of core members of the honey bee (Apis mellifera) gut microbiota. Additionally, we assess the impact of glyphosate, a widely used herbicide with antimicrobial properties, and a glyphosate-based herbicide formulation on growth and biofilm formation in bee gut symbionts as well as in other biofilm-forming bacteria associated with diverse animals and plants. Our results demonstrate that several strains of core bee gut bacterial species can colonize the bee gut, which probably depends on their ability to form biofilms. Furthermore, glyphosate exposure elicits variable effects on bacterial growth and biofilm formation. In some instances, the effects correlate with the bacteria's ability to encode a susceptible or tolerant version of the enzyme inhibited by glyphosate in the shikimate pathway. However, in other instances, no such correlation is observed. Testing the herbicide formulation further complicates comparisons, as results often diverge from glyphosate exposure alone, suggesting that co-formulants influence bacterial growth and biofilm formation. These findings highlight the nuanced impacts of environmental stressors on microbial biofilms, with both ecological and host health-related implications.

IMPORTANCE

Biofilms are essential for microbial communities to establish and thrive in diverse environments. In the honey bee gut, the core microbiota member Snodgrassella alvi forms biofilms, potentially aiding the establishment of other members and promoting interactions with the host. In this study, we show that specific strains of other core members, including Bifidobacterium, Bombilactobacillus, Gilliamella, and Lactobacillus, also form biofilms in vitro. We then examine the impact of glyphosate, a widely used herbicide that can disrupt the bee microbiota, on bacterial growth and biofilm formation. Our findings demonstrate the diverse effects of glyphosate on biofilm formation, ranging from inhibition to enhancement, reflecting observations in other beneficial or pathogenic bacteria associated with animals and plants. Thus, glyphosate exposure may influence bacterial growth and biofilm formation, potentially shaping microbial establishment on host surfaces and impacting health outcomes.

Biofilm and bacterial membrane vesicles: recent advances

INTRODUCTION

Bacterial Membrane Vesicles (MVs) play important roles in cell-to-cell communication and transport of several molecules. Such structures are essential components of Extracellular Polymeric Substances (EPS) biofilm matrix of many bacterial species displaying a structural function and a role in virulence and pathogenesis.

AREAS COVERED

In this review were included original articles from the last ten years by searching the keywords 'biofilm' and 'vesicles' on PUBMED and Scopus databases. The articles available in literature mainly describe a positive correlation between bacterial MVs and biofilms formation. The research on Espacenet and Google Patent databases underlines the available patents related to the application of both biofilm MVs and planktonic MVs in inhibiting biofilm formation.

EXPERT OPINION

This review covers and analyzes recent advances in the study of the relationship between bacterial vesicles and biofilm. The huge number of papers discussing the role of MVs confirms the interest aimed at developing new applications in the medical field. The study of the MVs composition and biogenesis may contribute to the identification of components which could be (i) the target for the development of new drugs inhibiting the biofilm establishment; (ii) candidates for the development of vaccines; (iii) biomarkers for the diagnosis of bacterial infections.

K1 capsule-dependent phage-driven evolution in Escherichia coli leading to phage resistance and biofilm production

AIMS

Understanding bacterial phage resistance mechanisms has implications for developing phage-based therapies. This study aimed to explore the development of phage resistance in Escherichia coli K1 isolates' to K1-ULINTec4, a K1-dependent bacteriophage.

METHODS AND RESULTS

Resistant colonies were isolated from two different strains (APEC 45 and C5), both previously exposed to K1-ULINTec4. Genome analysis and several parameters were assessed, including growth capacity, phage adsorption, phenotypic impact at capsular level, biofilm production, and virulence in the in vivo Galleria mellonella larvae model. One out of the six resistant isolates exhibited a significantly slower growth rate, suggesting the presence of a resistance mechanism altering its fitness. Comparative genomic analysis revealed insertion sequences in the region 2 of the kps gene cluster involved in the capsule biosynthesis. In addition, an immunoassay targeting the K1 capsule showed a very low positive reaction compared to the control. Nevertheless, microscopic images of resistant strains revealed the presence of capsules with a clustered organization of bacterial cells and biofilm assessment showed an increased biofilm production compared to the sensitive strains. In the G. mellonella model, larvae infected with phage-resistant isolates showed better survival rates than larvae infected with phage-sensitive strains.

CONCLUSIONS

A phage resistance mechanism was identified at the genomic level and had a negative impact on the K1 capsule production. The resistant isolates showed an increased biofilm production and a decreased virulence in vivo.

Bacterial capsules: Occurrence, mechanism, and function

In environments characterized by extended multi-stress conditions, pathogens develop a variety of immune escape mechanisms to enhance their ability to infect the host. The capsules, polymers that bacteria secrete near their cell wall, participates in numerous bacterial life processes and plays a crucial role in resisting host immune attacks and adapting to their niche. Here, we discuss the relationship between capsules and bacterial virulence, summarizing the molecular mechanisms of capsular regulation and pathogenesis to provide new insights into the research on the pathogenesis of pathogenic bacteria.

Bacterium secretes chemical inhibitor that sensitizes competitor to bacteriophage infection

To overtake competitors, microbes produce and secrete secondary metabolites that kill neighboring cells and sequester nutrients. This natural product-mediated competition likely evolved in complex microbial communities that included viral pathogens. From this ecological context, we hypothesized that microbes secrete metabolites that "weaponize" natural pathogens (i.e., bacteriophages) to lyse their competitors. Indeed, we discovered a bacterial secondary metabolite that sensitizes other bacteria to phage infection. We found that this metabolite provides the producer (a Streptomyces sp.) with a fitness advantage over its competitor (Bacillus subtilis) by promoting phage infection. The phage-promoting metabolite, coelichelin, sensitized B. subtilis to a wide panel of lytic phages, and it did so by preventing the early stages of sporulation through iron sequestration. Beyond coelichelin, other natural products may provide phage-mediated competitive advantages to their producers-either by inhibiting sporulation or through yet-unknown mechanisms.

Bacterial adhesion inhibition by microalgal EPSs from Cylindrotheca closterium and Tetraselmis suecica biofilms

In the food industry, successful bacterial pathogen colonization and persistence begin with their adhesion to a surface, followed by the spatial development of mature biofilm of public health concerns. Compromising bacterial settlement with natural inhibitors is a promising alternative to conventional anti-fouling treatments typically based on chemical biocides that contribute to the growing burden of antimicrobial resistance. In this study, three extracellular polymeric substance (EPS) fractions extracted from microalgae biofilms of Cylindrotheca closterium (fraction C) and Tetraselmis suecica (fraction Ta rich in insoluble scale structure and fraction Tb rich in soluble EPS) were screened for their anti-adhesive properties, against eight human food-borne pathogens belonging to Escherichia coli, Staphylococcus aureus, Salmonella enterica subsp. enterica, and Listeria monocytogenes species. The results showed that the fraction Ta was the most effective inducing statistically significant reduction for three strains of E. coli, S. aureus, and L. monocytogenes. Overall, EPSs coating on polystyrene surfaces of the different fractions increased the hydrophilic character of the support. Differences in bacterial adhesion on the different coated surfaces could be explained by several dissimilarities in the structural and physicochemical EPS compositions, according to HPLC and ATR-FTIR analysis. Interestingly, while fractions Ta and Tb were extracted from the same microalgal culture, distinct adhesion patterns were observed, highlighting the importance of the extraction process. Overall, the findings showed that EPS extracted from microalgal photosynthetic biofilms can exhibit anti-adhesive effects against food-borne pathogens and could help develop sustainable and non-toxic anti-adhesive surfaces for the food industry. KEY POINTS: •EPSs from a biofilm-based culture of C. closterium/T. suecica were characterized. •Microalgal EPS extracted from T. suecica biofilms showed bacterial anti-adhesive effects. •The anti-adhesive effect is strain-specific and affects both Gram - and Gram + bacteria.

Exopolysaccharides produced by Bacillus spp. inhibit biofilm formation by Staphylococcus aureus strains associated with bovine mastitis

Bovine mastitis is a costly disease in the dairy sector worldwide. Here the objective was to identify and characterize anti-biofilm compounds produced by Bacillus spp. against S. aureus associated with bovine mastitis. Results showed that cell-free supernatants of three Bacillus strains (out of 33 analysed) reduced S. aureus biofilm formation by approximately 40 % without affecting bacterial growth. The anti-biofilm activity was associated with exopolysaccharides (EPS) secreted by Bacillus spp. The EPS decreased S. aureus biofilm formation in a dose-dependent manner, inhibiting biofilm formation by 83 % at 1 mg/mL. The EPS also showed some biofilm disruption activity (up to 36.4 %), which may be partially mediated by increased expression of the aur gene. The characterization of EPS produced by Bacillus velezensis 87 and B. velezensis TR47II revealed macromolecules with molecular weights of 31.2 and 33.7 kDa, respectively. These macromolecules were composed mainly of glucose (mean = 218.5 μg/mg) and mannose (mean = 241.5 μg/mg) and had similar functional groups (pyranose ring, beta-type glycosidic linkage, and alkynes) as revealed by FT-IR. In conclusion, this study shows the potential applications of EPS produced by B. velezensis as an anti-biofilm compound that could contribute to the treatment of bovine mastitis caused by S. aureus.

Latent evolution of biofilm formation depends on life-history and genetic background

Adaptation to one environment can often generate phenotypic and genotypic changes which impact the future ability of an organism to thrive in other environmental conditions. In the context of host-microbe interactions, biofilm formation can increase survival rates in vivo upon exposure to stresses, like the host's immune system or antibiotic therapy. However, how the generic process of adaptation impacts the ability to form biofilm and how it may change through time has seldomly been studied. To do so, we used a previous evolution experiment with three strains of the Klebsiella pneumoniae species complex, in which we specifically did not select for biofilm formation. We observed that changes in the ability to form biofilm happened very fast at first and afterwards reverted to ancestral levels in many populations. Biofilm changes were associated to changes in population yield and surface polysaccharide production. Genotypically, mutations in the tip adhesin of type III fimbriae (mrkD) or the fim switch of type I fimbriae were shaped by nutrient availability during evolution, and their impact on biofilm formation was dependent on capsule production. Analyses of natural isolates revealed similar mutations in mrkD, suggesting that such mutations also play an important role in adaptation outside the laboratory. Our work reveals that the latent evolution of biofilm formation, and its temporal dynamics, depend on nutrient availability, the genetic background and other intertwined phenotypic and genotypic changes. Ultimately, it suggests that small differences in the environment can alter an organism's fate in more complex niches like the host.

Bacterial capsular polysaccharides with antibiofilm activity share common biophysical and electrokinetic properties

Bacterial biofilms are surface-attached communities that are difficult to eradicate due to a high tolerance to antimicrobial agents. The use of non-biocidal surface-active compounds to prevent the initial adhesion and aggregation of bacterial pathogens is a promising alternative to antibiotic treatments and several antibiofilm compounds have been identified, including some capsular polysaccharides released by various bacteria. However, the lack of chemical and mechanistic understanding of the activity of these polymers limits their use to control biofilm formation. Here, we screen a collection of 31 purified capsular polysaccharides and first identify seven new compounds with non-biocidal activity against Escherichia coli and/or Staphylococcus aureus biofilms. We measure and theoretically interpret the electrophoretic mobility of a subset of 21 capsular polysaccharides under applied electric field conditions, and we show that active and inactive polysaccharide polymers display distinct electrokinetic properties and that all active macromolecules share high intrinsic viscosity features. Despite the lack of specific molecular motif associated with antibiofilm properties, the use of criteria including high density of electrostatic charges and permeability to fluid flow enables us to identify two additional capsular polysaccharides with broad-spectrum antibiofilm activity. Our study therefore provides insights into key biophysical properties discriminating active from inactive polysaccharides. The characterization of a distinct electrokinetic signature associated with antibiofilm activity opens new perspectives to identify or engineer non-biocidal surface-active macromolecules to control biofilm formation in medical and industrial settings.

Antibiofilm activity from endophyte bacteria, Vibrio cholerae strains, and actinomycetes isolates in liquid and solid culture

Background

Biofilm-associated infections are a global threat to our economy and human health; as such, development of antibiofilm compounds is an urgent need. Our previous study identified eleven environmental isolates of endophyte bacteria, actinomycetes, and two strains of Vibrio cholerae as having strong antibiofilm activity, but only tested crude extracts from liquid culture. Here we grew the same bacteria in solid culture to induce the formation of colony biofilms and the expression of genes that may ultimately produce antibiofilm compounds. This research aimed to compare antibiofilm inhibition and destruction activities between liquid and solid cultures of these eleven environmental isolates against the biofilms of representative pathogenic bacteria.

Results

We measured antibiofilm activity using the static antibiofilm assay and crystal violet staining. The majority of our isolates exhibited higher inhibitory antibiofilm activity in liquid media, including all endophyte bacteria, V. cholerae V15a, and actinomycetes strains (CW01, SW03, CW17). However, for V. cholerae strain B32 and two actinomycetes bacteria (TB12 and SW12), the solid crude extracts showed higher inhibitory activity. Regarding destructive antibiofilm activity, many endophyte isolates and V. cholerae strains showed no significant difference between culture methods; the exceptions were endophyte bacteria isolate JerF4 and V. cholerae B32. The liquid extract of isolate JerF4 showed higher destructive activity relative to the corresponding solid culture extract, while for V. cholerae strain B32 the solid extract showed higher activity against some biofilms of pathogenic bacteria.

Conclusions

Culture conditions, namely solid or liquid culture, can influence the activity of culture extracts against biofilms of pathogenic bacteria. We compared the antibiofilm activity and presented the data that majority of isolates showed a higher antibiofilm activity in liquid culture. Interestingly, solid extracts from three isolates (B32, TB12, and SW12) have a better inhibition or/and destruction antibiofilm activity compared to their liquid culture. Further research is needed to characterize the activities of specific metabolites in solid and liquid culture extracts and to determine the mechanisms of their antibiofilm actions.

Yersinia enterocolitica-Derived Outer Membrane Vesicles Inhibit Initial Stage of Biofilm Formation

Yersinia enterocolitica (Y. enterocolitica) is an important food-borne and zoonotic pathogen. It can form biofilm on the surface of food, increasing the risk to food safety. Generally, outer membrane vesicles (OMVs) are spherical nanostructures secreted by Gram-negative bacteria during growth. They play a role in biological processes because they contain biologically active molecules. Several studies have reported that OMVs secreted by various bacteria are associated with the formation of biofilms. However, the interactions between Y. enterocolitica OMVs and biofilm are unknown. This study aims to investigate the effect of Y. enterocolitica OMVs on biofilm formation. Firstly, OMVs were extracted from Y. enterocolitica Y1083, which has a strong biofilm-forming ability, at 15 °C, 28 °C and 37 °C and then characterized. The characterization results showed differences in the yield and protein content of three types of OMVs. Next, by co-culturing the OMVs with Y. enterocolitica, it was observed that the OMVs inhibited the initial stage of Y. enterocolitica biofilm formation but did not affect the growth of Y. enterocolitica. Furthermore, biofilm formation by Salmonella enteritidis and Staphylococcus aureus were also inhibited by OMVs. Subsequently, it was proved that lipopolysaccharides (LPS) in OMVs inhibited biofilm formation., The proteins, DNA or RNA in OMVs could not inhibit biofilm formation. Bacterial motility and the expression of the biofilm-related genes pgaABC, motB and flhBD were inhibited by LPS. LPS demonstrated good anti-biofilm activity against various bacteria. This study provides a new approach to the prevention and control of pathogenic bacterial biofilm.

Synergy of R-(-)carvone and cyclohexenone-based carbasugar precursors with antibiotics to enhance antibiotic potency and inhibit biofilm formation

The widespread use of antibiotics in recent decades has been a major factor in the emergence of antibiotic resistances. Antibiotic-resistant pathogens pose increasing challenges to healthcare systems in both developing and developed countries. To counteract this, the development of new antibiotics or adjuvants to combat existing resistance to antibiotics is crucial. Glycomimetics, for example carbasugars, offer high potential as adjuvants, as they can inhibit metabolic pathways or biofilm formation due to their similarity to natural substrates. Here, we demonstrate the synthesis of carbasugar precursors (CSPs) and their application as biofilm inhibitors for E. coli and MRSA, as well as their synergistic effect in combination with antibiotics to circumvent biofilm-induced antibiotic resistances. This results in a biofilm reduction of up to 70% for the CSP rac-7 and a reduction in bacterial viability of MRSA by approximately 45% when combined with the otherwise ineffective antibiotic mixture of penicillin and streptomycin.

Lactobacillus crispatus-derived exopolysaccharides with antibacterial activity limit Salmonella typhimurium invasion by inhibiting inflammasome-mediated pyroptosis

In this study, a novel heteropolysaccharide (EPS 7-4) with a molecular weight of 53 387 Da was isolated from Lactobacillus crispatus, and it was mainly composed of mannose (36.9%) and glucose (30.8%). EPS 7-4 showed excellent inhibitory effects on the proliferation, biofilm formation, and virulence factor gene expression of Salmonella typhimurium (S. typhimurium) by disrupting the integrity of the bacterial wall. Furthermore, EPS 7-4 can effectively restrict bacterial translocation, upregulate the abundance of Lactobacillus spp. and Bifidobacterium spp., and alleviate the S. typhimurium induced severe inflammatory response in the intestinal tract of mice. Besides, we demonstrated that EPS 7-4 can protect mice by inhibiting S. typhimurium induced pyroptosis, with the mechanism that EPS 7-4 affects ASC oligomerization during inflammasome-mediated pyroptosis. Therefore, due to its excellent anti-bacterial and anti-inflammatory abilities, EPS 7-4 is a promising health regulator owing to its excellent antibacterial and anti-inflammatory abilities.

An Overview of Biofilm Formation-Combating Strategies and Mechanisms of Action of Antibiofilm Agents

Biofilm formation on surfaces via microbial colonization causes infections and has become a major health issue globally. The biofilm lifestyle provides resistance to environmental stresses and antimicrobial therapies. Biofilms can cause several chronic conditions, and effective treatment has become a challenge due to increased antimicrobial resistance. Antibiotics available for treating biofilm-associated infections are generally not very effective and require high doses that may cause toxicity in the host. Therefore, it is essential to study and develop efficient anti-biofilm strategies that can significantly reduce the rate of biofilm-associated healthcare problems. In this context, some effective combating strategies with potential anti-biofilm agents, including plant extracts, peptides, enzymes, lantibiotics, chelating agents, biosurfactants, polysaccharides, organic, inorganic, and metal nanoparticles, etc., have been reviewed to overcome biofilm-associated healthcare problems. From their extensive literature survey, it can be concluded that these molecules with considerable structural alterations might be applied to the treatment of biofilm-associated infections, by evaluating their significant delivery to the target site of the host. To design effective anti-biofilm molecules, it must be assured that the minimum inhibitory concentrations of these anti-biofilm compounds can eradicate biofilm-associated infections without causing toxic effects at a significant rate.

The Chemical Profiling, Docking Study, and Antimicrobial and Antibiofilm Activities of the Endophytic fungi Aspergillus sp. AP5

Growing data suggest that Aspergillus niger, an endophytic fungus, is a rich source of natural compounds with a wide range of biological properties. This study aimed to examine the antimicrobial and antibiofilm capabilities of the Phragmites australis-derived endophyte against a set of pathogenic bacteria and fungi. The endophytic fungus Aspergillus sp. AP5 was isolated from the leaves of P. australis. The chemical profile of the fungal crude extract was identified by spectroscopic analysis using LC-HRESIMS. The fungal-derived extract was evaluated for its antimicrobial activity towards a set of pathogenic bacterial and fungal strains including Staphylococcus aureus, Pseudomonas aeruginosa, Proteus vulgaris, Klebsiella sp., Candida albicans, and Aspergillus niger. Moreover, antibiofilm activity toward four resistant biofilm-forming bacteria was also evaluated. Additionally, a neural-networking pharmacophore-based visual screening predicted the most probable bioactive compounds in the obtained extract. The AP5-EtOAc extract was found to have potent antibacterial activities against S. aureus, E. coli, and Klebsiella sp., while it exhibited low antibacterial activity toward P. Vulgaris and P. aeruginosa and displayed anticandidal activity. The AP5-EtOAc extract had significant antibiofilm activity in S. aureus, followed by P. aeruginosa. The active metabolites’ antifungal and/or antibacterial activities may be due to targeting the fungal CYP 51 and/or the bacterial Gyr-B.

Deinococcus radiodurans Exopolysaccharide Inhibits Staphylococcus aureus Biofilm Formation

Deinococcus radiodurans is an extremely resistant bacterium against extracellular stress owing to on its unique physiological functions and the structure of its cellular constituents. Interestingly, it has been reported that the pattern of alteration in Deinococcus proportion on the skin is negatively correlated with skin inflammatory diseases, whereas the proportion of Staphylococcus aureus was increased in patients with chronic skin inflammatory diseases. However, the biological mechanisms of deinococcal interactions with other skin commensal bacteria have not been studied. In this study, we hypothesized that deinococcal cellular constituents play a pivotal role in preventing S. aureus colonization by inhibiting biofilm formation. To prove this, we first isolated cellular constituents, such as exopolysaccharide (DeinoPol), cell wall (DeinoWall), and cell membrane (DeinoMem), from D. radiodurans and investigated their inhibitory effects on S. aureus colonization and biofilm formation in vitro and in vivo. Among them, only DeinoPol exhibited an anti-biofilm effect without affecting bacterial growth and inhibiting staphylococcal colonization and inflammation in a mouse skin infection model. Moreover, the inhibitory effect was impaired in the Δdra0033 strain, a mutant that cannot produce DeinoPol. Remarkably, DeinoPol not only interfered with S. aureus biofilm formation at early and late stages but also disrupted a preexisting biofilm by inhibiting the production of poly-N-acetylglucosamine (PNAG), a key molecule required for S. aureus biofilm formation. Taken together, the present study suggests that DeinoPol is a key molecule in the negative regulation of S. aureus biofilm formation by D. radiodurans. Therefore, DeinoPol could be applied to prevent and/or treat infections or inflammatory diseases associated with S. aureus biofilms.

Control of Multidrug-Resistant Pathogenic Staphylococci Associated with Vaginal Infection Using Biosurfactants Derived from Potential Probiotic Bacillus Strain

Biosurfactants exhibit antioxidant, antibacterial, antifungal, and antiviral activities. They can be used as therapeutic agents and in the fight against infectious diseases. Moreover, the anti-adhesive properties against several pathogens point to the possibility that they might serve as an anti-adhesive coating agent for medical inserts and prevent nosocomial infections, without using synthetic substances. In this study, the antimicrobial, antibiofilm, cell surface hydrophobicity, and antioxidative activities of biosurfactant extracted from Bacillus sp., against four pathogenic strains of Staphylococcus spp. associated with vaginal infection, were studied. Our results have shown that the tested biosurfactant possesses a promising antioxidant potential, and an antibacterial potency against multidrug clinical isolates of Staphylococcus, with an inhibitory diameter ranging between 27 and 37 mm, and a bacterial growth inhibition at an MIC of 1 mg/ mL, obtained. The BioSa3 was highly effective on the biofilm formation of different tested pathogenic strains. Following their treatment by BioSa3, a significant decrease in bacterial attachment (p < 0.05) was justified by the reduction in the optical (from 0.709 to 0.111) following their treatment by BioSa3. The antibiofilm effect can be attributed to its ability to alter the membrane physiology of the tested pathogens to cause a significant decrease (p < 0.05) of over 50% of the surface hydrophobicity. Based on the obtained result of the bioactivities in the current study, BioSa3 is a good candidate in new therapeutics to better control multidrug-resistant bacteria and overcome bacterial biofilm-associated infections by protecting surfaces from microbial contamination.

Opportunities and Challenges of Bacterial Glycosylation for the Development of Novel Antibacterial Strategies

Glycosylation is a ubiquitous process that is universally conserved in nature. The various products of glycosylation, such as polysaccharides, glycoproteins, and glycolipids, perform a myriad of intra- and extracellular functions. The multitude of roles performed by these molecules is reflected in the significant diversity of glycan structures and linkages found in eukaryotes and prokaryotes. Importantly, glycosylation is highly relevant for the virulence of many bacterial pathogens. Various surface-associated glycoconjugates have been identified in bacteria that promote infectious behavior and survival in the host through motility, adhesion, molecular mimicry, and immune system manipulation. Interestingly, bacterial glycosylation systems that produce these virulence factors frequently feature rare monosaccharides and unusual glycosylation mechanisms. Owing to their marked difference from human glycosylation, bacterial glycosylation systems constitute promising antibacterial targets. With the rise of antibiotic resistance and depletion of the antibiotic pipeline, novel drug targets are urgently needed. Bacteria-specific glycosylation systems are especially promising for antivirulence therapies that do not eliminate a bacterial population, but rather alleviate its pathogenesis. In this review, we describe a selection of unique glycosylation systems in bacterial pathogens and their role in bacterial homeostasis and infection, with a focus on virulence factors. In addition, recent advances to inhibit the enzymes involved in these glycosylation systems and target the bacterial glycan structures directly will be highlighted. Together, this review provides an overview of the current status and promise for the future of using bacterial glycosylation to develop novel antibacterial strategies.

Interspecific Niche Competition Increases Morphological Diversity in Multi-Species Microbial Communities

Intraspecific competition for limited niches has been recognized as a driving force for adaptive radiation, but results for the role of interspecific competition have been mixed. Here, we report the adaptive diversification of the model bacteria Pseudomonas fluorescens in the presence of different numbers and combinations of four competing bacterial species. Increasing the diversity of competitive community increased the morphological diversity of focal species, which is caused by impeding the domination of a single morphotype. Specifically, this pattern was driven by more diverse communities being more likely to contain key species that occupy the same niche as otherwise competitively superior morphotype, and thus preventing competitive exclusion within the focal species. Our results suggest that sympatric adaptive radiation is driven by the presence or absence of niche-specific competitors.

Environmentally friendly antibiofilm strategy based on cationized phytoglycogen nanoparticles

Biofilm tolerance to antibiotics has led to the search for new alternatives in treating biofilms. The use of metallic nanoparticles has been a suggested strategy against biofilms, but their potential environmental toxicity and high cost of synthesizing have limited their applications. In this study, we investigate the potential of polysaccharidic phytoglycogen nanoparticles extracted from corn, in treating cyanobacterial biofilms, which are the source of toxins and pollution in aquatic environments. Our results revealed that the surface of cyanobacterial cells was dominated by the negatively charged functional groups such as carboxylic and phosphoric groups. The native phytoglycogen (PhX) nanoparticles were dominated with non-charged groups, such as hydroxyl groups, and the cationized phytoglycogen (PhXC) nanoparticles showed positively charged surfaces due to the presence of quaternary ammonium cations. Our results indicated that, as opposed to PhX, PhXC strongly inhibited biofilm formation when dispersed in the culture medium. PhXC also eradicated the already grown cyanobacterial biofilms. The antibiofilm properties of PhXC were attributed to its strong electrostatic interactions with the cyanobacterial cells, which could inhibit cell/cell and cell/substrate interactions and nutrient exchange with the media. This class of antibacterial polysaccharide nanoparticles may provide a novel cost-effective and environment-friendly strategy for treating biofilm formation by a broad spectrum of bacteria.

Nanotoxicity of 2D Molybdenum Disulfide, MoS2, Nanosheets on Beneficial Soil Bacteria, Bacillus cereus and Pseudomonas aeruginosa

Concerns arising from accidental and occasional releases of novel industrial nanomaterials to the environment and waterbodies are rapidly increasing as the production and utilization levels of nanomaterials increase every day. In particular, two-dimensional nanosheets are one of the most significant emerging classes of nanomaterials used or considered for use in numerous applications and devices. This study deals with the interactions between 2D molybdenum disulfide (MoS2) nanosheets and beneficial soil bacteria. It was found that the log-reduction in the survival of Gram-positive Bacillus cereus was 2.8 (99.83%) and 4.9 (99.9988%) upon exposure to 16.0 mg/mL bulk MoS2 (macroscale) and 2D MoS2 nanosheets (nanoscale), respectively. For the case of Gram-negative Pseudomonas aeruginosa, the log-reduction values in bacterial survival were 1.9 (98.60%) and 5.4 (99.9996%) for the same concentration of bulk MoS2 and MoS2 nanosheets, respectively. Based on these findings, it is important to consider the potential toxicity of MoS2 nanosheets on beneficial soil bacteria responsible for nitrate reduction and nitrogen fixation, soil formation, decomposition of dead and decayed natural materials, and transformation of toxic compounds into nontoxic compounds to adequately assess the environmental impact of 2D nanosheets and nanomaterials.

An anti-biofilm material: polysaccharides prevent the precipitation reaction of silver ions and chloride ions and lead to the synthesis of nano silver chloride

The formation of biofilm is one of the causes of bacterial pathogenicity and drug resistance. Recent studies have reported a variety of anti-biofilm materials and achieved good results. However, it is still very important to develop some materials with wider application scenarios or higher biofilm resistance. In this study, a new method to rapidly synthesize nano silver chloride with anti-biofilm activity is proposed. It is a generalizable method in which bacterial extracellular polysaccharides are used to adsorb silver ions, thereby inhibiting the formation of white large-size silver chloride precipitates, and then ultraviolet light is used to induce the synthesis of small-sized nano silver chloride. A variety of polysaccharides can be utilized in the synthesis of nano silver chloride particles. The generated complex was characterized by XRD, UV-vis, EDX, FTIR and TEM methods. Further, the novel complex was found to show highly effective anti-biofilm and bactericidal activity within the biosafety concentration. In view of the high stability of nano sliver chloride, we propose that the novel nano material has the potential as a long-term antibacterial material.

Matrix inhibition by Salmonella excludes uropathogenic E. coli from biofilm

Biofilm is a predominant lifestyle of bacteria that comprises of cells as collectives enmeshed in a polymeric matrix. Biofilm formation is vital for bacterial species as it provides access to nutrients and protects the cells from environmental stresses. Here we show that interference in biofilm matrix production is a strategy by the competing bacterial species to reduce the ability of the other species to colonize a surface. Escherichia coli colonies that differ in matrix production display different morphologies on Congo red agar media, which we exploited for screening bacterial isolates capable of inhibiting the matrix. The cell-free supernatants from growth culture of the screened isolates impaired uropathogenic E. coli (UPEC) UTI89 strain's biofilm. A physicochemical analysis suggested that the compound could be a glycopeptide or a polysaccharide. Isolates that inhibited matrix production belonged to species of the family Enterobacteriaceae such as Shigella, Escherichia, Enterobacter and Salmonella. Competition experiments between the isolates and the UPEC strain resulted in mutual inhibition, particularly during biofilm formation causing significant reduction in productivity and fitness. Furthermore, we show that Salmonella strains competitively excluded the UPEC strain in the biofilm by inhibiting its matrix production, highlighting the role of interference competition.

Antibiofilm Activity of Antarctic Sponge-Associated Bacteria against Pseudomonas aeruginosa and Staphylococcus aureus

Bioprospecting in unusual marine environments provides an innovative approach to search novel biomolecules with antibiofilm activity. Antarctic sponge-associated bacteria belonging to Colwellia, Pseudoalteromonas, Shewanella and Winogradskyella genera were evaluated for their ability to contrast the biofilm formation by Pseudomonas aeruginosa ATCC 27853 and Staphylococcus aureus ATCC 29213, as model organisms. All strains were able to produce biofilm at both 4 and 25 °C, with the highest production being for Colwellia, Shewanella and Winogradskyella strains at 4 °C after 24 h. Antibiofilm activity of cell-free supernatants (CFSs) differed among strains and on the basis of their incubation temperature (CFSs4°C and CFSs25°C). The major activity was observed by CFSs4°C against S. aureus and CFSs25°C against P. aeruginosa, without demonstrating a bactericidal effect on their growth. Furthermore, the antibiofilm activity of crude extracts from Colwellia sp. GW185, Shewanella sp. CAL606, and Winogradskyella sp. CAL396 was also evaluated and visualized by confocal laser scanning microscopic images. Results based on the surface-coating assay and surface tension measurements suggest that CFSs and the crude extracts may act as biosurfactants inhibiting the first adhesion of P. aeruginosa and S. aureus. The CFSs and the novel biopolymers may be useful in applicative perspectives for pharmaceutical and environmental purposes.

Characterization of Kazachstania slooffiae, a Proposed Commensal in the Porcine Gut

Kazachstania slooffiae is a fungus commonly isolated from the gastrointestinal tract and feces of post-weaning pigs. Studies have implicated its ability to positively alter piglet gut health through potential symbioses with beneficial bacteria, including Lactobacillus and Prevotella, in providing amino acids as an energy source for microbial and piglet growth, and it has been found to be positively correlated with short-chain fatty acids in the piglet gut. However, basic mycological information remains limited, hampering in vitro studies. In this study, we characterized the growth parameters, biofilm formation ability, susceptibility to antimicrobials, and genetic relatedness of K. slooffiae to other fungal isolates. Optimal fungal growth conditions were determined, no antifungal resistance was found against multiple classes of antifungal drugs (azoles, echinocandins, polyenes, or pyrimidine analogues), and dimorphic growth was observed. K. slooffiae produced biofilms that became more complex in the presence of Lactobacillus acidophilus supernatant, suggesting positive interactions with this bacterium in the gut, while Enterococcus faecalis supernatant decreased density, suggesting an antagonistic interaction. This study characterizes the in vitro growth conditions that are optimal for further studies of K. slooffiae, which is an important step in defining the role and interactions of K. slooffiae in the porcine gut environment.

Maipomycin A, a Novel Natural Compound With Promising Anti-biofilm Activity Against Gram-Negative Pathogenic Bacteria

Pathogenic bacterial biofilms play an important role in recurrent nosocomial and medical device-related infections. Once occurred, the complex structure of the biofilm promotes the development of antibiotic resistance and becomes extremely difficult to eradicate. Here we describe a novel and effective anti-biofilm compound maipomycin A (MaiA), which was isolated from the metabolites of a rare actinomycete strain Kibdelosporangium phytohabitans XY-R10. Its structure was deduced from analyses of spectral data and confirmed by single-crystal X-ray crystallography. This natural product demonstrated a broad spectrum of anti-biofilm activities against Gram-negative bacteria. Interestingly, the addition of Fe(II) or Fe(III) ions could block the biofilm inhibition activity of MaiA because it is an iron chelator. However, not all iron chelators showed biofilm inhibition activity, suggesting that MaiA prevents biofilm formation through a specific yet currently undefined pathway. Furthermore, MaiA acts as a synergist to enhance colistin efficacy against Acinetobacter baumannii. Our results indicate that MaiA may potentially serve as an effective antibiofilm agent to prevent Gram-negative biofilm formation in future clinical applications.

Inhibitory Effects of Escherichia coli on the Formation and Development of Staphylococcus epidermidis Biofilm

In the present study, we examined whether a commensal gut bacterium Escherichia coli might prevent the formation and development of the biofilm of Staphylococcus epidermidis, a nosocomial extraintestinal pathogen but not a gut microorganism. When co-cultured with S. epidermidis, E. coli strain ATCC 35218, a non-pathogenic strain, was found to be dominant in the biofilm formed on the surface of wells of a microtiter plate. In addition, E. coli significantly incorporated and grew in a niche preoccupied by S. epidermidis biofilm. Two other E. coli strains (strain K-12 and B) also showed to interfere the biofilm formation by S. epidermidis. In contrast, S. epidermidis could not grow in a niche preoccupied by E. coli biofilm. These results suggest that, through inhibition of the formation and development of the biofilm, E. coli may eliminate S. epidermidis from the gastrointestinal tract.

Screening of antibiofilm and anti-quorum sensing activty of Actinomycetes isolates extracts against aquaculture pathogenic bacteria

Background

Indonesia is the third largest producer of fish and other aquaculture products in the world, making this industry a major contributor in the economy of Indonesia. However, this industry continually overcome challenges, one of them are bacterial outbreaks. In addition, the emergence of these bacterial outbreaks were worsen due to the biofilm produced by many significant pathogenic bacteria and the impact of increased antibiotic resistance. These issues have become a global concern, because antibiotics are currently one of the main treatments available to overcome this problems. Therefore, studies aimed at finding and characterizing bioactive compounds to combat these issues. In this study actinomycetes isolates were screened and characterized for their bioactive compounds produced which have inhibitory and destructive activity and also QS inhibitors against biofilm structure of aquatic pathogenic bacteria, such as Vibrio harveyi, A. hydrophila, and S. agalactiae.

Result

Extracts (20 mg/mL) produced by sixteen Actinomycetes isolates showed anti-quorum sensing activity towards reporter stain Chromobacterium violaceum wild-type. Most of these extracts showed better inhibitory activity on all of the pathogenic bacteria biofilm structure tested than the destructive activity on the preformed of those biofilm structure. Subsequently, we also performed characterization of bioactive compound and found that in this study, polysaccharide is the most common antibiofilm agents, which were responsible to their antibiofilm activity. Finally, we found that the value of LC₅₀ of all extracts tested were more than 1 mg/mL, thereby all of extracts tested did not show cyto-toxic effect against Artemia salina.

Conclusion

All of the extracts of Actinomycetes isolates showed promising inhibitory activity towards biofilm structure of pathogenic bacteria tested. So far, all of the extracts are potential to be QS inhibitors and antibiofilm agents of all pathogenic bacteria tested.

Diversity of Bacteria and Bacterial Products as Antibiofilm and Antiquorum Sensing Drugs Against Pathogenic Bacteria

The increase in antibiotic resistance of pathogenic bacteria has led to the development of new therapeutic approaches to inhibit biofilm formation as well as interfere quorum sensing (QS) signaling systems. The QS system is a phenomenon in which pathogenic bacteria produce signaling molecules that are involved in cell to cell communication, production of virulence factors, biofilm maturation, and several other functions. In the natural environment, several non-pathogenic bacteria are present as mixed population along with pathogenic bacteria and they control the behavior of microbial community by producing secondary metabolites. Similarly, non-pathogenic bacteria also take advantages of the QS signaling molecule as a sole carbon source for their growth through catabolism with enzymes. Several enzymes are produced by bacteria which disrupt the biofilm architecture by degrading the composition of extracellular polymeric substances (EPS) such as exopolysaccharide, extracellular- DNA and protein. Thus, the interference of QS system by bacterial metabolic products and enzymatic catalysis, modification of the QS signaling molecules as well as enzymatic disruption of biofilm architecture have been considered as the alternative therapeutic approaches. This review article elaborates on the diversity of different bacterial species with respect to their metabolic products as well as enzymes and their molecular modes of action. The bacterial enzymes and metabolic products will open new and promising perspectives for the development of strategies against the pathogenic bacterial infections.

Antibiofilm Activity of Lactobacillus plantarum 12 Exopolysaccharides against Shigella flexneri

In developing countries, Shigella flexneri is the most common enteric pathogen causing bacillary dysentery. Biofilm formation by S. flexneri can cause the emergence of antibiotic-resistant strains, which poses serious threats to food safety and human health. In this study, the effects of Lactobacillus plantarum 12 exopolysaccharides (L-EPSs) and S. flexneri exopolysaccharides (S-EPSs) on S. flexneri CMCC51574 biofilm formation were investigated. The results showed that L-EPS could decrease polysaccharide production in the extracellular polymeric matrix of S. flexneri and inhibit biofilm formation by S. flexneri L-EPS could decrease the minimum biofilm elimination concentration (MBEC) of antibiotics against S. flexneri biofilm and inhibit S. flexneri adhesion to and invasion into HT-29 cell monolayers, which might be ascribed to S. flexneri biofilm disturbance by L-EPS. In contrast, S-EPS exhibited the opposite effects compared to L-EPS. The monosaccharide composition analysis showed that L-EPS was composed of mannose, glucuronic acid, galactosamine, glucose, galactose, and xylose, with the molar ratio of 32.26:0.99:1.79:5.63:0.05:4.07, while S-EPS was composed of mannose, glucuronic acid, galactosamine, glucose, and galactose, with the molar ratio of 25.43:2.28:7.13:5.35. L-EPS was separated into the neutral polysaccharide L-EPS 1-1 and the acidic polysaccharide L-EPS 2-1 by ion-exchange chromatography and gel chromatography. L-EPS 2-1 exerted higher antibiofilm activity than L-EPS 1-1. The antibiofilm activity of L-EPS might be associated with its structure.IMPORTANCES. flexneri is a widespread foodborne pathogen causing food contamination and responsible for food poisoning outbreaks related to various foods in developing countries. Not only has biofilm formation by S. flexneri been difficult to eliminate, but it has also increased the drug resistance of the strain. In the present study, it was demonstrated that L-EPSs secreted by Lactobacillus plantrum 12 could inhibit S. flexneri biofilm formation on, adhesion to, and invasion into HT-29 cells. Also, L-EPSs could decrease the minimum biofilm elimination concentration (MBEC) of the antibiotics used against S. flexneri biofilm. Therefore, L-EPSs were shown to be bioactive macromolecules with the potential ability to act against S. flexneri infections.

Antibacterial potential of a novel Lactobacillus casei strain isolated from Chinese northeast sauerkraut and the antibiofilm activity of its exopolysaccharides

Lactobacillus spp., as probiotics, have shown efficacy in the inhibition of pathogenic bacteria in the intestinal tract. In this study, we investigated the antibacterial activity of Lactobacillus casei NA-2, which was isolated from northeast sauerkraut in China. The results of co-culture suggested that L. casei NA-2 could inhibit the growth of Bacillus cereus, Staphylococcus aureus, Salmonella typhimurium and Escherichia coli O157:H7. Moreover, L. casei NA-2 could adhere to the four pathogenic bacteria potentially associated with its exopolysaccharide (EPS). EPS from L. casei NA-2 was then isolated and its activity determined. The results showed that EPS inhibited the biofilms of B. cereus, S. aureus, S. typhimurium and E. coli O157:H7, with the highest inhibition ratios of 95.5% ± 0.1%, 30.2% ± 3.3%, 14.3% ± 0.6%, and 16.9% ± 5.4%, respectively. Moreover, EPS was able to disperse B. cereus, S. aureus, S. typhimurium and E. coli O157:H7 by 94.1% ± 1.2%, 31.8% ± 8.6%, 40.8% ± 3.3% and 49.6% ± 3.8%, respectively. Results showed that EPS from L. casei NA-2 have potential antibacterial properties by inhibiting biofilm formation and dispersing pathogenic bacteria. In conclusion, the antibiofilm property of the EPS on the surface of L. casei NA-2 is one of the possible reasons for antibacterial activity of L. casei NA-2.

Inhibitory effect of trisodium citrate on biofilms formed by Klebsiella pneumoniae

OBJECTIVES

Klebsiella pneumoniae is a significant nosocomial pathogen related to ventilator-associated pneumonia owing to biofilm formation. Trisodium citrate (TSC) has antibacterial activity, but there is little research on the effect of TSC on biofilm formed by K. pneumoniae. The aims of this study were to evaluate the inhibitory effect of 4% TSC on K. pneumoniae biofilm formation and to determine the best time of TSC addition for biofilm inhibition.

METHODS

A total of 45 K. pneumoniae strains isolated from tracheal tip and sputum specimens were included. Modified Congo red agar was used to screen for biofilm production. Biofilm-positive strains were cultured for 4 days. TSC (4%) was added either initially or 3 days later. Crystal violet staining was used to quantify biofilm mass by measuring the optical density at 570 nm (OD₅₇₀). Scanning electron microscopy (SEM) was used to observe biofilm morphology.

RESULTS

The OD₅₇₀ was significantly lower in the 4% TSC group than that in the no-TSC group during the 4-day experiment. Compared with addition of TSC after 3 days, initial TSC addition resulted in a significant absorbance decrease (Day 4, 0.63 ± 0.11 later-TSC group vs. 0.41 ± 0.16 initial-TSC group). As observed by SEM, bacteria were stacked most densely in the no-TSC group on Day 4. In contrast, few bacteria were observed when TSC was added initially, whilst bacteria were obviously dispersed when TSC was added after 3 days.

CONCLUSION

TSC can inhibit K. pneumoniae biofilm formation and has the best effect when added initially.

Characterization of self-assembled bioflocculant from the microbial consortium and its applications

Bioflocculant has been recently exploited in various research activities. In this research, we report for the first time that a novel bioflocculant can self-assemble into nanoparticles with an irregular structure in solution. Bioflocculant has been developed from novel consortium encompassing Enterococcus faecalis, Proteus mirabilis, Lysini bacillus sp., inoculated into the modified medium such as hydrolyzed wheat bran and rice bran extract. Characterization of bioflocculant shows that it is made up of mannose, fructose, raffinose, and galactose with a slightly negative charges. They are further characterized by FTIR and XPS. 3D-EEM and MALDITOF-MS are confirmed the proteoglycan nature of the bioflocculant. These bioflocculant not only exhibits greater biosorption of heavy metals by self-flocculating (or) self-aggregating activity, but also possesses mosquitocidal and anti-biofilm activity due to its cell surface modification. Further research have to be carried out regarding the mechanism of self-assembly nature of bioflocculant into nanoparticle in solution which provide a new path for bioremediation and biomedical application.

Antibiofilm activity in the culture supernatant of a marine Pseudomonas sp. bacterium

In the marine environment, most solid surfaces are covered by microbial biofilms, mainly composed of bacteria and diatoms. The negative effects of biofilms on materials and equipment are numerous and pose a major problem for industry and human activities. Since marine micro-organisms are an important source of bioactive metabolites, it is possible that they synthesize natural ecofriendly molecules that inhibit the adhesion of organisms. In this work, the antibiofilm potential of marine bacteria was investigated using Flavobacterium sp. II2003 as a target. This strain is potentially a pioneer strain of bacteria that was previously selected from marine biofilms for its strong biofilm-forming ability. The culture supernatants of 86 marine heterotrophic bacteria were tested for their ability to inhibit Flavobacterium sp. II2003 biofilm formation and the Pseudomonas sp. IV2006 strain was identified as producing a strong antibiofilm activity. The Pseudomonas sp. IV2006 culture supernatant (SNIV2006) inhibited Flavobacterium sp. II2003 adhesion without killing the bacteria or inhibiting its growth. Moreover, SNIV2006 had no effect on the Flavobacterium sp. II2003 cell surface hydrophilic/hydrophobic and general Lewis acid–base characteristics, but modified the surface properties of glass, making it on the whole more hydrophilic and more alkaline and significantly reducing bacterial cell adhesion. The glass-coating molecules produced by Pseudomonas sp. IV2006 were found to probably be polysaccharides, whereas the antibiofilm molecules contained in SNIV2006 and acting during the 2 h adhesion step on glass and polystyrene surfaces would be proteinaceous. Finally, SNIV2006 exhibited a broad spectrum of antibiofilm activity on other marine bacteria such as Flavobacterium species that are pathogenic for fish, and human pathogens in both the medical environment, such as Staphylococcus aureus and Pseudomonas aeruginosa , and in the food industry, such as Yersinia enterocolitica . Thus, a wide range of applications could be envisaged for the SNIV2006 compounds, both in aquaculture and human health.

Single-species (bacterial, fungal, or mycobacterial) biofilms or dual-species (mycobacterial-fungal) biofilms formed in dialysis fluids

Continuous hemodialysis system monitoring is necessary to prevent microorganism growth and health problems. This study evaluates single- and dual-species biofilm formation in microtiter plates by using dialysis solutions under aerobiosis or 5% CO₂ atmosphere. Escherichia coli, Pseudomonas aeruginosa, Staphylococcus epidermidis, Candida parapsilosis sensu lato, and Mycobacterium smegmatis produce single-species biofilms in all dialysis solutions in both oxygenation conditions. Dual-species biofilm cultures grown at 5% CO₂ atmosphere and in dialysate containing glucose reveal that M. smegmatis benefits from its association with C. parapsilosis. The dialysate and its constituent solutions support the growth of all the mono-species and the inter-kingdom mycobacterial/yeast biofilms in both aerobiosis and microaerophilic conditions.

In vitro assessment of inter-kingdom biofilm formation by bacteria and filamentous fungi isolated from a drinking water distribution system

The main focus so far in the study of biofilm formation in drinking water has been bacteria. Studies on biofilm formation involving filamentous fungi are, therefore, scarce. This study aimed to assess and characterize the ability of these microorganisms to interact with bacteria whilst forming inter-kingdom biofilms. Biofilms were analysed in terms of total biomass, metabolic activity, bacterial colony forming units and morphology by epifluorescence microscopy. The quantitative methods revealed that biofilm mass increased over time for both single and inter-kingdom biofilms, while specific metabolic activity decreased, in general, along the time points evaluated. Microscopic data visually confirmed the biofilm mass increase over time. This study shows that fungal stage development is important in the first 24 h of biofilm formation. Inter-kingdom biofilm formation is microorganism dependent and inter-kingdom biofilms may provide an advantage to the opportunistic bacterium Acinetobacter calcoaceticus to replicate and proliferate when compared with Methylobacterium oryzae.

Preparation, partial characterization and biological activity of exopolysaccharides produced from Lactobacillus fermentum S1

A high slime-producing Lactobacillus fermentum strain (named as L. fermentum S1) was isolated from traditional fermented Fuyuan pickle, which was made of white turnip and collected from Fuyuan county, Yunnan province, China. We extracted and purified the exopolysaccharides from L. fermentum S1, and investigated their preliminary structure characteristics and biological activities. Three purified exopolysaccharide fractions, designated as EPS1, EPS2 and EPS3, were obtained from the culture supernatant of L. fermentum S1 by ethanol precipitation, anion exchange and gel filtration chromatography. The EPS2 and EPS3 were homogeneous with molecular weights of 4.45 × 10⁶ and 2.82 × 10⁶ Da, respectively. All the purified EPS fractions were composed of glucose, galactose, mannose and arabinose, but with different molar ratios. EPS1, EPS2 and EPS3 presented different surface morphologies and their degradation temperatures were 302.7°C, 316.3°C and 316.9°C, respectively. Bioactivity research showed that L. fermentum S1 EPS elicited free radical scavenging capacity and ferric reducing antioxidant power, and 1 mg/mL of EPS significantly improved the gastrointestinal transit tolerance of non EPS-producing strain L. fermentum LG1. Moreover, S1 EPS had a favorable anti-biofilm activity against Escherichia coli and Staphylococcus aureus. These results indicated that S1 EPS could be explored as a promising functional adjunct for application in foods.

A Putative Type V Pilus Contributes to Bacteroides thetaiotaomicron Biofilm Formation Capacity

Bacteroides thetaiotaomicron is a prominent anaerobic member of the healthy human gut microbiota. While the majority of functional studies on B. thetaiotaomicron addressed its impact on the immune system and the utilization of diet polysaccharides, B. thetaiotaomicron biofilm capacity and its contribution to intestinal colonization are still poorly characterized. We tested the natural adhesion of 34 B. thetaiotaomicron isolates and showed that although biofilm capacity is widespread among B. thetaiotaomicron strains, this phenotype is masked or repressed in the widely used reference strain VPI 5482. Using transposon mutagenesis followed by a biofilm positive-selection procedure, we identified VPI 5482 mutants with increased biofilm capacity corresponding to an alteration in the C-terminal region of BT3147, encoded by the BT3148-BT3147 locus, which displays homology with Mfa-like type V pili found in many Bacteroidetes We show that BT3147 is exposed on the B. thetaiotaomicron surface and that BT3147-dependent adhesion also requires BT3148, suggesting that BT3148 and BT3147 correspond to the anchor and stalk subunits of a new type V pilus involved in B. thetaiotaomicron adhesion. This study therefore introduces B. thetaiotaomicron as a model to study proteinaceous adhesins and biofilm-related phenotypes in this important intestinal symbiont.IMPORTANCE Although the gut anaerobe Bacteroides thetaiotaomicron is a prominent member of the healthy human gut microbiota, little is known about its capacity to adhere to surfaces and form biofilms. Here, we identify that alteration of a surface-exposed protein corresponding to a type of pili found in many Bacteroidetes increases B. thetaiotaomicron biofilm formation. This study lays the ground for establishing this bacterium as a model organism for in vitro and in vivo studies of biofilm-related phenotypes in gut anaerobes.

Polysaccharide Galactan Inhibits Pseudomonas aeruginosa Biofilm Formation but Protects Pre-formed Biofilms from Antibiotics

Microorganisms residing within a biofilm become more tolerant to antibiotics and other types of adverse impact, and biofilm formation by pathogenic bacteria is an important problem of current medicine. Polysaccharides that prevent biofilm formation are among the promising candidates to help tackle this problem. Earlier we demonstrated the ability of a potato polysaccharide galactan to inhibit biofilm formation by a Pseudomonas aeruginosa clinical isolate. Here we investigate the effect of potato galactan on P. aeruginosa biofilms in more detail. Microscopic analysis indicated that the galactan did not interfere with the adhesion of bacterial cells to the substrate but prevented the build-up of bacterial biomass. Moreover, the galactan not only inhibited biofilm formation, but partially destroyed pre-formed biofilms. Presumably, this activity of the galactan was due to the excessive aggregation of bacterial cells, which prohibited the formation and maintenance of proper biofilm architecture, or due to some other mechanisms of biofilm structure remodeling. This led to an unexpected effect, i.e., P. aeruginosa biofilms treated with an antibiotic and the galactan retained more viable bacterial cells compared to biofilms treated with the antibiotic alone. Galactan is the first polysaccharide demonstrated to exert such effect on bacterial biofilms.

Inhibition of Pseudomonas aeruginosa biofilm formation and expression of virulence genes by selective epimerization in the peptide Esculentin-1a(1-21)NH2

Pseudomonas aeruginosa is a pathogenic bacterium known to cause serious human infections, especially in immune-compromised patients. This is due to its unique ability to transform from a drug-tolerant planktonic to a more dangerous and treatment-resistant sessile life form, called biofilm. Recently, two derivatives of the frog skin antimicrobial peptide esculentin-1a, i.e. Esc(1-21) and its D-amino acids containing diastereomer Esc(1-21)-1c, were characterized for their powerful anti-Pseudomonal activity against both forms. Prevention of biofilm formation already in its early stages could be even more advantageous for counteracting infections induced by this bacterium. In this work, we studied how the diastereomer Esc(1-21)-1c can inhibit Pseudomonas biofilm formation in comparison to the parent peptide and two clinically-used conventional antibiotics, i.e. colistin and aztreonam, when applied at dosages below the minimal growth inhibitory concentration. Biofilm prevention was correlated to the peptides' ability to inhibit Pseudomonas motility and to reduce the production of virulent metabolites, for example, pyoverdine and rhamnolipids. Furthermore, the molecular mechanism underlying these activities was evaluated by studying the peptides' effect on the expression of key genes involved in the virulence and motility of bacteria, as well as by monitoring the peptides' binding to the bacterial signaling nucleotide ppGpp. Our results demonstrate that the presence of only two D-amino acids in Esc(1-21)-1c is sufficient to downregulate ppGpp-mediated expression of biofilm-associated genes, presumably as a result of higher peptide stability and therefore prolonged interaction with the nucleotide. Overall, these studies should assist efficient design and optimization of new anti-infective agents with multiple pharmacologically beneficial properties.

Super-Resolution Fluorescence Microscopy Study of the Production of K1 Capsules by Escherichia coli: Evidence for the Differential Distribution of the Capsule at the Poles and the Equator of the Cell

The production of Escherichia coli K1 serotype capsule was investigated using direct stochastic optical reconstruction microscopy with live bacteria and graphene oxide-coated coverslips, overcoming many morphological artifacts found in other high-resolution imaging techniques. Super-resolution fluorescence images showed that the K1 capsular polysaccharide is not uniformly distributed on the cell surface, as previously thought. These studies demonstrated that on the cell surfaces the K1 capsule at the poles had bimodal thicknesses of 238 ± 41 and 323 ± 62 nm, whereas at the equator, there was a monomodal thickness of 217 ± 29 nm. This bimodal variation was also observed in high-pressure light-scattering chromatography measurements of purified K1 capsular polysaccharide. Particle tracking demonstrated that the formation of the capsule was dominated by the expansion of lyso-phosphatidylglycerol (lyso-PG) rafts that anchor the capsular polysaccharide in the outer membrane, and the expansion of these rafts across the cell surface was driven by new material transported through the capsular biosynthesis channels. The discovery of thicker capsules at the poles of the cell will have implications in mediating interactions between the bacterium and its immediate environment.

Antimicrobial and antibiofilm activity of biopolymer-Ni, Zn nanoparticle biocomposites synthesized using R. mucilaginosa UANL-001L exopolysaccharide as a capping agent

Introduction: Global increase in the consumption of antibiotics has induced selective stress on wild-type microorganisms, pushing them to adapt to conditions of higher antibiotic concentrations, and thus an increased variety of resistant bacterial strains have emerged. Metal nanoparticles synthesized by green methods have been studied and proposed as potential antimicrobial agents against both wild-type and antibiotic-resistant strains; in addition, exopolysaccharides have been used as capping agent of metal nanoparticles due to their biocompatibility, reducing biological risks in a wide variety of applications. Purpose: In this work, we use an exopolysaccharide, from Rhodotorula mucilaginosa UANL-001L, an autochthonous strain from the Mexican northeast, as a capping agent in the synthesis of Zn, and Ni, nanoparticle biopolymer biocomposites. Materials and methods: To physically and chemically characterize the synthesized biocomposites, FT-IR, UV-Vs, TEM, SAED and EDS analysis were carried out. Antimicrobial and antibiofilm biological activity were tested for the biocomposites against two resistant clinical strains, a Gram-positive Staphylococcus aureus, and a Gram-negative Pseudomonas aeruginosa. Antimicrobial activity was determined using a microdilution assay whereas antibiofilm activity was analyzed through crystal violet staining. Results: Biocomposites composed of exopolysaccharide capped Zn and Ni metal nanoparticles were synthesized through a green synthesis methodology. The average size of the Zn and Ni nanoparticles ranged between 8 and 26 nm, respectively. The Ni-EPS biocomposites showed antimicrobial and antibiofilm activity against resistant strains of Staphylococcus aureus and Pseudomonas aeruginosa at 3 and 2 mg/mL, respectively. Moreover, Zn-EPS biocomposites showed antimicrobial activity against resistant Staphylococcus aureus at 1 mg/mL. Both biocomposites showed no toxicity, as renal function showed no differences between treatments and control in the in vivo assays with male rats tests in this study at a concentration of 24 mg/kg of body weight. Conclusion: The exopolysaccharide produced by Rhodotorula mucilaginosa UANL-001L is an excellent candidate as a capping agent in the synthesis of biopolymer-metal nanoparticle biocomposites. Both Ni and Zn-EPS biocomposites demonstrate to be potential contenders as novel antimicrobial agents against both Gram-negative and Gram-positive clinically relevant resistant bacterial strains. Moreover, Ni-EPS biocomposites also showed antibiofilm activity, which makes them an interesting material to be used in different applications to counterattack global health problems due to the emergence of resistant microorganisms.

Inhibition of Lactobacillus biofilm growth in fuel ethanol fermentations by Bacillus

Commercial fuel ethanol fermentations suffer from microbial contaminants, particularly species of Lactobacillus that may persist as antibiotic-resistant biofilms. In this study, culture supernatants from 54 strains of Bacillus known to produce lipopeptides were tested for inhibition of biofilm formation by Lactobacillus fermentum, L. plantarum, and L. brevis strains previously isolated as biofilm-forming contaminants of a commercial fuel ethanol facility. Eleven Bacillus strains inhibited biofilm formation by all three strains by at least 65% of controls. None of these strains inhibited Saccharomyces cerevisiae. Three strains also significantly inhibited planktonic cultures of Lactobacillus. Culture supernatants from B. nakamurai strain NRRL B-41091 were particularly effective. Inhibition was bacteriostatic rather than bacteriocidal, and appeared to be specific for strains of Lactobacillus. Furthermore, the inhibitor from B. nakamurai was shown to prevent stuck fermentations in a corn mash model fermentation system of S. cerevisiae contaminated with L. fermentum.

Genetic exchanges are more frequent in bacteria encoding capsules

Capsules allow bacteria to colonize novel environments, to withstand numerous stresses, and to resist antibiotics. Yet, even though genetic exchanges with other cells should be adaptive under such circumstances, it has been suggested that capsules lower the rates of homologous recombination and horizontal gene transfer. We analysed over one hundred pan-genomes and thousands of bacterial genomes for the evidence of an association between genetic exchanges (or lack thereof) and the presence of a capsule system. We found that bacteria encoding capsules have larger pan-genomes, higher rates of horizontal gene transfer, and higher rates of homologous recombination in their core genomes. Accordingly, genomes encoding capsules have more plasmids, conjugative elements, transposases, prophages, and integrons. Furthermore, capsular loci are frequent in plasmids, and can be found in prophages. These results are valid for Bacteria, independently of their ability to be naturally transformable. Since we have shown previously that capsules are commonly present in nosocomial pathogens, we analysed their co-occurrence with antibiotic resistance genes. Genomes encoding capsules have more antibiotic resistance genes, especially those encoding efflux pumps, and they constitute the majority of the most worrisome nosocomial bacteria. We conclude that bacteria with capsule systems are more genetically diverse and have fast-evolving gene repertoires, which may further contribute to their success in colonizing novel niches such as humans under antibiotic therapy.

Previous works showed that bacteria encoding capsules are better colonizers and are dominant in most environments suggesting a positive role for capsules in the genetic diversification of bacteria. Yet, it has been repeatedly suggested, based almost exclusively studies in few model species, that such bacteria are less diverse and engage in fewer genetic exchanges. Here, we reverse the current paradigm and show that bacteria encoding capsules have larger and more diverse gene repertoires, which change faster by horizontal gene transfer and recombination. Our study alters the traditional view of the capsule as a barrier to gene flow and raises novel questions about the role of capsules in bacterial adaptation.