The Bacillary Postbiotics, Including 2-Undecanone, Suppress the Virulence of Pathogenic Microorganisms.

Secreted molecules from probiotic Bacilli have often been considered potential pharmaceuticals to fight infections caused by bacterial or yeast pathogens. In the present study, we investigated the antagonistic potential of secreted probiotic filtrates (hereafter, postbiotics) derived from Lactobacillus plantarum cells against pathogenic microorganisms, such as Escherichia coli, Staphylococcus aureus, and Candida albicans. We found that the postbiotics mitigate the biofilms of the tested pathogens with no notable effect on their planktonic growth. In addition, the postbiotics suppressed some virulence traits, for instance, the dendrite swarming motility of E. coli and yeast-to-hyphal switch in C. albicans. Further assays with an active constituent produced by the L. plantarum cells-2-undecanone revealed two significant findings: (i) 2-undecanone inhibits C. albicans biofilms and hyphae in vitro and in a Caenorhabditis elegans model, and (ii) it interacts specifically with Gln 58 amino acid residue of hyphal wall protein-1 (Hwp-1) in molecular docking analysis. The results suggest the targeted mode of antagonistic action of 2-undecanone against C. albicans biofilm. In total, the findings of the study depict an appealing strategy to use postbiotics, including specific ketone molecules, produced by L. plantarum for developing novel antibiofilm and anti-hyphal pharmaceuticals.

Spatiotemporal bio-shielding of bacteria through consolidated geometrical structuring.

The probiotic bacterium Lactobacillus plantarum is often reckoned as a 'generalist' for its ability to adapt and survive in diverse ecological niches. The genomic signatures of L. plantarum have shown its intricate evolutionary ancestry and dynamic lifestyles. Here, we report on a unique geometrical arrangement of the multicellular population of L. plantarum cells. Prominently, a phenomenon of the cone-shaped colony formation and V-shaped cell chaining are discovered in response to the acidic-pH environment. Moreover, subsequent cold stress response triggers an unusual cellular arrangement of consolidated bundles, which appeared to be independently governed by a small heat shock protein (HSP 1). We further report that the V-shaped L. plantarum chaining demonstrates potent antagonistic activity against Candida albicans, a pathogenic yeast, both in vitro and in a Caenorhabditis elegans co-infection model. Finally, we deduce that the multifaceted traits manifested by this probiotic bacterium is an outcome of its dynamic flexibility and cellular heterogeneity.

Chickpea-Derived Prebiotic Substances Trigger Biofilm Formation by Bacillus subtilis.

Chickpea-based foods are known for their low allergenicity and rich nutritional package. As an essential dietary legume, chickpea is often processed into milk or hummus or as an industrial source of protein and starch. The current study explores the feasibility of using the chickpea-derived prebiotic substances as a scaffold for growing Bacillus subtilis (a prospective probiotic bacterium) to develop synbiotic chickpea-based functional food. We report that the chickpea-derived fibers enhance the formation of the B. subtilis biofilms and the production of the antimicrobial pigment pulcherrimin. Furthermore, electron micrograph imaging confirms the bacterial embedding onto the chickpea fibers, which may provide a survival tactic to shield and protect the bacterial population from environmental insults. Overall, it is believed that chickpea-derived prebiotic substances provide a staple basis for developing functional probiotics and synbiotic food.

Biofilm formation onto starch fibres by Bacillus subtilis governs its successful adaptation to chickpea milk.

Beneficial biofilms may confer effective adaptation to food matrices that assist bacteria in enduring hostile environmental conditions. The matrices, for instance, dietary fibres of various food products, might serve as a natural scaffold for bacterial cells to adhere and grow as biofilms. Here, we report on a unique interaction of Bacillus subtilis cells with the resistant starch fibresof chickpea milk (CPM), herein CPM fibres, along with the production of a reddish-pink pigment. Genetic analysis identified the pigment as pulcherrimin, and also revealed the involvement of Spo0A/SinI pathway in modulating the observed phenotypes. Besides, through successful colonization of the CPM fibres, the wild-type cells of B. subtilis displayed enhanced survivability and resilience to environmental stress, such as heat and in vitro gastrointestinal treatments. In total, we infer that the biofilm formation on CPM fibres is an adaptation response of B. subtilis for strategic survival.

Mitigating Milk-Associated Bacteria through Inducing Zinc Ions Antibiofilm Activity.

Dairy products are a sector heavily impacted by food loss, often due to bacterial contaminations. A major source of contamination is associated with the formation of biofilms by bacterial species adopted to proliferate in milk production environment and onto the surfaces of milk processing equipment. Bacterial cells within the biofilm are characterized by increased resistance to unfavorable environmental conditions and antimicrobial agents. Members of the Bacillus genus are the most commonly found spoilage microorganisms in the dairy environment. It appears that physiological behavior of these species is somehow depended on the availability of bivalent cations in the environment. One of the important cations that may affect the bacterial physiology as well as survivability are Zn2+ ions. Thus, the aim of this study was to examine the antimicrobial effect of Zn2+ ions, intending to elucidate the potential of a zinc-based antibacterial treatment suitable for the dairy industry. The antimicrobial effect of different doses of ZnCl2 was assessed microscopically. In addition, expression of biofilm related genes was evaluated using RT-PCR. Analysis of survival rates following heat treatment was conducted in order to exemplify a possible applicative use of Zn2+ ions. Addition of zinc efficiently inhibited biofilm formation by B. subtilis and further disrupted the biofilm bundles. Expression of matrix related genes was found to be notably downregulated. Microscopic evaluation showed that cell elongation was withheld when cells were grown in the presence of zinc. Finally, B. cereus and B. subtilis cells were more susceptible to heat treatment after being exposed to Zn2+ ions. It is believed that an anti-biofilm activity, expressed in downregulation of genes involved in construction of the extracellular matrix, would account for the higher sensitivity of bacteria during heat pasteurization. Consequently, we suggest that Zn2+ ions can be of used as an effective antimicrobial treatment in various applications in the dairy industry, targeting both biofilms and vegetative bacterial cells.

Antibacterial and antibiofilm activities of diphyllin against fish pathogens.

Annihilation of biofilm forming bacterial pathogens is a challenging aspect in seafood and aquaculture industries. Microbes growing as biofilms cause deleterious effects on food products leading to food spoilage or loss of shelf life. As a measure to fight biofilms, agents that prevent/disrupt biofilms are recurrently screened. The study exemplifies the bactericidal and biofilm disruption potentials of a plant derived compound, diphyllin, against fish pathogens that colonizes Oreochromis mossambicus and Oreochromis niloticus. Precisely, diphyllin disrupted Salmonella typhi biofilms by triggering reactive oxidative species (ROS). Diphyllin-induced ROS had satisfactory correlation with S. typhi cell membrane damage and intracellular DNA degradation profiles providing a putative mechanistic model. In conclusion, the study identifies diphyllin as a therapeutic and dispersal agent aimed at biofilms formed by food-borne pathogens that persistently plague food processing and aquaculture settings.

Binary and ternary sustainable composites of gellan gum, hydroxyethyl cellulose and lignin for food packaging applications: Biocompatibility, antioxidant activity, UV and water barrier properties.

Biopolymers of gellan gum (G), 2-hydroxyethyl cellulose (HEC), and lignin (L)-based binary and ternary sustainable composites were prepared for food packaging and biomedical application. The composite films were flexible and transparent or translucent with slight brown in color. The incorporation of lignin considerably improved the thermal and mechanical and hydrophobic properties of the composite films. The addition of 10 wt% of lignin to the composites increased the tensile strength by 54.3% and 59.2% respectively. The prepared lignin-based composite films showed high ultraviolet (UV) protection, with almost 100% protection against UVB (280-320 nm) and 90% against UVA (320-400 nm). The surface hydrophobicity of the composite films increased with the addition of lignin. The binary and ternary composites containing 1, 5, and 10 wt% lignin exhibited excellent radical scavenging activities. The gellan gum/HEC/lignin based composite films achieved the best biocompatibility. The obtained composites showed efficient antioxidant and non-cytotoxic activities, although there was no remarkable antimicrobial activity.

Nematicidal activity of 5-iodoindole against root-knot nematodes.

Multi-drug resistance in nematodes is a serious problem as lately several resistant phenotypes have emerged following the intermittent usage of synthetic nematicides. Contemporary research continues to focus on developing and/or repurposing small molecule inhibitors that are eco-friendly. Here, we describe the repurposing of the indole derivative, 5-iodoindole, as a nematicide for the root-knot nematode, Meloidogyne incognita. 5-Iodoindole effectively killed juveniles and freshly hatched juveniles by inducing multiple vacuole formation. Notably, at higher dosage (50 µg/mL), 5-iodoindole induced rapid juvenile death within 6 h. Microscopic analysis confirmed that the rapid death was due to the generation of reactive oxygen species (ROS). Computational docking attributed this ROS production to the antagonistic effect of 5-iodoindole on glutathione S-transferase (GST), which is known to play a critical role in the suppression of ROS in nematode models. Furthermore, 5-iodoindole also effectively reduced the gall formations and eggs masses of M. incognita on Solanum lycopersicum roots in pot experiments, and importantly it did not harm the physiological properties of the plant. Overall, the study provides valuable insights on the use of 5-iodoindole as an alternate measure to control root-knot nematodes. Overall, our findings suggest the efficacy of 5-iodoindole should be studied under field conditions.

Aripiprazole repurposed as an inhibitor of biofilm formation and sterol biosynthesis in multidrug-resistant Candida albicans.

Drug repurposing is an anticipative chemotherapeutic strategy that accentuates the inadequacy of antifungal drugs. The study identifies an antipsychotic drug, aripiprazole, as a biofilm and hyphal inhibitor of Candida albicans. Microtitre plate biofilm inhibition, metabolic activity and hyphal inhibitory assays were used to assess the potency of aripiprazole; and filipin staining, reactive oxygen species staining, cAMP rescue, propidium iodide staining, computational studies and qRT-PCR assays were used to elucidate its mode of action. The study revealed aripiprazole functioned in a manner similar to standard azoles, particularly the imidazole, ketoconazole, by inhibiting pseudohyphal formation during the early stages of hyphal development. The action of aripiprazole on C. albicans was dose-dependent and it exhibited varied mechanisms of action at low and high dosages. At low dosage, aripiprazole outperformed ketoconazole in terms of inhibiting biofilm formation, hyphal filamentations, and yeast flocculation, whereas at higher dosage it mimicked ketoconazole. This study illustrates the anti-candidal potential and mechanistic activities of aripiprazole, and indicates the future use of this drug as an anti-biofilm agent.

Antibiofilm and Antivirulence Efficacies of Flavonoids and Curcumin Against Acinetobacter baumannii.

Acinetobacter baumannii 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 A. baumannii 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 A. baumannii. Interestingly, curcumin also showed antibiofilm activity against Candida albicans and mixed cultures of C. albicans and A. baumannii. In silico 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 A. baumannii virulence in an in vivo Caenorhabditis elegans model without cytotoxicity. The study shows curcumin and other flavonoids have potential for controlling biofilm formation by and the virulence of A. baumannii.

Molecular docking and biological evaluation of novel urea-tailed mannich base against Pseudomonas aeruginosa.

Emergence of multi-drug resistant bacterial pathogens is escalating and it is essential to develop novel strategies to combat these super bugs. LasR is a regulator switch that plays a vital role in quorum sensing (QS) and pathogenesis of Pseudomonas aeruginosa. The present study reports two novel Mannich base (1-(phenyl (o-tolylamino) methyl) urea and 3-((1H-Imidazole-1-yl) methylnaphthalene-2-ol with enhanced anti-QS and antibiofilm activities. Synthetic compound revealed prolific interaction patterns with LasR quorum sensing receptor and showed to exhibit LasR antagonistic activities in P. aeruginosa. In-vitro LasR-inhibitory activities were further confirmed by biofilm and pyocyanin inhibition assays which showed a dose-dependent activity. The Mannich base also repressed the mRNA transcripts levels of lasA and lasB genes, confirming its active role in LasR inhibitory activity. Importantly, C1 and C2 played a crucial role in antagonizing LasR receptor by forming H-bonds with Tyr47 in the LasR active site and the presence of urea moiety on one of the Mannich base was a discrete advantage. Taken together, the insilico and invitro assays revealed similar evidences, thus confirming the mode of action of the Mannich bases. Overall the findings will assist in drug designing and for developing newer drugs with Mannich bases and its derivatives for treatment of P. aeruginosa.

Nematicidal and insecticidal activities of halogenated indoles.

Parasite death via ion channel activations is the hallmark of anthelmintic and antiparasitic drugs. Glutamate gated chloride channel (GluCl) is a prominent targets for drug selection and design in parasitology. We report several iodine-fluorine based lead activators of GluCl by computational studies and structure-activity relationship analysis. 5-Fluoro-4-iodo-1H-pyrrolo [2, 3-b] pyridine and 5-iodoindole were bioactive hits that displayed in vitro anthelmintic and insecticidal activities against Bursaphelenchus xylophilus, Meloidogyne incognita, and Tenebrio molitor. Two important findings stood out: (i) 5F4IPP induced parasite death, and interacted proficiently with Gln219 amino acid of pentameric GluCl in docking analysis, and (ii) 5-iodoindole appeared to act by forming giant vacuoles in nematodes, which led to a form of non-apoptotic death known as methuosis. The study suggests halogenated-indoles and 1H-pyrrolo [2, 3-b] pyridine derivatives be regarded potential biocides for plant-parasitic nematodes and insects, and warrants further research on the mode of actions, and field investigations.

Mannich base limits Candida albicans virulence by inactivating Ras-cAMP-PKA pathway.

Mannich bases and its derivatives are regarded as supreme pharmacophores in therapeutics. The study investigates the antimycotic potential of Mannich bases, 1-((1H-benzimidazol-1-yl) methyl) urea (C1) and 1-((3-hydroxynapthalen-2-yl) methyl) thiourea (C2), against Candida albicans. Biofilm and hyphal inhibitory activities of the Mannich bases were tested by crystal violet quantification, fluorescence imaging cAMP rescue, qRT PCR, and by molecular docking analysis. The compounds inhibited the biofilms of C. albicans and restrained the filamentation abilities of the pathogen. Structure-activity relationship studies revealed that the presence of urea or thiourea moiety in the tail section is essential for interacting with adenylate cyclase (AC). The Mannich bases seemed to block Ras-cAMP-PKA pathway by inhibiting second messenger activity required for hyphal induction and biofilm formation. In conclusion, the study warrants point-of-care testing of C1/C2 and provides a starting point for deriving several structurally modified Mannich bases which might plausibly replace the prevailing antimycotic drugs in future.

LED based real-time survival bioassays for nematode research.

Nematode bioassays are extensively conducted worldwide, either for screening anthelmintic drugs or for assessing the toxicity of drug candidates. Recently, the US Environmental Protection Agency mandated the use of invertebrate models including nematodes especially Caenorhabditis elegans, for toxicity testing as an alternative to rodent models. The significance of nematode bioassays in the biological sciences is escalating, but no standardized protocol is available to assess nematode mortality in a liquid medium. Manual counting under white light is the only approach currently practiced, which exhibit large variabilities and false positive results. Here, we describe an innovative counting strategy that employs light-emitting diode (LED) technology. We found that the nematodes stopped moving under white light (360-760 nm) when administered with sub-lethal dosage (LC50) of a toxic drug, whereas they responded rapidly to blue (450-490 nm) and ultraviolet (UV) (100-400 nm) LED lights. Furthermore, paralyzed nematodes responded in less than 5 seconds to a LED pulse. The response to the LED stimulus was distinctively noted in C. elegans dauers, which squirmed away from illuminated sites within seconds. LED produced an incoherent beam, and uniformly distributed light across the sampling area. In conclusion, this method is more accurate than the conventional counting techniques, and enables us to differentiate paralyzed and dead nematodes virtually in real-time. Furthermore, this technique would appear to be suitable for incorporating a motion-sensor based automated system.

The Mycotoxin Zearalenone Hinders Candida albicans Biofilm Formation and Hyphal Morphogenesis.

Yeast-mold mycobiota inhabit several natural ecosystems, in which symbiotic relationships drive strategic pathoadaptation. Mycotoxins are metabolites produced by diverse mycotoxigenic fungi as a defense against yeasts, though at times yeasts secrete enzymes that degrade, detoxify, or bio-transform mycotoxins. The present study is focused on the in vitro inhibitory effects of zearalenone (ZEN), a F2 mycotoxin produced by several Fusarium and Gibberella species, on different microbial strains. ZEN exhibited no effect on the planktonic growth or biofilms of several Gram positive and negative bacteria at the tested concentrations. Remarkably, Candida albicans biofilm formation and hyphal morphogenesis were significantly inhibited when treated with 100 µg/mL of ZEN. Likewise, ZEN proficiently disrupted pre-formed C. albicans biofilms without disturbing planktonic cells. Furthermore, these inhibitions were confirmed by crystal violet staining and XTT reduction assays and by confocal and scanning electron microscopy. In an in vivo model, ZEN significantly suppressed C. albicans infection in the nematode Caenorhabditis elegans. The study reports the in vitro antibiofilm efficacy of ZEN against C. albicans strains, and suggests mycotoxigenic fungi participate in asymmetric competitive interactions, such as, amensalism or antibiosis, rather than commensal interactions with C. albicans, whereby mycotoxins secreted by fungi destroy C. albicans biofilms.

Assessments of iodoindoles and abamectin as inducers of methuosis in pinewood nematode, Bursaphelenchus xylophilus.

Bursaphelenchus xylophilus is a quarantined migratory endoparasite known to cause severe economic losses in pine forest ecosystems. The study presents the nematicidal effects of halogenated indoles on B. xylophilus and their action mechanisms. 5-Iodoindole and abamectin (positive control) at low concentration (10 µg/mL) presented similar and high nematicidal activities against B. xylophilus. 5-Iodoindole diminished fecundity, reproductive activities, embryonic and juvenile lethality and locomotor behaviors. Molecular interactions of ligands with invertebrate-specific glutamate gated chloride channel receptor reinforced the notion that 5-iodoindole, like abamectin, rigidly binds to the active sites of the receptor. 5-Iodoindole also induced diverse phenotypic deformities in nematodes including abnormal organ disruption/shrinkage and increased vacuolization. These findings suggest the prospective role of vacuoles in nematode death by methuosis. Importantly, 5-iodoindole was nontoxic to two plants, Brassica oleracea and Raphanus raphanistrum. Henceforth, the study warrants the application of iodoindoles in ecological environments to control the devastating pine destruction by B. xylophilus.

Antibiofilm and Anti-ß-Lactamase Activities of Burdock Root Extract and Chlorogenic Acid against Klebsiella pneumoniae.

Small phytochemicals have been successfully adopted as antibacterial chemotherapies and are being increasingly viewed as potential antibiofilm agents. Some of these molecules are known to repress biofilm and toxin production by certain bacterial and yeast pathogens, but information is lacking with regard to the genes allied with biofilm formation. The present study was performed to investigate the inhibitory effect of burdock root extract (BRE) and of chlorogenic acid (CGA; a component of BRE) on clinical isolates of Klebsiella pneumoniae. BRE and CGA exhibited significant antibiofilm activity against K. pneumoniae without inflicting any harm to its planktonic counterparts. In vitro assays supported the ß-lactamase inhibitory effect of CGA and BRE while in silico docking showed that CGA bound strongly with the active sites of sulfhydryl-variable-1 ß-lactamase. Furthermore, the mRNA transcript levels of two biofilm-associated genes (type 3 fimbriae mrkD and trehalose-6-phosphate hydrolase treC) were significantly downregulated in CGA- and BRE-treated samples. In addition, CGA inhibited biofilm formation by Escherichia coli and Candida albicans without affecting their planktonic cell growth. These findings show that BRE and its component CGA have potential use in antibiofilm strategies against persistent K. pneumoniae infections.

Burdock root extracts limit quorum-sensing-controlled phenotypes and biofilm architecture in major urinary tract pathogens.

Bacterial biofilms are serious concern in patients infected with urinary tract infections, complicated urinary tract infections and other device-associated infections. Microbes within the biofilms are effectively shielded from antibiotics and host immune cells, hence can be treated only with agents which has the potential to disassemble the biofilms. The study is focused on the root extracts of Arctium lappa Linn. as a source for complementary medicine against three major biofilm forming clinical isolates of Escherichia coli, Proteus mirabilis, and Serratia marcescens. Methanol extracts of burdock roots (BR) showed no bactericidal activity (p > 0.05) against the uropathogens, whereas restrained the biofilms (p < 0.05) on polystyrene and glass surfaces at a biofilm inhibitory concentration of 100 µg/mL. The 3D confocal laser scanning microscopy was used to analyze the biofilm architecture which showed significant reduction in the surface area. Z-stack analysis has also revealed substantial reduction in the biofilm thickness (E. coli-50.79%, P. mirabilis-69.49%, and S. marcescens-75.84%). Further, BR extracts also inhibited quorum-sensing (QS)-controlled cellular phenotypes such as violacein, prodigiosin, swarming motility, and cell surface hydrophobicity. LC-MS/MS analysis of BR extracts identified the presence of two major quercetin derivatives (miquelianin and peltatoside) along with few other constituent components. Exploring such phytocompounds will provide potential agents to treat infections caused by biofilm forming uropathogens. The antibiofilm and anti-QS agents will ultimately serve as armor, facilitating the host immune system to fight infections.

Synergy of flavonoids with HDAC inhibitor: new approach to target Candida tropicalis biofilms.

Candida biofilms on various implanted medical devices and living tissues are serious concern in several hospital-acquired infections. The study was conducted to employ a new therapeutic strategy to inhibit the formation of Candida tropicalis biofilms. No significant antifungal or antibiofilm activity was observed when the sodium butyrate (SB), quercetin, and kaempferol were used as a lone drug. Significant decline (P<0·05) in biofilm formation was noted when sub-lethal concentration of SB (30 mM) was used in combination with the flavonoids (450 µg/ml). Z-stack analysis using 3D-confocal laser scanning microscopy (CLSM) also showed substantial reduction in the biofilm thickness in treated glass slides. In conclusion, this is the first report to our knowledge on implementing a combination therapy using flavonoids and histone deacetylase (HDAC) inhibitor.