The Union Is Strength: The Synergic Action of Long Fatty Acids and a Bacteriophage against Xanthomonas campestris Biofilm

Biovalorization of whey waste as economic nutriment for mycogenic production of single cell oils with promising antibiofilm and anticancer potentiality

The production of value-added bio-compounds from rejuvenated sources and their recruitment for healthcare services are paramount objectives in the agenda of white biotechnology. Hereupon, the current study focused on economic production of single cell oils (SCOs) from oleaginous fungi Alternaria sp. (A-OS) and Drechslera sp. (D-OS) using cheese whey waste stream, followed by their evaluation as antibiofilm and anticancer agents, for the first time. As a sole substrate for growth, the whey aided in lipid accumulation by 3.22 and 4.33 g/L, which representing 45.3 and 48.2% lipid content in Drechslera sp. (D-OS) and Alternaria sp. (A-OS), respectively. Meanwhile, a higher unsaturation degree was detected in A-OS by 62.18% comparing to 53.15% of D-OS, with advantageous presence of omega-6 poly unsaturated fatty acid by 22.67% and 15.04% for A-OS and D-OD, respectively, as revealed by GC-MS and FTIR characterization analysis. Interestingly, an eminent and significant (P ≤ 0.05) antibiofilm potency was observed in a dose-dependent modality upon employing both SCOs as antibiofilm agents. Whereas, 100 µg/mL of A-OS recorded superior inhibition of P. aeruginosa, S. aureus and C. albicans biofilms development by 84.10 ± 0.445, 90.37 ± 0.065 and 94.96 ± 0.21%, respectively. Whereas, D-OS (100 µg/mL) thwarted the biofilms of P. aeruginosa, S. aureus and C. albicans by 47.41 ± 2.83, 62.63 ± 5.82 and 78.67 ± 0.23%, correspondingly. Besides, the metabolic performance of cells within biofilm matrix, protein, carbohydrate contents and hydrophobicity of examined biofilms were also curtailed in a significant correlation with biofilm biomass (r ≥ 0.9). Further, as anticancer agents, D-OS recorded higher potency against A549 and CaCo-2 cell lines with IC50 values of 2.55 and 3.425% and SI values of 10.1 and 7.5, respectively. However, A-OS recorded 8.275% and 2.88 for IC50 and SI of Caco-2 cells, respectively. Additionally, A-OS activated caspase 3 by 64.23 ± 1.18% and 53.77 ± 0.995% more than D-OS (52.09 ± 0.222% and 49.72 ± 0.952%) in A549 and Caco-2 cells, respectively. Furthermore, the enzymes, which associated with cancer invasion, metastasis, and angiogenesis (i.e., MMP2 and MMP9) were strongly inhibited by A-OS with 18.58% and 8.295%, respectively as IC50 values; while D-OS results recorded 23.61% and 13.16%, respectively, which could be ascribed to the higher ω-6/ω-3 contents of A-OS. The promising results of the current study opens up the vision to employ SCOs as anti-infective nutraceuticals and in complementary/alternative therapy and prophylactic programs as well.

Artemisia arborescens (Vaill.) L.: Micromorphology, Essential Oil Composition, and Its Potential as an Alternative Biocontrol Product

Artemisia arborescens is a Mediterranean evergreen shrub, with silver grey-green tomentose leaves and a strong scent. It has various ethnopharmacological uses and its secondary metabolites have demonstrated antimicrobial, antiviral, pharmaceutical, phytotoxic, and insecticidal activities. Different extracts obtained from aerial parts of this species are known for their allelopathic effect, but similar studies on its essential oil (EO) are lacking. Therefore, we carried out a pharmacognostic study, obtaining the characterization of the secretory structures and the EO produced. Trans-thujone and camphor are the main components, followed by aromadendrene, camphene, and 8-cedren-13-ol. EO phytotoxic activity was tested on weed plants (Lolium multiflorum Lam. and Sinapis arvensis L.) and crops (Raphanus sativus L. and Cucumis sativus L.), showing inhibition on both germination and radical growth of the two weeds tested. The effects of the EO against the bacterial plant pathogens Xanthomonas campestris pv. campestris (Gram-) and Pseudomonas syringae pv. tomato (Gram+) was also assayed. The minimum inhibitory concentration (MIC) was observed when it was used undiluted [100% v/v], and growth inhibition when diluted at different doses. The antimicrobial activity was also confirmed by the cellular material release and biofilm formation assays. The overall data show that A. arborescens EO can find application as a potential alternative biocontrol product against weeds and plant pathogens. This goal is particularly important from the perspective of replacing synthetic pesticides with natural products, which safeguard both the environment and the health of consumers.

Nano-Bio Interactions: Biofilm-Targeted Antibacterial Nanomaterials

Biofilm is a spatially organized community formed by the accumulation of both microorganisms and their secretions, leading to persistent and chronic infections because of high resistance toward conventional antibiotics. In view of the tunable physicochemical properties and the related unique biological behavior (e.g., size-, shape-, and surface charge-dependent penetration, protein corona endowed targeting, catalytic- and electronic-related oxidative stress, optical- and magnetic-associated hyperthermia, etc.), nanomaterials-based therapeutics are widely used for the treatment of biofilm-associated infections. In this review, the biological characteristics of biofilm are introduced. And the nanomaterials-based antibacterial strategies are further discussed via biofilm targeting, including preventing biofilm formation, enhancing biofilm penetration, disrupting the mature biofilm, and acting as drug delivery systems. In which, the interactions between biofilm and nanomaterials include mechanical disruption, electron transfer, enzymatic degradation, oxidative stress, and hyperthermia. Additionally, the current advances of nanomaterials for antibacterial nanomaterials by biofilm targeting are summarized. This review aims to present a complete vision of antibacterial nanomaterials-biofilm (nano-bio) interactions, paving the way for the future development and clinical translation of effective antibacterial nanomedicines.

Biofilm-based technology for industrial wastewater treatment: current technology, applications and future perspectives

The microbial community in biofilm is safeguarded from the action of toxic chemicals, antimicrobial compounds, and harsh/stressful environmental circumstances. Therefore, biofilm-based technology has nowadays become a successful alternative for treating industrial wastewater as compared to suspended growth-based technologies. In biofilm reactors, microbial cells are attached to static or free-moving materials to form a biofilm which facilitates the process of liquid and solid separation in biofilm-mediated operations. This paper aims to review the state-of-the-art of recent research on bacterial biofilm in industrial wastewater treatment including biofilm fundamentals, possible applications and problems, and factors to regulate biofilm formation. We discussed in detail the treatment efficiencies of fluidized bed biofilm reactor (FBBR), trickling filter reactor (TFR), rotating biological contactor (RBC), membrane biofilm reactor (MBfR), and moving bed biofilm reactor (MBBR) for different types of industrial wastewater treatment. Besides, biofilms have many applications in food and agriculture, biofuel and bioenergy production, power generation, and plastic degradation. Furthermore, key factors for regulating biofilm formation were also emphasized. In conclusion, industrial applications make evident that biofilm-based treatment technology is impactful for pollutant removal. Future research to address and improve the limitations of biofilm-based technology in wastewater treatment is also discussed.

Horizontal Gene Transfer of Antibiotic Resistance Genes in Biofilms

Most bacteria attach to biotic or abiotic surfaces and are embedded in a complex matrix which is known as biofilm. Biofilm formation is especially worrisome in clinical settings as it hinders the treatment of infections with antibiotics due to the facilitated acquisition of antibiotic resistance genes (ARGs). Environmental settings are now considered as pivotal for driving biofilm formation, biofilm-mediated antibiotic resistance development and dissemination. Several studies have demonstrated that environmental biofilms can be hotspots for the dissemination of ARGs. These genes can be encoded on mobile genetic elements (MGEs) such as conjugative and mobilizable plasmids or integrative and conjugative elements (ICEs). ARGs can be rapidly transferred through horizontal gene transfer (HGT) which has been shown to occur more frequently in biofilms than in planktonic cultures. Biofilm models are promising tools to mimic natural biofilms to study the dissemination of ARGs via HGT. This review summarizes the state-of-the-art of biofilm studies and the techniques that visualize the three main HGT mechanisms in biofilms: transformation, transduction, and conjugation.

Anticandidal and Antibiofilm Effect of Synbiotics including Probiotics and Inulin-Type Fructans

Background: There is great interest in the search for new alternatives to antimicrobial drugs, and the use of synbiotics is a promising approach to this problem. This study evaluated the growth inhibition and antibiofilm activity of the short-chain fatty acids produced by Lacticaseibacillus rhamnosus and Pediococcus acidilactici in combination with inulin-type fructans against Candida albicans. Methods: The growth inhibition of Candida was evaluated using microdilution analysis in 96-well microtiter plates; different concentrations of cell-free supernatants of Lacticaseibacillus rhamnosus and Pediococcus acidilactici were exposed to Candida albicans. The antibiofilm assessment was carried out using the crystal violet staining assay. The short-chain fatty acids were analyzed by gas chromatography. Results: The clinically isolated Candida albicans interacted with supernatants from Lacticaseibacillus rhamnosus and Pediococcus acidilactici and showed significant growth inhibition and antibiofilm formation versus the controls. Lactate and acetic acid were elevated in the supernatants. The results suggest that the supernatants obtained from the synbiotic combinations of Lacticaseibacillus rhamnosus and Pediococcus acidilactici with inulin-type fructans can inhibit the growth and biofilm formation against a clinically isolated Candida albicans strain. Conclusions: These results suggest that synbiotic formulations could be a promising alternative to antifungal drugs in candidiasis therapy.

Exploiting the antibacterial mechanism of phenazine substances from Lysobacter antibioticus 13-6 against Xanthomonas oryzae pv. oryzicola

Bacterial leaf streak caused by Xanthomonas oryzae pv. oryzicola (Xoc) is one of the most destructive diseases affecting rice production worldwide. In this study, we extracted and purified phenazine substances from the secondary metabolites of Lysobacter antibioticus 13-6. The bacteriostatic mechanism of phenazine substances against Xoc was investigated through physiological response and transcriptomic analysis. Results showed that phenazine substances affects the cell membrane permeability of Xoc, which causes cell swelling and deformation, blockage of flagellum synthesis, and imbalance of intracellular environment. The changes in intracellular environment affect the physiological and metabolic functions of Xoc, which reduces the formation of pathogenic factors and pathogenicity. Through transcriptomic analysis, we found that among differentially expressed genes, the expression of 595 genes was induced significantly (275 up-regulated and 320 down-regulated). In addition, we observed that phenazine substances affects three main functions of Xoc, i.e., transmembrane transporter activity, DNA-mediated transposition, and structural molecular activity. Phenazine substances also inhibits the potassium ion transport system that reduces Xoc resistance and induces the phosphate ion transport system to maintain the stability of the internal environment. Finally, we conclude that phenazine substances could retard cell growth and reduce the pathogenicity of Xoc by affecting cell structure and physiological metabolism. Altogether, our study highlights latest insights into the antibacterial mechanism of phenazine substances against Xoc and provides basic guidance to manage the incidence of bacterial leaf streak of rice.

Mechanisms of interactions between bacteria and bacteriophage mediate by quorum sensing systems

Bacteriophage (phage) and their host bacteria coevolve with each other over time. Quorum sensing (QS) systems play an important role in the interaction between bacteria and phage. In this review paper, we summarized the function of QS systems in bacterial biofilm formation, phage adsorption, lysis-lysogeny conversion of phage, coevolution of bacteria and phage, and information exchanges in phage, which may provide reference to future research on alternative control strategies for antibiotic-resistant and biofilm-forming pathogens by phage. KEY POINTS: • Quorum sensing (QS) systems influence bacteria-phage interaction. • QS systems cause phage adsorption and evolution and lysis-lysogeny conversion. • QS systems participate in biofilm formation and co-evolution with phage of bacteria.

Pentadecanoic acid against Candida albicans-Klebsiella pneumoniae biofilm: towards the development of an anti-biofilm coating to prevent polymicrobial infections

The ability to form biofilms is a common feature of microorganisms, which can colonize a variety of surfaces, such as host tissues and medical devices, resulting in infections highly resistant to conventional drugs. This aspect is particularly critical in polymicrobial biofilms involving both fungi and bacteria, therefore, to eradicate such severe infections, new and effective anti-biofilm strategies are needed. The efficacy of pentadecanal and pentadecanoic acid as anti-biofilm agents has been recently reported against different bacterial strains. Their chemical similarity with diffusible signal factors (DSFs), plus the already known ability of fatty acids to act as anti-biofilm agents, suggested to explore their use against Candida albicans and Klebsiella pneumoniae mixed biofilm. In this work, we demonstrated the ability of both molecules to prevent the formation and destabilize the structure of the dual-species biofilm. Moreover, the pentadecanoic acid anti-biofilm coating, previously developed through the adsorption of the fatty acid on polydimethylsiloxane (PDMS), was proved to prevent the polymicrobial biofilm formation in dynamic conditions by confocal laser scanning microscopy analysis. Finally, the evaluation of the expression levels of some biofilm-related genes of C. albicans and K. pneumoniae treated with pentadecanoic acid provided some insights into the molecular mechanisms underpinning its anti-biofilm effect.

Bacterial Biofilm Destruction: A Focused Review On The Recent Use of Phage-Based Strategies With Other Antibiofilm Agents

Biofilms are bacterial communities that live in association with biotic or abiotic surfaces and enclosed in an extracellular polymeric substance. Their formation on both biotic and abiotic surfaces, including human tissue and medical device surfaces, pose a major threat causing chronic infections. In addition, current antibiotics and antiseptic agents have shown limited ability to completely remove biofilms. In this review, the authors provide an overview on the formation of bacterial biofilms and its characteristics, burden and evolution with phages. Moreover, the most recent possible use of phages and phage-derived enzymes to combat bacteria in biofilm structures is elucidated. From the emerging results, it can be concluded that despite successful use of phages and phage-derived products in destroying biofilms, they are mostly not adequate to eradicate all bacterial cells. Nevertheless, a combined therapy with the use of phages and/or phage-derived products with other antimicrobial agents including antibiotics, nanoparticles, and antimicrobial peptides may be effective approaches to remove biofilms from medical device surfaces and to treat their associated infections in humans.

Lactoferrin, Quercetin, and Hydroxyapatite Act Synergistically against Pseudomonas fluorescens

Pseudomonas fluorescens is an opportunistic, psychotropic pathogen that can live in different environments, such as plant, soil, or water surfaces, and it is associated with food spoilage. Bioactive compounds can be used as antimicrobials and can be added into packaging systems. Quercetin and lactoferrin are the best candidates for the development of a complex of the two molecules absorbed on bio combability structure as hydroxyapatite. The minimum inhibiting concentration (MIC) of single components and of the complex dropped down the single MIC value against Pseudomonas fluorescens. Characterization analysis of the complex was performed by means SEM and zeta-potential analysis. Then, the synergistic activity (C_syn) of single components and the complex was calculated. Finally, the synergistic activity was confirmed, testing in vitro its anti-inflammatory activity on U937 macrophage-like human cell line. In conclusion, the peculiarity of our study consists of optimizing the specific propriety of each component: the affinity of lactoferrin for LPS; that of quercetin for the bacterial membrane. These proprieties make the complex a good candidate in food industry as antimicrobial compounds, and as functional food.