Antipathogenic Activity Research Articles

Application of Tarkhineh Fermented Product to Produce Potato Chips With Strong Probiotic Properties, High Shelf-Life, and Desirable Sensory Characteristics.

The application of Tarkhineh texture to protect probiotics in potato chips has been investigated as the main goal in this paper. In this study, the probiotic assessments, morphological characteristics, sensory evaluation, and survival rates of the covered probiotic cells with Tarkhineh in potato chips during storage time were assessed. Based on results, T34 isolated from traditional Tarkhineh as a safe strain had a high tolerance to low pH and bile salt conditions, displayed acceptable anti-pathogenic activities, and also showed desirable antibiotic susceptibility. Two types of Tarkhineh formulations (plain Tarkhineh and turmeric Tarkhineh) were applied using a simple spraying method for covering T34 cells in potato chips. All formulations showed elliptical to spherical (480-770 μm) shape probiotic drops. Storage stability results revealed that T34 cells mixed with turmeric and plain Tarkhineh during 4 months of storage at 4°C displayed excellent protection abilities with about 3.70 and 2.85 log decreases in CFU/g respectively. Additionally, probiotic potato chips compared to non-probiotic and commercial potato chips, exhibited probiotic product criteria such as excellent quality and superior sensory properties during storage time. In conclusion, Tarkhineh showed high potential as a protective matrix for probiotic cells in potato chips.

Rifaximin: unique selective antibiotic for the treatment of gastrointestinal diseases

The human gut microbiota has been a major focus of scientific research in recent years. Studies based on metagenomic methods have revealed the multifaceted abilities of gut microbes, from metabolic functions to immunomodulation, from antipathogenic activity to behavioral formation. Since the gut microbiota plays a crucial role in maintaining human health, more or less specific changes in the gut microbiota are associated with various gastrointestinal diseases. These data strongly support the use of gut microbiota modulators, such as antibiotics, prebiotics and probiotics, as the choice for almost all gastrointestinal disorders. The traditional use of antibiotics in clinical practice is to counteract local or systemic infections. It can be assumed that antibiotics have a detrimental effect on the intestinal ecology. However, this is not true for all antibiotics.Rifaximin is a non-systemic oral antibiotic derived from rifampin and is characterized by a broad spectrum of antibacterial activity against Gram-positive and negative, aerobic and anaerobic bacteria. Rifaximin was first approved in Italy in 1987 and then in many other countries of the world for the treatment of several gastrointestinal diseases. This review presents the pharmacology and pharmacodynamics of rifaximin, describing various actions beyond its antibacterial activity, such as altering virulence, preventing intestinal mucosal adhesion and bacterial translocation. Key studies on the different uses of rifaximin are also described. In addition, rifaximin has some anti-inflammatory effects with minimal impact on the overall composition of the gut microbiota. All of these properties make rifaximin a good candidate for the treatment of various gastrointestinal diseases.

In vitro examination of antibacterial and immunomodulatory activities of cinnamon, white thyme, and clove essential oils

• Cinnamon EO showed a highest antibacterial activity against intestinal pathogenic bacteria. • Essential oils inhibits probiotic bacteria growth at the 0.1% (v/v) concentration. • Cinnamon EO present better inhibitory and immunomodulatory properties than the rest of the EOs. • Cinnamon EO seems to modulate IL-2 secretion and TLR signalling pathway in Caco-2 cells. The present study was conducted to evaluate the in vitro antimicrobial effect of three essential oils (cinnamon, white thyme, and clove) on selected intestinal pathogen bacteria, probiotic strains, and commensal bacteria. Additionally, their effects on inflammatory gene expression were also evaluated in a well-known intestinal human cellular model (Caco-2 cells). Cinnamon showed the highest antipathogenic microbial activity, followed by white thyme and clove. In the case of the probiotic strains, the inhibitory effect was observed at 0.1% (v/v), although growth recovery was seen after 24 h of incubation. Besides, cinnamon down-regulated the expression of genes related to the Toll-like receptor, nitric oxide, and apoptosis pathways. Similarly, secretion of interleukin 2 was inhibited by cinnamon. Results support the potential use of essential oils in the food industry for their antimicrobial and immunomodulatory effects; however, the underlying mechanisms are unknown and warrant further research.

One-step vapor deposition of fluorinated polycationic coating to fabricate antifouling and anti-infective textile against drug-resistant bacteria and viruses.

The ongoing pandemic caused by the novel coronavirus has turned out to be one of the biggest threats to the world, and the increase of drug-resistant bacterial strains also threatens the human health. Hence, there is an urgent need to develop novel anti-infective materials with broad-spectrum anti-pathogenic activity. In the present study, a fluorinated polycationic coating was synthesized on a hydrophilic and negatively charged polyester textile via one-step initiated chemical vapor deposition of poly(dimethyl amino methyl styrene-co-1H,1H,2H,2H-perfluorodecyl acrylate) (P(DMAMS-co-PFDA), PDP). The surface characterization results of SEM, FTIR, and EDX demonstrated the successful synthesis of PDP coating. Contact angle analysis revealed that PDP coating endowed the polyester textile with the hydrophobicity against the attachment of different aqueous foulants such as blood, coffee, and milk, as well as the oleophobicity against paraffin oil. Zeta potential analysis demonstrated that the PDP coating enabled a transformation of negative charge to positive charge on the surface of polyester textile. The PDP coating exhibited excellent contact-killing activity against both gram-negative Escherichia coli and gram-positive methicillin-resistant Staphylococcus aureus, with the killing efficiency of approximate 99.9%. In addition, the antiviral capacity of PDP was determined by a green fluorescence protein (GFP) expression-based method using lentivirus-EGFP as a virus model. The PDP coating inactivated the negatively charged lentivirus-EGFP effectively. Moreover, the coating showed good biocompatibility toward mouse NIH 3T3 fibroblast cells. All the above properties demonstrated that PDP would be a promising anti-pathogenic polymeric coating with wide applications in medicine, hygiene, hospital, etc., to control the bacterial and viral transmission and infection.

Bisazo dye compounds based on aliphatic and aromatic diamine linking groups: Thermal behavior, chemical stability, electrochemical study, interaction with AgNPs and in vitro anti-pathogen activity

In this study, a family of bisazo dye molecules (BA1-BA5) has been investigated as versatile compounds. Influence of various linking groups in amine moiety on thermal stability and electrochemical behavior of the compounds was determined and discussed. BA1 and BA2 with aliphatic-based diamine moiety have been found to be more thermal stable than others. Besides, the chemical stability of BA1-BA5 was studied in boiling water, acid and base media. All compounds showed strong resistance toward boiling water. Moreover, BA3-BA5 containing aromatic diamine moiety were stable after treatment with 6 N HCl. This feature may make them suitable as dye media in optical recording devices. Ag nanoparticles reacted with various bisazo dye molecules in a green approach to produce AgNPs/BA1-BA5 hybrids. Ag content in each hybrid was determined using an atomic absorption spectrometer (AAS). Antimicrobial activity of bisazo compounds and their nano silver counterparts has been screened in vitro against various pathogens including Methicillin-resistant Staphylococcus aureus (MRSA), Enterococcus faecalis (E. faecalis), Salmonella typhi (S.typhi), Pseudomonas aeruginosa (P. aeruginosa), Escherichia coli (E. coli), Staphylococcus aureus (S. aureus) and Aspergillus fungi. Contrary to the bisazo compounds, AgNPs/BA hybrids were effective on both Gram-positive and negative bacteria. Moreover, AgNPs/BA3 and AgNPs/BA5 were able to efficaciously inhibit the growth of Aspergillus fungus.

The neutrophil antimicrobial peptide cathelicidin promotes Th17 differentiation.

The host defence peptide cathelicidin (LL-37 in humans, mCRAMP in mice) is released from neutrophils by de-granulation, NETosis and necrotic death; it has potent anti-pathogen activity as well as being a broad immunomodulator. Here we report that cathelicidin is a powerful Th17 potentiator which enhances aryl hydrocarbon receptor (AHR) and RORγt expression, in a TGF-β1-dependent manner. In the presence of TGF-β1, cathelicidin enhanced SMAD2/3 and STAT3 phosphorylation, and profoundly suppressed IL-2 and T-bet, directing T cells away from Th1 and into a Th17 phenotype. Strikingly, Th17, but not Th1, cells were protected from apoptosis by cathelicidin. We show that cathelicidin is released by neutrophils in mouse lymph nodes and that cathelicidin-deficient mice display suppressed Th17 responses during inflammation, but not at steady state. We propose that the neutrophil cathelicidin is required for maximal Th17 differentiation, and that this is one method by which early neutrophilia directs subsequent adaptive immune responses.

Honeysuckle Aqueous Extracts Induced let-7a Suppress EV71 Replication and Pathogenesis In Vitro and In Vivo and Is Predicted to Inhibit SARS-CoV-2.

Honeysuckle (Lonicera japonica Thunb) is a traditional Chinese medicine (TCM) with an antipathogenic activity. MicroRNAs (miRNAs) are small non-coding RNA molecules that are ubiquitously expressed in cells. Endogenous miRNA may function as an innate response to block pathogen invasion. The miRNA expression profiles of both mice and humans after the ingestion of honeysuckle were obtained. Fifteen overexpressed miRNAs overlapped and were predicted to be capable of targeting three viruses: dengue virus (DENV), enterovirus 71 (EV71) and SARS-CoV-2. Among them, let-7a was examined to be capable of targeting the EV71 RNA genome by reporter assay and Western blotting. Moreover, honeysuckle-induced let-7a suppression of EV71 RNA and protein expression as well as viral replication were investigated both in vitro and in vivo. We demonstrated that let-7a targeted EV71 at the predicted sequences using luciferase reporter plasmids as well as two infectious replicons (pMP4-y-5 and pTOPO-4643). The suppression of EV71 replication and viral load was demonstrated in two cell lines by luciferase activity, RT-PCR, real-time PCR, Western blotting and plaque assay. Furthermore, EV71-infected suckling mice fed honeysuckle extract or inoculated with let-7a showed decreased clinical scores and a prolonged survival time accompanied with decreased viral RNA, protein expression and virus titer. The ingestion of honeysuckle attenuates EV71 replication and related pathogenesis partially through the upregulation of let-7a expression both in vitro and in vivo. Our previous report and the current findings imply that both honeysuckle and upregulated let-7a can execute a suppressive function against the replication of DENV and EV71. Taken together, this evidence indicates that honeysuckle can induce the expression of let-7a and that this miRNA as well as 11 other miRNAs have great potential to prevent and suppress EV71 replication.

Personalized Reusable Face Masks with Smart Nano-Assisted Destruction of Pathogens for COVID-19: A Visionary Road.

The Coronavirus disease 2019 (COVID-19) emergency has demonstrated that the utilization of face masks plays a critical role in limiting the outbreak. Healthcare professionals utilize masks all day long without replacing them very frequently, thus representing a source of cross-infection for patients and themselves. Nanotechnology is a powerful tool with the capability to produce nanomaterials with unique physicochemical and antipathogen properties. Here, how to realize non-disposable and highly comfortable respirators with light-triggered self-disinfection ability by bridging bioactive nanofiber properties and stimuli-responsive nanomaterials is outlined. The visionary road highlighted in this Concept is based on the possibility of developing a new generation of masks based on multifunctional membranes where the presence of nanoclusters and plasmonic nanoparticles arranged in a hierarchical structure enables the realization of a chemically driven and on-demand antipathogen activities. Multilayer electrospun membranes have the ability to dissipate humidity present within the mask, enhancing the wearability and usability. The photothermal disinfected membrane is the core of these 3D printed and reusable masks with moisture pump capability. Personalized face masks with smart nano-assisted destruction of pathogens will bring enormous advantages to the entire global community, especially for front-line personnel, and will open up great opportunities for innovative medical applications.

Corchorus olitorius aqueous extract attenuates quorum sensing-regulated virulence factor production and biofilm formation

Objective: To investigate the effect of Corchorus olitorius aqueous fraction (COAF) on quorum sensing (QS)-regulated virulence factors and biofilm formation in Pseudomonas aeruginosa (PAO1). Methods: The preliminary screening of the anti-QS effect of COAF was performed by evaluating the anti-pathogenic activity against Chromobacterium violaceum CV026 biosensor strain. Next, the inhibitory effects of COAF on QS-regulated pyocyanin production, proteolytic and elastolytic activities, swarming motility, and biofilm formation were evaluated in PAO1. Results: The results showed that the treatment of COAF significantly decreased the biofilm biomass, attenuated virulence factors, and inhibited swarming motility of PAO1 without affecting the growth of the bacteria in a dose-dependent manner. COAF at 2 000 μg/mL significantly decreased Las B elastase activity in PAO1 culture, exopolysaccharide production, swarming motility, pyocyanin level, and biomass of PAO1 by 55% (P<0.05), 60% (P<0.01), 61% (P<0.01), 65%(P<0.01) and 73% (P<0.01), respectively. In addition, the production of violacein was decreased by 62% (P<0.01) with the treatment of a high dose of COAF. Conclusions: These findings indicate that COAF can be a potential source of anti-QS agents.

Probiotic potential and anticancer properties of Pediococcus sp. isolated from traditional dairy products

Herein, 18 lactic acid bacteria isolated from 30 samples of traditional dairy products were identified, and their probiotic potential was evaluated. According to the results, almost all strains showed the probiotic properties sufficiently, though M1 had better characterise. 16S rRNA gene sequencing revealed that this strain belongs to the Pediococcus sp. (<95 % similarity). This strain had substantial antipathogenic activity and did not show any worrying antibiotic resistance. Also, the strain was resistant to high concentrations of bile salt (1 %), NaCl (6.5 %), and low pH (2). Furthermore, it was revealed that cell-free supernatant (CFS), heat-killed cells and live cells derived from M1 significantly decreased the viability of MCF-7 cells so that the CFS resulted in 85 % cell death. Flow cytometry and western blot analysis determined that this compound induced apoptosis in the cancerous cells through increasing the BAX protein expression and decreasing the Bcl-2 protein expression.

Research Article: Antimicrobial effects of silver/copper/titanium dioxide-nanocomposites synthesised by chemical reduction method to increase the shelf life of caviar (Huso huso)

By chemical reduction method and incorporating of Ag and Cu nanoparticles in TiO2 composite, a TiO2/Ag/Cu nanocomposite was synthesised with considerable antipathogenic activity against food borne microorganisms. Scanning electron microscopy analysis exhibited that Ag nanoparticles and Cu nanoparticles were homogeneously distributed into the TiO2 composite. The presence of TiO2, Ag and Cu led to higher convinced surface area, smaller particle size, reduced release of nanoparticles and more photoactivity than that of other nanocomposite in the similar studies. The antimicrobial effect of TiO2/ Ag /Cu nanocomposite demonstrated as followed E. coli > S. aureus > A. niger. ICP-MS results showed that 0/168 ppm of silver was released to caviar samples at 32th day and 62th day of experiment. The TiO2/Ag/ Cu nanocomposite also tested for packaging and results confirmed the extension of caviar shelf life and It can be concluded that utilizing TiO2/Ag/Cu nanocomposite is an ideal choice for caviar packaging.

Structural and functional relationship of mammalian and nematode ferritins.

Ferritin is a unique buffering protein in iron metabolism. By storing or releasing iron in a tightly controlled manner, it prevents the negative effects of free ferrous ions on biomolecules in all domains of life - from bacteria to mammals. This review focuses on the structural features and activity of the ferritin protein family with an emphasis on nematode ferritins and the similarities in their biological roles with mammalian ferritins. The conservative characteristic of the ferritin family across the species originates from the ferroxidase activity against redox-active iron. The antioxidative function of these proteins translates into their involvement in a wide range of important biological processes, e.g., aging, fat metabolism, immunity, anticancer activity, and antipathogenic activity. Moreover, disturbances in ferritin expression lead to severe iron-associated diseases. Research on the Caenorhabditis elegans model organism may allow us to better understand the wide spectrum of mechanisms involving ferritin activity.

Research progress of epigallocatechin-3-gallate (EGCG) on anti-pathogenic microbes and immune regulation activities.

At the end of 2019, the COVID-19 virus spread worldwide, infecting millions of people. Infectious diseases induced by pathogenic microorganisms such as the influenza virus, hepatitis virus, and Mycobacterium tuberculosis are also a major threat to public health. The high mortality caused by infectious pathogenic microorganisms is due to their strong virulence, which leads to the excessive counterattack by the host immune system and severe inflammatory damage of the immune system. This paper reviews the efficacy, mechanism and related immune regulation of epigallocatechin-3-gallate (EGCG) as an anti-pathogenic microorganism drug. EGCG mainly shows both direct and indirect anti-infection effects. EGCG directly inhibits early infection by interfering with the adsorption on host cells, inhibiting virus replication and reducing bacterial biofilm formation and toxin release; EGCG indirectly inhibits infection by regulating immune inflammation and antioxidation. At the same time, we reviewed the bioavailability and safety of EGCG in vivo. At present, the bioavailability of EGCG can be improved to some extent using nanostructured drug delivery systems and molecular modification technology in combination with other drugs. This study provides a theoretical basis for the development of EGCG as an adjuvant drug for anti-pathogenic microorganisms.

Lactobacillus johnsonii 3-1 and Lactobacillus crispatus 7-4 promote the growth performance and ileum development and participate in lipid metabolism of broilers.

Long-term use of antibiotic growth promoter (AGP) in animal production is the main cause of antimicrobial resistance of pathogenic bacteria. Therefore, seeking alternatives to AGP is crucial for animal husbandry. Among all AGP alternatives, probiotics are promising candidates. In this study, two strains of lactic acid bacteria, L. johnsonii 3-1 and L. crispatus 7-4, were isolated from the feces of wild Gallus gallus, which exhibited obvious anti-pathogenic activity and improved the growth performance of broilers. Furthermore, we found that these two strains participated in the lipid metabolism of broilers by reducing the content of TC and TG in ileal epithelial cells and up-regulating the liver AMPKα/PPARα/CPT-1 pathway, which affects abdominal fat deposition. In summary, L. johnsonii 3-1 and L. crispatus 7-4 have the potential to be used as AGP substitutes and participate in the lipid metabolism of broilers to reduce abdominal fat deposition. Importantly, our study reveals for the first time that L. crispatus participates in liver lipid metabolism to reduce abdominal fat deposition in broilers.

Comparative and Functional Analyses of Two Sequenced Paenibacillus polymyxa Genomes Provides Insights Into Their Potential Genes Related to Plant Growth-Promoting Features and Biocontrol Mechanisms.

Many bacteria belonging to Paenibacillus polymyxa are plant growth-promoting rhizobacteria (PGPR) with the potential to promote plant growth and suppress phytopathogens and have been used as biological control agents (BCAs). However, the growth promotion and biocontrol mechanisms of P. polymyxa have not been thoroughly elucidated thus far. In this investigation, the genome sequences of two P. polymyxa strains, ZF129 and ZF197, with broad anti-pathogen activities and potential for growth promotion were comparatively studied. Comparative and functional analyses of the two sequenced P. polymyxa genomes showed that the ZF129 genome consists of one 5,703,931 bp circular chromosome and two 79,020 bp and 37,602 bp plasmids, designated pAP1 and pAP2, respectively. The complete genome sequence of ZF197 consists of one 5,507,169 bp circular chromosome and one 32,065 bp plasmid, designated pAP197. Phylogenetic analysis revealed that ZF129 is highly similar to two P. polymyxa strains, HY96-2 and SQR-21, while ZF197 is highly similar to P. polymyxa strain J. The genes responsible for secondary metabolite synthesis, plant growth-promoting traits, and systemic resistance inducer production were compared between strains ZF129 and ZF197 as well as other P. polymyxa strains. The results indicated that the variation of the corresponding genes or gene clusters between strains ZF129 and ZF197 may lead to different antagonistic activities of their volatiles or cell-free supernatants against Fusarium oxysporum. This work indicates that plant growth promotion by P. polymyxa is largely mediated by phytohormone production, increased nutrient availability and biocontrol mechanisms. This study provides an in-depth understanding of the genome architecture of P. polymyxa, revealing great potential for the application of this bacterium in the fields of agriculture and horticulture as a PGPR.

Broad-Spectrum Activity of Volatile Organic Compounds from Three Yeast-like Fungi of the Galactomyces Genus Against Diverse Plant Pathogens

The application of antagonistic fungi for plant protection has attracted considerable interest because they may potentially replace the use of chemical pesticides. Antipathogenic activities confirmed in volatile organic compounds (VOCs) from microorganisms have potential to serve as biocontrol agents against pre- and post-harvest diseases. In the present study, we investigated Galactomyces fungi isolated from rotten leaves and the rhizosphere of cherry tomato (Lycopersicon esculentum var. cerasiforme). VOCs produced by Galactomyces fungi negatively affected the growth of phytopathogenic fungi and the survival of nematodes. Mycelial growths of all nine examined phytopathogenic fungi were inhibited on agar plate, although the inhibition was more intense in Athelia rolfsii JYC2163 and Cladosporium cladosporioides JYC2144 and relatively moderate in Fusarium sp. JYC2145. VOCs also efficiently suppressed the spore germination and mycelial growth of A. rolfsii JYC2163 on tomatoes. The soil nematode Caenorhabditis elegans exhibited higher mortality in 24 h in the presence of VOCs. These results suggest the broad-spectrum activity of Galactomyces fungi against various plant pathogens and the potential to use VOCs from Galactomyces as biocontrol agents.

Fabrication of inorganic alumina particles at nanoscale by a pulsed laser ablation technique in liquid and exploring their protein binding, anticancer and antipathogenic activities

The interaction of nanoparticles with biological systems can provide useful information about their therapeutic applications. The aluminum nanoparticles (Al2O3 NPs) were synthesized by laser ablation technique and well-characterized by different methods. Fluorescence spectroscopy, circular dichroism (CD) spectroscopy, and molecular docking studies were employed to evaluate the effect of Al2O3 NPs on the protein structure. Growth inhibitory and apoptotic effects of the Al2O3 NPs against K562 cancer cells and lymphocyte cells were assessed using [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] (MTT), flow cytometry, and real time polymerase chain reaction (PCR) assays. The antipathogenic activity of Al2O3 NPs against a diverse range of Gram-negative and Gram-positive pathogens was explored through a disk diffusion method. The characterization techniques determined that the Al2O3 NPs were successfully synthesized in the nanoscales. Intrinsic, 1-anilino-8-naphthalenesulfonate (ANS) and acrylamide fluorescence spectroscopy studies disclosed that Al2O3 NPs can partially change the tertiary structure of human serum albumin (HSA), whereas CD spectroscopy investigation depicted that the secondary structure of HSA remained intact. Molecular docking investigation also manifest that the Al2O3 nano-clusters preferably bind to electrostatic residues. Al2O3 NPs exhibited promising and selective anticancer features through reactive oxygen species (ROS) production, apoptosis induction, and elevation of Bax/Bcl-2 mRNA ratio. Furthermore, the Al2O3 NP showed a remarkable antibacterial activity against both Gram-negative and Gram-positive pathogens. In conclusion, it may be suggested that the synthesized Al2O3 NPs can be integrated in the development of anticancer and antipathogenic agents.

Anti-pathogenic activity of graphene nanomaterials: A review

Graphene and its derivatives are promising candidates for a variety of biological applications, among which, their anti-pathogenic properties are highly attractive due to the outstanding physicochemical characteristics of these novel nanomaterials. The antibacterial, antiviral and antifungal performances of graphene are increasingly becoming more important due to the pathogen's resistance to existing drugs. Despite this, the factors influencing the antibacterial activity of graphene nanomaterials, and consequently, the mechanisms involved are still controversial. This review aims to systematically summarize the literature, discussing various factors that affect the antibacterial performance of graphene materials, including the shape, size, functional group and the electrical conductivity of graphene flakes, as well as the concentration, contact time and the pH value of the graphene suspensions used in related microbial tests. We discuss the possible surface and edge interactions between bacterial cells and graphene nanomaterials, which cause antibacterial effects such as membrane/oxidative/photothermal stresses, charge transfer, entrapment and self-killing phenomena. This article reviews the anti-pathogenic activity of graphene nanomaterials, comprising their antibacterial, antiviral, antifungal and biofilm-forming performance, with an emphasis on the antibacterial mechanisms involved.

Evaluation of the Antibacterial Activity and Probiotic Potential of Lactobacillus plantarum Isolated from Chinese Homemade Pickles

This study investigated the antipathogenic activity and probiotic potential of indigenous lactic acid bacteria (LAB) isolated from Chinese homemade pickles. In total, 27 samples were collected from different sites in China. Fifty-nine yielded pure colonies were identified by 16S rRNA gene sequencing as LAB and were initially evaluated for the antibacterial activity in vitro. Initial screening yielded Lactobacillus plantarum GS083, GS086, and GS090, which showed a broad-spectrum antibacterial activity against food-borne pathogens, especially multidrug-resistant pathogens. Meanwhile, organic acids were mainly responsible for the antimicrobial activity of the LAB strains, and the most abundant of these was lactic acid (19.32 ± 0.95 to 24.79 ± 0.40 g/l). Additionally, three L. plantarum strains demonstrated several basic probiotic characteristics including cell surface hydrophobicity, autoaggregation, and survival under gastrointestinal (GI) tract conditions. The safety of these isolates was also evaluated based on their antibiotic susceptibility, hemolytic risk, bile salt hydrolase activity, and existence of virulence or antibiotic resistance genes. All strains were safe at both the genomic and phenotypic levels. Therefore, L. plantarum GS083, GS086, and GS090 are fairly promising probiotic candidates and may be favorable for use as preservatives in the food industry.

Antagonistic effect of volatile and non-volatile compounds from Streptomyces strains on cultures of several phytopathogenic fungi

Fungi and oomycetes are important plant pathogens that constantly attacked plants, thus compromising the production of foods worldwide. Streptomyces strains might be useful to control fungal pathogens by different mechanism. The in vitro antagonistic activity of non-volatile and volatile metabolites from four Streptomyces strains was evaluated over cultures of phytopathogenic fungi and oomycetes. The non-volatile compounds from Streptomyces strains significantly reduced (44.2 to 92.1%) the growth of aerial mycelium of pathogens. The volatile compounds (VOCs) from Streptomyces strains reduced both aerial mycelium (22.5 to 96.7%) and mycelium growing inside of culture medium (0.0 - 9.4%). The pathogens maintained their capacity to grow normally in fresh culture medium without antagonists after confrontations with antagonist VOCs. The analysis of VOCs by gas chromatography coupled to mass spectrometry revealed different kinds of VOCs included alcohols, aldehydes, ketones, esters, terpenes, terpenoids, thioethers, among others. The most abundant VOCs were trans-1,10-dimethyl-trans-9-decalol (geosmin), 2-methylisoborneol, 2-methyl-2-bornene, 1,4-dimethyladamantane, and 4-penten-1-ol, trifluoroacetate. The antipathogenic activity of nine pure VOCs that had been identified in cultures of the Streptomyces strains alone was evaluated in vitro against phytopathogenic fungi and oomycetes. Trans-2-hexenal was the most effective of these VOCs, inhibiting completely the growth of tested phytopathogens. The volatile and non-volatile compounds from Streptomyces strains effectively reduced the in vitro growth of phytopathogens and they might be used as biological control. Further studies are required to demonstrate this activity on open field conditions.