Phage-induced bacterial morphological changes reveal a phage-derived antimicrobial affecting cell wall integrity

In a looming post-antibiotic era, antibiotic alternatives have become key players in the combat against pathogens. Although recent advances in genomic research allow scientists to fully explore an organism's genome in the search for novel antibacterial molecules, laborious work is still needed in order to dissect each individual gene product for its antibacterial activity. Here, we exploited phage-induced bacterial morphological changes as anchors to explore and discover a potential phage-derived antimicrobial embedded in the phage genome. We found that, upon vibriophage KVP40 infection, Vibrio parahaemolyticus exhibited morphological changes similar to those observed when treated with mecillinam, a cell wall synthesis inhibitor, suggesting the mechanism of pre-killing that KVP40 exerts inside the bacterial cell upon sieging the host. Genome analysis revealed that, of all the annotated gene products in the KVP40 genome that are involved in cell wall degradation, lytic transglycosylase (LT) is of particular interest for subsequent functional studies. A single-cell morphological analysis revealed that heterologous expression of wild-type KVP40-LT induced similar bacterial morphological changes to those treated with the whole phage or mecillinam, prior to cell burst. On the contrary, neither the morphology nor the viability of the bacteria expressing signal-peptide truncated- or catalytic mutant E80A- KVP40-LT was affected, suggesting the necessity of these domains for the antibacterial activities. Altogether, this research paves the way for the future development of the discovery of phage-derived antimicrobials that is guided through phage-induced morphological changes.

A Perspective on Current Therapeutic Molecule Screening Methods Against 'Candidatus Liberibacter asiaticus', the Presumed Causative Agent of Citrus Huanglongbing

Huanglongbing (HLB), referred to as citrus greening disease, is a bacterial disease impacting citrus production worldwide and is fatal to young trees and mature trees of certain varieties. In some areas, the disease is devastating the citrus industry. A successful solution to HLB will be measured in economics: citrus growers need treatments that improve tree health, fruit production, and most importantly, economic yield. The profitability of citrus groves is the ultimate metric that truly matters when searching for solutions to HLB. Scientific approaches used in the laboratory, greenhouse, or field trials are critical to the discovery of those solutions and to estimate the likelihood of success of a treatment aimed at commercialization. Researchers and the citrus industry use a number of proxy evaluations of potential HLB solutions; understanding the strengths and limitations of each assay, as well as how best to compare different assays, is critical for decision-making to advance therapies into field trials and commercialization. This perspective aims to help the reader compare and understand the limitations of different proxy evaluation systems based on the treatment and evaluation under consideration. The researcher must determine the suitability of one or more of these metrics to identify treatments and predict the usefulness of these treatments in having an eventual impact on citrus production and HLB mitigation. As therapies advance to field trials in the next few years, a reevaluation of these metrics will be useful to guide future research efforts on strategies to mitigate HLB and vascular bacterial pathogens in other perennial crops.

Development of New Azomethine Metal Chelates Derived from Isatin: DFT and Pharmaceutical Studies

Through the condensation of isatin (indoline-2, 3-dione) and aniline in a 1:1 ratio, a Schiff base ligand was synthesized and characterized via (¹H-NMR, mass, IR, UV-Vis) spectra. Elemental analyses, spectroscopy (¹H-NMR, mass, UV-Vis), magnetic susceptibility, molar conductivity, mass spectra, scanning electron microscope (SEM), and thermal analysis have all been used to characterize a series of Cr(III), Mn(II), Fe(III), Co(II), Ni(II), Cu(II), Zn(II), and Cd(II) metal complexes derived from the titled ligand. The metal-to-ligand ratio is 1:1, according to the analytical data. The Schiff base ligand displayed bidentate behavior with NO coordination sites when it bonded to metal ions, as seen by the IR spectra. The magnetic moment measurement and UV-Vis spectral investigation showed the octahedral geometry of the Cr(III), Fe(III), Co(II), Ni(II), and Zn(II) complexes, whereas they suggested the tetrahedral geometry of the Mn(II), Cu(II), and Cd(II) complexes. The thermal analysis study confirmed the presence of both hydrated and coordinated water molecules in all the compounds, except for the Mn(II) complex, and showed that the complexes decomposed in three or five decomposition steps leaving the corresponding metal oxide as a residue. The ligand and its metal complexes' antibacterial efficacy were evaluated. The findings showed that the metal complexes had stronger antibacterial properties than the ligand alone. The ligand and its metal complexes' anticancer properties were also investigated. A DFT investigation is also reported to gather information regarding the electronic features of the ligand and its metal complexes. Finally, drug-likeness and ADME characteristics were also calculated as parameters.

A Study on the Effect of Nanoscale MgO and Hydrogen Bonding in Nanofiber Mats for the Controlled Drug Release along with In Vitro Breast Cancer Cell Line and Antimicrobial Studies

Nanosized metal oxide-incorporated drug carriers have received significant attention due to their biocompatibility, mechanical strength, controlled drug release, and biodegradability. Herein, an attempt was made to fabricate polycaprolactone-based electrospun nanofiber mats involving the 5-fluorouracil (5Fu) drug, MgO nanoparticle, methyl cellulose, and polyethylene glycol. The chemical interactions, surface wettability, mechanical properties, structural and morphological changes, and thermal stability were studied by the respective analyses. The ionic interaction between 5Fu, MgO, and polymers were found to be responsible for the controlled drug release. Zero-order kinetic and model data also revealed that a controlled drug release pattern was observed in a period of 16 days. Furthermore, the nanofiber mats were subjected to cytotoxicity studies against MDA-MB-231 cancer cell line and the results showed higher cytotoxicity in a short time of 24 h and less toxicity to normal L929 fibroblast cell line. The apoptosis in cancer cell lines was also tested by AO/PI staining assay and confirmed by fluorescence microscopy. In addition, the growth inhibition of several bacterial and fungal strains was tested for the mats and the results exhibited good inhibition activity. Hence, the reported nanofiber drug carrier was found to be an efficient implant for the controlled release of anticancer drug along with other significant properties.

In Vitro Assessment of Antimicrobial, Antioxidant, and Cytotoxic Properties of Saccharin-Tetrazolyl and -Thiadiazolyl Derivatives: The Simple Dependence of the pH Value on Antimicrobial Activity

The antimicrobial, antioxidant, and cytotoxic activities of a series of saccharin-tetrazolyl and -thiadiazolyl analogs were examined. The assessment of the antimicrobial properties of the referred-to molecules was completed through an evaluation of minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values against Gram-positive and Gram-negative bacteria and yeasts. Scrutiny of the MIC and MBC values of the compounds at pH 4.0, 7.0, and 9.0 against four Gram-positive strains revealed high values for both the MIC and MBC at pH 4.0 (ranging from 0.98 to 125 µg/mL) and moderate values at pH 7.0 and 9.0, exposing strong antimicrobial activities in an acidic medium. An antioxidant activity analysis of the molecules was performed by using the DPPH (2,2-diphenyl-1-picrylhydrazyl) method, which showed high activity for the TSMT (N-(1-methyl-2H-tetrazol-5-yl)-N-(1,1-dioxo-1,2-benzisothiazol-3-yl) amine, 7) derivative (90.29% compared to a butylated hydroxytoluene positive control of 61.96%). Besides, the general toxicity of the saccharin analogs was evaluated in an Artemia salina model, which displayed insignificant toxicity values. In turn, upon an assessment of cell viability, all of the compounds were found to be nontoxic in range concentrations of 0-100 µg/mL in H7PX glioma cells. The tested molecules have inspiring antimicrobial and antioxidant properties that represent potential core structures in the design of new drugs for the treatment of infectious diseases.

Genome Features and Secondary Metabolites Biosynthetic Potential of the Class Ktedonobacteria

The prevalence of antibiotic resistance and the decrease in novel antibiotic discovery in recent years necessitates the identification of potentially novel microbial resources to produce natural products. Ktedonobacteria, a class of deeply branched bacterial lineage in the ancient phylum Chloroflexi, are ubiquitous in terrestrial environments and characterized by their large genome size and complex life cycle. These characteristics indicate Ktedonobacteria as a potential active producer of bioactive compounds. In this study, we observed the existence of a putative "megaplasmid," multiple copies of ribosomal RNA operons, and high ratio of hypothetical proteins with unknown functions in the class Ktedonobacteria. Furthermore, a total of 104 antiSMASH-predicted putative biosynthetic gene clusters (BGCs) for secondary metabolites with high novelty and diversity were identified in nine Ktedonobacteria genomes. Our investigation of domain composition and organization of the non-ribosomal peptide synthetase and polyketide synthase BGCs further supports the concept that class Ktedonobacteria may produce compounds structurally different from known natural products. Furthermore, screening of bioactive compounds from representative Ktedonobacteria strains resulted in the identification of broad antimicrobial activities against both Gram-positive and Gram-negative tested bacterial strains. Based on these findings, we propose the ancient, ubiquitous, and spore-forming Ktedonobacteria as a versatile and promising microbial resource for natural product discovery.

Chemical Composition, Antimicrobial and Antiparasitic Screening of the Essential Oil from Phania matricarioides (Spreng.) Griseb

Essential oils (EOs) have gained increasing attention due to their pharmacological effectiveness, and they also constitute some of the most popular natural products. In this study, we present the chemical characterization of the EO from Phania matricarioides and the in vitro activity/selectivity against a wide panel of bacteria, fungi and parasitic protozoa. Forty-five compounds were identified in the studied EO, of which lavandulyl acetate (40.1%) and thymyl isobutyrate (13.9%) were the major components. The EO did not inhibit bacterial or fungal growth at the maximum concentration tested (64 µg/mL), although it displayed activity on all evaluated protozoa (IC₅₀ values ranging from 2.2 to 56.6 µg/mL). In parallel, the EO demonstrated a noteworthy cytotoxic activity against peritoneal macrophages (CC₅₀ values of 28.0 µg/mL). The most sensitive microorganism was Trypanosoma cruzi, which had a superior activity (IC₅₀ = 2.2 µg/mL) and selectivity (SI = 13) in respect to other parasitic protozoa and the reference drug (p < 0.05). Further in vivo studies are needed to evaluate the potential use of this EO and the main compounds as antitrypanosomal agents. To our knowledge, this is the first report of chemical characterization and antimicrobial assessment of the EO from P. matricarioides.

Total syntheses of surinone B, alatanones A-B, and trineurone A

The total syntheses of four polyketides, surinone B (1), alatanones A-B (2-3), and trineurone A (4) were accomplished through an efficient and unified strategy via one-pot C-acylation reaction coupling 1,3-cyclohexadiones with EDC-activated acids under mild conditions. Alatanone A (2) was found to be a potent anti-microbial agent against Gram-positive and Gram-negative bacteria with MIC 31.25 μg/ml while alatanone B (3) was found to be a potent anti-fungal agent against Cladosporium cladosporioides with MIC 62.5 μg/ml compared to cycloheximide MIC 125 μg/ml. Our methodology allows performing kilogram scale of these scarce polyketides for the development of new antimicrobials.

Utility of Lauroyl Isothiocyanate as a Scaffold in the Synthesis of Some Novel Pyrimidine Derivatives and Their Antimicrobial Assessment

The reaction of lauroyl isothiocyanate 1 with enaminonitrile derivative 2 furnished N-(6-cyano-3, 4-diphenylthieno[2,3-c]pyridazin-5-yl-carbamothioyl)dodecanamide 3, which was used as precursor for the synthesis of novel heterocyclic systems. Polyfunctional pyrimidine and fused pyrimidine derivatives were obtained by the cyclization of compound 3 under different basic conditions as well as its reactions with thiourea, o-aminothiophenol, hydrazine hydrate, phenyl hydrazine, ethyl phenyl acetate or ethyl benzoyl acetate. The structures of the new compounds were confirmed by microanalytical and spectral properties. The synthesised compounds were tested in-vitro for their antimicrobial activity and showed congruent results against most of the tested microorganisms compared to the standard drugs Gentamycin and Ketoconazol.

IN VITRO ANTIMICROBIAL SCREENING OF AQUILARIA AGALLOCHA ROOTS

Background:

It was previously shown that some parts of Aquilaria agallocha, which is commonly known as oud or oodh, such as roots have been used as a traditional medical herbal in different countries. In Turkey A. agallocha is one of the ingredients while preparing famous Mesir paste, which was invented as a medicinal paste and used from the Ottoman period to now at least for 500 years. The identification the in vitro antimicrobial activity of ethanol extract of A. agallocha roots is main purpose of this analysis.

Materials and Methods:

By using 17 bacteria and 1 fungi, which include Bacillus, Candida, Enterobacter, Enterococcus, Escherichia, Klebsiella, Listeria, Pseudomonas, Salmonella and Staphylococcus genera, the activity of A. agallocha root extracts were analysed by the help of the disk diffusion method, that is one of the methods commonly used to determine antimicrobial activities.

Results:

As a result of the study it was observed that ethanol extracts of A. agallocha roots have a clear antimicrobial activity against nearly all microorganism used in the study, but only two bacteria namely E. coli ATCC 25922 and S. typhimurium SL 1344.

Conclusion:

According to the disk diffusion test results it may be possible to propose that A. agallocha roots should have a medicinal uses especially against E. faecium, L. monocytogenes ATCC 7644, B. subtilis DSMZ 1971, C. albicans DSMZ 1386, S. epidermidis DSMZ 20044 and S. aureus ATCC 25923.

Screening and Optimizing Antimicrobial Peptides by Using SPOT-Synthesis

Peptide arrays on cellulose are a powerful tool to investigate peptide interactions with a number of different molecules, for examples antibodies, receptors or enzymes. Such peptide arrays can also be used to study interactions with whole cells. In this review, we focus on the interaction of small antimicrobial peptides with bacteria. Antimicrobial peptides (AMPs) can kill multidrug-resistant (MDR) human pathogenic bacteria and therefore could be next generation antibiotics targeting MDR bacteria. We describe the screen and the result of different optimization strategies of peptides cleaved from the membrane. In addition, screening of antibacterial activity of peptides that are tethered to the surface is discussed. Surface-active peptides can be used to protect surfaces from bacterial infections, for example implants.

IN VITRO ANTIMICROBIAL ACTIVITY SCREENING OF XYLARIA HYPOXYLON

Background:

Fungi have a potential of using both as nutritive and medicinal food stuff. Because of containing several therapeutic agents, they are reported to be used for hundreds of years to treat several diseases caused by bacteria, fungi, viruses and parasites. The aim of this study is to determine the in vitro antimicrobial activity of Xylaria hypoxylon, which were collected from Yomra, Trabzon, Turkey.

Materials and Methods:

X. hypoxylon samples were air dried and extracted by using ethanol. Antimicrobial activity of X. hypoxylon ethanol extracts were investigated against 21 bacterial and 2 fungal strains, namely, Bacillus subtilis DSMZ 1971, Bacillus subtilis ATCC 6633, Candida albicans ATCC 10231, Candida albicans DSMZ 1386, Enterobacter aerogenes ATCC 13048, Enterococcus durans, Enterococcus faecalis ATCC 29212, Enterococcus faecium, Escherichia coli ATCC 25922, Escherichia coli CFAI, Klebsiella pneumoniae, Listeria innocula, Listeria monocytogenes ATCC 7644, Pseudomonas aeruginosa DSMZ 50071, Pseudomonas fluorescence P1, Salmonella enteritidis ATCC 13075, Salmonella infantis, Salmonella kentucky, Salmonella typhimurium SL 1344, Staphylococcus aureus ATCC 25923, Staphylococcus carnosus MC1.B, Staphylococcus epidermidis DSMZ 20044 and Streptococcus agalactiae DSMZ 6784 by using the disk diffusion method.

Results:

It is observed that ethanol extracts of X. hypoxylon has antimicrobial activity against several Gram positive and Gram negative microorganisms tested. As a result of the study, an antimicrobial activity of X. hypoxylon found against most of strains used in the study.

Conclusion:

The results of our study clearly puts forward that X. hypoxylon could have a possible medicinal use.

Microscale Adaptation of In Vitro Transcription/Translation for High-Throughput Screening of Natural Product Extract Libraries

Novel antimicrobials that effectively inhibit bacterial growth are essential to fight the growing threat of antibiotic resistance. A promising target is the bacterial ribosome, a 2.5 MDa organelle susceptible to several biorthogonal modes of action used by different classes of antibiotics. To promote the discovery of unique inhibitors, we have miniaturized a coupled transcription/translation assay using E. coli and applied it to screen a natural product library of ~30 000 extracts. We significantly reduced the scale of the assay to 2 μL in a 1536-well plate format and decreased the effective concentration of costly reagents. The improved assay returned 1327 hits (4.6% hit rate) with %CV and Z' values of 8.5% and 0.74, respectively. This assay represents a significant advance in molecular screening, both in miniaturization and its application to a natural product extract library, and we intend to apply it to a broad array of pathogenic microbes in the search for novel anti-infective agents.

Westerdykella reniformis sp. nov., producing the antibiotic metabolites melinacidin IV and chetracin B

Westerdykella reniformis Ebead & Overy sp. nov. is described based on morphology and phylogenetic analyses using ITS, nLSU rDNA, and β-tubulin gene sequences. Westerdykella reniformis is characterized by the production of cleistothecioid ascomata, containing small globose to subglobose asci with 32, aseptate, dark colored, pronouncedly reniform ascospores having a concave central groove. The isolate was obtained from a red alga (Polysiphonia sp.) collected from the tidal zone in Canada at low tide. Organic extracts enriched in extrolites, obtained from fermentation on a rice-based media, inhibited the growth of methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant Enterococcus faecium (VRE), S. warneri, and Proteus vulgaris. Presented here is the identification of the compounds responsible for the observed antimicrobial activity, the taxonomic description of W. reniformis, and a dichotomous key to the known species of Westerdykella based on macro- and micromorphological characters.