Genomic insights into antibiotic resistance genes in Leuconostoc citreum strains isolated from artisanal buffalo milk curd in Bangladesh through whole-genome sequencing.

We sequenced the genome of Leuconostoc citreum strains BSMRAU-M1L6 and BSMRAU-M1L13 isolated from artisanal buffalo milk curd in Bangladesh. The draft genomes of BSMRAU-M1L6 and BSMRAU-M1L13 are 1,869,891 and 1,890,611 bp, respectively, with 50.0× coverage (both) and 65 and 75 contigs, respectively.

Virulence and antibiotic-resistance genes in Enterococcus faecalis associated with streptococcosis disease in fish.

Enterococcus faecalis is associated with streptococcosis like infection in fish. A whole-genome sequence study was conducted to investigate the virulence factor and antibiotic-resistance genes in three fish pathogenic E. faecalis. Genomic DNA was extracted from three strains of E. faecalis isolated from streptococcosis infected Nile tilapia (strains BF1B1 and BFFF11) and Thai sarpunti (strain BFPS6). The whole genome sequences of these three strains were performed using a MiSeq sequencer (Illumina, Inc.). All three strains conserved 69 virulence factor such as genes associated with protection against oxidative stress, bacterial cell wall synthesis, gelatinase toxin, multiple biofilm-associated genes and capsule producing genes. Moreover, 39 antibiotic-resistance genes against sixteen major groups of antibiotics were identified in the genome sequences of all three strains. The most commonly used antibiotic Tetracycline resistance genes were found only in BFPS6 strain, whereas, Bacteriocin synthesis genes were identified in both BFFF11 and BFPS6 strain. Phylogenetic analysis revealed that strains BF1B1 and BFFF1 form a different cluster than BFPS6. This is one of the first whole-genome sequence study of fish pathogenic E. faecalis, unfold new information on the virulence factor and Antibiotic resistance genes linked to pathogenicity in fish.

Targeting Estrogen Signaling in the Radiation-induced Neurodegeneration: A Possible Role of Phytoestrogens.

Radiation for medical use is a well-established therapeutic method with an excellent prognosis rate for various cancer treatments. Unfortunately, a high dose of radiation therapy comes with its own share of side effects, causing radiation-induced non-specific cellular toxicity; consequently, a large percentage of treated patients suffer from chronic effects during the treatment and even after the post-treatment. Accumulating data evidenced that radiation exposure to the brain can alter the diverse cognitive-related signaling and cause progressive neurodegeneration in patients because of elevated oxidative stress, neuroinflammation, and loss of neurogenesis. Epidemiological studies suggested the beneficial effect of hormonal therapy using estrogen in slowing down the progression of various neuropathologies. Despite its primary function as a sex hormone, estrogen is also renowned for its neuroprotective activity and could manage radiation-induced side effects as it regulates many hallmarks of neurodegenerations. Thus, treatment with estrogen and estrogen-like molecules or modulators, including phytoestrogens, might be a potential approach capable of neuroprotection in radiation-induced brain degeneration. This review summarized the molecular mechanisms of radiation effects and estrogen signaling in the manifestation of neurodegeneration and highlighted the current evidence on the phytoestrogen mediated protective effect against radiationinduced brain injury. This existing knowledge points towards a new area to expand to identify the possible alternative therapy that can be taken with radiation therapy as adjuvants to improve patients' quality of life with compromised cognitive function.

Suppression of Streptococcosis and Modulation of the Gut Bacteriome in Nile Tilapia (Oreochromis niloticus) by the Marine Sediment Bacteria Bacillus haynesii and Advenella mimigardefordensis.

Streptococcosis is one of the major threats to Nile tilapia (Oreochromis niloticus) in most regions of the world. Recently, Enterococcus faecalis has been widely reported to be involved in streptococcosis in O. niloticus in Asia and Africa. This study aimed to isolate beneficial marine bacteria to evaluate their effects on growth, hematological parameters, nonspecific immunity, the gut bacteriome, and streptococcosis prevention efficacy in O. niloticus. A total of 36 marine soil bacteria were isolated, and in vitro screening was conducted to determine their antibacterial activities against fish pathogens. Two antagonistic bacteria were identified based on 16S rRNA gene sequencing, Bacillus haynesii CD223 and Advenella mimigardefordensis SM421. These bacteria were incorporated into fish feed and fed to O. niloticus for 90 days. The application of these strains via incorporation into fish feed significantly promoted growth, improved hematological parameters and immunoglobulin M (IgM) levels, modulated the gut bacteriome by reducing the load of pathogenic Enterococcus spp., and developed disease prevention efficacy in O. niloticus. Furthermore, in vivo assays revealed that the inclusion of extracellular products (ECPs) (at 250 µg mL-1) of CD223 and SM421 with feed significantly enhanced the rate of survival (100%) of O. niloticus from streptococcosis compared to the controls (only 30%). The ECPs of these bacteria also prevented 90 to 100% of fish from developing streptococcosis. These strains could be promising for safe use in O. niloticus farming to prevent and control the emergence of streptococcosis caused by E. faecalis. IMPORTANCE Nile tilapia (Oreochromis niloticus) is one of the most economically important cultured fish species throughout the world. Streptococcosis is a significant threat to global Nile tilapia farming. Enterococcus faecalis has recently emerged as an important pathogen of streptococcosis in Asia and Africa. The application of antibiotics and probiotics and vaccination are the major ways to combat streptococcosis. However, the extensive use of antibiotics leads to the development of antibiotic resistance in pathogenic as well as environmental bacteria, which is a great threat to public health. There is no study on preventing streptococcosis caused by E. faecalis using beneficial bacteria. For the first time, the present study demonstrated that two marine bacteria, Bacillus haynesii strain CD223 and Advenella mimigardefordensis strain SM421, have great potential for controlling streptococcosis in Nile tilapia. These bacteria also enhanced the growth, improved hematological parameters and IgM levels, and positively modulated the gut bacteriome of Nile tilapia.

Fabrication of highly and poorly oxidized silver oxide/silver/tin(IV) oxide nanocomposites and their comparative anti-pathogenic properties towards hazardous food pathogens.

Herein, we report the fabrication of highly oxidized silver oxide/silver/tin(IV) oxide (HOSBTO or Ag3+-enriched AgO/Ag/SnO2) nanocomposite under a robust oxidative environment created with the use of concentrated nitric acid. Tin(IV) hydroxide nanofluid is added to the reaction mixture as a stabilizer for the Ag3+-enriched silver oxide in the nanocomposite. The formation of Ag nanoparticles in this nanocomposite originates from the decomposition of silver oxides during calcination at 600 °C. For comparison, poorly oxidized silver oxide/silver/tin(IV) oxide (POSBTO with formula AgO/Ag/SnO2) nanocomposite has also been prepared by following the same synthetic procedures, except for the use of concentrated nitric acid. Finally, we studied in detail the anti-pathogenic capabilities of both nanocomposites against four hazardous pathogens, including pathogenic fish bacterium (Stenotrophomonas maltophilia stain EP10), oomycete (Phytophthora cactorum strain P-25), and two different strains of pathogenic strawberry fungus, BRSP08 and BRSP09 (Collectotrichum siamense). The bioassays reveal that the as-prepared HOSBTO and POSBTO nanocomposites exhibit significant inhibitory activities against the tested pathogenic bacterium, oomycete, and fungus in a dose-dependent manner. However, the degree of dose-dependent effectiveness of the two nanocomposites against each pathogen largely varies.

Genomic diversity and evolution, diagnosis, prevention, and therapeutics of the pandemic COVID-19 disease.

The coronavirus disease 19 (COVID-19) is a highly transmittable and pathogenic viral infection caused by a novel evolutionarily divergent RNA virus, the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The virus first emerged in Wuhan, China in December 2019, and subsequently spreaded around the world. Genomic analyses revealed that this zoonotic virus may be evolved naturally but not a purposefully manipulated laboratory construct. However, currently available data are not sufficient to precisely conclude the origin of this fearsome virus. Comprehensive annotations of the whole-genomes revealed hundreds of nucleotides, and amino acids mutations, substitutions and/or deletions at different positions of the ever changing SARS-CoV-2 genome. The spike (S) glycoprotein of SARS-CoV-2 possesses a functional polybasic (furin) cleavage site at the S1-S2 boundary through the insertion of 12 nucleotides. It leads to the predicted acquisition of 3-O-linked glycan around the cleavage site. Although real-time RT-PCR methods targeting specific gene(s) have widely been used to diagnose the COVID-19 patients, however, recently developed more convenient, cheap, rapid, and specific diagnostic tools targeting antigens or CRISPR-Cas-mediated method or a newly developed plug and play method should be available for the resource-poor developing countries. A large number of candidate drugs, vaccines and therapies have shown great promise in early trials, however, these candidates of preventive or therapeutic agents have to pass a long path of trials before being released for the practical application against COVID-19. This review updates current knowledge on origin, genomic evolution, development of the diagnostic tools, and the preventive or therapeutic remedies of the COVID-19. We also discussed the future scopes for research, effective management, and surveillance of the newly emerged COVID-19 disease.

First report of basal rot of dragon fruit caused by Fusarium oxysporum in Bangladesh.

Dragon fruit (Hylocereus polyrhizus) is a high value newly introduced fruit crop in Bangladesh. It has drawn considerable public attention due to its appealing flesh color, sweet taste and fruit qualities. Recently, basal rot of dragon fruit plants was observed in several farmer's fields, nurseries and in the research field of Bangabandhu Sheikh Mujibur Rahman Agricultural University (BSMRAU) where about 10-15% of plants were infected in each location. Initially, the symptoms appeared in the basal part near the soil as brown lesions which gradually extended to the upper stem and finally becoming soft and watery (Figure 1a). Infected plants were collected from Kapasia of Gazipur district (Latitude 24.266 and Longitude 90.633) to isolate the causal organism. Isolations were carried out following the procedure reported by Briste et al. (2019). Briefly, infected plant parts were surface sterilized in 2% NaOCl for 1 min followed by 70% ethanol for 5 min and rinsed 3 times with sterile double distilled water. A large piece of a surface sterilized plant was cut into small pieces (2 mm × 2 mm) from the margin of the necrotic lesion and placed on half strength potato dextrose agar (PDA) and incubated for 7 days at 25 °C. The BTFD1 and BTFD4 isolates were purified from single spores resulting in white colonies with a growth rate of 1cm/day on PDA (Figure 1b). Colonies produced single celled microconidia from unbranched, short monophialidic conidiophores and septate macroconidia as well as chlamydospores in PDA which is consistent with Fusarium oxysporum (Figure 1c). To confirm the identity of the isolates, the internal transcribed spacer (ITS1, 5.8S rRNA and ITS2) and translation elongation factor-1alpha (EF-1α) were amplified using primers ITS-1/ ITS-4 and EF1-728F/ EF1-986R, respectively (Surovy et al. 2018). The ITS sequences of the isolates BTFD1 and BTFD4 (GenBank accession # MN727096 and MN727095, respectively) showed 100% similarity with the sequence from F. oxysporum strain JJF2 (MN626452). Sequence identity for EF-1α (GenBank accession # MN752123 and MN752124, respectively) was 100% with the sequence from F. oxysporum strain CAV041_EO (MK783088). The isolates (BTFD1 and BTFD4) were identified as F. oxysporum based on the aligned sequences of ITS and EF-1α, molecular phylogenetic analyses by maximum likelihood tree (Figure 2a) and maximum parsimony tree methods (Figure 2b). The isolates were stored at 4°C on dried filter paper as well as in an ultra-low temperature freezer (-80°C) at IBGE, BSMRAU, Bangladesh and are available on request. To ensure pathogenicity, isolate BTFD1 was grown on PDA, incubated at 25°C for 7 days and 250 ml conidial suspension (with 1 × 105 conidia/ml) was prepared. Twelve,three-month-old healthy dragon fruit plants were inoculated. Pathogenicity tests were carried out in two sets using three replications in each set. In one set, only the basal part of the plants was dipped into the conidial suspension and in another set the whole plant was dipped into the conidial suspension for two hours. Sterile distilled water was also used in another set of plants as a control. The inoculated plants were placed on wet tissue in a plastic box (31cm × 24cm × 8cm) covered and incubated at 25°C. After 10 days, all inoculated plants in both sets developed rot symptoms similar to those observed in the field, while the control plants remained healthy (Figure 1d). The pathogen was successfully re-isolated from the inoculated symptomatic parts on half strength PDA medium and had morphology as characterized before, thus fulfilling Koch's postulates. This disease has been reported in Argentina and Malaysia (Wright et al. 2007; Hafifi et al. 2019). To the bet of our knowledge, this is the first report of Fusarium basal rot of dragon fruit in Bangladesh caused by F. oxysporum.

Cytotoxic and anti-inflammatory resorcinol and alkylbenzoquinone derivatives from the leaves of Ardisia sieboldii.

Medicinal plants belonging to the genus Ardisia are traditionally used to cure various human diseases including inflammation and cancer. This study aimed to purify and characterize cytotoxic and anti-inflammatory compounds from Ardisia sieboldii leaves. Bioassay-guided chromatographic analyses yielded three compounds, 2-methyl-5-(8Z-heptadecenyl) resorcinol (1), 5-(8Z-heptadecenyl) resorcinol (2), and ardisiaquinone A (3), whereas liquid chromatography-electrospray ionisation-mass spectrometry chemical profiling revealed the presence of diverse resorcinol and alkylbenzoquinone derivatives in cytotoxic 70% methanol extracts. Chemical structures of 1-3 were confirmed by spectroscopic methods including 1H NMR (nuclear magnetic resonance), 13C NMR, and electrospray ionisation-mass spectrometry. Compounds 1 and 2 were purified from A. sieboldii for the first time, and all three compounds showed cytotoxicity against a panel of cancer cell lines and brine shrimps in a dose-response manner. Among them, compound 2 exhibited the highest cytotoxicity on cancer cells (IC50 values of 8.8-25.7 µM) as well as on brine shrimps (IC50 value of 5.1 µM). Compounds 1-3 exhibited anti-inflammatory effects through inhibiting protein denaturation (IC50 values of 5.8-9.6 µM), cyclooxygenase-2 activity (IC50 values of 34.5-60.1 µM), and nitrite formation in RAW 264.7 cells. Cytotoxic and anti-inflammatory activities of 1-3 demonstrated in this study deserve further investigation for considering their suitability as candidates or leads to develop anticancer and anti-inflammatory drugs.

Salinity stress accelerates nutrients, dietary fiber, minerals, phytochemicals and antioxidant activity in Amaranthus tricolor leaves.

Impact of salinity stress were investigated in three selected Amaranthus tricolor accessions in terms of nutrients, dietary fiber, minerals, antioxidant phytochemicals and total antioxidant activity in leaves. Salinity stress enhanced biochemical contents and antioxidant activity in A. tricolor leaves. Protein, ash, energy, dietary fiber, minerals (Ca, Mg, Fe, Mn, Cu, Zn, and Na), ß-carotene, ascorbic acid, total polyphenol content (TPC), total flavonoid content (TFC), total antioxidant capacity (TAC) (DPPH and ABTS+) in leaves were increased by 18%, 6%, 5%, 16%, 9%, 16%, 11%, 17%, 38%, 20%, 64%, 31%, 22%, 16%, 16%, 25% and 17%, respectively at 50 mM NaCl concentration and 31%, 12%, 6%, 30%, 57%, 35%, 95%, 96%, 82%, 87%, 27%, 63%, 82%, 39%, 30%, 58% and 47%, respectively at 100 mM NaCl concentration compared to control condition. Contents of vitamins, polyphenols and flavonoids showed a good antioxidant activity due to positive and significant interrelationships with total antioxidant capacity. It revealed that A. tricolor can tolerate a certain level of salinity stress without compromising the nutritional quality of the final product. This report for the first time demonstrated that salinity stress at certain level remarkably enhances nutritional quality of the leafy vegetable A. tricolor. Taken together, our results suggest that A. tricolor could be a promising alternative crop for farmers in salinity prone areas- in the tropical and sub-tropical regions with enriched nutritional contents and antioxidant activity.

Chitosan biopolymer promotes yield and stimulates accumulation of antioxidants in strawberry fruit.

Strawberry is a well-known source of natural antioxidants with excellent free radical scavenging capacity. This study determined the effects of chitosan application in field condition on plant growth, fruit yield and antioxidant activities in strawberry fruit. Foliar applications of chitosan on strawberry significantly increased plant growth and fruit yield (up to 42% higher) compared to untreated control. Increased fruit yield was attributed to higher plant growth, individual fruit weight and total fruit weight/plant due to the chitosan application. Surprisingly, the fruit from plants sprayed with chitosan also had significantly higher contents (up to 2.6-fold) of carotenoids, anthocyanins, flavonoids and phenolics compared to untreated control. Total antioxidant activities in fruit of chitosan treated plants were also significantly higher (ca. 2-fold) (p< 0.05) than untreated control. To the best of our knowledge, this is the first report of chitosan applied on field plants providing significant improvement of both yield and health benefiting biochemical contents in strawberry fruit. Further study on the elucidation of mechanisms involved with enhancement of growth, yield and biochemical contents by chitosan is needed to promote sustainable production of strawberry.

Preparation of Ultraviolet Curing Type Silicone Rubbers Containing Mesoporous Silica Fillers.

Here we have been focusing on mesoporous silica (MPS) as inorganic filler material to improve the mechanical strength of silicone rubbers. The MPS particles are more effective in reducing the coefficient of thermal expansion (CTE) and hardening silicone rubber composites when compared to commercially available nonporous silica particles. In this study, we utilize ultraviolet curing type silicone rubbers and prepare MPS composites according to a simple single-step method. From an industrial viewpoint, simplifying the fabrication processes is critical. The thermal stability and mechanical strength are examined in detail in order to showcase the effectiveness of MPS particles as filler materials.

Tuning Wall Thicknesses in Mesoporous Silica Films for Optimization of Optical Anti-Reflective Properties.

This work reports the fabrication of mesoporous silica films with controllable wall thicknesses by spin coating of precursor solutions consisting of polystyrene-block-polybutadiene-block-polystyrene based triblock copolymers (Hydrogenated methyl Styrene Ethylene Butadiene methyl Styrene, HmSEBmS) and tetraethyl orthosilicate (TEOS) followed by calcination in air at 600 °C, for optical anti-reflection films. By changing the relative weight of the triblock polymer to TEOS, the pore-to-pore distance in the mesoporous silica film can be controlled without significantly affecting the size of the mesopores, thus, enabling effective control of the refractive index and porosity of the films. In terms of optical properties, the transmittance of the fabricated mesoporous silica film is approximately 3.3% higher than that of the uncoated glass substrate in the wavelength range of 400 to 750 nm.

Anti-Staphylococcal Calopins from Fruiting Bodies of Caloboletus radicans.

Three new and seven known calopins were isolated from Caloboletus radicans. The structures of the new cyclocalopins, 8-deacetylcyclocalopin B (1), cyclocalopin A-15-ol (2), and 12,15-dimethoxycyclocalopin A (3), were mainly elucidated by NMR and MS data analysis. The stereochemistry of 1-3 was assigned based on NOE correlations and coupling constants and by comparison of their CD spectra with those of similar known calopins. While 1-10 were inactive against two cancer cell lines, they displayed anti-staphylococcal activity against methicillin-resistant Staphylococcus aureus strains (MRSA) with MIC values of 16-256 µg/mL. Moreover, some calopins were active against the fish pathogen Enterococcus faecalis F1B1.

Synthesis of MOF-525 Derived Nanoporous Carbons with Different Particle Sizes for Supercapacitor Application.

Nanoporous carbon (NC) materials have attracted great research interest for supercapacitor applications, because of their excellent electrochemical and mechanical stability, good electrical conductivity, and high surface area. Although there are many reports on metal-organic framework (MOF)-derived carbon materials, previous synthetic studies have been hindered by imperfect control of particle sizes and shapes. Here, we show precise control of the particle sizes of MOF-525 from 100 nm to 750 nm. After conversion of MOF-525 to NC, the effects of variation of the particle size on the electrochemical performance have been carefully investigated. The results demonstrate that our NC is a potential candidate for practical supercapacitor applications.

Molecular Identification of Multiple Antibiotic Resistant Fish Pathogenic Enterococcus faecalis and their Control by Medicinal Herbs.

The opportunistic fish pathogen, Enterococcus faecalis has been reported to cause mass mortality in several fish species in different countries. The objectives of this study were to (i) identify E. faecalis from the diseased fishes through molecular techniques; (ii) assess the antibiotic susceptibility profile of E. faecalis isolates; and (iii) control disease in tilapia fish by treatment with medicinal plant extracts. A total of 48 isolates were phenotypically identified as Enterococcus species from tilapia, stinging catfish and walking catfish cultivated in several fish farms in Gazipur. Ten randomly selected isolates were identified as E. faecalis by 16S rRNA gene sequencing. Artificial infection revealed that most of the isolates caused moderate to high mortality in fishes with characteristic disease symptoms. These isolates exhibited resistance to multiple antibiotics in vitro. Bioassay revealed that organic extracts of Tamarindus indica and Emblica officinalis leaves, Allium sativum bulb, and Syzygium aromaticum bud inhibited the growth of E. faecalis. Methanol extracts of A. sativum and methanol and acetone extracts of S. aromaticum significantly reduced the mortality of fish artificially infected with E. faecalis as both preventive and therapeutic agents. This is the first report on molecular identification, and herbal control of fish pathogenic E. faecalis in Bangladesh.

Mesoporous metallic rhodium nanoparticles.

Mesoporous noble metals are an emerging class of cutting-edge nanostructured catalysts due to their abundant exposed active sites and highly accessible surfaces. Although various noble metal (e.g. Pt, Pd and Au) structures have been synthesized by hard- and soft-templating methods, mesoporous rhodium (Rh) nanoparticles have never been generated via chemical reduction, in part due to the relatively high surface energy of rhodium (Rh) metal. Here we describe a simple, scalable route to generate mesoporous Rh by chemical reduction on polymeric micelle templates [poly(ethylene oxide)-b-poly(methyl methacrylate) (PEO-b-PMMA)]. The mesoporous Rh nanoparticles exhibited a ∼2.6 times enhancement for the electrocatalytic oxidation of methanol compared to commercially available Rh catalyst. Surprisingly, the high surface area mesoporous structure of the Rh catalyst was thermally stable up to 400 °C. The combination of high surface area and thermal stability also enables superior catalytic activity for the remediation of nitric oxide (NO) in lean-burn exhaust containing high concentrations of O2.

Gold Nanoparticles Supported on Mesoporous Titania Thin Films with High Loading as a CO Oxidation Catalyst.

In the present work, 2.4 nm gold nanoparticles (Au NPs) are uniformly dispersed on mesoporous titania thin films which are structurally tuned by controlling the calcination temperature. The gold content of the catalyst is as high as 27.8 wt %. To our knowledge, such a high loading of Au NPs with good dispersity has not been reported until now. Furthermore, the reaction rate of the gold particles is enhanced by one order of magnitude when supported on mesoporous titania compared to non-porous titania. This significant improvement can be explained by an increase in the diffusivity of the substrate due to the presence of mesopores, the resistance to agglomeration, and improved oxygen activation.

Inhibitory Effects of Macrotetrolides from Streptomyces spp. On Zoosporogenesis and Motility of Peronosporomycete Zoospores Are Likely Linked with Enhanced ATPase Activity in Mitochondria.

The release of zoospores from sporangia and motility of the released zoospores are critical in the disease cycle of the Peronosporomycetes that cause devastating diseases in plants, fishes, animals and humans. Disruption of any of these asexual life stages eliminates the possibility of pathogenesis. In the course of screening novel bioactive secondary metabolites, we found that extracts of some strains of marine Streptomyces spp. rapidly impaired motility and caused subsequent lysis of zoospores of the grapevine downy mildew pathogen Plasmopara viticola at 10 µg/ml. We tested a number of secondary metabolites previously isolated from these strains and found that macrotetrolide antibiotics such as nonactin, monactin, dinactin and trinactin, and nactic acids such as (+)-nonactic acid, (+)-homonactic acid, nonactic acid methyl ester, homonactic acid methyl ester, bonactin and feigrisolide C impaired motility and caused subsequent lysis of P. viticola zoospores in a dose- and time-dependent manners with dinactin being the most active compound (MIC 0.3 µg/ml). A cation channel-forming compound, gramicidin, and a carrier of monovalent cations, nigericin also showed similar biological activities. Among all 12 compounds tested, gramicidin most potently arrested the motility of zoospores at concentrations starting from 0.1 µg/ml. All macrotetrolide antibiotics also displayed similar motility impairing activities against P. viticola, Phytophthora capsici, and Aphanomyces cochlioides zoospores indicating non-specific biological effects of these compounds toward peronosporomyctes. Furthermore, macrotetrolide antibiotics and gramicidin also markedly suppressed the release of zoospores from sporangia of P. viticola in a dose-dependent manner. As macrotetrolide antibiotics and gramicidin are known as enhancers of mitochondrial ATPase activity, inhibition of zoosporogenesis and motility of zoospores by these compounds are likely linked with hydrolysis of ATP through enhanced ATPase activity in mitochondria. This is the first report on motility inhibitory and lytic activities of macrotetrolide antibiotics and nactic acids against the zoospores of peronosporomycete phytopathogens.

Gageopeptins A and B, new inhibitors of zoospore motility of the phytopathogen Phytophthora capsici from a marine-derived bacterium Bacillus sp. 109GGC020.

The motility of zoospores is critical in the disease cycles of the peronosporomycetes that cause devastating diseases in plants, fishes, vertebrates, and microbes. In the course of screening for secondary metabolites regulating the motility of zoospores of Phytophthora capsici, we discovered two new inhibitors from the ethyl acetate extract of the fermentation broth of a marine-derived strain Bacillus sp. 109GGC020. The structures of these novel metabolites were elucidated as new cyclic lipopeptides and named gageopeptins A (1) and B (2) by spectroscopic analyses including high resolution MS and extensive 1D and 2D NMR. The stereoconfigurations of 1 and 2 were assigned based on the chemical derivatization studies and reviews of the literature data. Although compounds 1 and 2 impaired the motility of zoospores of P. capsici in dose- and time-dependent manners, compound 1 (IC50 = 1 µg/ml) was an approximately 400-fold stronger motility inhibitor than 2 (IC50 = 400 µg/ml). Interestingly, the zoospores halted by compound 1 were subsequently lysed at higher concentrations (IC50 = 50 µg/ml). Compounds 1 and 2 were also tested against some bacteria and fungi by broth dilution assay, and exhibited moderate antibacterial and good antifungal activities.

Non-cytotoxic antifungal agents: isolation and structures of gageopeptides A-D from a Bacillus strain 109GGC020.

Antifungal resistance and toxicity problems of conventional fungicides highlighted the requirement of search for new safe antifungal agents. To comply with the requirement, we discovered four new non-cytotoxic lipopeptides, gageopeptides A-D, 1-4, from a marine-derived bacterium Bacillus subtilis. The structures and stereochemistry of gageopeptides were determined by NMR data analysis and chemical means. Gageopeptides exhibited significant antifungal activities against pathogenic fungi Rhizoctonia solani, Botrytis cinerea, and Colletotrichum acutatum with minimum inhibitory concentration (MIC) values of 0.02-0.06 µM. In addition, these lipopeptides showed significant motility inhibition and lytic activities against zoospores of the late blight pathogen Phytophthora capsici. These compounds also showed potent antimicrobial activity against Gram positive and Gram negative bacteria with MIC values of 0.04-0.08 µM. However, gageopeptides A-D did not exhibit any cytotoxicity (GI50 > 25 µM) against cancer cell lines in sulforhodamine B (SRB), 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT), and WST-1 ((4-[3-4-iodophenyl]-2-(4-nitrophenyl)-2H-5-tetrazolio)-1,3-benzene disulfonate)) assays, demonstrating that these compounds could be promising candidates for the development of non-cytotoxic antifungal agents.