Antibacterial activity of a sulfated galactan extracted from the marine alga <Emphasis Type="Italic">Chaetomorpha aerea</Emphasis> against <Emphasis Type="Italic">Staphylococcus aureus</Emphasis>

The in vitro antimicrobial activity of the marine green algae Chaetomorpha aerea was investigated against gram-positive bacteria, gram-negative bacteria, and a fungus. The water-soluble extract of algae was composed of a sulfated (6.3%) galactan with a molecular weight of 1.160 × 10⁶ Da and a global composition close to commercial polysaccharides, such as dextran sulfate or fucoidan. The polysaccharide was composed of 18% arabinose, 24% glucose, and 58% galactose. The re-suspended extracts (methanol, water) exhibited selective antibacterial activities against 3 gram-positive bacteria including Staphylococcus aureus (ATCC 25923). Minimum inhibitory concentration and minimum bactericidal concentration tests showed that the sulfated galactan could be a bactericidal agent for this strain (40 mg/mL). The results of this study confirmed the potential use of the green algae Chaetomorpha aerea as a source of antibacterial compounds.     

New water-soluble prodrugs of HIV protease inhibitors based on O-->N intramolecular acyl migration

To improve the low water-solubility of HIV protease inhibitors, we synthesized water-soluble prodrugs of KNI-272 and KNI-279 which are potent HIV-1 protease inhibitors consisting of an Apns–Thz core structure (Apns; allophenylnorstatine, Thz; thiazolidine-4-carboxylic acid) as an inhibitory machinery. The prodrugs, which contained an O-acyl peptidomimetic structure with an ionized amino group leading to the increase of water-solubility, were designed to regenerate the corresponding parent drugs based on the O→N intramolecular acyl migration reaction at the -hydroxy-β-amino acid residue, that is allophenylnorstatine. The synthetic prodrugs 3, 4, 6, and 7 improved the water-solubility (>300 mg/mL) more than 4000-fold in comparison with the parent compounds, which is the practically acceptable value as water-soluble drugs. These prodrugs were stable as an HCl salt and in a strongly acidic solution corresponding to gastric juice (pH 2.0), and could be converted to the parent compounds promptly in the aqueous condition from slightly acidic to basic pH at 37 °C, with the suitable migration rate, via a five-membered ring intermediate. Using a similar method, we synthesized a prodrug (12) of ritonavir, a clinically useful HIV-1 protease inhibitor as an anti-AIDS drug. In contrast to the prodrugs 3, 4, 6, and 7, the prodrug 12 was very slowly converted to ritonavir probably through a six-membered ring intermediate, with the t_1/2 value of 32 h that may not be suitable for practical use.     

Forage Crop <Emphasis Type="Italic">Lolium multiflorum</Emphasis> Assisted Synthesis of AgNPs and Their Bioactivities Against Poultry Pathogenic Bacteria in In Vitro

Italian ryegrass is one of main feed for livestock animals/birds. It has potential antioxidant metabolites that can improve their health and protect them against various infectious diseases. In this work, we studied synthesis of silver nanoparticles assisted by forage crop Lolium multiflorum as a green synthesis way. Potential antibacterial efficacy of these synthesized nanosized silver nanoparticles against poultry pathogenic bacteria was then studied. Aqueous extract of IRG was used as reducing agent for bio-reduction of silver salt to convert Ag⁺ to Ag⁰ metallic nano-silver. Size, shape, metallic composition, functional group, and crystalline nature of these synthesized silver nanoparticles were then characterized using UV–Vis spectrophotometer, FESEM, EDX, FT-IT, and XRD, respectively. In addition, antibacterial effects of these synthesized AgNPs against poultry pathogenic bacteria were evaluated by agar well diffusion method. UV–Vis spectra showed strong absorption peak of 440–450 nm with differ reaction time ranging from 30 min to 24 h. FESEM measurements revealed particles sizes of around 20–100 nm, majority of which were spherical in shape while a few were irregular. These biosynthesized silver nanoparticles using IRG extract exhibited strong antibacterial activities against poultry pathogenic microorganisms, including Pseudomonas aeruginosa, Salmonella typhi, Escherichia coli, and Bacillus subtilis. Overall results confirmed that IRG plant extract possessed potential bioactive compounds for converting silver ions into nanosized silver at room temperature without needing any external chemical for redox reaction. In addition, such synthesized AgNPs showed strong antibacterial activities against pathogenic bacteria responsible for infectious diseases in poultry.     

Antibacterial activity and mechanism of action of chitosan solutions against apricot fruit rot pathogen Burkholderia seminalis

The in vitro antibacterial activity and mechanism of action of two kinds of acid-soluble chitosan and one water-soluble chitosan against apricot fruit rot pathogen Burkholderia seminalis was examined in this study. Results showed that water-soluble chitosan displayed limited antibacterial activity at four tested concentrations. However, two kinds of acid-soluble chitosan solution at 2.0 mg/mL had strong antibacterial activity against B. seminalis although weak antibacterial activity was observed at a concentration lower than 1 mg/mL. The antibacterial activity of acid-soluble chitosan may be due to membrane disruption, cell lysis, abnormal osmotic pressure, and additional chitosan coating around the bacteria based on integrity of cell membranes test, out membrane permeability assays and transmission electron microscopy observation. In addition, biofilm biomass were markedly reduced after treating with two kinds of acid-soluble chitosan at concentrations of 2.0 and 1.0 mg/mL for 3 and 12 h, indicating the importance of biofilm formation in the antibacterial mechanism of chitosan. Overall, the results clearly indicated that two kinds of acid-soluble chitosan had a potential to control the contamination of apricot fruits caused by B. seminalis.     

Synthesis of Schiff Bases and Secondary Amines with Indane Skeleton; Evaluation of Their Antioxidant,Antibiotic, and Antifungal Activities

In this study, Schiff bases were synthesized by utilizing the reaction of 4- and 5-aminoindane with substituted benzaldehydes. After the reduction of isolated Schiff bases with NaBH₄, the corresponding secondary amine derivatives were obtained. The structures of all synthesized molecules were confirmed by ¹H-NMR, ¹³C-NMR, FT-IR, and ESI-MS. Antioxidant activities of all synthesized molecules were investigated by DPPH method, and IC₅₀ values were calculated. In addition, antibacterial activities of targets were investigated by the well diffusion method, and then MIC99 values were calculated. While only four of the sixteen synthesized molecules showed a high level of antioxidant activity, all of the molecules exhibited biological activity against Gram-positive and Gram-negative bacteria to varying degrees. In addition, all the synthesized molecules showed high antifungal activity. In antioxidant capacity studies, the IC₅₀ values of 2-(((2,3-dihydro-1H-inden-5-yl)amino)methyl)-6-methoxyphenol ( 4 d ) and 2-(((2,3-dihydro-1H-inden-4-yl)amino)methyl)-6-methoxyphenol ( 7 d ) were determined to be 18.1 μg and 35.1 μg, respectively, and these values are much stronger than BHT (butylated hydroxytoluene) and BHA (butylated hydroxyanisole) used as positive controls. The fact that targets have the same core structure with different substituents has revealed a good structure-activity relationship.     

Role of reactive oxygen species in the antibacterial mechanism of silver nanoparticles on Escherichia coli O157:H7

In this study, the conditions and mechanism of antibacterial activity of hydrophilic polymer coated silver nanoparticles (AgNPs) against E. coli O157:H7 (CMCC44828) as model pathogen was studied. The AgNPs were coated with amphiphilic polymer that introduced carboxyl groups on the surface to make it water-soluble. The AgNPs were exposed to various treatment conditions of pH and temperature before these were combined with the E. coli. The mechanism of the antibacterial activity was studied through the formation of reactive oxygen species (ROS) that was later suppressed with antioxidant to establish correlation with the AgNPs antimicrobial activity. Studies were carried out at both anaerobic and aerobic conditions. The results indicated that 5 mg/L AgNPs inhibited ~50% of the growth of 10⁶ colony forming units per milliliter (cfu/mL) E. coli cells in liquid Luria–Bertani (LB) medium. This dose-dependent antimicrobial activity was higher at increased temperature (37°C) but was lower when the AgNPs were treated with acid at pH 2 before exposure to the bacteria. It was also established that the conditions of higher antimicrobial effect generated more ROS that was dependent on the presence of oxygen. The antibacterial activity was suppressed in the presence of an antioxidant.     

The antibacterial and immunostimulative effect of chitosan-oligosaccharides against infection by <Emphasis Type="Italic">Staphylococcus aureus</Emphasis> isolated from bovine mastitis

Based on our previous study evaluating the in vivo cure efficacy of chitosan on bovine mastitis, a more water-soluble chitosan-oligosaccharide (OCHT) with a high degree of deacetylation and low molecular weight was prepared to obtain high antibiotic efficacy. The growth of Staphylococcus aureus isolated from bovine mastitis was inhibited within 10 min of treatment with OCHT in concentrations ranging from 0.0001 to 0.5%. Additionally, electron microscopic observation indicated that the surface of the OCHT-treated bacteria was expanded, distorted, and lysed compared to that of the control bacteria. In mice, the proportion of monocytes was elevated, and the levels of interleukin-6 and interferon-γ sharply increased l h after the peritoneal inoculation of the OCHT (0.5 to 1 mg per mouse). Mice challenged intraperitoneally with S. aureus (2.5 × 10⁸ colony forming units) after oral treatment with OCHT (0.5 to 2 mg per day) for 7 days showed a higher survival rate (70–100%) than that of the control (10%). We suggest that the OCHT prepared in this study is a potential agent for the prevention and treatment of bovine mastitis based on its strong antibacterial activity against S. aureus as well as the immunostimulative effect it exhibits on murine infection by S. aureus. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Design,characterization and expression of a novel hybrid peptides melittin (1–13)-LL37 (17–30)

Hybridizing of different antimicrobial peptides (AMPs) has been a common practice for obtaining novel hybrid AMPs with elevated antibacterial activity but minimized cytotoxicity. The hybrid peptides melittin (1-13)-LL37 (17-30) (M–L) combining the hydrophobic N-teriminal fragment of melittin (M) with the core antibacterial fragment of LL37 (L), was designed for the first time to explore its antibacterial activity and hemolytic activity against bacteria and sheep erythrocyte respectively. Results showed that M–L had an even more potent antibacterial activity against all indicator strains (especially gram-positive bacteria) than M and L, whereas didn’t exhibit hemolytic activity to sheep erythrocytes, implying M–L can be served as a potential therapeutic drug to substitute traditional antibiotics. However the high expense of biosynthesis limited its further research, therefore fusion expression of M–L was carried out in Escherichia coli (E. coli) for overproducing the hybrid peptide so as to solve the problem. The DNA sequence encoding M–L with preferred codons was cloned into the pET-SUMO vector for protein expression in E. coli BL21 (DE3). After IPTG induction, approximately 165 mg soluble fusion protein SUMO-M–L was recovered per liter supernatant of the fermentation ultrasonic lysate using Ni–NTA Sepharose column (92 % purity). And 23 mg recombinant M–L was obtained per liter culture after cleavage of SUMO protease and purification of Ni–NTA Sepharose column. In sum, this research not only supplied an effective approach for overproducing hybrid peptide M–L, but paved the way for its further exploration on pharmaceutical potential and medical importance.     

Imidazo[4,5-<Emphasis Type="Italic">a</Emphasis>]quinindolines as highly effective antibacterial agents

Resistance to antimicrobial agents is a concern that exists globally and has a considerable impact on human and animal health, so that the discovery of new antibacterial compounds has become increasingly more important in combating infectious disease. In this paper, imidazo[4,5-a]quinindolines are introduced as new antibacterial agents against Gram-positive and Gram-negative bacteria. These pentacyclic compounds are synthesized by the reaction of N-alkyl-5-nitrobenzimidazoles with 2-(1-alkyl-1H-3-indolyl)acetonitrile under basic conditions in excellent yields. The structures of newly synthesized compounds were characterized by IR, ¹H NMR, ¹³C NMR, and mass spectral data. The antibacterial activities of the synthesized compounds were screened against standard strains of two Gram-positive and two Gram-negative bacteria using the broth microdilution method. Most of the compounds studied showed promising activities against both types of bacteria.     

Antiproliferative and antibacterial activity of some glutarimide derivatives

Antiproliferative and antibacterial activities of nine glutarimide derivatives (1–9) were reported. Cytotoxicity of compounds was tested toward three human cancer cell lines, HeLa, K562 and MDA-MB-453 by MTT assay. Compound 7 (2-benzyl-2-azaspiro[5.11]heptadecane-1,3,7-trione), containing 12-membered ketone ring, was found to be the most potent toward all tested cell lines (IC₅₀?=?9–27?μM). Preliminary screening of antibacterial activity by a disk diffusion method showed that Gram-positive bacteria were more susceptible to the tested compounds than Gram-negative bacteria. Minimum inhibitory concentration (MIC) determined by a broth microdilution method confirmed that compounds 1, 2, 4, 6–8 and 9 inhibited the growth of all tested Gram-positive and some of the Gram-negative bacteria. The best antibacterial potential was achieved with compound 9 (ethyl 4-(1-benzyl-2,6-dioxopiperidin-3-yl)butanoate) against Bacillus cereus (MIC 0.625?mg/mL; 1.97?×?10^?3?mol/L). Distinction between more and less active/inactive compounds was assessed from the pharmacophoric patterns obtained by molecular interaction fields.     

Long-Term Fungal Inhibitory Activity of Water-Soluble Extracts of Phaseolus vulgaris cv. Pinto and Sourdough Lactic Acid Bacteria during Bread Storage

The antifungal activity of proteinaceous compounds from different food matrices was investigated. In initial experiments, water-soluble extracts of wheat sourdoughs, cheeses, and vegetables were screened by agar diffusion assays with Penicillium roqueforti DPPMAF1 as the indicator fungus. Water-soluble extracts of sourdough fermented with Lactobacillus brevis AM7 and Phaseolus vulgaris cv. Pinto were selected for further study. The crude water-soluble extracts of L. brevis AM7 sourdough and P. vulgaris cv. Pinto had a MIC of 40 mg of peptide/ml and 30.9 mg of protein/ml, respectively. MICs were markedly lower when chemically synthesized peptides or partially purified protein fractions were used. The water-soluble extract of P. vulgaris cv. Pinto showed inhibition toward a large number of fungal species isolated from bakeries. Phaseolin alpha-type precursor, phaseolin, and erythroagglutinating phytohemagglutinin precursor were identified in the water-soluble extract of P. vulgaris cv. Pinto by nano liquid chromatography-electrospray ionization-tandem mass spectrometry. When the antifungal activity was assayed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, all three proteins were inhibitory. A mixture of eight peptides was identified from the water-soluble extract of sourdough L. brevis AM7, and five of these exhibited inhibitory activity. Bread was made at the pilot plant scale by sourdough fermentation with L. brevis AM7 and addition of the water-soluble extract (27%, vol/wt; 5 mg of protein/ml) of P. vulgaris cv. Pinto. Slices of bread packed in polyethylene bags did not show contamination by fungi until at least 21 days of storage at room temperature, a level of protection comparable to that afforded by 0.3% (wt/wt) calcium propionate.     

Water-soluble prodrugs of dipeptide HIV protease inhibitors based on O-->N intramolecular acyl migration: Design, synthesis and kinetic study

To improve the low water-solubility of HIV protease inhibitors, we synthesized water-soluble prodrugs of KNI-727, a potent small-sized dipeptide-type HIV-1 protease inhibitor consisting of an Apns-Dmt core (Apns; allophenylnorstatine, Dmt; (R)-5,5-dimethyl-1,3-thiazolidine-4-carboxylic acid) as inhibitory machinery. These prodrugs contained an O-acyl peptidomimetic structure with an ionized amino group leading to an increase in water-solubility, and were designed to regenerate the corresponding parent drugs based on the O-->N intramolecular acyl migration reaction via a five-membered ring intermediate at the alpha-hydroxy-beta-amino acid residue, that is Apns. The synthetic prodrug 3a improved the water-solubility (13 mg/mL) more than 8000-fold in comparison with the parent compound, which is the practically acceptable value as water-soluble drug. Furthermore, to understand the structural effects of the O-acyl moiety on the migration rate, we evaluated several phenylacetyl-type and benzoyl-type prodrugs. These prodrugs were stable as an HCl salt and in a strongly acidic solution corresponding to gastric juice (pH 2.0), and could be converted to the parent compounds promptly under aqueous conditions from slightly acidic to basic pH at 37 degrees C.     

Antioxidant,Cytotoxic and Antimicrobial Activity of Chitosan Preparations Extracted from Ganoderma Lucidum Mushroom

Two chitosan extracts were prepared by chemical and enzymatic treatment of Ganoderma lucidum mushroom, as an alternative source to crustacean shells. The molecular weight of the enzymatic extract was lower than that of the chemical one and of shrimp chitosan, as determined by viscosity measurements. Characteristic signals were identified in the ¹H‐NMR spectra and high deacetylation degree indicated good physico‐chemical properties for both mushroom chitosan extracts. The scavenging capacity of mushroom chitosan extracts was moderate against the synthetic radicals of 2,2′‐azinobis(3‐ethylbenzothiazoline‐6‐sulfonic acid) (ABTS) and 1,1‐diphenyl‐2‐picrylhydrazyl (DPPH), but higher values were observed for the enzymatic extract, compared to the chemical extract and shrimp chitosan. In vitro cytotoxicity was evaluated in L929 mouse fibroblast cell lines and the results of MTT assay showed good cytocompatibility in the tested range of concentrations. The growth of Gram‐positive bacteria was inhibited more than Gram‐negative bacteria in the presence of mushroom chitosan extracts, in particular by the chemical one, indicating their efficiency as antimicrobial agents. All these results strengthen the evidence of mushroom polysaccharide preparations availability for biomedical applications.     

Synthesis, characterization, cytotoxicity and antibacterial studies of chitosan, O-carboxymethyl and N,O-carboxymethyl chitosan nanoparticles

Chitosan (CS) is a naturally occurring biopolymer. It has important biological properties such as biocompatibility, antifungal and antibacterial activity, wound healing ability, anticancerous property, anticholesteremic properties, and immunoenhancing effect. Recently, CS nanoparticles have been used for biomedical applications. However, due to the limited solubility of CS in water its water-soluble derivatives are preferred for the above said applications. In this work, the nanoparticles of CS and its water-soluble derivatives such as O-carboxymethyl chitosan (O-CMC) and N,O-carboxymethyl chitosan (N,O-CMC) was synthesized and characterized. In addition, cytotoxicity and antibacterial activity of the prepared nanoparticles was also evaluated for biomedical applications.     

Synthesis of a novel nanocomposite containing chitosan as a three-dimensional printed wound dressing technique: Emphasis on gene expression

In this study, a highly porous three-dimensional (3D)-printed wound healing core/shell scaffold fabricated using poly-lactic acid (PLA). The core of scaffold was composed of hyaluronic acid (HA), copper carbon dots (Cu-CDs), rosmarinic acid, and chitosan hydrogel. Cu-CDs were synthesized using ammonium hydrogen citrate under hydrothermal conditions. Formulation containing 1 mg ml⁻¹concentration of Cu-CDs showed an excellent antibacterial activity against gram bacteria. At 0.25 mg ml⁻¹ of Cu-CDs concentration, scaffold had a good biocompatibility as confirmed by cytotoxicity assay on L929 fibroblast stem cells. in vivo wound healing experiments on groups of rats revealed that after 15 days of treatment, the optimal formulation of composite scaffold significantly improves the wound healing process compared to the PLA scaffold. This finding was confirmed by histological analysis and the relative expression of PDGF, TGF-β, and MMP-1 genes. The biocompatible antibacterial CU-CDS/PLA/HA/chitosan/rosmarinic acid nanocomposite is a promising wound healing scaffold which highly accelerates the process of skin regeneration.     

Identification of the Enzyme Responsible for N-Acetylation of Norfloxacin by Microbacterium sp. Strain 4N2-2

Microbacterium sp. 4N2-2, isolated from a wastewater treatment plant, converts the antibacterial fluoroquinolone norfloxacin to N-acetylnorfloxacin and three other metabolites. Because N-acetylation results in loss of antibacterial activity, identification of the enzyme responsible is important for understanding fluoroquinolone resistance. The enzyme was identified as glutamine synthetase (GS); N-acetylnorfloxacin was produced only under conditions associated with GS expression. The GS gene (glnA) was cloned, and the protein (53 kDa) was heterologously expressed and isolated. Optimal conditions and biochemical properties (K_m and V_max) of purified GS were characterized; the purified enzyme was inhibited by Mn²⁺, Mg²⁺, ATP, and ADP. The contribution of GS to norfloxacin resistance was shown by using a norfloxacin-sensitive Escherichia coli strain carrying glnA derived from Microbacterium sp. 4N2-2. The GS of Microbacterium sp. 4N2-2 was shown to act as an N-acetyltransferase for norfloxacin, which produced low-level norfloxacin resistance. Structural and docking analysis identified potential binding sites for norfloxacin at the ADP binding site and for acetyl coenzyme A (acetyl-CoA) at a cleft in GS. The results suggest that environmental bacteria whose enzymes modify fluoroquinolones may be able to survive in the presence of low fluoroquinolone concentrations.     

Effect of levamisole on cytotoxic T-cell-mediated immune resistance to L1210 murine leukemia in hyperimmune mice

Summary The effect of levamisole (LMS) on T-cell-mediated antitumor immunity was examined in adult and aged mice hyperimmune to L1210 leukemia. The immune resistance of aged mice was depressed compared with that of adult mice, which almost completely rejected 5×10⁷ L1210 cells inoculated IP. A significant level of tumor-specific cytotoxicity was detected in the spleen cells of adult hyperimmune mice by the ⁵¹Cr-release assay after in vitro sensitization with mitomycin C-treated L1210 cells. This was mediated by cytotoxic T cells, since in vivo administration of antithymocyte serum or in vitro treatment of the spleen cells with anti-Thy 1.2 antibody and complement abrogated the cytotoxicity completely. In aged mice, however, cytotoxic T-cell activity was lower although the animals were immune to L1210.Administration of LMS (0.38 mg/kg) restored the depressed cytotoxicity of aged mice to the level seen in adult mice. Furthermore, in adult hyperimmune mice LMS augmented T-cell-mediated cytotoxic activity and restored the reduced cytotoxicity caused by in vivo administration of antithymocyte serum. These results indicate that LMS was effective in augmenting T-cell-mediated tumor immunity in immunologically competent or deficient hosts.     

Novel strategies of essential oils,chitosan, and nano- chitosan for inhibition of multi-drug resistant: E. coli O157:H7 and Listeria monocytogenes

Despite the wide range of available antibiotics, food borne bacteria demonstrate a huge spectrum of resistance. The current study aims to use natural components such as essential oils (EOs), chitosan, and nano-chitosan that have very influential antibacterial properties with novel technologies like chitosan solution/film loaded with EOs against multi-drug resistant bacteria. Two strains of Escherichia coli O157:H7 and three strains of Listeria monocytogenes were used to estimate antibiotics resistance. Ten EOs and their mixture, chitosan, nano-chitosan, chitosan plus EO solutions, and biodegradable chitosan film enriched with EOs were tested as antibacterial agents against pathogenic bacterial strains. Results showed that E. coli O157:H7 51,659 and L. monocytogenes 19,116 relatively exhibited considerable resistance to more than one single antibiotic. Turmeric, cumin, pepper black, and marjoram did not show any inhibition zone against L. monocytogenes; Whereas, clove, thyme, cinnamon, and garlic EOs exhibited high antibacterial activity against L. monocytogenes with minimum inhibitory concentration (MIC) of 250–400 μl 100^?1 ml and against E. coli O157:H7 with an MIC of 350–500 μl 100^?1 ml, respectively. Among combinations, clove, and thyme EOs showed the highest antibacterial activity against E. coli O157:H7 with MIC of 170 μl 100^?1 ml, and the combination of cinnamon and clove EOs showed the strongest antibacterial activity against L. monocytogenes with an MIC of 120 μl 100^?1 ml. Both chitosan and nano-chitosan showed a promising potential as an antibacterial agent against pathogenic bacteria as their MICs were relatively lower against L. monocytogenes than for E. coli O157:H7. Chitosan combined with each of cinnamon, clove, and thyme oil have a more effective antibacterial activity against L. monocytogenes and E. coli O157:H7 than the mixture of oils alone. Furthermore, the use of either chitosan solution or biodegradable chitosan film loaded with a combination of clove and thyme EOs had the strongest antibacterial activity against L. monocytogenes and E. coli O157:H7. However, chitosan film without EOs did not exhibit an inhibition zone against the tested bacterial strains.     

牛蒡提取液对副溶血性弧菌的抑制作用

研究了牛蒡提取物对副溶血性弧菌的抑制作用。采用80%乙醇分别浸提两个牛蒡品种柳川理想及黄肌牛蒡根的皮及去皮根,四种提取物分别命名为LP、LR、HP和HR。采用滤纸片扩散和最低抑菌浓度法筛选了四种提取物的抑菌效果,时变抑菌研究了常温(25℃)和低温(4℃)下牛蒡提取物在无菌蒸馏水(DW)以及脑心浸汤(BHI)中对副溶血性弧菌的抑制效果。结果显示,四种提取物中LP的抑菌活性最好;经1000μL/mL LP提取液7小时处理,在4℃和25℃DW环境均未有副溶血性弧菌检出;经各浓度提取液1天处理,在4℃和25℃BHI环境均未有副溶血性弧菌检出。LP对副溶血性弧菌弧菌具有良好的抑制作用。     

<Emphasis Type="Italic">Paenibacillus polymyxa</Emphasis> JB05-01-1 and its perspectives for food conservation and medical applications

The aim of this study was to isolate a novel bacterial strain with strong and broad spectrum antibacterial activity from a livestock feed prebiotic supplement. A novel strain, termed Paenibacillus polymyxa JB05-01-1, was isolated using traditional microbiological methods and identified on the basis of its phenotypic and biochemical properties as well as its 16S rRNA gene sequence. This strain was able to inhibit growth of gram-negative bacteria including Escherichia coli RR1, Pseudomonas fluorescens R73, Pantoea agglomerans BC1, Butyrivibrio fibrisolvens OR85, and Fibrobacter succinogenes. The above antagonism against the aforementioned bacteria was attributed to production of an antimicrobial substance(s) termed “JB05-01-1.” Its production was optimal during the stationary phase. JB05-01-1 has a molecular weight of 2.5 KDa, its mode of action is bactericidal, and the divalent cations, Ca²⁺ and Mn²⁺, reduced its lethality. The antibacterial activity was heat-stable and was effective at a pH range of 2–9. Enzymes like trypsin, α-chymotrypsin, and proteinase K have abolished the antibacterial activity of JB05-01-1 indicating a proteinaceous motif. This type of naturally occurring bacteria and inhibitory substance(s) could represent an additional value in livestock feed supplements. The natural presence of antibacterial activity indicates an opportunity to decrease the addition of antibiotics.