Antibacterial Activities
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Imad H. Khaleel ◽  
Abdulkareem A. Alkhafaji ◽  
Hussein A. Miran ◽  
Zainab N. Jaf

In this research, a novel thin film Si-GO10 and nano-powders Si-GO30 of silica-graphene oxide composite were prepared via sol-gel method and deposited on glass substrates using spray pyrolysis. XRD results showed a relatively strong peak in graphite layer that corresponds to the plane of (002). TEM images displayed that SiO<sub>2</sub> nano-particles were randomly distributed on the surface of Si-GO30 sample, and the particle size in these nano-powders was below 50 nm. Moreover, silica nano-particles on the surface of GO plates exhibited almost a spherical and rod-like nanoparticles shapes, which in turn confirmed the formation of SiO<sub>2</sub>-GO nano-hybrids. FESEM analysis reveals a different morphology, the Si-GO10 sample is so rough and crumble, while the Si-GO30 sample is relatively smooth on the surface. Photocatalytic investigations revealed the composite materials exhibit high activity for dye adsorption and decomposition. Si-GO10 thin film did not undergo degradation after 120 minutes, however, for Si-GO30 nano-powder, the adsorption peak intensity was reduced to 665 nm, indicating a decrease in the dye concentration in the solution. FTIR analysis demonstrated that carboxylic functional groups are decreased by increasing silica particles. Photo-Luminescence (PL) spectrum in Si-GO10 thin film disclosed a severe emission peak at about 675 nm. This spectrum was completely disappeared in Si-GO30 nano-powders. Results of the antibacterial properties emphasized that Si-GO30 nano-particle would prevent Escherichia. coli growth after 20 hours. The presented methodology allows for the synthesis of graphene oxide supported silicon dioxide nano-particles for promising applications in photocatalytic and antibacterial fields.

2021 ◽  
Vol 12 ◽  
Tingting Guo ◽  
Mengying Li ◽  
Xiaoli Sun ◽  
Yuhang Wang ◽  
Liying Yang ◽  

Acinetobacter baumannii is an opportunistic pathogen predominantly associated with nosocomial infections. With emerging resistance against polymyxins, synergistic combinations of drugs are being investigated as a new therapeutic approach. Capsaicin is a common constituent of the human diet and is widely used in traditional alternative medicines. The present study evaluated the antibacterial activities of capsaicin in combination with colistin against three unrelated colistin-resistant Acinetobacter baumannii strains in vitro and in vivo, and then further studied their synergistic mechanisms. Using the checkerboard technique and time-kill assays, capsaicin and colistin showed a synergistic effect on colistin-resistant A. baumannii. A mouse bacteremia model confirmed the in vivo effects of capsaicin and colistin. Mechanistic studies shown that capsaicin can inhibit the biofilm formation of both colistin-resistant and non-resistant A. baumannii. In addition, capsaicin decreased the production of intracellular ATP and disrupted the outer membrane of A. baumannii. In summary, the synergy between these drugs may enable a lower concentration of colistin to be used to treat A. baumannii infection, thereby reducing the dose-dependent side effects. Hence, capsaicin–colistin combination therapy may offer a new treatment option for the control of A. baumannii infection.

Ying Liu ◽  
Sabir Khan ◽  
Panpan Wu ◽  
Bowen Li ◽  
Lanlan Liu ◽  

Erythromycins produced by Saccharopolyspora erythraea have broad-spectrum antibacterial activities. Recently, several TetR-family transcriptional regulators (TFRs) were identified to control erythromycin production by multiplex control modes; however, their regulatory network remains poorly understood. In this study, we report a novel TFR, SACE_0303, positively correlated with erythromycin production in Sac. erythraea. It directly represses its adjacent gene SACE_0304 encoding a MarR-family regulator and indirectly stimulates the erythromycin biosynthetic gene eryAI and resistance gene ermE. SACE_0304 negatively regulates erythromycin biosynthesis by directly inhibiting SACE_0303 as well as eryAI and indirectly repressing ermE. Then, the SACE_0303 binding site within the SACE_0303-SACE_0304 intergenic region was defined. Through genome scanning combined with in vivo and in vitro experiments, three additional SACE_0303 target genes (SACE_2467 encoding cation-transporting ATPase, SACE_3156 encoding a large transcriptional regulator, SACE_5222 encoding α-ketoglutarate permease) were identified and proved to negatively affect erythromycin production. Finally, by coupling CRISPRi-based repression of those three targets with SACE_0304 deletion and SACE_0303 overexpression, we performed stepwise engineering of the SACE_0303-mediated mini-regulatory network in a high-yield strain, resulting in enhanced erythromycin production by 67%. In conclusion, the present study uncovered the regulatory network of a novel TFR for control of erythromycin production and provides a multiplex tactic to facilitate the engineering of industrial actinomycetes for yield improvement of antibiotics.

2021 ◽  
Vol 22 (18) ◽  
pp. 9943
Zélia Alves ◽  
Nuno M. Ferreira ◽  
Sónia Mendo ◽  
Paula Ferreira ◽  
Cláudia Nunes

Bionanocomposite materials have been designed as a promising route to enhance biopolymer properties, especially for food packaging application. The present study reports the preparation of bionanocomposite films of alginate with different loadings of pure reduced graphene oxide (rGO) or of mixed zinc oxide-rGO (ZnO-rGO) fillers by solvent casting. Sepiolite is used to make compatible rGO with the hydrophilic matrix. The addition of fillers to alginate matrix maintains the low water solubility promoted by the calcium chloride treatment, and, additionally, they demonstrate a weaker mechanical properties, and a slight increase in water vapor permeability and wettability. Due to the properties of ZnO-rGO, the alginate bionanocomposites show an increase of electrical conductivity with the increase of filler content. While the highest electrical conductivity (0.1 S/m) is achieved by the in-plane measurement, it is in the through-plane measurement the remarkable enhancement of almost 30 times greater than the alginate film. With 50% of ZnO-rGO filler, the bionanocomposites present the highest antioxidant and antibacterial activities. The combination of electrical conductivity with bioactive properties makes these films promising not only to extend food shelf-life but also to allow packaged food sterilization at low temperature.

2021 ◽  
Vol 38 (1) ◽  
pp. 7-13
Md Shafiqur Rahman ◽  
Tithi Roy

The emergence of antibiotic-resistant bacteria is a major public health problem. Consequently, the development of new antimicrobials that act on novel bacterial targets and are less susceptible to resistance are of primary importance to researchers in academia and industry alike. The present study was aimed to determine the antimicrobial and antibiofilm activities of Nigella sativa seed extracts. For this, primary (qualitative) and quantitative antibacterial activities of Nigella sativa seed extracts were determined against ten human pathogenic bacteria including four biofilm producing bacterial strains Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumoniae and Staphylococcus aureus. The antibacterial activities as well as minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of the extracts were evaluated using disc diffusion and macro-broth dilution methods, respectively. The seed extracts of N. sativa exhibited the highest extract yields (w/v) 23.3% and 21.35% with ethanol and petroleum ether, respectively. The crude extract (essential oil) of petroleum ether exhibited superior antibacterial activity (36 mm in diameter zone of inhibition) against biofilm forming E. coli on a disc diffusion assay at a concentration of 1000 μg/disc when compared to that of ethanolic crude extract. Moreover, the lowest MIC and MBC values were determined as 500 μg/ml and 1500 μg/ml respectively with the same petroleum ether extract against E. coli. However, N. sativa essential oil obtained from petroleum ether extract of seed inhibited 94% biofilm formation of E. coli at 2×MIC concentration. Moreover, at the same concentration (2×MIC), the ethanol extract inhibited 56% biofilm formation of P. aeruginosa. These results consistently revealed that it is possible to isolate novel antimicrobial agents capable of completely eradicating microbial infections including antibiotic resistance. Therefore, bioactive natural products present in plant resources would represent a noteworthy alternative to commercial antibiotics helping treatment of human antibiotic resistant infections. Bangladesh J Microbiol, Volume 38, Number 1, June 2021, pp 7-13

2021 ◽  
Vol 13 (5) ◽  
pp. 1086-1096
Hlapisi Hlapisi N ◽  
Maliehe Maliehe TS ◽  
Oluwafemi Oluwafemi OS ◽  
Songca Songca SP ◽  
Linganiso Linganiso L ◽  

2021 ◽  
Vol 68 (3) ◽  
pp. 567-574
Guo-Xu He ◽  
Ling-Wei Xue

A series of three new hydrazone compounds derived from the condensation reactions of 4-dimethylaminobenzohydrazide with 4-dimethylaminobenzaldehyde, 2-chloro-5-nitrobenzaldehyde and 3-methoxybenzaldehyde, respectively, were prepared. The compounds were characterized by elemental analysis, infrared and UV-vis spectra, HRMS, 1H NMR and 13C NMR spectra, and single crystal X-ray diffraction. Crystals of the compounds are stabilized by hydrogen bonds. The compounds were assayed for antibacterial (Bacillus subtilis, Escherichia coli, Pseudomonas fluorescence and Staphylococcus aureus) and antifungal (Aspergillus niger and Candida albicans) activities by MTT method. The results indicated that compound 2 is an effective antibacterial material.

2021 ◽  
Vol 68 (3) ◽  
pp. 700-708
Heng-Yu Qian

Two new polynuclear zinc complexes [Zn2Br2(L1)2] (1) and [Zn(μ1,5-dca)L2]n (2), and two new mononuclear cobalt(III) complexes [CoL1N3(Brsal)] (3) and [CoL2(HL2)] (4), where L1 = 5-bromo-2-(((2-dimethylamino)ethyl)imino)methyl)phenolate, L2 = 5-bromo-2-(((2-hydroxyethyl)imino)methyl)phenolate, dca = dicyanoamide, Brsal = 5-bromo-2-formylphenolate, have been synthesized and characterized. The complexes were characterized by elemental analyses, IR, UVVis spectra, molar conductivity, and single crystal X-ray diffraction. X-ray analysis indicates that the Zn atoms in complex 1 are in distorted square pyramidal coordination, the Zn atoms in complex 2 are in distorted trigonal bipyramidal coordination, and the Co atoms in complexes 3 and 4 are in octahedral coordination. The molecules of the complexes are stacked through π···π interactions and hydrogen bonds. The complexes were assayed for antibacterial activities against three Gram-positive bacterial strains (B. subtilis, S. aureus, and St. faecalis) and three Gram-negative bacterial strains (E. coli, P. aeruginosa, and E. cloacae) by MTT method.

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