| Due to the unique physical and chemical properties,silver nanoparticles(AgNPs)have a wide range of applications in various fields like optical,electronic,catalytic,medicine and so on.In the past decade,numerous methods have been formulated to synthesize AgNPs with different sizes,shapes and controlled surface morphologies.Biological method for synthesis of AgNPs using various bacteria,fungi and plants is an emerging field in nano science,with emphasis to avoid the use of toxic chemicals.Compared with the traditional physical and chemical methods,biological method because of low-cost and eco-friendly advantages attracted many researchers' attention.In this study,the traditional enrichment method combine with spot inoculation was used based on a marine sediment sample collected from Xiaoshi Island to isolate the antagonistic bacteria,and antimicrobial substance produced from one strain was used to synthesis of AgNPs.The newly synthesized AgNPs were characterized byUV-Vis spectroscopy,scanning electron microscopy(SEM)and X-ray powder diffraction(XRD);the antibacterial potential of AgNPs was determined against two different pathogenic bacteria(Escherichia coli and Staphylococcus aureus).In this study,a marine sediment sample was collected from Xiaoshi Island(37°31' 2" N,1220 1' 19" E).Antagonistic bacteria against Escherichia coli ATCC 25922,Staphylococcus aureus ATCC 29213,Acinetobacter baumannii ATCC 19606 and Vibrio sp.were screened using the spot inoculation,and 242 bacteria strains were isolated from this sample,in which 177 bacteria strains with antimicrobial activity.These antagonistic bacteria were identified using 16S rDNA gene sequencing,result indicated that most isolates were in the Phylum Firmicutes.After cloning and sequencing,the complete 16S rRNA gene sequence(1474 bp)of strain DXFD1 was submitted to the GenBank database to assess the similarity of sequence.The result indicated that strain DXFD1 was most closely related to the species Bacillus subtilis subsp.subtilis NCIB 3610T with 99.59%16S rDNA gene sequence similarity.AgNPs were synthesized by adding AgNO3 solution to antibacterial material solution produced from strain DXFD1.AgNPs were characterized by UV-Vis spectroscopy,SEM and XRD.Results indicated that AgNPs were spherical or nearly spherical,in the range of 30-70 nm;UV-Vis spectra of the solution containing AgNPs has shown the absorption maximum at 480 nm.The antibacterial activities of AgNPs have been evaluated against E.coli ATCC 25922 and S.aureus ATCC 29213.The AgNPs showed a significant antibacterial activity.Minimum inhibitory concentration value of AgNPs determined against E.coli ATCC 25922 and S.aureus ATCC 29213 were 5 ?g/mL.Minimal bactericidal concentration value of AgNPs determined against E.coli ATCC 25922 and S.aureus ATCC 29213 were 10 ?g/mL.The antibacterial activity of AgNPs which were removed the surface substance has been detected and found that the antibacteria]effect was reduced.The antibacterial substance could combine with AgNPs in the process of synthesis and improve the antibacterial properties.In this study,strains P131T,N62T,X7T,WDS2C4TandJZ3A21 were isolated from samples collected from the coast of Weihai,a solar saltern of Wendeng and a solar saltern of city Feicheng,respectively,and subjected to the polyphasic study.A Gram-stain-negative,aerobic,non-gliding,rod-shaped and orange-coloured bacterium,designated P131T,was isolated from marine sediment of the coast of Weihai,China,and subjected to a polyphasic study.Strain P131T was found to grow optimally at 28-30?,pH 7.0-7.5 and in the presence of 2.0-3.0%(w/v)NaCL In a phylogenetic analysis based on 16S rDNA gene sequences,strain P131T was found to belong to the genus Bizionia and exhibited 94.6-97.0%of 16S rDNA gene sequence similarity with recognized Bizionia species.The dominant cellular fatty acids of strain P131T were identified as iso-C15:0,iso-C15:0 G,iso-C17:0 3-OH and iso-C17:1 ?9c.The predominant polar lipids were phosphatidylethano lamine,two aminolipids,aminophospholip id,phospholipid and other lipids.The predominant respiratory quinone was identified as MK-6 and the DNA G+C content was determined to be 36.7 mol%.On the basis of the phylogenetic and phenotypic evidences,strain P131T represents a novel species of the genus Bizionia,for which the name Bizionia sediminis sp.nov.is proposed.The type strain is P131T(=KCTC 42587T=MCCC 1H00124T).A Gram-stain-ne gative,facultatively anaerobic,non-motile,rod-shaped and(?)orange-coloured bacterium,designated N62T,was isolated from marine sediment of the coast of Weihai,China.Strain N62T was found to grow optimally at 28-30?,pH 7.0-7.5 and with 2.0-3.0%(w/v)NaCL The dominant cellular fatty acids of strain N62T were iso-C15:0,iso-C15:0 G,iso-C1:0 3-OH and iso-C17:1 3-OH.The major respiratory quinone was MK-6,and the DNA G+C content was 35.3 mol%.The predominant polar lipids were phosphatidylethanolamine,two unidentified aminoli ids,an unidentified glycolipid and three unidentified lipids.Phylogenetic analysis based on 16S rDNA gene sequences revealed that N62T was a memeber of the family Crocinitomicaceae and had a 16S rDNA gene sequence similarity of 95.8-97.2%with recognized Brumimicrobium species.On the basis of the phylogenetic and phenotypic evidences,strain N62T represents a novel species of the genus Brumimicrobium,for which the name Brumimicrobium aurantiacum sp.nov.is proposed.The type strain is N62T(=KCTC 42589T=MCCC 1H00117T).A novel Gram-stain-negative,non-gliding,facultatively anaerobic and rod-shaped bacterium,designated X7T,was isolated from marine sediment taken from the coast of Weihai,China.Strain X7T grew optimally at 28-30?,at pH 7.0 and in the presence of 2.0-3.0%(w/v)NaCL Based on the 16S rDNA gene sequence analysis,strain X7T was a member of the genus Salinimicrobium and was most closely related to the species Salinimicrobium gaetbulicola with 96.3%16S rDNA gene sequence similarity.The major cellular fatty acids of strain X7T were anteiso-C15:0,iso-C15:0,anteiso-C17:1 ?9c,iso-C17:1 ?9c,C17:0 2-OH and iso-C17:0 3-OH.The major polar lipids of strain X7T were one phosphatidylethanolamine,one phospholipid,two aminolipids and five unidentified lipids.The predominant respiratory quinone was MK-6,and the genomic DNA G+C content was 46.7 mol%.Phylogenetic,phenotypic,chemotaxonomic and genotypic results indicated that strain X7T represents a novel species of the genus Salinimicrobium,for which the name Salinimicrobium flavum sp.nov.is proposed.The type strain is X7T(=KCTC 42585T =MCCC 1H00115T).Two novel Gram-stain-negative,rod-shaped,aerobic and non-gliding bacteria,designated WDS2C4T and JZ3A21,were isolated from salterm environments and studied using a polyphasic taxonomic approach.The strains grew with 1.0-20.0%(w/v)(?)NaCl(optimum 6-10%NaCl),at 20-50?(optimum 37-40?)and at pH 6.5-9.5(optimum 7.0-8.0).The predominant fatty acids of strain WDS2C4T and JZ3A21 all were cyclo-C19:0 ?8c,summed features 8(C18:1 ?7c and/or C18:1 ?6c,),C18:0,C17:0,C16:0 and 11-methyl C18:1 ?7c.Strains WDS2C4T and JZ3A21 were determined to contain Q-10 as the major respiratory quinone.The G+C content of strains WDS2C4T and JZ3A21 were 67.7 mol%and 67.3 mol%,respectively.The predominant polar lipids were two phospholipids,unidentified aminolipid,phosphatidyl glycerol,phosphatidylcholine and two unidentified glycolipids.Strain WDS2C4T was most closely related to the type strains of recognized species Rhodovulum marinum(95.11%16S rDNA gene sequence similarity).And strain WDS2C4T exhibited the highest 16S rDNA gene sequence similarity values to the type strains of Albidovulum xiamenense(94.75%),Paracoccus aestuarii(94.00%),Rhodobacter vinaykumarii(93.88%)and Roseivivax pacificus(93.85%).Neighbour-joining,maximum-likelihood and maximum-parsimony phylogenetic trees based on 16S rDNA gene sequences showed that strains WDS2C4T and JZ3A21 formed a separate branch within the family Rhodobacteraceae.On the basis of extensive phenotypic and phylogenetic analysis,strains WDS2C4T and JZ3A21 were considered to represent a novel genus and species,for which the name Albihalobacter halophilus gen.nov.,sp.nov.is proposed.The type strain of the type species is WDS2C4T(=KCTC 52227-T =NBRC 112331T =MCCC 1H00148T). |
PDF Full Text Request