Salunke Bipinchandra K, Sawant Shailesh S, Kim Beom Soo
Department of Chemical Engineering, Chungbuk National University, Cheongju, Chungbuk, 361-763, Republic of Korea.
Appl Biochem Biotechnol. 2014 Sep;174(2):587-601. doi: 10.1007/s12010-014-1077-x. Epub 2014 Aug 2.
Silver nanoparticles (AgNPs) were synthesised using Kalopanax septemlobus plant leaf extracts. UV-visible spectrophotometric, Fourier-transform infrared, electron dispersive X-ray spectroscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analyses confirmed synthesis of AgNPs. TEM micrographs revealed presence of well-dispersed AgNPs predominantly of small size and different shapes with an average particle size of 30.8 nm. Antimicrobial susceptibility tests of AgNP treatments revealed variability in sensitivity of bacteria Bacillus cereus and Saccharophagus degradans under study. Minimum inhibitory concentration (MIC) values of the AgNPs for B. cereus and S. degradans were found to be 30 and 10 μg/mL, respectively. The mixed culture of B. cereus and S. degradans treated with AgNPs at 10 μg/mL showed increase in growth with time, suggesting survival of bacteria in liquid media. The plating of mixed culture before AgNP treatment showed presence of both bacteria, but 24-h-old mixed culture treated with AgNPs at the concentration of 10 μg/mL showed presence of B. cereus colonies. SEM micrographs revealed damage to S. degradans cells but no effect on B. cereus cells after AgNP treatment. Confocal microscopic observations of AgNP-treated mixed cultures by Nile blue A staining indicated intact polyhydroxyalkanoates producing flourescent cells of B. cereus but damage and deformities in S. degradans cells. This study suggests that AgNPs can selectively inhibit growth of S. degradans and retain B. cereus at MIC of S. degradans. This report is a case study for selective inhibition of one bacteria and growth of the other in a culture using plant-synthesized silver nanoparticles.
利用刺楸植物叶提取物合成了银纳米颗粒（AgNPs）。紫外可见分光光度法、傅里叶变换红外光谱法、电子色散X射线光谱法、扫描电子显微镜（SEM）和透射电子显微镜（TEM）分析证实了AgNPs的合成。TEM显微照片显示存在分散良好的AgNPs，其主要为小尺寸且形状各异，平均粒径为30.8 nm。AgNP处理的抗菌药敏试验显示，所研究的蜡样芽孢杆菌和嗜糖降解菌的敏感性存在差异。发现AgNPs对蜡样芽孢杆菌和嗜糖降解菌的最低抑菌浓度（MIC）值分别为30和10 μg/mL。用10 μg/mL的AgNPs处理的蜡样芽孢杆菌和嗜糖降解菌的混合培养物随时间显示出生长增加，表明细菌在液体培养基中存活。AgNP处理前混合培养物的平板培养显示两种细菌均存在，但用10 μg/mL浓度的AgNPs处理24小时的混合培养物显示存在蜡样芽孢杆菌菌落。SEM显微照片显示，AgNP处理后嗜糖降解菌细胞受损，但对蜡样芽孢杆菌细胞无影响。通过尼罗蓝A染色对AgNP处理的混合培养物进行共聚焦显微镜观察表明，蜡样芽孢杆菌产生荧光的细胞中完整的聚羟基脂肪酸酯存在，但嗜糖降解菌细胞存在损伤和畸形。本研究表明，AgNPs可以在嗜糖降解菌的MIC水平上选择性抑制嗜糖降解菌的生长并保留蜡样芽孢杆菌。本报告是一个利用植物合成的银纳米颗粒在培养物中选择性抑制一种细菌并促进另一种细菌生长的案例研究。
