Chatterjee Tanaya, Chatterjee Barun K, Majumdar Dipanwita, Chakrabarti Pinak
Department of Biochemistry, Bose Institute, P-1/12 CIT Scheme VIIM, Kolkata 700054, India.
Department of Physics, Bose Institute, 93/1 A.P.C. Road, Kolkata 700009, India.
Biochim Biophys Acta. 2015 Feb;1850(2):299-306. doi: 10.1016/j.bbagen.2014.10.022. Epub 2014 Oct 27.
An alternative to conventional antibiotics is needed to fight against emerging multiple drug resistant pathogenic bacteria. In this endeavor, the effect of silver nanoparticle (Ag-NP) has been studied quantitatively on two common pathogenic bacteria Escherichia coli and Staphylococcus aureus, and the growth curves were modeled.
The effect of Ag-NP on bacterial growth kinetics was studied by measuring the optical density, and was fitted by non-linear regression using the Logistic and modified Gompertz models. Scanning Electron Microscopy and fluorescence microscopy were used to study the morphological changes of the bacterial cells. Generation of reactive oxygen species for Ag-NP treated cells were measured by fluorescence emission spectra.
The modified Gompertz model, incorporating cell death, fits the observed data better than the Logistic model. With increasing concentration of Ag-NP, the growth kinetics of both bacteria shows a decline in growth rate with simultaneous enhancement of death rate constants. The duration of the lag phase was found to increase with Ag-NP concentration. SEM showed morphological changes, while fluorescence microscopy using DAPI showed compaction of DNA for Ag-NP-treated bacterial cells.
E. coli was found to be more susceptible to Ag-NP as compared to S. aureus. The modified Gompertz model, using a death term, was found to be useful in explaining the non-monotonic nature of the growth curve.
The modified Gompertz model derived here is of general nature and can be used to study any microbial growth kinetics under the influence of antimicrobial agents.
对抗新出现的多重耐药病原菌需要传统抗生素的替代物。在此过程中，已对银纳米颗粒（Ag-NP）对两种常见病原菌大肠杆菌和金黄色葡萄球菌的作用进行了定量研究，并对生长曲线进行了建模。
通过测量光密度研究Ag-NP对细菌生长动力学的影响，并使用逻辑斯蒂模型和修正的冈珀茨模型进行非线性回归拟合。使用扫描电子显微镜和荧光显微镜研究细菌细胞的形态变化。通过荧光发射光谱测量Ag-NP处理细胞产生的活性氧。
包含细胞死亡的修正冈珀茨模型比逻辑斯蒂模型更能拟合观测数据。随着Ag-NP浓度的增加，两种细菌的生长动力学均显示生长速率下降，同时死亡率常数增加。发现延迟期的持续时间随Ag-NP浓度增加。扫描电子显微镜显示形态变化，而使用4',6-二脒基-2-苯基吲哚（DAPI）的荧光显微镜显示Ag-NP处理的细菌细胞的DNA浓缩。
发现大肠杆菌比金黄色葡萄球菌对Ag-NP更敏感。发现使用死亡项的修正冈珀茨模型有助于解释生长曲线的非单调性质。
此处推导的修正冈珀茨模型具有普遍性质，可用于研究抗菌剂影响下的任何微生物生长动力学。
