Margaryan A, Badalyan H, Trchounian A
Department of Microbiology, Plants and Microbes Biotechnology, Faculty of Biology, Yerevan State University, 1 Alex Manoogian Str, 0025, Yerevan, Armenia.
Research Institute of Biology, Faculty of Biology, Yerevan State University, 1 Alex Manoogian Str, 0025, Yerevan, Armenia.
Cell Biochem Biophys. 2016 Sep;74(3):381-9. doi: 10.1007/s12013-016-0748-3. Epub 2016 Jun 22.
Microorganisms have a large number of tools to withstand different, and sometimes strong, environmental stresses, including irradiation, but this ability should be further evaluated for certain applications. Growth inhibition and morphological alterations of Escherichia coli M-17 and Pseudomonas aeruginosa GRP3 wild-type cells caused by UV-A irradiation have been detected in the present study. Comparative analysis was carried out using well-established microbiological methods (determination of specific growth rate, growth lag phase duration, and colony-forming unit number-CFU) and computational approaches, employing light microscopy and digital image analysis to evaluate bacterial cell morphology. Decreases in the specific growth rate, prolonged lag-phases, and lowered CFUs were observed after 5 and 10 min of UV irradiation (approx. 40 Gy) compared to the control (nonirradiated) cells. Accordingly, two computational parameters-the average bacterial cell surface area and the bacterial cell perimeter (i.e., of the 2D projection of bacterial cells in microscopy image)-were reduced. The ratio of bacterial cell surface area (S) to the square of the perimeter (p (2) ) was reduced after 5 min of irradiation, but after 10 min of irradiation the studied bacterial cells became flat cylinders. The revealed findings are concluded to be highly useful in developing new, rapid analysis methods to monitor environmental and UV irradiation effects on bacteria and to detect bacterial cell morphology alterations.
微生物有大量工具来抵御不同的、有时是强烈的环境压力，包括辐射，但对于某些应用而言，这种能力仍需进一步评估。在本研究中，已检测到紫外线A照射对大肠杆菌M-17和铜绿假单胞菌GRP3野生型细胞的生长抑制和形态改变。采用成熟的微生物学方法（测定比生长速率、生长滞后期持续时间和菌落形成单位数-CFU）和计算方法进行比较分析，利用光学显微镜和数字图像分析来评估细菌细胞形态。与对照（未照射）细胞相比，紫外线照射5分钟和10分钟（约40 Gy）后，比生长速率降低、滞后期延长且CFU减少。相应地，两个计算参数——细菌细胞平均表面积和细菌细胞周长（即显微镜图像中细菌细胞的二维投影）——减小。照射5分钟后，细菌细胞表面积（S）与周长平方（p(2)）的比值降低，但照射10分钟后，所研究的细菌细胞变成扁平圆柱体。研究结果对于开发新的快速分析方法以监测环境和紫外线照射对细菌的影响以及检测细菌细胞形态改变具有重要意义。
