Document Type : Original Article
Authors
1
Science and Technology Center of Laser and Optics, Faculty of Basics Science, Imam Hossein University, Tehran, Iran
2
Associate Professor of Imam Hossein Comprehensive University, Tehran, Iran.
3
Assistant Professor, Malik Ashtar University of Technology, Tehran, Iran.
4
Assistant Professor، Imam Hossein Comprehensive ، University, Tehran, Iran.
Abstract
Due to the limitations of conventional biological identification methods, spectroscopic methods, including laser induced breakdown spectroscopy, have been used to characterize the genus, species and strains of different bacteria in the static phase of growth. Due to the increading importance of biological problems, the characterization, detection and classification of bacterial specimens has been considered by researchers in the military, industrial and medical fields. In this paper, in order to monitor the changes in the elemental structure of bacteria in the growth process, the constituent elements of the two phases of exponential and static growth of Escherichia coli were studied and compared based on this spectroscopic method. In this experiment, Nd: YAG laser with 100 mJ pulse energy, spectrometer and CCD detector were used. The industrial strain of gram-negative Escherichia coli BL21 bacteria was selected. Bacteria were selected at three different times (2.5, 4 and 6 hours after inoculation) during the growth process in broth, at optical density of 0.4 and 0.8 (exponential growth phase) and optical density of 1.2 (Static growth phase), respectively, and after dry freezing, under pressure has been pressed into tablets. Considering the chemical structure of Escherichia coli, the elements of phosphorus, carbon, calcium, sodium, magnesium, potassium, oxygen, nitrogen and hydrogen were considered in the sample. The results showed that Escherichia coli bacteria in the growth process have different patterns of recognizable elemental composition in its structure in the growth process. It is predicted that due to the change in the composition of structural elements of bacteria in growth phases, the use of this spectroscopic method to identify bacteria will be dependent on the growth phase. The results of this study showed that this method can play an effective role in the development of polyphasic methods to indentify bacteria, determine the composition of the culture medium as well as optimizing and evaluating the production conditions in this industrial strain.
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