Detecting the cellular response of Lactobacillus reuteri with nanospray desorption electrospray ionization mass spectrometry

UNCG Author/Contributor (non-UNCG co-authors, if there are any, appear on document)
Agbo-Oma A. Uwakweh (Creator)
The University of North Carolina at Greensboro (UNCG )
Web Site:
Norman Chiu

Abstract: Mass spectrometry has proven to be a useful tool in microbiology research, especially for rapid identification of bacterial strains based on their unique mass spectral pattern. Traditionally, matrix-assisted laser desorption/ionization (MALDI) mass spectrometry is used for the analysis of intact bacterial cells. Studies have demonstrated the capability of MALDI mass spectrometry as a tool in distinguishing cellular response to various stressing conditions based on their mass spectral pattern. Ambient ionization techniques allow intact bacterial cells to be analysed in their native state without the use of a matrix for ionization. Several ambient ionization techniques have been utilized as a means of analysing whole cells without any specific reagents or extraction procedures. One of these techniques, called nanospray desorption electrospray ionization (nanospray DESI), is a modification of DESI mass spectrometry that has been used to analyse bacteria directly on the agar plate. In this project, nanospray DESI mass spectrometry will be explored as a tool for rapidly distinguishing the response of bacterial cells to low pH conditions. Probiotic Gram-positive Lactobacillus reuteri cells were utilized as a model cell culture because of their importance in maintaining the health of the human digestive tract. After culturing the L. reuteri cells under 5% CO2 in the darkness, the cells were harvested and washed prior to the nanospray DESI measurements. A clear, reproducible spectral pattern of the untreated cells was obtained using a solvent of 50% methanol and water. Adjustments of the methods revealed that at an OD600 of 1.8, and when washed with water only, the spectral pattern was visible and reproducible. Exposure to low pH conditions was conducted by incubating the L. reuteri cells in pH adjusted media for one hour and four hours. By setting the mass spectral pattern of the untreated bacterial cells as a reference, our results show that the spectra of the bacterial cells exposed to the low pH media differs from the untreated cells. These findings demonstrate the capability of nanospray DESI mass spectrometry as a tool for rapidly distinguishing the bacterial response to stress. Using these protocols, this method can be expanded to study the cellular response of bacteria to different types of cellular stress.

Additional Information

Language: English
Date: 2017
Bacterial cells, Mass spectral pattern, Nanospray DESI, Whole cell mass spectrometry
Electrospray ionization mass spectrometry
Stress (Physiology) $x Research
Cell physiology $x Research

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