The Influence of Metabolic Inhibitors, Antibiotics, and Microgravity on Intact Cell MALDI-TOF Mass Spectra of the Cyanobacterium Synechococcus Sp. UPOC S4.

Marek Šebela,Vladan Ondřej,Martin Raus,Petr Hašler

doi:10.3390/molecules26061683

Marek Šebela, Vladan Ondřej + Show 2 more

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https://doi.org/10.3390/molecules26061683

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Abstract

The aim and novelty of this paper are found in assessing the influence of inhibitors and antibiotics on intact cell MALDI-TOF mass spectra of the cyanobacterium Synechococcus sp. UPOC S4 and to check the impact on reliability of identification. Defining the limits of this method is important for its use in biology and applied science. The compounds included inhibitors of respiration, glycolysis, citrate cycle, and proteosynthesis. They were used at 1–10 μM concentrations and different periods of up to 3 weeks. Cells were also grown without inhibitors in a microgravity because of expected strong effects. Mass spectra were evaluated using controls and interpreted in terms of differential peaks and their assignment to protein sequences by mass. Antibiotics, azide, and bromopyruvate had the greatest impact. The spectral patterns were markedly altered after a prolonged incubation at higher concentrations, which precluded identification in the database of reference spectra. The incubation in microgravity showed a similar effect. These differences were evident in dendrograms constructed from the spectral data. Enzyme inhibitors affected the spectra to a smaller extent. This study shows that only a long-term presence of antibiotics and strong metabolic inhibitors in the medium at 10−5 M concentrations hinders the correct identification of cyanobacteria by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF).

Highlights

Cyanobacteria represent a phylum of photosynthesizing bacteria
We focused on the influence of metabolic inhibitors and antibiotics at micromolar concentrations on MALDI-TOF mass spectrometric profiles of the cyanobacterium Synechococcus sp
UPOC S4 cells were cultivated in the presence of metabolic inhibitors and antibiotics to evaluate their impact on the reliability of species identification by IC MALDI-TOF MS

Summary

Introduction

Cyanobacteria represent a phylum of photosynthesizing bacteria. The small size of cells, overlapping features, and complicated life cycles are the traditional base for their classification. Numerous papers have appeared describing the applicability of intact cell matrixassisted laser desorption/ionization time-of-flight mass spectrometry (IC MALDI-TOF MS) for identification and typing of bacteria, yeasts, and fungi [2,3]. Especially for pathogenic microorganisms, microbial cells are inactivated and extracted prior to the preparation of MALDI probe. The analysis of cellular pathogens is possible from positive blood cultures or body fluids [4]. The pattern of molecular masses in the profile MALDI spectrum (usually signals of ribosomal and other abundant proteins are predominantly represented) is compared with a reference spectral database to assign the result [2]

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