Cyanobacterial Classification with the Toxicity Using MALDI Biotyper

An abnormal growth of cyanobacteria in eutrophicated freshwaters can cause various environmental problems. In particular, Microcystis producing hepatotoxic cyclic heptapeptides microcystins (MCs) has been globally observed. Recent studies have demonstrated that matrix-assisted laser desorption/ioniz...

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Bibliographic Details
Published in:	Journal of the American Society for Mass Spectrometry Vol. 31; no. 7; pp. 1572 - 1578
Main Authors:	Asukabe, Hirohiko, Akahori, Satoko, Ueno, Ema, Nakayama, Takuma, Yamashita, Ryuji, Arii, Suzue, Harada, Ken-ichi, Imanishi, Susumu Y
Format:	Journal Article
Language:	English
Published:	United States American Chemical Society 01-07-2020
Subjects:	Bacterial Typing Techniques - methods Cluster Analysis Microcystins - chemistry Microcystins - classification Microcystis - chemistry Microcystis - classification Microcystis - cytology Software Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization - methods microcystins MALDI Biotyper profiling cyanobacteria
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Summary:	An abnormal growth of cyanobacteria in eutrophicated freshwaters can cause various environmental problems. In particular, Microcystis producing hepatotoxic cyclic heptapeptides microcystins (MCs) has been globally observed. Recent studies have demonstrated that matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) offers a rapid classification of cyanobacteria; however, they have not fully considered the toxicity yet. In this study, we have performed MALDI-TOF MS for intact cyanobacterial cells using Biotyper software and optimized their conditions to achieve cyanobacterial classification with the toxicity. The detection mass range used for Biotyper was extended to cover small molecules, but their intense ions were suppressed as a function of the used instrument Autoflex Speed, which enabled simultaneous observations of large molecular fingerprints and small MCs with comparable ion intensity. Hierarchical clustering of mass spectra obtained under the optimized conditions differentiated toxic and non-toxic clusters of Microcystis strains and furthermore formed a tight cluster of non-toxic strains possessing the MC biosynthesis gene mcyG. Spectral libraries were expanded to >30 genera (>80 strains) under the default and optimized conditions to improve the confidence of cyanobacterial classification. Consequently, spectral library searching allowed for characterization of cyanobacteria from a field sample as mixed toxic and non-toxic Microcystis cells, without isolating those cells.
ISSN:	1044-0305 1879-1123
DOI:	10.1021/jasms.0c00148