Rapid Classification and Identification of Microcystis aeruginosa Strains Using MALDI-TOF MS and Polygenetic Analysis.

Li-Wei Sun,Wen-Jing Jiang,Xi-Wu Lu,Hiroaki Sato,Masanobu Kawachi

doi:10.1371/journal.pone.0156275

Abstract

Matrix-assisted laser desorption–ionization-time-of-flight mass spectrometry (MALDI–TOF MS) was used to establish a rapid, simple, and accurate method to differentiate among strains of Microcystis aeruginosa, one of the most prevalent types of bloom-forming cyanobacteria. M. aeruginosa NIES-843, for which a complete genome has been sequenced, was used to characterize ribosomal proteins as biomarkers and to optimize conditions for observing ribosomal proteins as major peaks in a given mass spectrum. Thirty-one of 52 ribosomal subunit proteins were detected and identified along the mass spectrum. Fifty-five strains of M. aeruginosa from different habitats were analyzed using MALDI–TOF MS; among these samples, different ribosomal protein types were observed. A polygenetic analysis was performed using an unweighted pair-group method with arithmetic means and different ribosomal protein types to classify the strains into five major clades. Two clades primarily contained toxic strains, and the other three clades contained exclusively non-toxic strains. This is the first study to differentiate cyanobacterial strains using MALDI–TOF MS.

Highlights

Toxic cyanobacterial blooms have been identified in fresh and brackish waterbodies for over 100 years [1]
We propose a new approach to this process by using matrix-assisted laser desorption ionization (MALDI) time-of-flight (TOF) mass spectrometry (MS) to create a rapid, high resolution method for identifying and distinguishing toxic M. aeruginosa strains from non-toxic strains
A list of the calculated molecular weights corresponding to the ribosomal subunit proteins of the M. aeruginosa strain NIES-843 was prepared (Table 1)

Summary

Introduction

Toxic cyanobacterial blooms have been identified in fresh and brackish waterbodies for over 100 years [1]. They are known to cause the deaths of wild and domestic animals worldwide [2] and threaten the health of human beings who use waterbodies with such blooms for recreation or drinking [3]. Some strains produce hepatotoxins called microcystins (MCs), which have been suspected of causing human hepatocellular carcinoma in China [3]. MCs exist within cyanobacteria and are released after cyanobacterial cells lyse. Their distribution is highly correlated with the distribution of cyanobacteria. MC concentrations shift with the PLOS ONE | DOI:10.1371/journal.pone.0156275 May 26, 2016

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Conclusion