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Ion trap mass spectrometry of surfactins produced by Bacillus subtilis SZMC 6179J reveals novel fragmentation features of cyclic lipopeptides
Rationale Surfactins are mixtures of cyclic lipopeptides consisting of variants of a heptapeptide and a linked β‐hydroxy fatty acid with various chain lengths of 13–15 carbon atoms. A lactone bridge between the β‐hydroxy functional group of the fatty acid and the carboxy terminal functional componen...
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Published in: | Rapid communications in mass spectrometry 2016-07, Vol.30 (13), p.1581-1590 |
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Main Authors: | , , , , , , , |
Format: | Article |
Language: | English |
Subjects: | |
Citations: | Items that this one cites Items that cite this one |
Online Access: | Get full text |
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Summary: | Rationale
Surfactins are mixtures of cyclic lipopeptides consisting of variants of a heptapeptide and a linked β‐hydroxy fatty acid with various chain lengths of 13–15 carbon atoms. A lactone bridge between the β‐hydroxy functional group of the fatty acid and the carboxy terminal functional component of the peptide chain form their cyclic structures. Such lipopeptides, produced mainly by Bacillus species, possess several remarkable biological effects such as antitumor and antimicrobial activities, some of which are highly promising for utilization in plant disease biocontrol. The strain Bacillus subtilis SZMC 6179J was previously shown to exert significant antifungal properties against various phytopathogenic filamentous fungi; therefore, we characterized the structural features of the surfactins produced by this strain in order to explore the origin of the observed antagonistic effects of this potential biocontrol organism.
Methods
Bacillus subtilis SZMC 6179J was used to produce surfactins, which were characterized by high‐performance liquid chromatography/electrospray ionisation ion trap mass spectrometry (HPLC/ESI‐ITMS) techniques after precipitation and extraction steps.
Results
The 26 isoforms separated and identified represent three types of known surfactin variants and a fourth, previously unknown group characterised by the replacement of the leucine residue by valine in position 2. The relative amounts of this newly identified surfactin group were below 1%, and their cyclic structures were closed by C13–C15 hydroxy fatty acids. The structural assessment of the isoforms by MS2 measurements led to the characterisation and description of a new fragmentation mechanism of surfactins.
Conclusions
The detected new natural lipoheptapeptide compounds with modified structures have significant potential for biotechnological and biocontrol applications. The complementary ITMS2 data as well as the described internal fragmentation mechanism obtained from the sodiated surfactin molecules may further facilitate the structural elucidation of cyclic lipopeptides in the future. Copyright © 2016 John Wiley & Sons, Ltd. |
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ISSN: | 0951-4198 1097-0231 |
DOI: | 10.1002/rcm.7592 |