LC-MS method for screening unknown microbial carotenoids and isoprenoid quinones

Area of Science:

• Microbiology
• Analytical Chemistry
• Natural Product Chemistry

Background:

• Microbial secondary metabolites, such as isoprenoid quinones and carotenoids, are crucial for microbial characterization and chemotaxonomic classification.
• Isoprenoid quinones are well-established markers for distinguishing photosynthetic microorganisms and are also present in non-photosynthetic microbes.
• Carotenoids often co-occur with isoprenoid quinones in various microorganisms.

Purpose of the Study:

• To develop and validate a robust liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for the analysis and identification of microbial isoprenoids.
• To enable the structural characterization of both known and potentially novel isoprenoid quinones and carotenoids from diverse microbial sources.
• To establish a foundation for the discovery and analysis of unknown microbial isoprenoids using advanced mass spectrometry techniques.

Main Methods:

• Utilized liquid chromatography (LC) for effective separation of isoprenoid compounds and their ester derivatives.
• Employed positive atmospheric pressure chemical ionization (APCI) for ionization and collisionally induced dissociation (CID) for fragmentation.
• Implemented enhanced product ion (EPI) scans in a linear ion trap with information-dependent data acquisition (IDA) to capture fragment spectra from low-abundance isoprenoids.

Main Results:

• Successfully developed an LC-MS/MS method capable of separating and analyzing microbial isoprenoids.
• Generated informative fragment spectra for structural elucidation by comparing unknown compounds with standard isoprenoids and published data.
• Screened 17 microorganisms, suggesting probable structures for identified isoprenoid quinones and carotenoids.

Conclusions:

• The developed LC-MS/MS method is effective for the analysis and structural characterization of microbial isoprenoids, including quinones and carotenoids.
• This methodology provides a valuable tool for microbial chemotaxonomy and the discovery of novel secondary metabolites.
• The study lays the groundwork for future investigations into the vast, yet uncharacterized, world of microbial isoprenoids.