Large scale MALDI-TOF MS based taxa identification to identify novel pigment producers in a marine bacterial culture collection.

A challenge in the rational exploitation of microbial culture collections is to avoid superfluous testing of replicas. MALDI-TOF MS has been shown to be an efficient dereplication tool as it can be used to discriminate between bacterial isolates at the species level. A bacterial culture collection of more than 10,000 heterotrophic marine bacterial isolates from sea-water surface layers of the Norwegian Trondheimsfjord and neighbouring coastal areas has been established. A sub-collection of pigmented isolates was earlier screened for novel carotenoids with UVA-Blue light absorbing properties. This was a comprehensive analytical task and it was observed that a significant number of extracts with identical pigment profile were recovered. Hence, this study was undertaken to explore the use of MALDI-TOF MS as a dereplication tool to quickly characterize the bacterial collection. Furthermore, LC-DAD-MS analysis of pigment profiles was performed to check if pigment profile diversity was maintained among isolates kept after the potential MALDI-TOF MS selection step. Four hundred isolates comprising both pigmented and non-pigmented isolates were used for this study. The resulting MALDI-TOF MS dendrogram clearly identified a diversity of different taxa and these were supported by the pigment profile clustering, thus linking the pigment production as species-specific properties. Although one exception was found, it can be concluded that MALDI-TOF MS dereplication is a promising pre-screening tool for more efficient screening of microbial culture collection containing pigments with potential novel properties.