Abstract
Marine invertebrate-associated symbiotic bacteria produce a plethora of novel secondary metabolites which may be structurally unique with interesting pharmacological properties. Selection of strains usually relies on literature searching, genetic screening and bioactivity results, often without considering the chemical novelty and abundance of secondary metabolites being produced by the microorganism until the time-consuming bioassay-guided isolation stages. To fast track the selection process, metabolomic tools were used to aid strain selection by investigating differences in the chemical profiles of 77 bacterial extracts isolated from cold water marine invertebrates from Orkney, Scotland using liquid chromatography-high resolution mass spectrometry (LC-HRMS) and nuclear magnetic resonance (NMR) spectroscopy. Following mass spectrometric analysis and dereplication using an Excel macro developed in-house, principal component analysis (PCA) was employed to differentiate the bacterial strains based on their chemical profiles. NMR 1H and correlation spectroscopy (COSY) were also employed to obtain a chemical fingerprint of each bacterial strain and to confirm the presence of functional groups and spin systems. These results were then combined with taxonomic identification and bioassay screening data to identify three bacterial strains, namely Bacillus sp. 4117, Rhodococcus sp. ZS402 and Vibrio splendidus strain LGP32, to prioritize for scale-up based on their chemically interesting secondary metabolomes, established through dereplication and interesting bioactivities, determined from bioassay screening.
Highlights
Marine invertebrates such as sponges are a rich source of novel metabolites that are of medicinal interest due to their anti-cancer, anti-tumor, anti-viral and antibacterial properties [1,2,3,4]
Specimens were inoculated onto various types of agar media, which yielded a total of 77 isolates
principal component analysis (PCA) was shown to be an effective tool to differentiate bacterial strains based on their chemical diversity and novelty of metabolites, providing a means to select bacterial isolates with diverse chemistry without having to carry out full isolation work on each extract
Summary
Marine invertebrates such as sponges are a rich source of novel metabolites that are of medicinal interest due to their anti-cancer, anti-tumor, anti-viral and antibacterial properties [1,2,3,4]. Sponge-associated endosymbiotic bacteria are highly concentrated within the sponge matrix making up to 50%–60% of the dry weight of the sponge [5] They are hypothesized to stabilize the sponge skeleton, process metabolic waste and provide chemical defense against environmental stresses such as predators and overgrowth of fouling organisms, by producing a plethora of novel secondary metabolites that may be structurally unique with interesting pharmacological properties [5,6,7], e.g., as antimicrobials [8] or anti-cancer drugs [9]. The anti-tumor drug bryostatin 1, isolated from the marine bryozoan Bugula neritina and synthesized by the symbiotic bacterium Candidatus Endobugula sertula [9], is produced using a large-scale fermentation process to ensure supply [17]
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