Omics tools applied to the discovery of tetrodotoxin producing organisms and biosynthetic genes

Abstract

Tetrodotoxin (TTX) is a highly lethal neurotoxin, isolated from organisms belonging to six phyla within the kingdom Animalia. It is still unclear why or how TTX occurs in different phylogenetically unrelated organisms. Among the hypotheses which have been proposed to reveal the biogenetic origin of TTX, the most widely accepted one suggests that symbiotic or commensal bacteria perform an important role in the biosynthesis of this toxin. With the advent of new tools and approaches to assign the actual producer of secondary metabolites, and corresponding biosynthetic genes, it would be possible to unveil the biogenic origin and biosynthesis of TTX. Metagenomics analysis encompasses the isolation and analysis of the total genomic DNA of complex biological matrixes. It also enables the investigation of the genome of complex microbial consortia embedded in a holobiont. "Omics" complementary approaches, such as metaproteomics and metabolomics, help to find, identify and characterize secondary metabolites involved in biochemical and ecological processes of holobionts. We intend to analyze the microbiome associated with different TTX-bearing puffer fishes by using metagenome and metabolomics analyses, looking for the TTX biological origin and biosynthetic genes. The genome of a TTX-producing bacterium, Shewanella algae, will be used as reference for TTX biosynthetic gene mining and metabolomics analyses. Metagenomics libraries will be used to compare genes and/or gene clusters from the species under study in order to identify which of them may be involved in the biosynthesis of the toxin, as well as discover its biogenic origin. (AU)