Cryptic Diversity of Black Band Disease Cyanobacteria in Corals Revealed by Chemical Ecology and Comparative Genome-Resolved Metagenomics

Black band disease is a globally distributed and easily recognizable coral disease. Despite years of study, the etiology of this coral disease, which impacts dozens of stony coral species, is not completely understood. Although black band disease mats are predominantly composed of the cyanobacterial species , other filamentous cyanobacterial strains and bacterial heterotrophs are readily detected. Through chemical ecology and metagenomic sequencing, we uncovered cryptic strains of species from corals that differ from those on other corals in the Caribbean and Pacific. Isolation of metabolites from -derived revealed the prevalence of unique forms of looekeyolides, distinct from previously characterized strains. In addition, comparative genomics of strains showed that only -based strains have the genetic capacity to produce lasso peptides, a family of compounds with diverse biological activity. All nine strains examined here shared the genetic capacity to produce looekeyolides and malyngamides, suggesting these compounds support the ecology of this genus. Similar biosynthetic gene clusters are not found in other cyanobacterial genera associated with black band disease, which may suggest that looekeyolides and malyngamides contribute to disease etiology through yet unknown mechanisms.