Microbiota of Healthy Corals Are Active against Fungi in a Light-Dependent Manner

Abstract

Coral reefs are intricate ecosystems that harbor diverse organisms, including 25% of all marine fish. Healthy corals exhibit a complex symbiosis between coral polyps, endosymbiotic alga, and an array of microorganisms, called the coral holobiont. Secretion of specialized metabolites by coral microbiota is thought to contribute to the defense of this sessile organism against harmful biotic and abiotic factors. While few causative agents of coral diseases have been unequivocally identified, fungi have been implicated in the massive destruction of some soft corals worldwide. Because corals are nocturnal feeders, they may be more vulnerable to fungal infection at night, and we hypothesized that the coral microbiota would have the capability to enhance their defenses against fungi in the dark. A Pseudoalteromonas sp. isolated from a healthy octocoral displayed light-dependent antifungal properties when grown adjacent to Penicilliumcitrinum (P. citrinum) isolated from a diseased Gorgonian octocoral. Microbial MALDI-imaging mass spectrometry (IMS) coupled with molecular network analyses revealed that Pseudoalteromonas produced higher levels of antifungal polyketide alteramides in the dark than in the light. The alteramides were inactivated by light through a photoinduced intramolecular cyclization. Further NMR studies led to a revision of the stereochemical structure of the alteramides. Alteramide A exhibited antifungal properties and elicited changes in fungal metabolite distributions of mycotoxin citrinin and citrinadins. These data support the hypothesis that coral microbiota use abiotic factors such as light to regulate the production of metabolites with specialized functions to combat opportunistic pathogens at night.

Structural diversity of anti-pancreatic cancer capsimycins identified in mangrove-derived Streptomyces xiamenensis 318 and post-modification via a novel cytochrome P450 monooxygenase

“…The MS/MS fragmentation patterns for PTMs ( 1–7 ) were examined as a convenient method for the fast detection of new metabolites and for de-replication of the known ones31. The PTM chemical structure is composed of two major moieties (the carbocyclic and macrolactam rings) and post-modifications, including methoxylation of the C - 30 side chain.…”

Mass spectrometry tools and workflows for revealing microbial chemistry

“…For example, molecular networking is an organizing principle for visualizing tandem MS data from an experiment 126 . Multiple publications have demonstrated the potential of molecular networking in microbial metabolomics and NPs identification/dereplication studies, with capacity of analyzing large scale datasets 68, 74, 83, 84, 113, 126, 155, 159, 165–171 . The rationale behind molecular networking analysis is that molecular fragmentation is not a random event resulting in similar fragmentation patterns, but highly conserved bond breakage 126, 159, 172 .…”

Diversity and composition of the bacterial community in Amphioxus feces

“…Pseudoalteromonas sp. has been reported as the commensal bacteria of octocoral . As for other two genera, genus Marinifilum was specific to wild Amphioxus feces and contributes 79.60% of the phylum Bacteroidetes.…”