title: Genome streamlining and chemical defense in a coral reef symbiosis.
abstract: Secondary metabolites are ubiquitous in bacteria, but by definition, they are thought to be nonessential. Highly toxic secondary metabolites such as patellazoles have been isolated from marine tunicates, where their exceptional potency and abundance implies a role in chemical defense, but their biological source is unknown. Here, we describe the association of the tunicate Lissoclinum patella with a symbiotic α-proteobacterium, Candidatus Endolissoclinum faulkneri, and present chemical and biological evidence that the bacterium synthesizes patellazoles. We sequenced and assembled the complete Ca. E. faulkneri genome, directly from metagenomic DNA obtained from the tunicate, where it accounted for 0.6% of sequence data. We show that the large patellazoles biosynthetic pathway is maintained, whereas the remainder of the genome is undergoing extensive streamlining to eliminate unneeded genes. The preservation of this pathway in streamlined bacteria demonstrates that secondary metabolism is an essential component of the symbiotic interaction.
authors.affiliation: Department of Medicinal Chemistry, University of Utah, Salt Lake City, UT 84112, USA.
authors.forename: Jason C
authors.initials: JC
authors.lastname: Kwan
authors.forename: Mohamed S
authors.initials: MS
authors.lastname: Donia
authors.forename: Andrew W
authors.initials: AW
authors.lastname: Han
authors.forename: Euichi
authors.initials: E
authors.lastname: Hirose
authors.forename: Margo G
authors.initials: MG
authors.lastname: Haygood
authors.forename: Eric W
authors.initials: EW
authors.lastname: Schmidt
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001393:Azoles / Q000737:chemistry / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D057894:Coral Reefs; D016680:Genome, Bacterial; D054892:Metagenome; D008954:Models, Biological; D008969:Molecular Sequence Data; D010802:Phylogeny; D048630:Polyketide Synthases / Q000235:genetics / Q000378:metabolism; D019691:Prochloron / Q000235:genetics* / Q000502:physiology; D012329:RNA, Bacterial / Q000235:genetics; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D012244:Rhodospirillaceae / Q000235:genetics* / Q000502:physiology; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction; D013559:Symbiosis / Q000235:genetics / Q000502:physiology; D014561:Urochordata / Q000382:microbiology* / Q000502:physiology
chemical_list: D001393:Azoles; D001426:Bacterial Proteins; D012329:RNA, Bacterial; D012336:RNA, Ribosomal, 16S; D048630:Polyketide Synthases