Geographically conserved microbiomes of four temperate water tunicates

Area of Science:

• Marine Biology
• Microbiology
• Immunology

Background:

• Tunicates possess innate immune systems analogous to chordates, making them valuable models for microbiome research.
• Understanding the microbial communities associated with tunicates is crucial for deciphering host-microbe interactions.

Purpose of the Study:

• To compare the tunic microbiomes of four tunicate species: Ciona robusta, Ciona savignyi, Botrylloides leachi, and Botryllus schlosseri.
• To investigate the conservation of bacterial phylotypes within each species across different geographic locations.
• To determine if tunic and tunic+cuticle subsamples harbor different microbial communities.

Main Methods:

• Automated ribosomal RNA intergenic spacer analysis (ARISA) and High-Throughput Sequencing were employed.
• Tunic microbiomes were sampled from three distinct locations with limited genetic connectivity.
• Bacterial operational taxonomic unit (OTU) diversity and community composition were analyzed.

Main Results:

• Bacterial phylotype profiles were conserved within each tunicate species.
• No significant differences were found between tunic and tunic+cuticle subsamples.
• Bacterial OTU diversity varied significantly, with Ciona savignyi showing the lowest and Botryllus schlosseri the highest diversity.
• Each species exhibited a distinct bacterial OTU set, with notable OTUs including Alphaproteobacteria, Phyllobacteriaceae, and Endozoicomonas.

Conclusions:

• Tunicates harbor species-specific and defined microbiomes.
• The within-species conservation of core OTUs across populations supports the hypothesis of stable host-microbe associations.
• Tunicates serve as robust models for studying the development and stability of host-associated microbial communities.