Symbiont diversity within Loripes orbiculatus and the case for multiple hosts

Area of Science:

• Marine Biology
• Microbial Ecology
• Symbiosis Research

Background:

• Seagrasses are vital coastal ecosystems supporting biodiversity.
• Lucinid bivalves, common in seagrass meadows, host specific Ca. Thiodiazotropha symbionts.
• Previous studies hinted at Ca. Thiodiazotropha on seagrass roots, but direct comparison with bivalve symbionts was lacking.

Purpose of the Study:

• To investigate the diversity of Ca. Thiodiazotropha symbionts in lucinid bivalves and on seagrass roots.
• To determine if symbionts are shared between bivalves and seagrasses at the same location and time.
• To obtain a closed genome for a prominent Ca. Thiodiazotropha symbiont.

Main Methods:

• 16S rRNA gene amplicon sequencing of microbial communities.
• Metagenome sequencing for deeper microbial insights.
• Comparative analysis of symbiont sequences from bivalve and seagrass samples.

Main Results:

• Unprecedented diversity of Ca. Thiodiazotropha symbionts was found in both lucinid bivalves and on seagrass roots in the Adriatic Sea.
• The complete genome of a key symbiont species was successfully sequenced.
• Two specific Ca. Thiodiazotropha amplicon sequence variants (ASVs) from seagrass roots were identical to those found within bivalve hosts at the same sites.

Conclusions:

• Evidence suggests symbiont sharing between lucinid bivalves and seagrasses within the same habitat.
• This inter-host symbiont exchange has significant implications for the evolution and ecology of both seagrasses and their associated fauna.
• The findings highlight the complex symbiotic relationships within seagrass ecosystems.