Chlamydiae in corals: shared functional potential despite broad taxonomic diversity.

Area of Science:

• Microbiology
• Marine Biology
• Genomics

Background:

• Cnidarians harbor diverse bacteria crucial for host health and nutrient cycling.
• The role of obligate intracellular bacteria, particularly Chlamydiota (chlamydiae), in cnidarian hosts, especially corals, remains largely unknown.
• Understanding these bacterial associations is vital for comprehending coral holobiont function.

Purpose of the Study:

• To investigate the diversity and functional potential of cnidarian-associated chlamydiae.
• To determine the lifestyle and host specificity of chlamydiae in coral and jellyfish.
• To provide insights into the chlamydial lifestyle and host range within marine invertebrates.

Main Methods:

• Meta-analysis of 16S rRNA gene metabarcoding data from cnidarians.
• Assembly and analysis of nine metagenome-assembled genomes (MAGs) from coral and jellyfish-associated chlamydiae.
• Comparative genomic analysis to identify key functional genes and metabolic pathways.

Main Results:

• Enormous diversity of cnidarian-associated chlamydiae was observed.
• Six out of nine MAGs belonged to the Simkaniaceae family, with others in Parasimkaniaceae, Rhabdochlamydiaceae, and Anoxychlamydiaceae.
• All MAGs lacked genes for independent existence but possessed hallmark chlamydial genes, indicating an obligate intracellular lifestyle and broad host association.

Conclusions:

• Coral-associated chlamydiae are obligate intracellular bacteria with a wide host range, lacking unique genes for specific coral interactions.
• This study enhances understanding of coral microbiomes and the chlamydial lifestyle.
• Further research is needed to elucidate specific host-microbe interactions within coral holobionts.