Evolution and function of eukaryotic-like proteins from sponge symbionts.

Area of Science:

• Marine biology
• Microbial ecology
• Evolutionary biology

Background:

• Sponges host diverse microbial communities, crucial for their health and function.
• Molecular mechanisms governing sponge-microbe symbiosis are largely unknown.
• Eukaryotic-like proteins (ELPs) are abundant in sponge-associated bacterial symbionts.

Purpose of the Study:

• To investigate the evolution and function of ELPs from various sponge symbionts.
• To understand the role of ELPs in mediating bacteria-eukaryote interactions.
• To determine if different ELP classes impact phagocytosis.

Main Methods:

• Phylogenetic analyses of nine ELPs.
• Recombinant expression of ELPs in Escherichia coli.
• Phagocytosis assays using Acanthamoeba castellanii and ELP-expressing E. coli.

Main Results:

• Phylogenetic analysis revealed ELPs are closely related to eukaryotic or eukaryotic-associated bacterial proteins.
• Escherichia coli expressing ankyrin repeat (AR), TPR-SEL1, and NHL ELP classes showed increased phagocytosis by Acanthamoeba castellanii.
• Various ELP classes significantly increased the percentage of amoebas containing bacteria and the average number of intracellular bacteria.

Conclusions:

• ELPs from sponge symbionts have evolved from or are associated with eukaryotic-interacting bacteria.
• Multiple classes of ELPs can modulate phagocytosis, indicating a conserved mechanism for host interaction.
• ELPs play a significant, broad role in mediating symbiotic interactions between bacteria and sponges.