Unveiling in situ interactions between marine protists and bacteria through single cell sequencing

Area of Science:

• Marine microbiology
• Protist ecology
• Symbiotic interactions

Background:

• Heterotrophic protists are vital marine ecosystem components.
• Species-specific prey preferences and symbiotic interactions remain largely unknown.
• Understanding these interactions is crucial for marine biogeochemistry.

Purpose of the Study:

• To investigate species-specific prey preferences of marine heterotrophic protists.
• To identify symbiotic interactions between protists and prokaryotes in situ.
• To demonstrate the utility of single-cell sequencing for ecological studies.

Main Methods:

• Collecting individual, uncultured protist cells from marine environments.
• Utilizing flow cytometry for cell sorting.
• Sequencing eukaryote and bacterial small subunit ribosomal RNA (SSU rRNA) genes from single cells.

Main Results:

• Identified specific bacterial prey (e.g., Pelagibacter ubique, actinobacteria, bacteroidetes) associated with various protist groups.
• Provided evidence for predator-prey interactions through identical phylotypes in protists and free bacterioplankton.
• Discovered novel symbionts related to Rickettsiales and candidate divisions ZB3 and TG2 associated with Cercozoa and Chrysophyta.

Conclusions:

• Single-cell sequencing is a powerful tool for resolving ecological interactions between uncultured protists and prokaryotes.
• This approach advances our understanding of marine microbial food webs and symbiotic relationships.
• The findings highlight the diversity of protist-prokaryote associations in marine ecosystems.