Interactions with bacteria shape diatom adaptation to carbon concentration changes.

Area of Science:

• Marine microbiology
• Symbiotic relationships
• Biogeochemical cycles

Background:

• Diatoms are vital primary producers in oceans.
• Long-term co-evolution has led to intricate diatom-bacterial partnerships.
• Understanding these symbioses is key to marine carbon cycling.

Purpose of the Study:

• To investigate the syntrophic relationship between Phaeodactylum tricornutum and Loktanella vestfoldensis.
• To determine how this partnership facilitates indirect glucose utilization by diatoms.
• To assess the ecological relevance of diatom-bacterial interactions in marine environments.

Main Methods:

• Co-culture experiments with diatoms and bacteria.
• Metagenomic data analysis (Tara Oceans).
• Transcriptomic and metabolomic analyses of P. tricornutum.

Main Results:

• Loktanella vestfoldensis enables Phaeodactylum tricornutum to grow using glucose as the sole carbon source.
• A reciprocal dependency exists, with L. vestfoldensis relying on P. tricornutum when CO2 is the sole carbon source.
• Frequent co-occurrence of Loktanella with diatoms like Chaetoceros and Thalassiosira suggests ecological significance.
• Co-culture supports growth of other diatoms (Chaetoceros muelleri, Thalassiosira pseudonana) with glucose.
• P. tricornutum maintains photoautotrophy, while L. vestfoldensis likely supplies CO2 and metabolites like indole-3-acetic acid.

Conclusions:

• Bacterial-algal symbioses can facilitate diatom adaptation to varying carbon availability.
• These interactions play a significant role in marine carbon cycling.
• The syntrophy between diatoms and bacteria is ecologically relevant and impacts primary production.