Unveiling Crocosphaera Responses to Phosphorus Depletion: Insights From Genome Analysis and Functional...

Area of Science:

• Marine microbiology
• Biogeochemical cycles
• Genomics

Background:

• Unicellular, nitrogen-fixing cyanobacteria (UCYN) are crucial for marine primary production and nitrogen cycling in nutrient-poor oceans.
• Crocosphaera species are adapted to low phosphate (P_i) environments, but their coping mechanisms remain unclear.

Purpose of the Study:

• To investigate the genetic basis of P_i stress response in Crocosphaera.
• To understand how Crocosphaera utilizes dissolved organic phosphorus (DOP) and its growth strategies under P_i limitation.

Main Methods:

• Genomic analysis of six Crocosphaera watsonii strains and two coastal strains (C. subtropica, C. chwakensis).
• Physiological monitoring of C. watsonii WH8501 under P_i depletion and DOP addition.
• Transcriptional analysis of P_i-related and clock genes.

Main Results:

• Identified genes involved in P_i signaling, uptake, and DOP hydrolysis, revealing strain-specific genetic potentials for P_i scarcity.
• C. watsonii WH8501 survived P_i depletion for nine days with altered stoichiometry and efficiently recovered growth upon DOP addition.
• Diel expression patterns of P_i-related genes and clock genes suggest circadian regulation of P_i metabolism.

Conclusions:

• Crocosphaera exhibits diverse strategies for coping with P_i limitation, including efficient DOP utilization.
• Circadian regulation may play a role in managing P_i stress responses in marine cyanobacteria.
• This research enhances understanding of microbial resilience and nutrient cycling in oligotrophic marine ecosystems.