Community structural differences shape microbial responses to high molecular weight organic matter.

Area of Science:

• Marine microbiology
• Biogeochemistry
• Oceanography

Background:

• The relationship between microbial community structure and organic matter (OM) degradation is not fully understood.
• Marine microbial communities are diverse and inhabit various oceanic environments.

Purpose of the Study:

• To investigate how distinct marine microbial communities from North Atlantic surface and bottom waters respond to high molecular weight organic matter (HMW-OM).
• To test if microbial communities exhibit varying compositional succession and functional shifts when exposed to HMW-OM.
• To determine if HMW-OM exposure broadens the spectrum of microbial enzymes, indicating enhanced degradation potential.

Main Methods:

• Utilized mesocosms to culture distinct marine microbial communities.
• Amended mesocosms with a consistent pool of HMW-OM.
• Monitored microbial community succession, bacterial production, and enzymatic activities over time.

Main Results:

• Community succession correlated with cell growth, increased bacterial production, and significant shifts in enzymatic activities.
• Initially rare bacterial taxa became dominant, coinciding with a broader spectrum of detected enzymes.
• Despite similar responses in enzyme production, distinct differences were observed in community-level succession and enzymatic activity progression among different water masses.

Conclusions:

• Bacterial community structure significantly influences the degradation rates and pathways of HMW-OM.
• Rare bacterial taxa are crucial players in ocean carbon cycling.
• Understanding microbial community dynamics is essential for predicting ocean carbon sequestration and OM decomposition.