Microbial survival mechanisms within serpentinizing Mariana forearc sediments

Area of Science:

• Marine microbiology
• Geomicrobiology
• Extremophile research

Background:

• Deep subsurface marine sediments harbor microbial life under energy-limited conditions.
• The Mariana forearc presents extreme conditions (pH 10-12.5, low nutrients) ideal for studying microbial resilience.
• Serpentinizing seamounts in the Mariana forearc are rich in methane, hydrogen, and sulfide.

Purpose of the Study:

• To investigate microbial community structure and function in the Mariana forearc.
• To understand how microbes survive and metabolize in extreme deep-sea environments.
• To identify key metabolic pathways and survival mechanisms of deep subsurface microbes.

Main Methods:

• Sampling of serpentinizing seamounts during International Ocean Discovery Program Expedition 366.
• Metatranscriptomic analysis to identify active microbial genes and pathways.
• Detection of metabolic intermediates to confirm in situ activity.

Main Results:

• Dominant transcripts indicated cellular maintenance (cell wall/membrane repair).
• Key metabolic pathways included the Entner-Doudoroff pathway, tricarboxylic acid cycle, and sulfur cycling (taurine assimilation).
• Microbial communities comprised Bacteria, Archaea, and Eukarya, with aerobic methane oxidation and denitrification transcripts detected.

Conclusions:

• Mariana forearc microbes utilize basic survival strategies and coupled metabolic reactions.
• These communities are metabolically active despite extreme environmental pressures.
• The study reveals the adaptability of microbial life in deep-sea, energy-limited ecosystems.