Measuring bacterial activity and community composition at high hydrostatic pressure using a novel experimental...

Area of Science:

• Marine microbiology
• High-pressure systems
• Deep-sea ecology

Background:

• Deep-sea environments harbor unique microbial communities adapted to extreme pressures.
• Understanding bacterial activity at high hydrostatic pressure is crucial for marine biogeochemical cycling.
• Previous methods limited the study of microbial activity under sustained high pressure due to decompression issues.

Purpose of the Study:

• To introduce and validate a novel high-pressure incubation system for subsampling pressurized cultures without decompression.
• To investigate the effects of high pressure (up to 27 MPa) on bacterial protein production and cell multiplication rates.
• To analyze deep-sea bacterial community composition and identify pressure-adapted species.

Main Methods:

• Development of a high-pressure incubation system enabling multiple subsamples.
• Incubation of piezophilic (Photobacterium profundum) and piezotolerant (Colwellia maris) bacterial strains at varying pressures.
• Analysis of Mediterranean deep-sea samples (3044 m) under high pressure.
• Measurement of bacterial protein production (BPP) and bacterial cell multiplication (BCM) rates.
• Determination of bacterial community composition using molecular techniques.

Main Results:

• Bacterial protein production increased significantly at high pressures (1.5-3.9 fold for pure cultures, 6.9 fold for field samples).
• Bacterial cell multiplication rates were elevated at high pressure (3.1-2.9 fold for pure cultures).
• Deep-sea bacterial communities rapidly selected for piezotolerant bacteria, with Exiguobacterium dominating after 3 days at 27 MPa.

Conclusions:

• The novel incubation system effectively allows for the study of microbial activity under sustained high pressure.
• High hydrostatic pressure significantly enhances bacterial protein production and cell multiplication rates.
• The findings provide critical data for modeling oceanic carbon pump efficiency and understanding deep-sea microbial ecology.