Ultrastructural changes in an obligately barophilic marine bacterium after decompression

Area of Science:

• Microbiology
• Oceanography
• Cell Biology

Background:

• The bacterial isolate MT-41 was obtained from a depth of 10,476 meters.
• MT-41 is an obligately barophilic bacterium, meaning it requires high pressure to survive.

Purpose of the Study:

• To investigate the morphological alterations of MT-41 following decompression from high hydrostatic pressure to atmospheric pressure.
• To observe the effects of prolonged incubation at atmospheric pressure on the cell structure and viability of MT-41.

Main Methods:

• Cultures of MT-41 were grown at 103.5 MPa and 2°C.
• Cultures were decompressed to 0.101 MPa (atmospheric pressure).
• Morphological and ultrastructural changes were assessed via microscopy at various time points post-decompression, with viability assessed by colony-forming units (CFU).

Main Results:

• Decompression did not cause immediate morphological changes, but prolonged exposure to atmospheric pressure led to significant ultrastructural degradation.
• Observed changes included intracellular vesicles, membrane fragments, plasmolysis, cell lysis, extracellular vesicle formation, and ghost cells.
• Bacterial viability (CFU) decreased over time at atmospheric pressure, and nucleoid fibrils were poorly stained in surviving cells.

Conclusions:

• Hadal deep-sea bacteria are highly sensitive to pressure changes.
• Immediate in situ or surface fixation of deep-sea samples is essential to prevent structural degradation and ensure accurate ecological assessments.