Under the microscope: microbial life at pore scale under extreme deep-environment conditions

Area of Science:

• Microbiology
• Biotechnology
• Geochemistry

Background:

• Extremophiles are microorganisms adapted to extreme environments.
• Studying extremophile motility and tropism is crucial for understanding life's limits.
• Custom micromodels are expensive and complex for in situ studies.

Purpose of the Study:

• To evaluate microcapillaries as an alternative to custom micromodels for studying extremophile behavior.
• To investigate the motility and tropism of extremophiles under simulated in situ conditions.
• To identify practical challenges and solutions for using microcapillaries in anoxic environments.

Main Methods:

• Utilized microcapillaries for culturing and observing extremophiles.
• Employed widefield transmission and fluorescence microscopy.
• Applied a particle tracking algorithm for motility analysis.
• Modeled gas diffusion and pH changes using numerical solutions.

Main Results:

• Microcapillaries proved to be a viable, cost-effective tool.
• Unexpected mortality was observed in mixed cultures of Thermodesulfatator atlanticus and Methanocaldococcus villosus.
• T. atlanticus showed vigorous growth near the gas-liquid interface under high pressure and temperature.
• Numerical modeling predicted quasi-stationary conditions at the growth site.

Conclusions:

• Microcapillaries are a practical and affordable alternative for extremophile research.
• Environmental conditions, particularly gas concentrations and pH gradients, significantly impact extremophile survival and growth.
• Further research is needed to optimize microcapillary-based studies for extremophiles.