Organic sulfur metabolisms in hydrothermal environments

Area of Science:

• Biogeochemistry
• Microbial Ecology
• Extreme Environments

Background:

• Organic sulfur cycling is well-studied in cold anaerobic environments but less so in hydrothermal systems.
• Deep-sea hydrothermal vents represent unique extreme environments with distinct geochemical conditions.
• Understanding microbial metabolism is key to comprehending biogeochemical cycles in these systems.

Purpose of the Study:

• To evaluate energy yields for potential organic sulfur-based metabolisms in deep-sea hydrothermal environments.
• To predict fluid compositions resulting from mixing hydrothermal fluid with bottom seawater.
• To assess the influence of metabolic strategy and sulfur compound activity on energy yields.

Main Methods:

• Utilized recently published thermodynamic data for aqueous alkyl thiols and sulfides.
• Employed geochemical mixing models to simulate end-member hydrothermal fluid and seawater mixing.
• Calculated energy yields for various metabolic strategies including aerobic respiration and anaerobic metabolisms.

Main Results:

• Aerobic respiration provides high energy yields at lower temperatures, but is limited by oxygen availability at high temperatures.
• Nitrite reduction to N₂ shows the highest energy yields at temperatures above ~40 °C.
• Sulfate reduction and other anaerobic sulfur metabolisms yield lower but feasible energy, with metabolic strategy being more critical than specific organic sulfur compounds.

Conclusions:

• Organic sulfur-based metabolisms are likely prevalent in deep-sea hydrothermal vent microbial communities.
• Multiple metabolic strategies can be exergonic within the modeled mixing regime.
• Geochemical conditions and microbial metabolic capabilities interact to shape sulfur cycling in hydrothermal vents.