Archaea and their interactions with bacteria in a karst ecosystem

Area of Science:

• Microbial Ecology
• Geomicrobiology
• Cave Science

Background:

• Karst ecosystems cover 15-20% of Earth's land surface, yet their microbial ecology is poorly understood.
• Understanding subsurface microbial communities is vital for comprehending ecosystem function and stability.

Purpose of the Study:

• To investigate the microbial ecology of Heshang Cave and its overlying soils.
• To identify key microbial taxa and their ecological roles, particularly in nitrogen cycling.
• To explore microbial community structure and interactions within karst environments.

Main Methods:

• Sampling of diverse karst niches: weathered rock, sediment, drip water, and overlying soils (forest, farmland, pristine).
• High-throughput sequencing of the 16S rRNA gene (V4-V5 region).
• Multivariate statistical analysis to determine community composition and predictor variables.

Main Results:

• Archaeal communities were dominated by Thaumarchaeota; bacterial communities by Actinobacteria.
• Distinct predictor groups were identified inside (e.g., Thermoplasmata, Nitrosopumilaceae) and outside (e.g., Candidatus Nitrososphaera) the cave, correlated with different environmental factors (e.g., NH4+, pH, Ca2+).
• Chemolithoautotrophic archaea and bacteria were identified as keystone taxa involved in nitrogen cycling and maintaining ecosystem stability.

Conclusions:

• Karst microbial communities exhibit unique compositions and ecological roles, with archaea playing a significant part in nitrogen cycling.
• Microbial network structures varied between archaeal and bacterial communities, with tighter networks in archaea.
• This research enhances understanding of microbial dark matter in subsurface karst ecosystems and highlights the importance of archaeal functions.