Geospatial variation in co-occurrence networks of nitrifying microbial guilds

Area of Science:

• Soil microbiology
• Biogeochemical cycles
• Microbial ecology

Background:

• Microbial communities drive nitrogen cycling in soil, with nitrification a key two-step process involving ammonia-oxidizing bacteria (AOB) and archaea (AOA), and nitrite-oxidizing bacteria (NOB).
• The spatial variation in nitrifier community structure is poorly understood, particularly the role of interactions between ammonia oxidizers and nitrite oxidizers.

Purpose of the Study:

• To investigate the nonrandom associations between ammonia-oxidizing (AO) and nitrite-oxidizing bacteria (NOB) lineages.
• To determine how these interactions and edaphic factors influence field-scale spatial patterns of nitrifying communities.

Main Methods:

• Quantified the abundance of ammonia-oxidizing archaea (AOA), ammonia-oxidizing bacteria (AOB), and Nitrospira and Nitrobacter NOB communities across a 44-hectare agricultural site.
• Employed network analysis and geostatistical modeling to reveal co-occurrence patterns and spatial distribution.
• Assessed associations between microbial abundances and edaphic factors.

Main Results:

• Nitrobacter NOB abundance correlated with AOB, while Nitrospira NOB correlated with AOA.
• Network analysis identified distinct modules of co-occurring AO and NOB groups in different areas, each associated with specific lineages and edaphic factors.
• Local nitrifier communities showed a high proportion of module-connecting nodes, suggesting adaptation to fluctuating soil conditions.

Conclusions:

• Biotic interactions between ammonia oxidizers and nitrite oxidizers significantly influence nitrifier community structure at a field scale.
• Edaphic factors and microbial co-occurrence patterns define distinct spatial niches for nitrifying communities.
• Network analysis is a valuable tool for understanding microbial interactions and niche partitioning in soil ecosystems relevant to management.