Divergent assemblage patterns of abundant and rare microbial sub-communities in response to inorganic carbon stresses in a simultaneous anammox and denitrification (SAD) system.

Inorganic carbon has profound influence on anammox system and distinct microbial communities play pivotal roles in nitrogen removal, yet little is known about the ecological patterns of abundant and rare sub-communities in response to inorganic carbon stresses in simultaneous anammox and denitrification systems. Here the aspects of community ecology of abundant and rare taxa under abiotic constraints were explored. Results showed that different IC/NH4 + -N ratios have significant influences on NH4 + -N and TN removal. Co-occurrence networks revealed that abundant and rare taxa present contrasting assemblage patterns and ecological strategies. Spearman's correlation indicated that environmental filtering had discrepancy influences on these two bacterial sub-communities. Moreover, rare taxa were the key regulators for NH4 + -N accumulation and NO2 - -N consumption. qPCR results indicated that nitrogen removal was mediated by multiple nitrogen transformation pathways. These findings collectively suggest that abundant and rare sub-communities have discrepant ecological patterns and provide insights into their structure-functional relationships.