Interactive Effects between the Bio-Reactivity Continuum and the Ecological Role of Soluble Microbial Products during Biotransformation

In this study, well-controlled bioassays were performed to investigate degradation behaviors and bacterial responses during soluble microbial product (SMP) transformation. Reactivity continuum (RC) modeling was first used to mimic the transformation behaviors of the SMP and it revealed that the subpools with higher bio-reactivity (e.g., k >= 0.01 h(-1)) accounted for a higher proportion under aerobic (5.43%) than anoxic (0.24%) conditions. Size exclusion chromatography with continuous organic carbon detection analysis indicated that hydrophobic organic compounds were substantially more degradable under aerobic than anoxic conditions. Sloan's neutral model results showed that Herbaspirillum and Acinetobacter were consistently selected to be present at higher frequencies than the model prediction under both conditions, suggesting their exceptional metabolic capability of the SMP. Dominant deterministic assembly coupled with higher bacterial diversity and functional redundancy was observed in the microbiota under aerobic conditions, supporting the faster SMP transformation (i.e., higher bio-reactivity). Furthermore, the differential bio-RC led to distinct bacterial interaction patterns of the co-occurring species, shifting from dominant competition (aerobic) to dominant cooperation (anoxic). Nonetheless, the keystone taxa under both conditions were mainly shaped by deterministic selection. This work offers ecological insights into the interactive effects between the bio-RC and bacterial responses during SMP biotransformation.