Species-specific glucose mineralization in artificial soil: insights from Bacillus subtilis and Streptomyces cinnamoneus mono- and co-cultures

Soil microbes play a critical role in carbon (C) cycling, yet assessing the direct impact of individual microbes and their interactions on C mineralization remains poorly understood due to confounding effects under fluctuated physicochemical and biological variables in natural soils. “Artificial soil systems” enable precise control in a uniform environment to directly quantify species-specific carbon cycling, yet it has not been sufficiently demonstrated whether they can isolate competitive dynamics and metabolic roles of individual microbes in C mineralization. This study used an artificial soil system to quantify glucose mineralization through a 14-day incubation experiment using Bacillus subtilis NBRC 101584 ( B. subtilis ) and Streptomyces cinnamoneus NBRC 13823 ( S. cinnamoneus ). In monoculture incubations, B. subtilis showed a rapid mineralization rate and high cumulative respiration, whereas S. cinnamoneus exhibited delayed and lower respiration. In co-culture incubation, cumulative respiration and DNA yields converged to that of the B. subtilis monoculture, and positively correlated with its relative abundance. In contrast, S. cinnamoneus markedly reduced soil pH despite lower respiration, highlighting a distinct ecological trade-off. These findings demonstrate that artificial soil systems provide the basis for directly evaluating species-specific mineralization patterns, competitive interactions, and microenvironmental modifications. This controlled approach provides an effective tool for elucidating microbial mechanisms regulating soil C dynamics. IMPORTANCE The role of individual soil microorganisms in carbon dynamics has long been obscured by the extreme complexity of natural soil environments. This study utilized a controllable artificial soil system to directly quantify the glucose mineralization rate using Bacillus subtilis NBRC 101584 ( B. subtilis ) and Streptomyces cinnamoneus NBRC 13823 ( S. cinnamoneus ). As a result, B. subtilis achieved fast glucose mineralization and elevated cumulative CO 2 production, in contrast to S. cinnamoneu s, which demonstrated slower mineralization and reduced overall respiration. These results highlight that artificial soil systems offer a critical and enabling framework for resolving species-specific mechanisms in soil carbon cycling.