【Objective】 Soil profile is a model system for deciphering the formation and maturation of organic matter-centric fertility. However, the physiological metabolic potential of the soil profile microbial community and the mechanism of its transformation of labile carbon are not clear.【Method】The metabolic mechanisms of soil microbial communities under exogenous carbon and nitrogen input scenarios were investigated by using 13C-labeled glucose and ammonium nitrate to cultivate soils in the surface (0~10 cm), middle (30~40 cm), and deep (90~100 cm) layers of a typical thin-layered black soil. The insoluble organic carbon (13C-SOC) synthesized by microbial growth and reproduction, 13CO2 produced by heterogeneous metabolism, the priming effect, the efficiency of 13C-carbon utilization, and their nitrogen limitation features were determined.【Result】The increase in soil respiration intensity after exogenous 13C-glucose addition was in the order of surface (3.2-fold), middle (11.3-fold), and deep soil (14.5-fold) compared to the control water treatment; the relative priming effect was 43.5%, 150.5%, and 267.0%; carbon utilization efficiency was 34.9%, 37.3%, and 32.9%, respectively. Approximately 45%~50% of glucose was isomerized and metabolized to 13CO2. Also, the number of soil microorganisms increased by about 85.0% in the surface and middle layers and 1.9 times in the deep layer while the 13C-SOC of insoluble cellular biomass synthesized by microorganisms using glucose was 111.6±11.7 mg kg-1 (surface soil), 119.5±3.4 mg kg-1 (middle soil), and 105.2±21.6 mg kg-1 (deep soil). However, the proportion of the total soil organic carbon, in descending order was 0.98% (surface layer) < 1.70% (middle layer) < 4.76% (deep layer). Interestingly, the 13C-SOC tended to increase after nitrogen addition although it was not statistically differentiated, however, it significantly suppressed the relative priming effect. High-throughput sequencing revealed that surface, middle, and deep soil microbial communities clustered independently regardless of carbon and nitrogen treatments under glucose addition conditions. Micrococcaceae were significantly increased in the surface soil and were probably the main contributor of organic carbon from insoluble microbial sources whereas Nocardioides were the main contributors of organic carbon from microbial sources in the middle and deep soil.【Conclusion】These results suggest that the deep soil, despite its lower diversity and abundance, can utilize exogenous and readily decomposable organic carbon to rapidly colonize and produce insoluble organic carbon of microbial origin and its total new carbon inputs were almost identical to those of the surface soil. Soil microbial communities in black soil profiles developed strong functional plasticity during long-term adaptation to geo-climatic variability, which provides an important basis for the stability of soil ecosystem structures and functions.