Specific response of soil fungi and bacteria to carbon availability indicated by the transformation dynamics of soil amino sugars

摘要

Microorganisms in terrestrial ecosystems are usually in dormancy due to carbon starvation. Labile carbon sources enhance microbial assimilation of extraneous N but carbon availability regulates the specific response of fungus and bacterium populationsas well as the community structure of the microbiota. The dynamics of ~(15)N incorporation into fungus-derived glucosamine (GluN) and bacterium-originated muramic acid (MurN) can reflect the ever-active response of these two populations during the immobilization of extraneous ~(15)N-NH_4~+. For glucose amendment, the more rapid ~(15)N transformation into MurN than GluN indicated that bacteria were more competitive initially than fungi, but the successional growth of fungi was dominant over time, resulting in the continuous increase of ~(15)N enrichment in GluN. However, the addition of maize stalk was of more benefit to the reproduction of fungi and retarded the rapid growth of bacteria in soil, thus the ~(15)N enrichment in GluN and MurN was increased initially and then became stable. After being incubated with maize stalks for 18 weeks, the assimilation capacity of reproduced fungi to simple substrates was enhanced while that of bacteria was weakened in soil microcosms. The findings indicate that soil fungi and bacteria respond to different carbon sources specifically.