The microbial community composition and function of three self-heating maize straw composts were compared by integrated meta-omics. The results revealed that the fungal communities were primarily dominated by the phylum Ascomycota (>90%) regardless of different nitrogen sources, which were exclusively composed of the Thermomyces, a genus of hemicellulose degraders. The bacterial community composition was affected by the addition of nitrogen sources, as the abundance of the Actinobacteria increased, while the Proteobacteria and Bacteroidetes decreased. Various hemicellulases and cellulases were detected in the composts, and the major xylanase secreted by Thermomyces lanuginosus was always present, revealing that it was the dominant fungus in hemicellulose hydrolysis and that bacteria and fungi might synergistically degrade lignocellulose. Thus, microbial communities in composts may develop a simple and stable structure of a dominant fungal species and limited numbers of bacterial species under the selective pressure of high temperature and maize straw as starting materials. (C) 2015 Elsevier Ltd. All rights reserved.