The addition of species of Trichoderma to compost is a widespread technique used to control different plant diseases.The biological control activity of these species is mainly attributable to a combination of several mechanisms of action, which may affect the microbiota involved in the suppressiveness of compost.This study was therefore performed to determine the effect of inoculation of T.harzianum on compost,focusing on bacterial community structure (16S rRNA) and chitinase gene diversity.