The relationship between the actinobacterial community composition and environmental factors was assessed in two soil horizons in the summer and winter seasons using a taxonomic microarray and cloning-sequencing of 16S rRNA genes. The community differing significantly between horizons and seasons was characterized by high incidence (80%) of a separate clade sharing an ancestral node with Streptosporangineae, and, in the upper horizon, also of the genus Mycobacterium.