Actinobacteria is a phylum of Gram-positive bacteria with high guanine and cytosine content in their DNA.[1] The G+C content of Actinobacteria can be as high as 70%, though some may have a low G+C content.[2] They can be terrestrial or aquatic.[3] Although understood primarily as soil bacteria, they might be more abundant in freshwaters.[4] Actinobacteria is one of the dominant bacterial phyla and contains one of the largest of bacterial genera, Streptomyces.[5] Analysis of glutamine synthetase sequence has been suggested for phylogenetic analysis of Actinobacteria.[6]