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With the aim of studying the biodiversity and the antimicrobial potential of three rare actinobacterial genera: Planomonospora, Saccharothrix and Actinophytocola in Algerian Saharan soils, 65 isolates representing the morphological characteristics of Planomonospora (17) and Saccharothrix/Actinophytocola (48) were isolated from 13 soil samples at 4 different sites in southern Algeria. The isolation was carried out on humic acid-vitamin agar medium using dilution techniques with several soil pretreatment and antibiotics as selective agents. Based on preliminary examination, 21 out of 65 isolates were kept for further investigations: Planomonospora (10) and Saccharothrix/Actinophytocola (11). 16S rRNA gene sequence analysis and DNA/DNA hybridization (DDH) showed that four strains, isolated from two different sites: Béchar (PM3) and Ghardaïa (MB20 and MB27), were found to represent four novel species. Moreover, they formed a distinct phyletic line within the clade of the most related genus: PM3 (DSM 46752T) with Planomonospora, MB27 (DSM 46885T) and MB46 (DSM 46886T) with Saccharothrix and MB20 (DSM 46746T) with Actinophytocola. While many novel species belonging to the genera Saccharothrix have been isolated from Algerian Saharan soils, this is the first report to describe the isolation of new species of Planomonospora and Actinophytocola from this extreme habitat. An assessment of the antimicrobial properties of the actinobacterial strains showed that 38 out of 65 have moderate to strong antimicrobial activities against Gram positive bacteria, fungi or yeasts. These results indicated the importance of further exploration of rare Saharan Actinobacteria for potentially original antimicrobial agents. [ABSTRACT FROM AUTHOR]