Exploration of actinobacteria communities in seawater and sediments of mediterranean basin from Algerian coast displays hight diversity with new taxa and antibacterial potential

The biodiversity of actinobacteria in the Mediterranean Sea habitat has drawn limited attention compared to that paid to terrestrial habitats. The work presented here focused on the biodiversity of culturable marine actinobacteria from sediments and seawater collected from the Algerian coast, and led to the identification of 114 actinobacterial isolates. The morphological study revealed higher actinobacterial diversity in sediment than in seawater. Fifty strains were selected for 16 S rRNAgene sequencing. The results revealed that the isolates belonged to ten different genera, Streptomyces (n = 17) and Micromonospora (n = 15) being the most dominant. The remaining actinobacterial isolates, identified as belonging to rare genera, included Nocardia (n = 5), Nocardiopsis (n = 3), Saccharothrix (n = 2), Rhodococcus (n = 2), Promicromonospora (n = 2), Nonomuraea (n = 2), Actinomadura (n = 1) and Saccharomonospora (n = 1). Interestingly, through 16 S rRNA sequence-based identification and phylogenetic analysis, two strains of the genus Streptomyces (MAT1 and MAS22) and a strain of the genus Nonomuraea (MAG8) both constituted a novel species. Screening of antibacterial activity of identified isolates against a panel of human pathogenic bacteria demonstrated that 36% of the isolates were active, particularly against Gram-positive bacteria. The ability to grow in the presence of NaCl and seawater revealed that 98% of the strains were halotolerant, with different levels of NaCl acceptance (from 3 to 13%) but no isolates required seawater to grow.