Abstract
tIn the present study, the ecological distribution of marine Actinobacteria isolated from seamount andnon-seamount stations in the Tyrrhenian Sea was investigated. A collection of 110 isolates was analyzedby Automated Ribosomal Intergenic Spacer Analysis (ARISA) and 16S rRNA gene sequencing of represen-tatives for each ARISA haplotype (n = 49). Phylogenetic analysis of 16S rRNA sequences showed a widediversity of marine isolates and clustered the strains into 11 different genera, Janibacter, Rhodococcus,Arthrobacter, Kocuria, Dietzia, Curtobacterium, Micrococcus, Citricoccus, Brevibacterium, Brachybacteriumand Nocardioides. Interestingly, Janibacter limosus was the most encountered species particularly inseamounts stations, suggesting that it represents an endemic species of this particular ecosystem. Theapplication of BOX-PCR fingerprinting on J. limosus sub-collection (n = 22), allowed their separation intoseven distinct BOX-genotypes suggesting a high intraspecific microdiversity among the collection. Fur-thermore, by screening the biotechnological potential of selected actinobacterial strains, J. limosus wasshown to exhibit the most important biosurfactant activity. Our overall data indicates that Janibacter isa major and active component of seamounts in the Tyrrhenian Sea adapted to low nutrient ecologicalniche.