Diversity of actinomycetes isolated from Challenger Deep sediment (10,898 m) from the Mariana Trench.

Thirty-eight actinomycetes were isolated from sediment collected from the Mariana Trench (10,898 m) using marine agar and media selective for actinomycetes, notably raffinose-histidine agar. The isolates were assigned to the class Actinobacteria using primers specific for members of this taxon. The phylogenetic analysis based on 16S rRNA gene sequencing showed that the isolates belonged to the genera Dermacoccus, Kocuria, Micromonospora, Streptomyces, Tsukamurella and Williamsia. All of the isolates were screened for genes encoding nonribosomal peptide and polyketide synthetases. Nonribosomal peptide synthetase sequences were detected in more than half of the isolates and polyketide synthases type I (PKS-I) were identified in five out of 38 strains. The Streptomyces isolates produced several unusual secondary metabolites, including a PKS-I associated product. In initial testing for piezotolerance, the Dermacoccus strain MT1.1 grew at elevated hydrostatic pressures.