Actinomycetes are among the most important sources for novel natural compounds. Recent efforts in actinomycetes bioprospecting have focused on unique environments to increase the probability of finding structurally novel secondary metabolites [1]. Antarctica is one of the most pristine environments. The diversity of Antarctic benthic ecosystems is expected to be a reservoir for unique communities, partly due to geographical isolation and the harsh environmental conditions [2]. The aim of this study is to investigate the biosynthetic potential of Antarctic actinomycetes to produce bioactive natural compounds and correlate their bioactivity with the uniqueness of the environment.

Marine sediment samples were collected from six locations in Antarctica with depths ranging from 140 to 1150 m. The isolation protocol was stepwise adapted by testing different parameters, such as sample acclimatization, pH, salinity, temperature, and culture media. In total, nine filamentous actinomycetes, including species from the genera Streptomyces, Nocardiopsis, Micromonospora, and several non-actinobacterial microorganisms were isolated. The actinomycetes were cultivated in ten different media and antimicrobial activity was assessed against a panel of test strains. Eight strains showed bioactivity against at least one test strain. A prioritized sub-set of strains was selected for genome sequencing. Phylogenomic analyses were carried out using the Type Strain Genome Server [3] to identify closely related non-Antarctic neighbours. Genome analysis was completed for two isolates: Micromonospora ureilytica DB10_83 and Streptomyces sp. DSM 109305, the latter being a potential new species.

In summary, novel Antarctic actinomycetes were isolated and proved to produce bioactive compounds. In further studies co-cultivation of the Antarctic actinomycetes and non-actinobacterial co-isolates will be performed. Metabolic analyses will be carried out to investigate the interaction and biosynthetic profile of Antarctic microorganisms.

[1] R. Subramani, D. Sipkema, Mar Drugs. 17 (2019).

[2] S. Soldatou et al., Mar Drugs. 19 (2021).

[3] J. P. Meier-Kolthoff, M. Göker, Nat Commun. 10 (2019).