Abstract
Marine-derived actinomycetes have demonstrated an ability to produce novel compounds with medically relevant biological activity. Studying the diversity and biogeographical patterns of marine actinomycetes offers an opportunity to identify genera that are under environmental pressures, which may drive adaptations that yield specific biosynthetic capabilities. The present study describes research efforts to explore regions of the Atlantic Ocean, specifically around the Madeira Archipelago, where knowledge of the indigenous actinomycete diversity is scarce. A total of 400 actinomycetes were isolated, sequenced, and screened for antimicrobial and anticancer activities. The three most abundant genera identified were Streptomyces, Actinomadura, and Micromonospora. Phylogenetic analyses of the marine OTUs isolated indicated that the Madeira Archipelago is a new source of actinomycetes adapted to life in the ocean. Phylogenetic differences between offshore (>100 m from shore) and nearshore (< 100 m from shore) populations illustrates the importance of sampling offshore in order to isolate new and diverse bacterial strains. Novel phylotypes from chemically rich marine actinomycete groups like MAR4 and the genus Salinispora were isolated. Anticancer and antimicrobial assays identified Streptomyces, Micromonospora, and Salinispora as the most biologically active genera. This study illustrates the importance of bioprospecting efforts at unexplored regions of the ocean to recover bacterial strains with the potential to produce novel and interesting chemistry.
Highlights
Marine actinomycetes have proven to be an important source of novel secondary metabolites, as well as a promising source of pharmaceutically important agents (Magarvey et al, 2004; Jensen et al, 2005a,b; Lam, 2006; Prudhomme et al, 2008; Asolkar et al, 2009; Rahman et al, 2011; Subramani and Aalbersberg, 2012)
Further evidence for the effect of biogeography and ecological adaptations on the diversity of microorganisms has been observed by the dispersal limitations that led to the establishment of endemic, microdiverse populations of Prochlorococcus (Martiny et al, 2009), as well as the fact that numerous bacteria show a limited distribution within specific habitat types (Nemergut et al, 2011)
The genus Salinispora is represented by only one Operational Taxonomic Units (OTUs), even though we know that two Salinispora species (Salinispora pacifica and S. arenicola) were isolated from the collected sediment
Summary
Marine actinomycetes have proven to be an important source of novel secondary metabolites, as well as a promising source of pharmaceutically important agents (Magarvey et al, 2004; Jensen et al, 2005a,b; Lam, 2006; Prudhomme et al, 2008; Asolkar et al, 2009; Rahman et al, 2011; Subramani and Aalbersberg, 2012). Different environmental pressures may drive bacteria to adapt to a certain location These bacteria may harbor specific genes responsible for the synthesis of large multienzymatic compounds like polyketides and non-ribosomal peptide, or hybrids of both (Penn et al, 2009; Bose et al, 2014). The actinomycete diversity from Atlantic Ocean sediments is highly unexplored (Weyland, 1969; Walker and Colwell, 1975; Williams et al, 1999; Fiedler et al, 2005) and some isolation studies have resulted in the isolation of several genera, including Nocardia, Micromonospora, Microbispora, and Streptomyces, from sediments collected in the Chesapeake Bay and North Sea (Weyland, 1969, 1984; Takizawa et al, 1993). Like deep sediments of the Macaronesia region which is influenced by Saharan debris flow, have been a good source of Streptomyces and Rhodococcus genera (Stach et al, 2003)
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