**1. Introduction**

New antibiotics in general and new types of antibiotics in particular are urgently needed to counter the increasing number of pathogenic bacteria resistant against present antibiotics [1]. Traditionally, actinobacteria have been the most prolific sources of novel antibiotics scaffolds, because many of the most important antimicrobials, such as β-lactames, tetracyclines, rifamycins, aminoglycosides, macrolides and glycopeptides, were discovered from them [2]. However, high rates of rediscovery of known compounds are observed when screening traditional producers, and the discovery of new molecules is getting more and more challenging. Therefore, current screening programs concentrate on discovering and isolating rare genera of microorganisms. Rare actinobacteria are regarded as actinomycete strains whose isolation frequency is much lower than that of *Streptomyces* spp. isolated by conventional methods. These rare actinobacteria are assessed as a potential storehouse for novel antibiotics due to their unique potential to produce novel metabolites [3,4].

The approach of utilizing rare organisms is accompanied by the screening of organisms from underexplored environments. Rare actinomycetes are widely distributed in terrestrial and aquatic ecosystems and the number of isolated genera and species is quickly increasing due to recently

developed taxonomically selective isolation procedures, cultivation methods and genetic techniques [5]. We isolated the new strain *Streptomonospora* sp. M2 from a Wadden Sea sample collected at a beach near Cuxhaven, Germany, which is an underexplored environment. Since crude extracts of *Streptomonospora* sp. M2 showed inhibitory activity against Gram-positive indicator organisms including *Micrococcus luteus, Staphylococcus aureus* and *Bacillus subtilis*, the strain was selected for a detailed analysis of its bioactive secondary metabolites, yielding the isolation and structure elucidation of two new thiopeptide antibiotics (Figure 1) with an uncommon activity profile.

**Figure 1.** Chemical structure of **1** and **2**.
