Exploration of the Bioactivity of Pigmented Extracts from Streptomyces Strains Isolated Along the Banks of the Guaviare and Arauca Rivers (Colombia)

Pigments are chemical compounds that impart color through mechanisms such as absorption, reflection, and refraction. While traditional natural pigments are derived from plant and insect tissues, microorganisms, including bacteria, yeasts, algae, and filamentous fungi, have emerged as promising sources for pigment production. In this study, we focused on pigment production by 20 Streptomyces isolates from our in-house actinobacteria strain collection, sourced from the Guaviare and Arauca Rivers in Colombia. The isolates were identified via 16S rRNA gene sequencing, and the bioactivities—including antioxidant, antibacterial, and cytotoxic properties—of their extracts obtained across four different culture media were assessed. Promising pigmented hydroalcoholic extracts demonstrating these bioactivities were further analyzed using LC-MS, leading to the annotation of a variety of pigment-related compounds. This study revealed that culture media significantly influenced both pigment production and bioactivity outcomes. Notably, anthraquinones, phenazines, and naphthoquinones were predominant pigment classes associated with cytotoxic and antimicrobial activities, while carotenoids were linked to antioxidant effects. For instance, S. murinus 4C171 produced various compounds exhibiting both cytotoxic and antioxidant activities. These findings highlighted a growth medium-dependent effect, as pigment production, coloration, and bioactivity outcomes were influenced by growth media. These results demonstrate the significant potential of Streptomyces isolates as sources of bioactive pigments for diverse applications.