A preliminary investigation of filamentous actinobacteria isolated from Algerian bee-collected pollen: diversity, characterization, and screening for extracellular enzyme production and antimicrobial activity.

Abstract

Actinobacteria, as one of the largest bacterial phyla, have the ability to produce various bioactive compounds with high biotechnological values, such as antibiotics and enzymes. This preliminary study aims to focus on the poorly studied diversity of actinobacteria associated with bee pollen and their antimicrobial and extracellular enzymatic activities. A total of 33 actinobacterial strains were isolated, morphologically and biochemically characterized, screened for extracellular enzyme production, examined with primary and secondary antimicrobial tests, and then clustered using UPGMA methods. The isolates formed six diversified clusters, with the majority producing extracellular hydrolytic enzymes, including proteases, amylases, and lipases. However, only five strains demonstrated antimicrobial activity in the primary screening. These five strains, namely A1, A6, A24, A27, and A28, were subsequently advanced to second screening for antimicrobial activity and identified by scanning electron microscopy and 16 S rRNA gene sequence analysis as Streptomyces spp. The strain A6 exhibited the strongest antibacterial and antifungal effects against S. aureus ATCC 25,923, B. subtilis ATCC 6633, and C. albicans ATCC 10,231, with inhibition zones of 70 mm, 64 mm, and 36 mm, respectively. This study demonstrates that bee pollen represents a promising source of actinobacterial strains, which have potential antimicrobial and enzymatic activities and provide valuable bioactive compounds for use in medical, food, and agricultural applications.