Diversity, abundance, and enzyme activity of Actinomycetes recovered from tropical freshwater sediment for potential biotechnological applications

Abstract

Abstract. Ajuzieogu CA, Onu GO, Onyekachi EO. 2025. Diversity, abundance, and enzyme activity of Actinomycetes recovered from tropical freshwater sediment for potential biotechnological applications. Asian J Trop Biotechnol 22: 23-29. Actinomycetes are a set of Gram-positive bacteria known for their ability to produce a wide variety of secondary metabolites, including antibiotics and enzymes. This study assessed the diversity of Actinomycetes in tropical freshwater sediment and their amylase production potential. Sediment samples were obtained from four points (shore, middle, downstream, and upstream) within a tropical freshwater system. Physicochemical analysis, bacterial isolation, and enumeration were conducted following standard methods. Tentative identification of isolates was done using culture-dependent methods. Results showed that the sediment samples belonged to the loam soil textural class; upstream sediment recorded the highest pH and total organic carbon content (6.3 and 0.98%, respectively), and middle sediment recorded the highest nitrate content (9.632 mg/kg). In comparison, sediment from the shore recorded the lowest pH (5.70) and highest phosphate level (8.716 mg/kg). The highest total culturable heterotrophic counts were observed in sediment from the middle point. A total of 9 Actinomycetes species were recovered, out of which six (6) were positive for amylase activity. The isolates were tentatively identified as Micrococcus spp., Streptomyces sp., Streptomyces coelicolor, and Actinomyces viscosus. This study revealed that tropical freshwater sediments harbor a diverse and abundant bacterial community, particularly Actinomycetes, with possible potential for biotechnological exploration.