Exploring Bacterial Diversity through Isolation and Characterization of Jamalpur and Sonatala Soil Series from Jamalpur District

Abstract Soil bacterial communities are essential contributors to nutrient cycling, organic matter decomposition, and overall soil fertility. This study aimed to isolate, enumerate, and characterize bacterial populations from agricultural soils of Jamalpur and Sonatala, Bangladesh. Topsoil samples (0–15 cm) were collected aseptically and subjected to serial dilution, followed by spread plate inoculation on nutrient agar to obtain pure bacterial cultures. Morphological characterization included assessment of colony size, form, margin, elevation, and pigmentation, while cellular features were analyzed using simple, negative, Gram, capsule, spore, and acid-fast staining techniques. A total of seven and six distinct bacterial colonies were isolated from Jamalpur and Sonatala soils, respectively. The isolates displayed diverse morphologies, including rod-shaped and cocci forms with single and chain arrangements. Both Gram-positive and Gram-negative bacteria were present, with several exhibiting spore- and capsule-forming abilities, while all isolates were non-acid fast. Colony size, pigmentation, and structural diversity reflected metabolic heterogeneity and adaptability under varying soil conditions. The total bacterial counts were 7. 5×10⁷ CFU/g soil for Jamalpur and 7. 4×10⁷ CFU/g soil for Sonatala, indicating active and resilient microbial populations. The dominance of spore-forming Bacillus species and the presence of other Gram-negative bacteria suggest ecological significance in soil nutrient dynamics and potential applications in sustainable agriculture. These findings provide insights into microbial diversity in Bangladeshi soils and form a basis for further functional and molecular characterization.