Isolation and Characterization of soil bacteria from Barishal and Jhalokathi series of Bangladesh

This study was conducted to isolate, quantify, and characterize bacterial populations from agricultural soils of Barishal and Jhalokathi regions of Bangladesh. Soil samples were collected from the surface layer (0–15 cm) under aseptic conditions and processed using standard microbiological techniques, including serial dilution, spread plate method, and staining procedures. The total viable bacterial count was found to be 7.6×10 CFU/g in Barishal soil and 9.4×10 CFU/g in Jhalokathi soil, indicating a high microbial load in both regions. A total of eight distinct bacterial colonies were isolated from Barishal soil, whereas six distinct colonies were obtained from Jhalokathi soil. Colony characteristics showed considerable variation in size, pigmentation (white, pink, and yellow), form (circular, irregular, rhizoid), margin (entire, lobate, serrate, undulate), and elevation (flat, raised, umbonate). Morphological and staining analyses revealed the presence of both rod-shaped and cocci bacteria with single and chain arrangements. The isolates included both Gram-positive and Gram-negative bacteria, with several exhibiting spore-forming and capsule-forming abilities. However, all isolates were non-acid fast. The findings indicate that both soils harbor diverse and heterogeneous bacterial populations with significant physiological and morphological variability. This study provides valuable baseline information on soil bacterial diversity and contributes to the understanding of microbial ecology in Bangladesh agricultural soils.