<p>This study investigates the use of <i>Bacillus megaterium</i>, an alkali-resistant, calcite-precipitating bacterium, to enhance the mechanical performance of concrete. Bacterial strains were isolated and introduced into the cement concrete mix at concentrations of 10⁶, 10⁷, and 10⁸ cfu/mL. The bacteria, known for high urease activity, facilitated the precipitation of calcium carbonate (CaCO₃) in the form of calcite, contributing to crack healing and matrix densification. Concrete specimens were tested for compressive, tensile, and flexural strength at 7, 28, 56, 90, and 180 days of curing. Microstructural characterization was conducted using scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). Results showed an increase of up to 15% in compressive strength compared to control specimens, with the 10⁷ cfu/mL concentration yielding the most significant and consistent improvements. The SEM and EDS confirmed dense microstructures and increased Ca and O content in bacterial concrete. Compared to earlier studies, this research highlights the importance of optimizing bacterial concentration to maximize performance. The findings underscore the potential of microbial concrete to enhance durability, reduce cement usage, and contribute to environmentally sustainable construction practices.</p>