Fig. 2

Isolation, screening, and identification of PSB and ACP-producing bacteria. a Isolation and qualitative screening of CaCO₃-solubilizing and ACP-producing bacteria. b A phylogenetic tree based on 16S rDNA gene sequence analysis shows the relationship of B. sonorensis strain ACP2 with reference strains (NCBI GenBank) constructed using the neighbor-joining method with the aid of the MEGA X program. c Gram-stain of the B. sonorensis strain ACP2 (using magnification, oil lens 100 x). d SEM micrograph of B. sonorensis strain ACP2 showing cell morphology at a magnification of 5000 and 10,000 × with 15 kv. e Cultural feature of B. sonorensis strain ACP2 agar plate