Inclusion of Bromothymol Blue Dye in Conventional Pikovskaya’s Medium for Rapid Screening of Phosphate Solubilizing Bacteria

The present study developed a modified plate assay and compared with previously reported techniques for the isolation and screening techniques of P-solubilizing bacteria. The newly developed plate assay is based on the inclusion of bromothymol blue (BTB), an acid-base indicator dye, which improves visualisation of halo zone formation surrounding the colonies on agar plates. Phosphate released in liquid medium showed a significant correlation (R = 0.91248) with the halo zone. This approach enhanced the visualisation of possible phosphate solubilizers and may be used to identify weak acid producers. The modified medium with BTB showed increased sensitivity and promising results, with all 9 isolates exhibiting clear halo zone formation, positively correlated with quantified phosphate. As a result, it is anticipated that using this qualitative analysis-based protocol will be salutary for the rapid screening of bacteria that solubilize phosphate.