Pikovskaya’s agar plates for phosphate solubilisation

I agree, let them grow on Pikovskaya's, maybe add an insoluble source of desired phosphate (e.g. hydroxyapatite) and measure phosphate in supernatants. For protocols see here:

https://www.researchgate.net/post/What_is_an_effective_method_to_measure_soluble_phosphate_high_concentration_in_wastewater

My research also based on phosphate solubilizing bacteria(PSB). There are few ways to determine Phosphate solubilizing activity(PSA).

• Colony diameter, clear zone, solubilization index (SI) and solubilization efficiency of isolated bacteria.

Sterile PKV medium was poured in to sterile petri plates and plates were allowed to solidification. Pure cultures of isolated colonies were obtained by performing isolation streak method. Inoculated plates were incubated at 30°C for 6 days. Clear zones were formed due to the solubilization of insoluble phosphate by PSB. Then colony diameter and diameter of clear zone of each colony was measured and SI value was calculated by using following equation.

SI=(Colony diameter + Halozone diameter )/(Colony diameter)

SE=( Halozone diameter )/(Colony diameter)×100

PVK Medium (Pikovskaya, 1948)

Glucose 10.0 g

Yeast Extract 0.5 g

Calcium phosphate 5.0 g

Ammonium sulphate 0.5 g

Potassium chloride 0.2 g

Magnesium sulphate 0.1 g

Manganese sulphate 0.0002 g

Ferrous sulphate 0.0002 g

Agar 15 g

Distilled water 1 L

pH 7.0

• Quantitative measurement of phosphate solubilization

The isolated bacterial strains were grown in sterilized liquid PVK medium (20 ml) at 30°C for 24 hours with continuous shaking at 150 rpm. The optical densities of bacterial suspensions were measured and the volume that gives 108 were calculated for each strain. Bacterial suspension (1 x 108 CFU mL-1) was then transferred into a 500 mL flask containing sterilized liquid PVK medium (200 mL) and incubated for 11 days with continuous shaking at 30°C. Sterilized uninoculated medium served as a control. Aliquot (5.0 mL) from each culture and control was taken at one,two, four, six, eight, nine,ten and eleven days for determination of pH and soluble phosphate.

Then suspension was centrifuged at 10000 rpm for 15 minutes. Supernatant was used to determine amout of soluble phosphours released into the medium using phosphomolybdate blue color method and pH of each supernantant was measured.

pH become decreases day by day and you can plot the graph of Days Vs pH . pH is directly proportional to PSA. phosphomolybdate blue color method is very accurate. But it takes more time.

Thank you.

Thank you very much dear sir for this kind of response