Aims: Phosphate is an essential nutrient required for plant growth, but its solubility in the soil is relatively low (0.1%). Microbes can dissolve phosphate to meet crop requirements. This study aimed to isolate phosphate solubilizing bacteria from indigenous microorganisms (IMO) of cow rumen. Methodology and results: The selection of isolates on a Pikovskaya medium was using a clear zone index and a spectrophotometer for phosphate solubilization measurements. Hypersensitivity was tested on tobacco leaves and tested antagonists within isolates. The results found that four selected isolates had the highest phosphate dissolving potential, namely, MTA1, SMAD1, SMAD2, and SMAD3. The culture of selected isolates on plate media showed that the morphological characters of the four colonies are the same. They had round form (circular), the edge of the colony were smooth, flat elevation, white and cream color. Isolate MTA1 had the highest phosphate solubilizing activity compared to the others. The isolate that showed the highest phosphate solubilizing activity were identified based on 16S rRNA gene. The result of molecular identification showed that strain MTA1 was closely related to Lactobacillus plantarum with a similarity level of 99%. L. plantarum performed the highest ability to form a clear zone (7.66 mm). The highest concentration of soluble phosphate was observed on day 5 (278.42 mg/L). Conclusion, significance, and impact of the study Lactobacillus plantarum which was isolated from the IMO of cow rumen in East Java, Indonesia was identified as one of the phosphate solubilizing bacteria that are useful for the development of eco-friendly biofertilizer. The application of phosphate solubilizing microbes can be used to increase the soil fertility.
Fertilizers--microbiology ; Indonesia (East Java)