Aktivitas Pelarutan Fosfat Aktinobakteri asal Tanah dan Endofit Tanaman

Abstract

Aktinobakteri memiliki kemampuan meningkatkan ketersediaan fosfat di tanah yang tersedia untuk tanaman melalui mekanisme pelarutan dan mineralisasi fosfat. Aktinobakteri dari beragam kondisi lingkungan telah diisolasi dan dikoleksi di Laboratorium Mikrobiologi IPB, namun belum diketahui kemampuannya dalam melarutkan fosfat. Penelitian ini bertujuan mengkarakterisasi dan menguji aktivitas pelarutan fosfat isolat aktinobakteri asal tanah dan endofit tanaman. Tahapan penelitian meliputi, pengujian aktivitas pelarutan fosfat secara kualitatif dan kuantitatif pada periode inkubasi 7, 10, dan 14 hari pada media Pikovskaya yang mengandung trikalsium fosfat, pengukuran pH filtrat kultur, penapisan potensi isolat serta karakterisasi morfologi koloni isolat terpilih. Sembilan isolat aktinobakteri mempunyai aktivitas pelarutan fosfat yang beragam. Uji kualitatif menunjukkan nilai IPF terbesar dimiliki XGS 4. Hasil uji konsentrasi fosfat anorganik terlarut oleh XGS 7 lebih tinggi dibandingkan XGS 4 yang memiliki nilai IPF lebih besar. Filtrat kultur mengalami penurunan pH dari netral ke arah masam (4-5). Empat isolat terpilih memiliki karakteristik morfologi yang mirip genus Streptomyces. Studi ini menunjukkan aktinobakteri asal tanah dan endofit tanaman memiliki kemampuan melarutkan fosfat anorganik.

Actinobacteria can increase the availability of phosphorus (P) in the soil through phosphate solubilizing and mineralization activities, and the available P will be absorbed by the plants. Actinobacteria have been isolated from various environments and collected in Microbiology Laboratory IPB, but their capability in solubilizing phosphate is still unknown. This study aimed to characterize and examine the phosphate-solubilization activity of actinobacteria isolated from soil and plant as endophytes. The activity of actinobacteria in solubilizing-phosphate was measured both qualitatively and quantitatively. Phosphate solubilization assay was conducted after incubation periods of 7, 10, and 14 days on Pikovskaya media containing tricalcium phosphate. To predict the mechanism of phosphate solubilization, the pH of the culture filtrate was measured throughout the experiment. Morphological characterization was conducted for the selected isolates. Various phosphate solubilization activities were found for the nine actinobacteria isolates examined. Qualitative tests revealed that XGS 4 had the highest IPF values. Meanwhile, based on dissolved inorganic phosphate concentration, XGS 7 showed to have higher activity than XGS 4 which was previously known to have a greater IPF value. Over the period of incubation, the pH of the culture has changed from neutral to acidic (4-5). The four selected isolates had morphological characteristics similar to the Streptomyces genus. This study shows that actinobacteria from soil and plant as endophytes can solubilize inorganic phosphate.