Isolasi, Seleksi, dan Karakterisasi Bakteri Pelarut Kalsium dari Batuan Kapur

NUUR FAIZAH, Ir. Ngadiman, M.Si., Ph.D. ; Agung Dian Kharisma, S.Pd.Si., M.Biotech., Ph.D.

2026 | Skripsi | MIKROBIOLOGI PERTANIAN

Kalsium merupakan unsur hara makro sekunder yang penting bagi pertumbuhan tanaman. Sebagian besar kalsium berada di alam dalam bentuk mineral yang sukar larut, sehingga memerlukan proses pelapukan. Bakteri pelarut kalsium berperan dalam mempercepat batuan karbonat dan meningkatkan ketersediaan kalsium di tanah. Penelitian ini bertujuan untuk mengisolasi, menyeleksi, dan mengkarakterisasi bakteri pelarut kalsium yang berasal dari batuan kapur. Sampel diambil dari batuan kapur, tanah di sekitar batuan kapur, dan rhizosfer tanaman pionir di batuan kapur yang ada di daerah Sentolo, Kulon Progo, Daerah Istimewa Yogyakarta. Isolasi dilakukan dengan media Deveze-Bruni, kemudian isolat diseleksi secara kualitatif berdasarkan pembentukan zona bening, dan secara kuantitatif berdasarkan kadar kalsium terlarut. Isolat terpilih dikarakterisasi berdasarkan sifat fenotipik (morfologi dan biokimia) serta diidentifikasi menggunakan sekuens gen 16S rRNA. Sebanyak tiga puluh isolat berhasil diisolasi dengan sembilan isolat menunjukkan kemampuan melarutkan kalsium. Empat Isolat dengan kemampuan pelarutan kalsium terbaik yaitu BK.06, BK.07, RB.07, dan TB.04 teridentifikasi sebagai Bacillus cereus, Bacillus proteolyticus, Bacillus albus, dan Bacillus subtilis dengan tingkat similaritas 99,17-99,86%. Hasil penelitian menunjukkan bahwa batuan kapur merupakan sumber potensial bakteri pelarut kalsium yang berpotensi dikembangkan sebagai agen hayati untuk meningkatkan ketersediaan unsur hara pada tanah.

Calcium is an essential secondary macronutrient for plant growth. Most naturally  occurring calcium exists in insoluble mineral form and therefore requires weathering before it becomes available for plant uptake. Calcium-solubilizing bacteria play an important role in accelerating weathering of carbonate rock and increasing calcium availability in soil. This research aimed to isolate, select, and characterize calcium-solubilizing bacteria from limestone. Samples were collected from limestone, soil surrounding limestone, and the rhizosphere of pioneer plants growing on limestone in Sentolo, Kulon Progo, Special Region of Yogyakarta. Isolation was performed using Deveze-Bruni medium, followed by qualitative screening based on halo-zone formation and quantitative screening based on soluble calcium concentration. Selected isolates were characterized based on their phenotypic (morphological and physiological characteristics) and identified through 16S rRNA gene sequencing. A total of thirty bacterial isolates were successfully obtained, of which nine exhibited calcium-solubilizing activity. Four isolates with the highest calcium-solubilizing capacity, namely BK.06. BK.07, RB.07, and TB.04 were identified as Bacillus cereus, Bacillus proteolyticus, Bacillus albus, and Bacillus subtilis with sequence similarities ranging from 99,17% to 99,86%. The resultsindicate that limestone is a promising source of calcium-solubilizing bacteria with potential; applications as biological agents to enhance nutrient availability in soil.

Kata Kunci : pelapukan batuan, bakteri, kalsium