Toleransi Salinitas Dari Bakteri Penambat Nitrogen Yang Diisolasi Dari Perairan Laut Pulau Seribu Dan Kemampuannya Dalam Melarutkan Fosfat

Isolates of nitrogen fixing bacteria (Rhizobium, Azotobacter and Azospirillum) were isolated from coastal mangrove in Pulau seribu. The aims of this experiment is to find out isolates of nitrogen fixing bacteria which were tolerant to salinity and able to dissolve inorganic phosphate. The isolates can be used as biofertilizer for improving crop yield in coastal agricultural field. 14 isolates of nitrogen fixing bacteria (Rhizobium, Azotobacter and Azospirillum) from coastal mangroves were tested for their ability to grow at media which were contained 1 persen, 2 persen and 3 persen of NaCl consentration and for their ability to dissolve inorganic phosphate ((Ca3PO4)2 and rock phosphate). The result showed that bacterial numbers indicated by viable counts were ranged from 0,05 104- 64 104 for Rhizobium, 0,5 104– 148 104 for Azotobacter and 0,02 104- 65 104 for Azospirillum. There were 9 isolates of Rhizobium and 4 isolates of Azotobacter which were tolerant to grow at 1 persen, 2 persen and 3 persen NaCl. From a total of 14 rhizobial isolates tested for phosphate solubilization by the formation of visible dissolution halos on agar plates, 12 and 6 of the isolates of Rhizobium solubilized (Ca3PO4)2 and rock phosphate, respectively. There were 2 isolates of Azospirillum and 5 isolates of Azotobacter solubilized (Ca3PO4)2 and rock phosphate. In the liquid Pikovskaya medium, nitrogen fixing bacteria released an average 1,41 – 8,52mg L-1 of P after 3 days incubation. Berkala Penelitian Hayati (Journal of Biological Researches) No. 4C. April 2011. P: 7-12.