Characterization of plant growth promoting bacteria isolated from water in mangrove ecosystem

Abstract

Mangrove is a unique and dynamic coastal ecosystem that is characterized by high salinity. It creates an ecological niche with varied environmental conditions and microbial communities, including Nitrogen Fixing Bacteria (NFB) and Phosphate Solubilizing Bacteria (PSB), which have great potential as Plant Growth Promoting Bacteria (PGPB). The study aims to obtain isolates of indigenous bacteria in a varied saline environment of the mangrove ecosystem that has the characteristics to promote plant growth or potential as PGPB. The bacteria were isolated from the mangrove ecosystem, which is the water of brackish zone using specific media with total plate count (TPC) technique. Furthermore, the PGPB characterization was analyzed using nitrogenase, ACC-deaminase, cellulose, salinity, Indole-3-Acetic Acid (IAA), dissolved P, and phosphatase (PME-ase) indicators in triplicate. The results showed that water salinity and pH in the mangrove ecosystem ranged from 1.12 to 1.73 ppt and 6.56 to 7.44, respectively. Furthermore, the bacteria isolated from water in the mangrove ecosystem produced IAA (6 isolates), dissolved P, acid and alkaline PMEase (11 isolates), saline tolerance (33 isolates), cellulose (14 isolates), nitrogenase (18 isolates), and ACC-deaminase (2 isolates) activity. One of the isolates (AZT5.1) identified as Bacillus cereus has potential as PGPB with the value of IAA production (18.61 ppm), 1.1cm P halo zone dissolved, 569.45 ppm dissolved P, 11.2 μg/pnitrofenol g-1h-1 acid, and 12.85 μg/pnitrofenol g-1h-1 alkaline PME-ase production, 1.30 cm cellulose halo zone, saline tolerance, nitrogenase, and ACC-deaminase activity. Therefore, the PGPB from this bacterium was the highest compared to other isolates.