Population and Biochemical Characteristics of Halotolerant N2 Fixing Rhizobacteria Isolated from Saline Soil Ecosystem

Abstract

<p>Utilization of halotolerant N2 fixing rhizobacteria (HNFR) in saline soil ecosystem has the potential to reduce the negative impact of soil salinity. The aim of this study was to obtain isolates of HNFR in saline soil ecosystem and identify their biochemical characteristics. The research was conducted at Sukajaya Village (Cilamaya Kulon District, Karawang Regency) and Biology Laboratory (Department of Soil and Land Resources, Faculty of Agriculture, Padjadjaran University) from September 2019 to November 2020. Soil samples were obtained from rhizosphere of rice, mangrove, and grass vegetations located around the shoreline affected by sea water intrusion. Isolation and characterization activities were done by using salinized Asbhy selective media. The population of HNFR in saline soil ecosystem was analyzed by using total plate count method. Biochemical characteristics were determined by analyzing the IAA hormone production using spectrophotometer, nitrogenase activity using gas chromatography, and DNA analysis using 16S rRNA gene sequence. The results showed that the number of HNFR obtained was 15 isolates with the highest population shown by Ab-P4, Ab-P5, and Ab-R5 isolates. Ab-P5 and Ab-R5 isolates which were obtained from rhizosphere of rice and grass, respectively, were able to produce IAA phytohormones reaching 0.89 and 0.61 μg/l and nitrogenase activity reaching 1.982 and 0.331 μM C2H4/ml/h, respectively. DNA analysis showed that the Ab-P5 and Ab-R5 isolates were Bacillus cereus and Delftia tsuruhatensis, respectively, and these isolates potentially can be used as active ingredients for biofertilizers that could be applied in saline soil ecosystem.</p>