Isolation characterization and potential assessment of non-symbotic nitrogen-fixing halophilic bacteria from saline soils

Abstract

Free-living bacteria which are capable of nitrogen fixing and high salinity condition tolerance should be exploited to support a sustainable agriculture. This study was undertaken to investigate the occurrence of free nitrogen-fixing halophilic bacteria from soils growing rice of Long An province. From randomly collected ten soil samples, 28 isolated nitrogen-fixing halophilic strains had been isolated. The study presented characteristics of purified strains through colony and cellular morphology, also through some biochemical properties. They were screened for nitrogen-fixing potential by Indophenol blue method. From this research, some strains were figured out that have ability of ammonium producing at high level, including LA5.2 (0.98mg/l) and LA2.9 (0.97mg/l). The amount of synthesized NH4+ ranged from 0.36mg/l to 0.98 mg/l after culturing in Ashby medium at third, fifth and seventh date. This study also found out correlation between nitrogen-fixing ability of halophilic strains with criteria of soil samples. From 28 isolates, it was noticeable in 2 halophilic strains could develop steadily through 5 levels of salinity stress, also had ability on ammonium producing considerably, which were LA2.4 (0.84mg/l) and LA6.3 (0.85mg/l). Keywords: Nitrogen fixing bacteria, halophilic, salinity stress.