Isolation and Characterization of Halophilic Bacteria from Salinity Soil of Shatkhira, Bangladesh

Abstract

Aim: The aim of this study was undertaken for the isolation and molecular characterization of the halophilic bacteria from salt affected soils. Place and Duration of Study: This study was conducted on the salinity affected area in Ramzan Nagor under Shamnagor Upazilla of Shatkhira District, Bangladesh. The collection of soil sample, isolation of halophilic bacteria and subsequent experiments were done from May to December 2018. Methodology: Salt affected soil could be good source of halophilic bacteria as it contain high amount of salt. Hence, one gram of salt affected soil sample which was containing high amount of salt was suspended to 100 ml sterile distilled water and one ml of sample from the top of the suspension were taken in to 250 ml Erlenmeyer flaks containing 100 ml of mineral salts (MS) medium. The primary enrichment was incubated for several days at 37°C with shaking at 120 rpm (revolution per minute) on an orbital shaker. Cultures which were found to be turbid after a period of up to 4 days were used as inocula in subsequent experiments. Results: Four halophilic bacterial strains viz. Bacillus sp. strain 8-15, Enterobacter sp. strain LCR75, Acinetobacter sp. strain 407 and Acinetobacter junii strain F27 were isolated from the saline soil and screened for their growth at a range of salt (NaCl) concentrations viz., 0%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5% and 5%. Out of four isolates, Bacillus sp. showed the highest capacity to tolerate 5% salt concentration whereas Enterobacter sp. and other two isolates (Acinetobacter sp. and Acinetobacter junii) showed the capacity to tolerate 4% and 2.5% salt concentration respectively. Based on their morphological and biochemical characteristics the isolates were found to be Gram-positive and Gram-negative, rod shaped, motile bacteria which were later identified on the basis of 16S rRNA gene sequencing. The optimum culture conditions of the isolates were pH 7.0 and temperature 37°C. Results on the antibiogram profiles of the isolates revealed that the strains were sensitive to most of the antibiotics used in this study except Kenamycin, Ceftazidime and Ampicillin. Conclusion: The isolated halophilic bacteria may play an important role to optimize the salt affected soil; hence they could be important candidates for further research on slat bioremediation.