Abstract:
Members of the Bacillus genus are generally found in soil and represent a wide range of physiological abilities, allowing the organism to grow in every environment due to its capability to form extremely resistant spores. Soil salinity affects agricultural production of crops, soil physico-chemical properties and ecological balance of the area. To mitigate the problem Bacillus species that can grow in every harsh environment is the best option. The objective of this study was to asses salt tolerant Bacillus from saline soil around Metema area, west of Gondar and to test their biodegradation ability of pesticides such as DDT. The study design is purposeful randomized laboratory based experimental design with 3 replications. The research was conducted from January, 2017-May, 2017. Randomized Purposive sampling technique was used to collect the soil sample from the area, and then bulked to make a composite sample. Isolation of Bacillus species using serial dilution and pure culture method was done. Biochemical, morphological and cellular characterization of the isolates were done. Then the isolates were further grown on different salt concentration and temperature for further identification. The isolates nearest Bacillus species include B.thuringiensis, B.subtilis, B.mycoides, and B.cereus and B.pumilis. The salt tolerant ability and bioremediation potential of the isolates was checked. Three isolates have a potential to tolerate salt stress of 9%, 16% and 18% NaCl these are isolates nearest relative to B6(B.thuringiensis), B3(B.subtilis) and B5(B.pumilus). Three isolates B.subtilis, B.mycoides and B.cereus grown and used DDT as a carbon source at concentration of 0ppm, 25ppm, 50ppm and 100ppm were identified. Each isolate have different optical density under different DDT concentration. The maximum optical density of 0.51(B3), 0.75(B4), 0.50(B10). This study showed that there are many Bacillus species in the saline soil which have better potential to use xenophobic chemicals as a carbon source and partially degraded them.
