Isolation and Characterization of Salt Tolerant Soil Bacteria from Selected Locations in the West Coast of Sri Lanka.

Abstract

BackgroundSoil salinity is one of the inherent problems in coastal soils. The increased soil salinity in costal soils results in low bacterial diversity. However, salt tolerant bacteria have the ability to survive in saline soils because of their unique salt tolerant mechanisms. The current study was focused on identifying the salinity tolerant bacteria in the West coast of Sri Lanka. The molecular characterization of potential salt tolerant bacteria was carried out by 16S rRNA sequencing. ResultsNegombo lagoon, Balapitiya coastal area and Beruwala coastal area were selected as three locations from the West coast of Sri Lanka. Twenty bacterial isolates namely NE01 to NE09 (Negombo lagoon), BA01 to BA07 (Balapitiya coastal area), BE01 to BE04 (Beruwala coastal area) were obtained from 12 soil samples of selected locations. The isolates were characterized based on the bacterial colony morphology, Grams stain and biochemical tests namely, catalase test, modified oxidase test, hemolytic reaction on blood agar and growth on MacConkey agar. All the bacterial isolates were screened for salt tolerance at different concentrations of NaCl ranging from 3 dS/m to 18 dS/m. All 20 bacterial isolates were found salt tolerant upto the highest NaCl concentration (18 dS/m). The salinity tolerant behavior of selected five isolates namely NE 03, NE 06, NE 07, BA 01 and BA 02 were observed by enumerating the number of colony forming units per milliliter (CFU/ml) with increasing salinity. Molecular identification of the above five isolates were carried out by sequencing the 16S rRNA gene and were identified upto their genus level as Bacillus sp., Aeromonas sp., Pseudomonas sp., Aeromonas sp. and Mangrovibacter sp. respectively. ConclusionsThe identified salt tolerant bacterial species can be screened for their plant growth promoting rhizobacterial (PGPR) activities such as phosphate solubilization, potassium solubilization, indole acetic acid (IAA) and nitrogen fixation. Therefore, there is a potential for using these isolates in biofertilizer formulations with the aim of increasing the productivity of saline affected soils of Sri Lanka.