Classification of Halophilic Heterotrophic Bacteria Thriving in the Jordanian Dead Sea Littoral Zone

Halophilic heterotrophic bacteria are distinguished group of microorganisms thriving at saline environments like natural salt lakes. The Dead sea of Jordan is one of the remarkable natural hypersaline inland salt lakes in the world. In this study, we aimed to classify bacterial species living in this unique environment. Water samples, collected during March, July, and October, 2011, were first analyzed in respect to salinity, pH, biological oxygen demand (BOD), and viable microbial number. The salinity of our samples were relatively very high (up to 38%), the pH was slightly low (5.6-6.3) and the BOD was very low (1-2 mg O2 L-1). These conditions were translated into very low viable plate count (2-60x102 CFU mL-1). To classify the indigenous halophilic heterotrophic bacterial species, water samples were first enriched in high salinity medium leading to isolation of 44 heterotrophic halophilic bacterial species, 11 of them were considered different based on Gram-stain as well as colonial and cell morphology. These strains were further analyzed by sequencing their 16S RNA gene. All isolates were found to belong to 7 genera of the domain of Bacteria: Arthrobacter, Kocuria, Vibrio, Salinivibrio, Chromohalobacter, Bacillus and Erythrobacter. Most strains have a high GC content (up to 58%) and some strains are not common in hypersaline environments.