Isolation of moderately halophilic bacteria from Tunisian soil samples and transformation by electroporation using Escherichia coli-Halomonas sp. shuttle vector

Halophilic and salt-resistant bacteria were isolated from soil samples collected from Tunisia. Among them, strain 21a grew at NaCl concentration ranging 1-15%, optimum at 3%, showing that it is moderately halophilic bacteria. Phylogenetic analysis based on the 16S rRNA gene sequence showed that strain 21a was closely related to Halomonas aquamarina and H. venusta with sequence similarities of 99.7, and 97.1%, respectively, suggesting that the strain belongs to the genus Halomonas. It was transformed by electroporation either with a plasmid vector pCCMR1, constructed with a replication region fragment from a cryptic plasmid of Chromohalobacter marismortui, or a transposon-complex. Segregational plasmid stability of strain 21a harboring pCCMR1 was higher when cultivated in low NaCl concentrations under non-selective pressure.