Haloarcula spp able to biosynthesize exo- and endopolymers

Three halobacteria strains (T5, T6, T7), growing optimally at a sodium chloride concentration of 3.5 M, were isolated from samples collected in the Tunisian marine saltern located close to Monastir. Although they were different in colony and cell morphology, the isolates were similar in most respects and all produced a homopolyester identified spectroscopically as polyhydroxybutyrate when grown on carbohydrates. Under the same conditions, the isolates formed acidic exopolysaccharides. Acid methanolysis of their complex lipids released archaeol (2,3-di-O-phytanyl-sn-glycerol). All the isolates had polar lipid patterns characteristic of representatives of the genus Haloarcula. Partial sequence analysis of 16S rRNA genes from strain T5 confirmed its assignment to the genus Haloarcula. Although strain T5 differed phenotypically from the species Haloarcula japonica in several respects, DNA–DNA hybridization indicated that the T5 isolate is a new strain of H. japonica.