Halo-thermophilic bacteria and heterocyst cyanobacteria found adjacent to halophytes at Sabkhas, Qatar: Preliminary study and possible roles

This study was conducted to investigate the halo-thermophilic bacteria and cyanobacteria adjacent to the halophytic plants, Suaeda virmiculata, Limonium axillare and Tetraena qatarense, and the microbial functionalities in Sabkhas of Qatar. These soils are alkaline and highly saline, and their moisture contents varied throughout the year. A significant presence of thermo-halophilic bacteria was found when selective media was used; however, bacterial populations were highest in soil samples taken adjacent to L. axillare as compared to those taken adjacent to other halophytes. They were lowest in samples taken close to S. virmiculata. Microscopic examinations revealed that the bacterial cells of isolated strains were Gram-positive rods with pointed ends that occurred singly, in pairs or in short chains. Most were bacilli, either Bacillus thuringenses or Bacillus cereus. These can form endospores to survive until more favorable environmental conditions allow them to resume growth and activity. Moreover, when Sabkhan soils were transferred to the laboratory under natural conditions, only cyanobacteria grew, and some produced biofilms. The most recognizable cyanobacteria were Anabaena and Nostoc. Some produced heterocysts and akinetes, which play important roles in soil biology and nitrogen fixation. The possible roles of these microorganisms in saline environment in Sabkhan soil appear to be support of halophyte growth by alleviating salt stress and other extreme environmental conditions.