Behavior Assessment of Moderately Halophilic Bacteria in Brines Highly Enriched with Heavy Metals: Sfax solar saltern (Tunisia), A Case Study

Adaptation to a solar saltern environment requires mechanisms providing tolerance not only to salinity but also to UV radiation (UVR) and to reactive oxygen species (ROS). We cultivated prokaryote halophiles from two different salinity ponds: the concentrator M1 pond (240 g·L–1NaCl) and the crystallizer TS pond (380 g·L–1NaCl). We then estimated UV-B and hydrogen peroxide resistance according to the optimal salt concentration for growth of the isolates. We observed a higher biodiversity of bacterial isolates in M1 than in TS. All strains isolated from TS appeared to be extremely halophilic Archaea from the genus Halorubrum . Culturable strains isolated from M1 included extremely halophilic Archaea (genera Haloferax , Halobacterium , Haloterrigena , and Halorubrum) and moderately halophilic Bacteria (genera Halovibrio and Salicola ). We also found that archaeal strains were more resistant than bacterial strains to exposure to ROS and UV-B. All organisms tested were more resistant to UV-B exposure at the optimum NaCl concentration for their growth, which is not always the case for H2O2. Finally, if these results are extended to other prokaryotes present in a solar saltern, we could speculate that UVR has greater impact than ROS on the control of prokaryote biodiversity in a solar saltern.

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Halobacillus profundi sp. nov. and Halobacillus kuroshimensis sp. nov., moderately halophilic bacteria isolated from a deep-sea methane cold seep

INTERNATIONAL JOURNAL OF SYSTEMATIC AND EVOLUTIONARY MICROBIOLOGY ◽

10.1099/ijs.0.64817-0 ◽

2007 ◽

Vol 57 (6) ◽

pp. 1243-1249 ◽

Cited By ~ 35

Author(s):

Ngoc-Phuc Hua ◽

Atsuko Kanekiyo ◽

Katsunori Fujikura ◽

Hisato Yasuda ◽

Takeshi Naganuma

Keyword(s):

Deep Sea ◽

Sequence Similarity ◽

Halophilic Bacteria ◽

Cold Seep ◽

16S Rrna Genes ◽

Rrna Genes ◽

High Sequence Similarity ◽

Moderately Halophilic ◽

Type Strains ◽

Moderately Halophilic Bacteria

Two Gram-positive, rod-shaped, moderately halophilic bacteria were isolated from a deep-sea carbonate rock at a methane cold seep in Kuroshima Knoll, Japan. These bacteria, strains IS-Hb4T and IS-Hb7T, were spore-forming and non-motile. They were able to grow at temperatures as low as 9 °C and hydrostatic pressures up to 30 MPa. Based on high sequence similarity of their 16S rRNA genes to those of type strains of the genus Halobacillus, from 96.4 % (strain IS-Hb7T to Halobacillus halophilus NCIMB 9251T) to 99.4 % (strain IS-Hb4T to Halobacillus dabanensis D-8T), the strains were shown to belong to this genus. DNA–DNA relatedness values of 49.5 % and 1.0–33.0 %, respectively, were determined between strains IS-Hb4T and IS-Hb7T and between these strains and other Halobacillus type strains. Both strains showed the major menaquinone MK7 and l-orn–d-Asp cell-wall peptidoglycan type. Straight-chain C16 : 0, unsaturated C16 : 1 ω7c alcohol and C18 : 1 ω7c and cyclopropane C19 : 0 cyc fatty acids were predominant in both strains. The DNA G+C contents of IS-Hb4T and IS-Hb7T were respectively 43.3 and 42.1 mol%. Physiological and biochemical analyses combined with DNA–DNA hybridization results allowed us to place strains IS-Hb4T (=JCM 14154T=DSM 18394T) and IS-Hb7T (=JCM 14155T=DSM 18393T) in the genus Halobacillus as the respective type strains of the novel species Halobacillus profundi sp. nov. and Halobacillus kuroshimensis sp. nov.

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