The organisms thriving under extreme conditions better than any other organism living on Earth, fascinate by their hostile growing parameters, physiological features, and their production of valuable bioactive metabolites. This is the case of microorganisms (bacteria, archaea, and fungi) that grow optimally at high salinities and are able to produce biomolecules of pharmaceutical interest for therapeutic applications. As along as the microbiota is being approached by massive sequencing, novel insights are revealing the environmental conditions on which the compounds are produced in the microbial community without more stress than sharing the same substratum with their peers, the salt. In this review are reported the molecules described and produced by halophilic microorganisms with a spectrum of action in vitro: antimicrobial and anticancer. The action mechanisms of these molecules, the urgent need to introduce alternative lead compounds and the current aspects on the exploitation and its limitations are discussed.

The Halobacteria are a well-studied archaeal class and numerous investigations are showing how their diversity is distributed amongst genomes and geographic locations. Evidence indicates that recombination between species continuously facilitates the arrival of new genes, and within species, it is frequent enough to spread acquired genes amongst all individuals in the population. To create permanent independent diversity and generate new species, barriers to recombination are probably required. The data support an interpretation that rates of evolution (e.g., horizontal gene transfer and mutation) are faster at creating geographically localized variation than dispersal and invasion are at homogenizing genetic differences between locations. Therefore, we suggest that recurrent episodes of dispersal followed by variable periods of endemism break the homogenizing forces of intrapopulation recombination and that this process might be the principal stimulus leading to divergence and speciation in Halobacteria.

A novel halophilic archaeon, strain CG-1^T, belonging to the genus Natronococcus was isolated from sediment of the soda lake Chagannor in Inner Mongolia, China. The colonies of this strain were pink pigmented, the intensity of the colour decreased when the cells grew at salt saturation levels. The cells were non-motile cocci and strictly aerobic. Hypotonic treatment did not cause cell lysis, even in distilled water. Strain CG-1^T grew at 15–30.0 % (w/v) NaCl and at 30–50 °C and pH 8.0–11.0, with optimal growth occurring at 25–30 % (w/v) NaCl, 37–45 °C and pH 9–9.5. MgCl₂ was not required for growth. Strain CG-1^T was most closely related to the type strains of Natronococcus amylolyticus Ah-36^T, Natronococcus jeotgali B1^T and Natronococcus occultus SP4^T, with which it shared 98.4 %, 96.2 and 95.7 % 16S rRNA gene sequence similarity, respectively. The polar lipids consisted of C₂₀C₂₀ and C₂₀C₂₅ derivatives of phosphatidylglycerol (PG), phosphatidylglycerol phosphate methyl ester (PGP-Me) and minor phospholipid components. No glycolipids were detected. The DNA G+C content of strain CG-1^T was 62.1 mol%. DNA–DNA hybridization with N. amylolyticus DSM 10524^T, phylogenetically the most closely related species, was 39 %; this value showed that strain CG-1^T constituted a different genospecies. The comparison of 16S rRNA gene sequences, detailed phenotypic characterization, polar lipid profile and DNA–DNA hybridization studies revealed that strain CG-1^T belongs to the genus Natronococcus and constitutes a novel species for which the name Natronococcus roseus sp. nov. is proposed. The type strain is CG-1^T ( = CECT 7984^T = IBRC-M 10656^T = JCM 17958^T).

Two novel haloalkaliphilic archaea, strains CG-6^T and CG-4, were isolated from sediment of the hypersaline Lake Chagannor in Inner Mongolia, China. Cells of the two strains were pleomorphic, non-motile and strictly aerobic. They required at least 2.5 M NaCl for growth, with optimum growth at 3.4 M NaCl. They grew at pH 8.0–11.0, with optimum growth at pH 9.0. Hypotonic treatment with less than 1.5 M NaCl caused cell lysis. The two strains had similar polar lipid compositions, possessing C₂₀C₂₀ and C₂₀C₂₅ derivatives of phosphatidylglycerol and phosphatidylglycerol phosphate methyl ester. No glycolipids were detected. Comparison of 16S rRNA gene sequences and morphological features placed them in the genus Natronorubrum. 16S rRNA gene sequence similarities to strains of recognized species of the genus Natronorubrum were 96.2–93.8 %. Detailed phenotypic characterization and DNA–DNA hybridization studies revealed that the two strains belong to a novel species in the genus Natronorubrum, for which the name Natronorubrum sediminis sp. nov. is proposed; the type strain is CG-6^T (=CECT 7487^T =CGMCC 1.8981^T =JCM 15982^T).