Sensing and Responding to Hypersaline Conditions and the HOG Signal Transduction Pathway in Fungi Isolated from Hypersaline Environments: Hortaea werneckii and Wallemia ichthyophaga

Sensing and responding to changes in NaCl concentration in hypersaline environments is vital for cell survival. In this paper, we identified and characterized key components of the high-osmolarity glycerol (HOG) signal transduction pathway, which is crucial in sensing hypersaline conditions in the extremely halotolerant black yeast Hortaea werneckii and in the obligate halophilic fungus Wallemia ichthyophaga. Both organisms were isolated from solar salterns, their predominating ecological niche. The identified components included homologous proteins of both branches involved in sensing high osmolarity (SHO1 and SLN1) and the homologues of mitogen-activated protein kinase module (MAPKKK Ste11, MAPKK Pbs2, and MAPK Hog1). Functional complementation of the identified gene products in S. cerevisiae mutant strains revealed some of their functions. Structural protein analysis demonstrated important structural differences in the HOG pathway components between halotolerant/halophilic fungi isolated from solar salterns, salt-sensitive S. cerevisiae, the extremely salt-tolerant H. werneckii, and halophilic W. ichthyophaga. Known and novel gene targets of MAP kinase Hog1 were uncovered particularly in halotolerant H. werneckii. Molecular studies of many salt-responsive proteins confirm unique and novel mechanisms of adaptation to changes in salt concentration.

Sensing and Responding to Hypersaline Conditions and the HOG Signal Transduction Pathway in Fungi Isolated from Hypersaline Environments: Hortaea werneckii and Wallemia ichthyophaga

Sensing and responding to changes in NaCl concentration in hypersaline environments is vital for cell survival. We have identified and characterized key components of the high-osmolarity glycerol (HOG) signal transduction pathway, which is crucial in sensing hypersaline conditions in the extremely halotolerant black yeast Hortaea werneckii and in the obligate halophilic fungus Wallemia ichthyophaga. Both organisms were isolated from solar salterns, their predominating ecological niche. The identified components included homologous proteins of both branches involved in sensing high osmolarity (SHO1 and SLN1) and the homologues of mitogen-activated protein kinase module (MAPKKK Ste11, MAPKK Pbs2, and MAPK Hog1). Functional complementation of the identified gene products in S. cerevisiae mutant strains revealed some of their functions. Structural protein analysis demonstrated important structural differences in the HOG pathway components between halotolerant/halophilic fungi isolated from solar salterns, salt-sensitive S. cerevisiae, the extremely salt-tolerant H. werneckii, and halophilic W. ichthyophaga. Known and novel gene targets of MAP kinase Hog1 were uncovered particularly in halotolerant H. werneckii. Molecular studies of many salt-responsive proteins confirm unique and novel mechanisms of adaptation to changes in salt concentration.

Halobacterium identification in saltworks of Gran Canaria (Canary Islands, Spain)

This work analyzes bacterial communities present in evaporation ponds of solar salterns of Gran Canaria and reveals specific organisms through molecular techniques. Solar salterns are protected areas in Canary Islands where salt is produced from sea water by solar and wind powered evaporation. Salt was an important product for ancient islanders who used it for a broad field of purposes, but also has a great importance in recent time for its implications in the island economy.Based on amplifications with specific primers for 16S ribosomal DNA (16S rDNA) and subsequent nested-PCR approaches, different amplicons were obtained, and analyzed in silico. A taxonomic classification was carried out through phylogenetic trees.Results revealed different bacteria according to the evaporation grade of crystallizer ponds in saline works. It is worthstanding the presence of the genus Halobacterium in all crystallizer ponds. This opens an interesting framework for further studies and continuative molecular characterization approaches of bacterial communities in solar salterns of Gran Canaria.

Salinigranum halophilum sp. nov., isolated from marine solar salterns

Three halophilic archaeal strains, YJ-53T, ZS-5 and DYF38, were isolated from marine solar salterns located in different provinces of China. The three strains formed a single cluster (99.7–99.8 and 97.9–99.2 % similarities, respectively) that was separate from the current two members of Salinigranum (96.7–98.0 and 89.8–92.9 % similarities, respectively) on the basis of 16S rRNA and rpoB′ gene sequence comparisons and phylogenetic analysis. Diverse phenotypic characteristics differentiated strains YJ-53T, ZS-5 and DYF38 from Salinigranum rubrum GX10T and Salinigranum salinum YJ-50-S2T. The major polar lipids of isolated strains were phosphatidylglycerol, phosphatidylglycerol phosphate methyl ester and two major glycolipids chromatographically identical to mannosyl glucosyl diether and sulfated mannosyl glucosyl diether, detected in the current members of Salinigranum . The OrthoANI and in silico DNA–DNA hybridization (DDH) values between the three strains were in the range of 97.7–98.4 % and 80.3–86.1 %, respectively, much higher than the threshold values proposed as species boundaries (average nucleotide identity 95–96 % and in silico DDH 70 %), revealing that the three strains represent one species. Results of comparative OrthoANI and in silico DDH analyses of the strains described in this study with validly described members of the genus Salinigranum supported that strains YJ-53T (=CGMCC 1.12860T=JCM 30238T), ZS-5 (=CGMCC 1.12867=JCM 30240) and DYF38 (=CGMCC 1.13779=JCM 33557) represent a novel species of the genus Salinigranum , for which the name Salinigranum halophilum sp. nov. is proposed.