title: Physiological and gene expression responses to nitrogen regimes and temperatures in Mastigocladus sp. strain CHP1, a predominant thermotolerant cyanobacterium of hot springs.
abstract: Cyanobacteria are widely distributed primary producers with significant implications for the global biogeochemical cycles of carbon and nitrogen. Diazotrophic cyanobacteria of subsection V (Order Stigonematales) are particularly ubiquitous in photoautotrophic microbial mats of hot springs. The Stigonematal cyanobacterium strain CHP1 isolated from the Porcelana hot spring (Chile) was one of the major contributors of the new nitrogen through nitrogen fixation. Further morphological and genetic characterization verified that the strain CHP1 belongs to Stigonematales, and it formed a separate clade together with other thermophiles of the genera Fischerella and Mastigocladus. Strain CHP1 fixed maximum N2in the light, independent of the temperature range. At 50°C nifH gene transcripts showed high expression during the light period, whereas the nifH gene expression at 45°C was arrhythmic. The strain displayed a high affinity for nitrate and a low tolerance for high ammonium concentrations, whereas the narB and glnA genes showed higher expression in light and at the beginning of the dark phase. It is proposed that Mastigocladus sp. strain CHP1 would represent a good model for the study of subsection V thermophilic cyanobacteria, and for understanding the adaptations of these photoautotrophic organisms inhabiting microbial mats in hot springs globally.
authors.affiliation: Department of Molecular Genetics and Microbiology, Pontificia Universidad Católica de Chile, Libertador Bernardo O'Higgins 340, Casilla 144-D, C.P. 651 3677 Santiago, Chile. Electronic address: mealcaman@uc.cl.
authors.forename: M Estrella
authors.initials: ME
authors.lastname: Alcamán
authors.affiliation: Department of Molecular Genetics and Microbiology, Pontificia Universidad Católica de Chile, Libertador Bernardo O'Higgins 340, Casilla 144-D, C.P. 651 3677 Santiago, Chile.
authors.forename: Jaime
authors.initials: J
authors.lastname: Alcorta
authors.affiliation: Department of Ecology, Environment and Plant Sciences and Science for Life Laboratory, Stockholm University, S-10691 Stockholm, Sweden.
authors.forename: Birgitta
authors.initials: B
authors.lastname: Bergman
authors.affiliation: Department of Molecular Genetics and Microbiology, Pontificia Universidad Católica de Chile, Libertador Bernardo O'Higgins 340, Casilla 144-D, C.P. 651 3677 Santiago, Chile.
authors.forename: Mónica
authors.initials: M
authors.lastname: Vásquez
authors.affiliation: Environmental Science and Engineering, Department of Civil and Environmental Engineering, Massachusetts Institute of Technology (MIT), 15 Vassar Street, Cambridge, MA 02139, USA.
authors.forename: Martin
authors.initials: M
authors.lastname: Polz
authors.affiliation: Department of Molecular Genetics and Microbiology, Pontificia Universidad Católica de Chile, Libertador Bernardo O'Higgins 340, Casilla 144-D, C.P. 651 3677 Santiago, Chile; Center for Climate and Resilience Research (CR)2, Chile. Electronic address: bdiez@bio.puc.cl.
authors.forename: Beatriz
authors.initials: B
authors.lastname: Díez
mesh_terms: D064751:Ammonium Compounds / Q000378:metabolism; D002677:Chile; D016000:Cluster Analysis; D000458:Cyanobacteria / Q000187:drug effects* / Q000528:radiation effects*; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D004275:DNA, Ribosomal / Q000737:chemistry / Q000235:genetics; D020869:Gene Expression Profiling; D005974:Glutamate-Ammonia Ligase / Q000096:biosynthesis; D045482:Hot Springs / Q000382:microbiology*; D008027:Light; D009566:Nitrates / Q000378:metabolism; D009584:Nitrogen / Q000378:metabolism*; D009586:Nitrogen Fixation; D010088:Oxidoreductases / Q000096:biosynthesis; D010802:Phylogeny; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D017422:Sequence Analysis, DNA; D013696:Temperature
chemical_list: D064751:Ammonium Compounds; D004269:DNA, Bacterial; D004275:DNA, Ribosomal; D009566:Nitrates; D012336:RNA, Ribosomal, 16S; D010088:Oxidoreductases; C029130:nitrogenase reductase; C081173:glutamine synthetase I; D005974:Glutamate-Ammonia Ligase; D009584:Nitrogen
keywords: Gene expression; Mastigocladus sp.; Nitrate/ammonium preference; Thermotolerance