title: Diversity of the ectoines biosynthesis genes in the salt tolerant Streptomyces and evidence for inductive effect of ectoines on their accumulation.
abstract: Streptomyces commonly produce ectoines as compatible solutes to prevent osmotic stresses. Fine structure of the genes producing ectoine (ectC) and hydroxyectoine (ectD) enzymes in Streptomyces rimosus C-2012 as a slightly halophilic bacterium is reported in this study. Deduced amino acid sequences of ectC and ectD genes from strain C-2012 and some other related species were compared and 72-90% and 13-81% identities were detected for ectC and ectD, respectively. High similarity of ectC between closely or distantly related Streptomyces to the strain C-2012 may indicate horizontal transfer of this gene. However, phylogenetic relationships of ectD were correlated with phylogenetic affiliation of the strains. It suggests that the ability of Streptomyces to produce hydroxyectoine has been the result of a vertical transfer event. HPLC analysis showed that strain C-2012 was able to produce ectoine and hydroxyectoine both in the presence and absence of external salinity (up to 0.45 M NaCl). Accordingly, reverse transcription quantitative PCR (RT-qPCR) showed that ectABCD operon in this strain is positively affected by salt. Also, inductive effect of the salt was increased when it was applied with 1 mM of ectoines. Transcription level of ectC was increased 2.7- and 2.9-fold in the medium supplied with salt and ectoine and salt and hydroxyectoine, respectively. The effect of salinity with or without ectoines was more on ectD transcription level than that of ectC. In S. rimosus under salt stress, ectoine and hydroxyectoine biosynthesis primarily depends on the stimulation of ectABCD operon transcription. However, drastic accumulation of ectoine and hydroxyectoine without increase in ectC and ectD transcripts was observed in the medium supplied with salt and ectoines and that suggest there might be additional posttranscriptional level of control. Increases in ratio of some intracellular free amino acids in salt stressed to unstressed conditions were observed in cells grown with ectoines. Our results suggest the possibility of a supplementary role of ectoines to improve structure and function of the cells in stressful environments as well as their important role as osmoprotectants.
authors.affiliation: Genetics Department, Faculty of Biological Science, Tarbiat Modares University, Tehran, Iran; Microbial Biotechnology and Biosafety Department, Agricultural Biotechnology Research Institute of Iran (ABRII), Karaj, Iran.
authors.forename: Akram
authors.initials: A
authors.lastname: Sadeghi
authors.affiliation: Genetics Department, Faculty of Biological Science, Tarbiat Modares University, Tehran, Iran. Electronic address: soltanib@modares.ac.ir.
authors.forename: Bahram M
authors.initials: BM
authors.lastname: Soltani
authors.affiliation: Microbial Biotechnology and Biosafety Department, Agricultural Biotechnology Research Institute of Iran (ABRII), Karaj, Iran.
authors.forename: Mojtaba Khayam
authors.initials: MK
authors.lastname: Nekouei
authors.affiliation: Microbial Biotechnology and Biosafety Department, Agricultural Biotechnology Research Institute of Iran (ABRII), Karaj, Iran.
authors.forename: Gholamreza Salehi
authors.initials: GS
authors.lastname: Jouzani
authors.affiliation: Medicinal and Natural Products Chemistry Research Centre, Shiraz University of Medical Sciences, Shiraz, Iran.
authors.forename: Hossein Hadavand
authors.initials: HH
authors.lastname: Mirzaei
authors.affiliation: Genetics Department, Faculty of Biological Science, Tarbiat Modares University, Tehran, Iran.
authors.forename: Majid
authors.initials: M
authors.lastname: Sadeghizadeh
mesh_terms: D000595:Amino Acid Sequence; D000599:Amino Acids, Diamino / Q000096:biosynthesis*; D001426:Bacterial Proteins / Q000235:genetics; D053898:Biosynthetic Pathways / Q000235:genetics*; D016000:Cluster Analysis; D003470:Culture Media / Q000737:chemistry; D020869:Gene Expression Profiling; D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects; D014644:Genetic Variation; D010802:Phylogeny; D054712:Salinity; D017386:Sequence Homology, Amino Acid; D012965:Sodium Chloride / Q000378:metabolism; D064411:Streptomyces rimosus / Q000235:genetics* / Q000378:metabolism*; D014158:Transcription, Genetic
chemical_list: D000599:Amino Acids, Diamino; D001426:Bacterial Proteins; D003470:Culture Media; C121557:hydroxyectoine; D012965:Sodium Chloride; C045628:ectoine
keywords: Amino acid; Ectoine; Hydroxyectoine; Phylogenetic analysis; Streptomyces; ectC; ectD