title: Role of trehalose synthesis pathways in salt tolerance mechanism of Rhodobacter sphaeroides f. sp. denitrificans IL106.
abstract: The photosynthetic bacterium Rhodobacter sphaeroides (R. sphaeroides) f. sp. denitrificans IL106 accumulates trehalose as the major organic osmoprotectant in response to a salt stress. An analysis of the R. sphaeroides 2.4.1 genome sequence revealed the presence of five different genes encoding enzymes belonging to three putative trehalose biosynthesis pathways (OtsA-OtsB, TreY-TreZ, and TreS). The function of the different pathways of trehalose was studied by characterizing strains defective in individual trehalose biosynthetic routes. A phenotypic comparison revealed that trehalose synthesis in R. sphaeroides f. sp. denitrificans IL106 is mediated mainly by the OtsA-OtsB pathway and, to some extent, by the TreY-TreZ pathway. Strains with the simultaneous inactivation of these two pathways were completely unable to synthesize trehalose. On the other hand, treS mutants showed an increase in the trehalose level. These results suggest that treS plays a role in trehalose degradation. In addition, treS was found to be important in reducing trehalose after osmotic stress was removed. In this report, we show that the strains that accumulate the most trehalose adapt to salt stress earlier. This is the first report of an organism using multiple pathways to synthesize trehalose solely for use as a compatible solute against salt stress.
authors.affiliation: Department of Applied Biological Chemistry, Graduate School of Agriculture and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo, 113-8657, Japan.
authors.forename: Fumihiro
authors.initials: F
authors.lastname: Makihara
authors.forename: Minoru
authors.initials: M
authors.lastname: Tsuzuki
authors.forename: Kiichi
authors.initials: K
authors.lastname: Sato
authors.forename: Shinji
authors.initials: S
authors.lastname: Masuda
authors.forename: Kenji V P
authors.initials: KV
authors.lastname: Nagashima
authors.forename: Mitsuru
authors.initials: M
authors.lastname: Abo
authors.forename: Akira
authors.initials: A
authors.lastname: Okubo
mesh_terms: D000222:Adaptation, Physiological; D015964:Gene Expression Regulation, Bacterial; D009994:Osmolar Concentration; D012242:Rhodobacter sphaeroides / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism; D012965:Sodium Chloride / Q000494:pharmacology*; D014199:Trehalose / Q000096:biosynthesis* / Q000737:chemistry
chemical_list: D012965:Sodium Chloride; D014199:Trehalose