Combined effect of the growth temperature and salinity of the medium on the accumulation of compatible solutes by Rhodothermus marinus and Rhodothermus obamensis

Abstract

In this study we propose revised structures for the two major compatible solutes of Rhodothermus marinus. We have also examined the accumulation of compatible solutes by the type strains of the slightly halophilic and thermophilic species Rhodothermus marinus and Rhodothermus obamensis at several growth temperatures and salinities. The major solutes of R. marinus were identified as alpha-mannosylglycerate (alpha-MG) and alpha-mannosylglyceramide (alpha-MGA), whereas R. obamensis accumulated only alpha-mannosylglycerate. The total osmolyte content was higher during the early exponential phase and decreased abruptly as growth continued into the stationary phase. At low growth temperatures. R. marinus responded to water stress by accumulation of alpha-mannosylglycerate and its amide, in addition to low levels of trehalose, glutamate, and glucose. At the highest growth temperature, alpha-mannosylglycerate was the major compatible solute and alpha-mannosylglyceramide was not detected. When both compounds were present, an increase in the salinity of the growth medium favored the accumulation of alpha-mannosylglyceramide over alpha-mannosylglycerate. The absence of alpha-mannosylglyceramide in R. obamensis at all growth temperatures and salinities constituted the most pronounced difference in the profiles of compatible solute accumulation by the two strains. Trehalose was also a prominent solute in this organism. Both organisms accumulated higher levels of alpha-mannosylglycerate as the temperature was raised. The importance of the two compounds in the mechanisms of thermoadaptation and osmoadaptation is discussed.

Genomic identification and in vitro reconstitution of a complete biosynthetic pathway for the osmolyte di- myo -inositol-phosphate

“…The identity of the resonances for these two compounds was confirmed by TOCSY and HMQC experiments (6,26). 13 C chemical shifts were obtained from an HMQC experiment and were consistent with published 13 C and 1 H shifts for these molecules (27). The MS analysis revealed the presence of 421.2 m/z peak consistent with the DIP anion and the 267.2 m/z peak likely corresponding to mannosylglycerate.…”

Organic solutes in Rubrobacter xylanophilus: the first example of di-myo-inositol-phosphate in a thermophile

“…Cell pellets were extracted twice with boiling 80% ethanol and the extracts were freeze-dried as described previously (Silva et al 1999). The dry weight of cells was determined by filtering cell suspensions under vacuum, through dried pre-weighted 0.22 lm pore size filters (Gelman).…”

“…Freeze-dried extracts were analyzed by nuclear magnetic resonance (NMR) as described previously (Silva et al 1999). The quantification of solutes was determined by comparing the intensities of resonances of the compounds in the sample with the one from a concentration standard, in our case formate.…”

Role of Periplasmic Trehalase in Uptake of Trehalose by the Thermophilic Bacterium Rhodothermus marinus

“…Trehalose is frequently used as a compatible solute both in mesophiles and in thermophiles and hyperthermophiles, but only minor amounts of this sugar accumulate in R. marinus (19). The expression of the trehalose transporter decreased with elevated salinity (4% NaCl), whereas trehalose-6-phosphate synthase, the first enzyme in the usual pathway for trehalose synthesis, was strongly induced under the same conditions (data not shown), a regulation pattern resembling that of E. coli (2).…”

“…In response to heat or osmotic stress, R. marinus accumulates mannosylglycerate and mannosylglyceramide as major compatible solutes, but minor amounts of glucose and trehalose are also present (19). Mannosylglycerate is commonly found in thermophilic and hyperthermophilic bacteria and archaea that colonize hot marine environments, while mannosylglyceramide has been found only in members of the genus Rhodothermus (16).…”