ORIGINAL PAPER Gluconeotrehalose is the principal organic solute in the psychrotolerant bacterium Carnobacterium strain 17-4 Pedro Lamosa • Ana I. Mingote • Tatiana Groudieva • Barbara Klippel • Ksenia Egorova • Dina Jabbour • Helena Santos • Garabed Antranikian Received: 10 February 2011 / Accepted: 7 April 2011 / Published online: 21 April 2011 Ó Springer 2011 Abstract A high proportion of microorganisms that col- onise cold environments originate from marine sites; hence, they must combine adaptation to low temperature with osmoregulation. However, little or nothing is known about the nature of compatible solutes used by cold-adap- ted organisms to balance the osmotic pressure of the external medium. We studied the intracellular accumula- tion of small organic solutes in the Arctic isolate Carno- bacterium strain 17-4 as a function of the growth temperature and the NaCl concentration in the medium. Data on 16S rDNA sequence and DNA–DNA hybridisation tests corroborate the assignment of this isolate as a new species of the bacterial genus Carnobacterium. The growth profiles displayed maximal specific growth rate at 30°C in medium without NaCl, and maximal values of final bio- mass at growth temperatures between 10 and 20°C. Therefore, Carnobacterium strain 17-4 exhibits halotolerant and psychrotolerant behaviours. The solute pool contained glycine-betaine, the main solute used for osmoregulation, and an unknown compound whose structure was identified as a-glucopyranosyl-(1-3)-b-glucopyranosyl-(1-1)-a-glu- copyranose (abbreviated as gluconeotrehalose), using nuclear magnetic resonance and mass spectrometry. This unusual solute consistently accumulated to high levels (0.35 ± 0.05 mg/mg cell protein) regardless of the growth temperature or salinity. The efficiency of gluconeotrehalose in the stabilisation of four model enzymes against heat damage was also assessed, and the effects were highly pro- tein dependent. The lack of variation in the gluconeotreha- lose content observed under heat stress, osmotic stress, and starvation provides no clue for the physiological role of this rare solute. Keywords Cold-adapted bacterium Á Osmoregulation Á a,b-Trehalose Á Enzyme stabilisation Á Trisaccharide Introduction One of the most common strategies used by micro-organ- isms to cope with environmental variations in water activity is the accumulation of compatible solutes inside the cell (da Costa et al. 1998; Wood et al. 2001). According to the initial description by Brown (1976), these are small organic solutes with no net charge that can accumulate to high levels in the cytoplasm with minimal metabolic per- turbation. Thus, by controlling the intracellular water activity, this strategy allows cells to maintain turgor, a prerequisite for cell viability. But compatible solutes appear to play a variety of functions besides maintaining osmotic balance. In fact, many organisms subjected to heat Communicated by M. da Costa. Electronic supplementary material The online version of this article (doi:10.1007/s00792-011-0377-0) contains supplementary material, which is available to authorized users. P. Lamosa Á A. I. Mingote Á H. Santos (&) Instituto de Tecnologia Quı ´mica e Biolo ´gica, Universidade Nova de Lisboa, Av. da Repu ´blica-EAN, Apartado 127, 2780-157 Oeiras, Portugal e-mail: santos@itqb.unl.pt P. Lamosa Centro de Ressona ˆncia Magne ´tica Anto ´nio Xavier, ITQB-UNL, Av. da Repu ´blica, EAN, Apartado 127, 2780-157 Oeiras, Portugal T. Groudieva Á B. Klippel Á K. Egorova Á D. Jabbour Á G. Antranikian Institute of Technical Microbiology, Hamburg University of Technology, Kasernenstr 12, 21073 Hamburg, Germany 123 Extremophiles (2011) 15:463–472 DOI 10.1007/s00792-011-0377-0