Molecular and Physiological Adaptations to Low Temperature in Strains Isolated from Soda Lakes with Different Temperature Regimes.

The genus comprises sulfur-oxidizing bacteria thriving in soda lakes at high pH and salinity. Depending on the geographical location and the season, these lakes can strongly vary in temperature. To obtain a comprehensive understanding of the molecular and physiological adaptations to low temperature, we compared the responses of two strains to low (10°C) and high (30°C) temperatures.

Exploiting Substrate Promiscuity of Ectoine Hydroxylase for Regio- and Stereoselective Modification of Homoectoine.

Extant enzymes are not only highly efficient biocatalysts for a single, or a group of chemically closely related substrates but often have retained, as a mark of their evolutionary history, a certain degree of substrate ambiguity. We have exploited the substrate ambiguity of the ectoine hydroxylase (EctD), a member of the non-heme Fe(II)-containing and 2-oxoglutarate-dependent dioxygenase superfamily, for such a task. Naturally, the EctD enzyme performs a precise regio- and stereoselective hydroxylation of the ubiquitous stress protectant and chemical chaperone ectoine (possessing a six-membered pyrimidine ring structure) to yield -5-hydroxyectoine.

Hydroxyl radical scavenging of the compatible solute ectoine generates two N-acetimides.

Living cells employ various defence mechanisms against reactive oxygen species and free radicals. Besides protecting enzymes such as superoxide dismutase, catalase and peroxidase, non-enzymatic antioxidant molecules also play an important role as radical scavengers. Within bacteria the amino acid derivative ectoine (2-methyl-3,4,5,6-tetrahydropyrimidine-4-carboxylate) is the most abundant compatible solute and stress protectant.

Homoectoine Protects Against Colitis by Preventing a Claudin Switch in Epithelial Tight Junctions.

Background: Inflammatory bowel diseases (IBD) are multifactorial disorders affecting millions of people worldwide with alarmingly increasing incidences every year. Dysfunction of the intestinal epithelial barrier is associated with IBD pathogenesis, and therapies include anti-inflammatory drugs that enhance intestinal barrier function. However, these drugs often have adverse side effects thus warranting the search for alternatives.

Methanonatronarchaeum thermophilum gen. nov., sp. nov. and 'Candidatus Methanohalarchaeum thermophilum', extremely halo(natrono)philic methyl-reducing methanogens from hypersaline lakes comprising a new euryarchaeal class Methanonatronarchaeia classis nov.

Methanogenic enrichments from hypersaline lakes at moderate thermophilic conditions have resulted in the cultivation of an unknown deep lineage of euryarchaeota related to the class Halobacteria. Eleven soda lake isolates and three salt lake enrichment cultures were methyl-reducing methanogens that utilize C1 methylated compounds as electron acceptors and H2 or formate as electron donors, but they were unable to grow on either substrates alone or to form methane from acetate. They are extreme halophiles, growing optimally at 4 M total Na and the first representatives of methanogens employing the 'salt-in' osmoprotective mechanism.

Engineering the Salt-Inducible Ectoine Promoter Region of Halomonas elongata for Protein Expression in a Unique Stabilizing Environment.

It has been firmly established that organic osmolytes (compatible solutes) of halophilic and have positive effects on conformation and activity of proteins, and may therefore improve their functional production. In particular, the amino acid derivative ectoine is known for its conformational stabilization, aggregation suppression, and radical protection properties. The natural producer and industrial production strain accumulates ectoine in the cytoplasm, and as a result offers a unique stabilizing environment for recombinant proteins.

Natronotalea proteinilytica gen. nov., sp. nov. and Longimonas haloalkaliphila sp. nov., extremely haloalkaliphilic members of the phylum Rhodothermaeota from hypersaline alkaline lakes.

Two proteolytic bacterial strains, BSker2 and BSker3, were enriched from sediments of hypersaline alkaline lakes in Kulunda Steppe (Altai, Russia) with chicken feathers as substrate, followed by pure culture isolation on hypersaline alkaline media with casein. The cells were non-motile, filamentous, flexible rods. The isolates were obligately aerobic heterotrophs utilizing proteins and peptides as growth substrates.

Discovery of extremely halophilic, methyl-reducing euryarchaea provides insights into the evolutionary origin of methanogenesis.

Methanogenic archaea are major players in the global carbon cycle and in the biotechnology of anaerobic digestion. The phylum Euryarchaeota includes diverse groups of methanogens that are interspersed with non-methanogenic lineages. So far, methanogens inhabiting hypersaline environments have been identified only within the order Methanosarcinales.

Influence of osmotic stress on desiccation and irradiation tolerance of (hyper)-thermophilic microorganisms.

This study examined the influence of prior salt adaptation on the survival rate of (hyper)-thermophilic bacteria and archaea after desiccation and UV or ionizing irradiation treatment. Survival rates after desiccation of Hydrogenothermus marinus and Archaeoglobus fulgidus increased considerably when the cells were cultivated at higher salt concentrations before drying. By doubling the concentration of NaCl, a 30 times higher survival rate of H.

Different strategies of osmoadaptation in the closely related marine myxobacteria SWB007 and SIR-1.

Only a few myxobacteria are known to date that are classified as marine, owing to their salt dependency. In this study, the salt tolerance mechanism of these bacteria was investigated. To this end, a growth medium was designed in which the mutated strain BKA13 served as sole food source for the predatory, heterotrophic myxobacteria.

The hydroxyectoine gene cluster of the non-halophilic acidophile Acidiphilium cryptum.

Acidiphilium cryptum is an acidophilic, heterotrophic α-Proteobacterium which thrives in acidic, metal-rich environments (e.g. acid mine drainage).

Glass-forming property of hydroxyectoine is the cause of its superior function as a desiccation protectant.

We were able to demonstrate that hydroxyectoine, in contrast to ectoine, is a good glass-forming compound. Fourier transform infrared and spin label electron spin resonance studies of dry ectoine and hydroxyectoine have shown that the superior glass-forming properties of hydroxyectoine result from stronger intermolecular H-bonds with the OH group of hydroxyectoine. Spin probe experiments have also shown that better molecular immobilization in dry hydroxyectoine provides better redox stability of the molecules embedded in this dry matrix.

Osmoadaptation strategy of the most halophilic fungus, Wallemia ichthyophaga, growing optimally at salinities above 15% NaCl.

Wallemia ichthyophaga is a fungus from the ancient basidiomycetous genus Wallemia (Wallemiales, Wallemiomycetes) that grows only at salinities between 10% (wt/vol) NaCl and saturated NaCl solution. This obligate halophily is unique among fungi. The main goal of this study was to determine the optimal salinity range for growth of the halophilic W.

Unexpected property of ectoine synthase and its application for synthesis of the engineered compatible solute ADPC.

A new cyclic amino acid was detected in a deletion mutant of the moderately halophilic bacterium Halomonas elongata deficient in ectoine synthesis. Using mass spectroscopy (MS) and nuclear magnetic resonance (NMR) techniques, the substance was identified as 5-amino-3,4-dihydro-2H-pyrrole-2-carboxylate (ADPC). We were able to demonstrate that ADPC is the product of a side reaction of lone ectoine synthase (EC 4.

Osmoadaptative accumulation of Nɛ-acetyl-β-lysine in green sulfur bacteria and Bacillus cereus CECT 148T.

The compatible solute N(ɛ)-acetyl-β-lysine (NeABL), thus far considered unique to methanogenic Archaea, has been found to accumulate in several strains of green sulfur bacteria (GSB) and Bacillus cereus CECT 148(T) under salt stress. A similar mixture of compatible solutes including trehalose, α-glutamate, β-glutamate and NeABL has been detected in salt-tolerant GSB strains of different phylogenetic branches. The ability of B.

Natural and engineered hydroxyectoine production based on the Pseudomonas stutzeri ectABCD-ask gene cluster.

We report on the presence of a functional hydroxyectoine biosynthesis gene cluster, ectABCD-ask, in Pseudomonas stutzeri DSM5190(T) and evaluate the suitability of P. stutzeri DSM5190(T) for hydroxyectoine production. Furthermore, we present information on heterologous de novo production of the compatible solute hydroxyectoine in Escherichia coli.

Thiohalorhabdus denitrificans gen. nov., sp. nov., an extremely halophilic, sulfur-oxidizing, deep-lineage gammaproteobacterium from hypersaline habitats.

Seven strains of extremely halophilic and obligately chemolithoautotrophic sulfur-oxidizing bacteria (SOB) were enriched and isolated at 4 M NaCl from sediments of hypersaline inland lakes in south-eastern Siberia and a Mediterranean sea solar saltern. Cells of the novel isolates were spindle-like, long and non-motile rods with a Gram-negative type of cell wall. They were obligately chemolithoautotrophic SOB using thiosulfate and tetrathionate as electron donors and represent the first example of extremely halophilic chemolithoautotrophs that are able to grow anaerobically with nitrate as electron acceptor.

A mathematical model for growth and osmoregulation in halophilic bacteria.

Many molecular details of the ecophysiology of halophilic bacteria that use compatible solutes to maintain osmotic equilibrium have been examined. We ask whether the details are consistent and complete enough to predict growth and osmoregulation in these bacteria by integrating this information in a mathematical model. Parameterized for the halophilic organism Halomonas elongata, the model predicts the substrate and salt dependence of growth, the uptake of potassium and ectoine and the synthesis of ectoine.

Heterologous ectoine production in Escherichia coli: by-passing the metabolic bottle-neck.

Transcription of the ectoine biosynthesis genes ectA, ectB and ectC from Marinococcus halophilus in recombinant Escherichia coli DH5alpha is probably initiated from three individual sigma70/sigmaA-dependent promoter sequences, upstream of each gene. Consequently, mRNA-fragments containing the single genes and combinations of the genes ectA and ectB or ectB and ectC, respectively, could be detected by Northern blot analysis. Under the control of its own regulatory promoter region (ectUp) a seemingly osmoregulated ectoine production was observed.

Sulfidogenesis under extremely haloalkaline conditions by Desulfonatronospira thiodismutans gen. nov., sp. nov., and Desulfonatronospira delicata sp. nov. - a novel lineage of Deltaproteobacteria from hypersaline soda lakes.

High rates of sulfidogenesis were observed in sediments from hypersaline soda lakes. Anaerobic enrichment cultures at 2 M Na(+) and pH 10 inoculated with sediment samples from these lakes produced sulfide most actively with sulfite and thiosulfate as electron acceptors, and resulted in the isolation of three pure cultures of extremely natronophilic sulfidogenic bacteria. Strain ASO3-1 was isolated using sulfite as a sole substrate, strain AHT 8 with thiosulfate and formate, and strain AHT 6 with thiosulfate and acetate.

Osmotic adaptation of the halophilic fungus Hortaea werneckii: role of osmolytes and melanization.

This study was intended to determine the osmoadaptation strategy of Hortaea werneckii, an extremely salt-tolerant melanized ascomycetous fungus that can grow at 0-5.1 M NaCl. It has been shown previously that glycerol is the major compatible solute in actively growing H.

Methylohalomonas lacus gen. nov., sp. nov. and Methylonatrum kenyense gen. nov., sp. nov., methylotrophic gammaproteobacteria from hypersaline lakes.

Aerobic enrichment at 4 M NaCl, pH 7.5, with methanol as carbon and energy source from sediments of hypersaline chloride-sulfate lakes in Kulunda Steppe (Altai, Russia) resulted in the isolation of a moderately halophilic and obligately methylotrophic bacterium, strain HMT 1(T). The bacterium grew with methanol and methylamine within a pH range of 6.