Non-disaccharide-based mechanisms of protection during drying

The biomedical potential of tardigrade proteins: A review

Tardigrades are ubiquitous microinvertebrates exhibiting extreme tolerance to various environmental stressors like low and high temperatures, lack of water, or high radiation. Although exact pathways behind the tardigrade extremotolerance are yet to be elucidated, some molecules involved have been identified. Their evidenced properties may lead to novel opportunities in biomedical and pharmacological development. This review aims to present the general characteristics of tardigrade intrinsically disordered proteins (TDPs: Dsup, CAHS, SAHS, MAHS) and late embryogenesis-abundant proteins (LEA) and provide an updated overview of their features and relevance for potential use in biomedicine and pharmacology. The Dsup reveals a promising action in attenuating oxidative stress, DNA damage, and pyrimidine dimerization, as well as increasing radiotolerance in transfected human cells. Whether Dsup can perform these functions when delivered externally is yet to be understood by in vivo preclinical testing. In turn, CAHS and SAHS demonstrate properties that could benefit the preservation of pharmaceuticals (e.g., vaccines) and biomaterials (e.g., cells). Selected CAHS proteins can also serve as inspiration for designing novel anti-apoptotic agents. The LEA proteins also reveal promising properties to preserve desiccated biomaterials and can act as anti-osmotic agents. In summary, tardigrade molecules reveal several potential biomedical applications advocating further research and development. The challenge of extracting larger amounts of these molecules can be solved with genetic engineering and synthetic biology tools. With new species identified each year and ongoing studies on their extremotolerance, progress in the medical use of tardigrade proteins is expected shortly.

Freeze-drying of nanoparticles: How to overcome colloidal instability by formulation and process optimization

Lyophilization of nanoparticle (NP) suspensions is a promising technology to improve stability, especially during long-term storage, and offers new routes of administration in solid state. Although considered as a gentle drying process, freeze-drying is also known to cause several stresses leading to physical instability, e.g. aggregation, fusion, or content leakage. NPs are heterogeneous regarding their physico-chemical properties which renders them different in their sensitivity to lyophilization stress and upon storage. But still basic concepts can be deducted. We summarize basic colloidal stabilization mechanisms of NPs in the liquid and the dried state. Furthermore, we give information about stresses occurring during the freezing and the drying step of lyophilization. Subsequently, we review the most commonly investigated NP types including lipophilic, polymeric, or vesicular NPs regarding their particle properties, stabilization mechanisms in the liquid state, and important freeze-drying process, formulation and storage strategies. Finally, practical advice is provided to facilitate purposeful formulation and process development to achieve NP lyophilizates with high colloidal stability.

Stabilization of Dry Sucrose Glasses by Four LEA_4 Proteins from Arabidopsis thaliana

Cells of many organisms and organs can withstand an (almost) total water loss (anhydrobiosis). Sugars play an essential role in desiccation tolerance due to their glass formation ability during dehydration. In addition, intrinsically disordered LEA proteins contribute to cellular survival under such conditions. One possible mechanism of LEA protein function is the stabilization of sugar glasses. However, little is known about the underlying mechanisms. Here we used FTIR spectroscopy to investigate sucrose (Suc) glass stability dried from water or from two buffer components in the presence of four recombinant LEA and globular reference proteins. Buffer ions influenced the strength of the Suc glass in the order Suc < Suc/Tris < Suc/NaP. LEA proteins strengthened the sugar H-bonded network and the molecular structure in the glassy state. The position of νOH peak and the wavenumber–temperature coefficient (WTC_g) provided similar information about the H-bonded network. Protein aggregation of LEA proteins was reduced in the desiccation-induced Suc glassy state. Detailed knowledge about the role of LEA proteins in the stabilization of dry sugar glasses yields information about their role in anhydrobiosis. This may open the possibility to use such proteins in biotechnical applications requiring dry storage of biologicals such as proteins, cells or tissues.

Epigenetic Integrity of Orthodox Seeds Stored under Conventional and Cryogenic Conditions

The level of 5-methylcytosine (m5C) in DNA has been observed to change in plants in response to biotic and abiotic stress factors. Little information has been reported on alterations in DNA methylation in orthodox tree seeds in response to storage conditions. In the current study, epigenetic integrity was analyzed in seeds of Pyrus communis L. in response to conventional and cryogenic storage. The results indicate that conventional storage under optimal conditions resulted in a significant increase in m5C. In contrast, a decrease in m5C level after cryostorage at high water content (WC) was observed, not only in seeds but also in 3-month-old seedlings which were smaller than seedlings obtained from seeds cryostored at optimal WC. This shows that non-optimal cryostorage conditions increase epigenetic instability in seeds and seedlings. Optimal procedures for germplasm conservation are very important for germplasm banking since they have serious implications for the quality of stored collections. Maintaining epigenetic integrity during WC adjustment and optimal storage is a characteristic feature of orthodox seeds. The current results underline the importance of proper protocols and techniques for conventional storage and particularly cryopreservation as a method for conservation of true-to-type germplasm for long periods.

Oxidation processes related to seed storage and seedling growth of Malus sylvestris, Prunus avium and Prunus padus

Seeds stored in controlled conditions in gene banks, faster or slower lose their viability. The effects of seed moisture content levels (ca. 5, 8, 11%) combined with storage temperatures (-3°, -18°, -196°C) were investigated in terms of the description of seeds defined as orthodox under oxidative stress after seed storage, during germination, and initial seedling growth. Hydrogen peroxide (H2O2), thiobarbituric acid reactive substances (TBARS) and ascorbate (Asc) were analyzed in relation to seed germinability and seedlings emergence in three species: Malus sylvestris L., Prunus avium L. and Prunus padus L. The effect of seed storage conditions on H2O2 levels appeared in germinated seeds after the third year of storage in each species. The H2O2 levels were negatively correlated with the germination and seedling emergence of P. avium seeds after three years of storage under all examined combinations. The emergence of P. padus seedlings was not linked to any of the stress markers tested. The P. padus seed biochemical traits were least altered by storage conditions, and the seeds produced tolerant seedlings of relatively high levels of H2O2 and TBARS. To cope with different H2O2 levels, TBARS levels, and Asc levels in seeds of three species varying storage conditions different molecular responses, i.e. repairing mechanisms, were applied during stratification to compensate for the storage conditions and, as a result, seeds remained viable and seedlings were successfully established.

Review of polysaccharide particle-based functional drug delivery

This review investigates the significant role polysaccharide particles play in functional drug delivery. The importance of these systems is due to the wide variety of polysaccharides and their natural source meaning that they can provide biocompatible and biodegradable systems with a range of both biological and chemical functionality valuable for drug delivery. This functionality includes protection and presentation of working therapeutics through avoidance of the reticuloendothelial system, stabilization of biomacromolecules and increasing the bioavailability of incorporated small molecule drugs. Transport of the therapeutic is also key to the utility of polysaccharide particles, moving drugs from the site of administration through mucosal binding and transport and using chemistry, size and receptor mediated drug targeting to specific tissues. This review also scrutinizes the methods of synthesizing and constructing functional polysaccharide particle drug delivery systems that maintain and extend the functionality of the natural polysaccharides.

Desiccation and radiation stress tolerance in cyanobacteria

Cyanobacteria are among the oldest living organisms on this planet, existing since more than 3 billion years. They are ideal organisms for investigating biological processes such as photosynthesis, respiration, circadian rhythm, photoregulation of gene expression, developmental gene rearrangements, and specialized cell differentiation. They are nearly ubiquitous in distribution, have colonized a wide range of ecosystems including soil, air, dry rock, and aquatic systems, and even occupy extreme niches that are inaccessible to other organisms. Such wide ecological distribution reflects their capacity to acclimate to extreme environments. They show great adaptive abilities and have survived various adverse physiological growth conditions like desiccation, high temperatures, extreme pH, cold, osmosis, salt, light, nitrogen, and high salinity. Their ancient origin and surviving through numerous stresses during evolution indicates their remarkable capabilities to survive and prevail under different environmental and man-made stresses. It has been hypothesized that similar and overlap stress response mechanisms help them to survive different stresses. It has been stated that responses against stresses like radiation has been accidental-exhibited because of similar response against desiccation stress, which has prevailed more during evolution. These overlaps and similarities in stress responses have been instrumental in making these organisms a large class of biological entities today. Present review discuss about stress tolerance in cyanobacteria against two extreme stresses - desiccation and gamma radiation. It also discuss the commonality and underlying molecular mechanisms in these two stress responses.

Genes for seed longevity in barley identified by genomic analysis on near isogenic lines

Genes controlling differences in seed longevity between 2 barley (Hordeum vulgare) accessions were identified by combining quantitative genetics "omics" technologies in near isogenic lines (NILs). The NILs were derived from crosses between the spring barley landraces L94 from Ethiopia and Cebada Capa from Argentina. A combined transcriptome and proteome analysis on mature, nonaged seeds of the 2 parental lines and the L94 NILs by RNA-sequencing and total seed proteomic profiling identified the UDP-glycosyltransferase MLOC_11661.1 as candidate gene for the quantitative trait loci on 2H, and the NADP-dependent malic enzyme (NADP-ME) MLOC_35785.1 as possible downstream target gene. To validate these candidates, they were expressed in Arabidopsis under the control of constitutive promoters to attempt complementing the T-DNA knockout line nadp-me1. Both the NADP-ME MLOC_35785.1 and the UDP-glycosyltransferase MLOC_11661.1 were able to rescue the nadp-me1 seed longevity phenotype. In the case of the UDP-glycosyltransferase, with high accumulation in NILs, only the coding sequence of Cebada Capa had a rescue effect.

Comparative studies on the chemical and enzymatic stability of alpha- and beta-arbutin

OBJECTIVE

The aim of this study was to establish a comparative analysis of the chemical and enzymatic stability of α- and β-arbutins as potential sources of the substance of concern hydroquinone (HQ). The study was performed using an array of techniques including HPLC-PDA, nuclear magnetic resonance (NMR) and optical rotation (OR). Both arbutins are emerging as popular and effective skin whiteners, acting as tyrosinase inhibitors in a fashion similar to the popular whitening agent HQ. Due to their structural similarity to the regulated agent HQ, both arbutins may be regarded as potential sources of the active aglycone after chemical or metabolic conversion.

METHODS

Various cosmetic formulations including creams, sera, gels and lotions were analysed by HPLC-PDA for their arbutin and HQ content in freshly opened and aged samples stored for 16 months. Solutions of pure compounds were also aged and periodically checked for degradation products using 1D and 2D NMR experiments and OR measurements. The metabolic stability was investigated using pear peels as a biological model.

RESULTS

Both arbutins were found to be stable in water and methanol solutions in the absence of buffer or stabilizers. Their stability in cosmetic formulations, however, was found to depend on the type of formulation and pH. Both compounds were unstable under strong hydrolytic conditions, with consequent release of HQ. Enzymatic instability of both arbutins was also observed, although no formation of HQ was observed under the chosen experimental conditions.

CONCLUSION

Both arbutins were found to possess similar stability profiles, and to be more prone to in vivo rather than in chemico degradation, although no HQ was found after enzymatic hydrolysis. Also, no epimerization was observed in any of the tested conditions. Diverse experimental approaches can be applied to analyse the chemical and enzymatic stability of arbutins in regard to the potential release of HQ in different types of preparations. These result showed the potential use of NMR and OR as complementary investigative tools for the stability and safety assessment of arbutin along with more established HPLC methods.

The intrinsically disordered protein LEA7 from Arabidopsis thaliana protects the isolated enzyme lactate dehydrogenase and enzymes in a soluble leaf proteome during freezing and drying

The accumulation of Late Embryogenesis Abundant (LEA) proteins in plants is associated with tolerance against stresses such as freezing and desiccation. Two main functions have been attributed to LEA proteins: membrane stabilization and enzyme protection. We have hypothesized previously that LEA7 from Arabidopsis thaliana may stabilize membranes because it interacts with liposomes in the dry state. Here we show that LEA7, contrary to this expectation, did not stabilize liposomes during drying and rehydration. Instead, it partially preserved the activity of the enzyme lactate dehydrogenase (LDH) during drying and freezing. Fourier-transform infrared (FTIR) spectroscopy showed no evidence of aggregation of LDH in the dry or rehydrated state under conditions that lead to complete loss of activity. To approximate the complex influence of intracellular conditions on the protective effects of a LEA protein in a convenient in-vitro assay, we measured the activity of two Arabidopsis enzymes (glucose-6-P dehydrogenase and ADP-glucose pyrophosphorylase) in total soluble leaf protein extract (Arabidopsis soluble proteome, ASP) after drying and rehydration or freezing and thawing. LEA7 partially preserved the activity of both enzymes under these conditions, suggesting its role as an enzyme protectant in vivo. Further FTIR analyses indicated the partial reversibility of protein aggregation in the dry ASP during rehydration. Similarly, aggregation in the dry ASP was strongly reduced by LEA7. In addition, mixtures of LEA7 with sucrose or verbascose reduced aggregation more than the single additives, presumably through the effects of the protein on the H-bonding network of the sugar glasses.

Interactions of the amphiphiles arbutin and tryptophan with phosphatidylcholine and phosphatidylethanolamine bilayers in the dry state

BACKGROUND

Water is essential for life, but some organisms can survive complete desiccation, while many more survive partial dehydration during drying or freezing. The function of some protective molecules, such as sugars, has been extensively studied, but much less is known about the effects of amphiphiles such as flavonoids and other aromatic compounds. Amphiphiles may be largely soluble under fully hydrated conditions, but will partition into membranes upon removal of water. Little is known about the effects of amphiphiles on membrane stability and how amphiphile structure and function are related. Here, we have used two of the most intensively studied amphiphiles, tryptophan (Trp) and arbutin (Arb), along with their isolated hydrophilic moieties glycine (Gly) and glucose (Glc) to better understand structure-function relationships in amphiphile-membrane interactions in the dry state.

RESULTS

Fourier-transform infrared (FTIR) spectroscopy was used to measure gel-to-liquid crystalline phase transition temperatures (Tm) of liposomes formed from phosphatidylcholine and phosphatidylethanolamine in the presence of the different additives. In anhydrous samples, both Glc and Arb strongly depressed Tm, independent of lipid composition, while Gly had no measurable effect. Trp, on the other hand, either depressed or increased Tm, depending on lipid composition. We found no evidence for strong interactions of any of the compounds with the lipid carbonyl or choline groups, while all additives except Gly seemed to interact with the phosphate groups. In the case of Arb and Glc, this also had a strong effect on the sugar OH vibrations in the FTIR spectra. In addition, vibrations from the hydrophobic indole and phenol moieties of Trp and Arb, respectively, provided evidence for interactions with the lipid bilayers.

CONCLUSIONS

The two amphiphiles Arb and Trp interact differently with dry bilayers. The interactions of Arb are dominated by contributions of the Glc moiety, while the indole governs the effects of Trp. In addition, only Trp-membrane interactions showed a strong influence of lipid composition. Further investigations, using the large structural diversity of plant amphiphiles will help to understand how their structure determines the interaction with membranes and how that influences their biological functions, for example under freezing or dehydration conditions.

A fluorometric assay for trehalose in the picomole range

BACKGROUND

Trehalose is a non-reducing disaccharide that is used as an osmolyte, transport sugar, carbon reserve and stress protectant in a wide range of organisms. In plants, trehalose 6-phosphate (Tre6P), the intermediate of trehalose biosynthesis, is thought to be a signal of sucrose status. Trehalose itself may play a role in pathogenic and symbiotic plant-microbe interactions, in responses to abiotic stress and in developmental signalling, but its precise functions are unknown. A major obstacle to investigating its function is the technical difficulty of measuring the very low levels of trehalose usually found in plant tissues, as most of the established trehalose assays lack sufficient specificity and/or sensitivity.

RESULTS

A kinetic assay for trehalose was established using recombinant Escherichia coli cytoplasmic trehalase (treF), which was shown to be highly specific for trehalose. Hydrolysis of trehalose to glucose is monitored fluorometrically and the trehalose content of the tissue extract is determined from an internal calibration curve. The assay is linear for 0.2-40 pmol trehalose, and recoveries of trehalose were ≥88%. A. thaliana Col-0 rosettes contain about 20-30 nmol g-1FW of trehalose, increasing to about 50-60 nmol g-1FW in plants grown at 8°C. Trehalose is not correlated with sucrose content, whereas a strong correlation between Tre6P and sucrose was confirmed. The trehalose contents of ear inflorescence primordia from the maize ramosa3 mutant and wild type plants were 6.6±2.6 nmol g-1FW and 19.0±12.7 nmol g-1FW, respectively. The trehalose:Tre6P ratios in the ramosa3 and wild-type primordia were 2.43±0.85 and 6.16±3.45, respectively.

CONCLUSION

The fluorometric assay is highly specific for trehalose and sensitive enough to measure the trehalose content of very small amounts of plant tissue. Chilling induced a 2-fold accumulation of trehalose in A. thaliana rosettes, but the levels were too low to make a substantial quantitative contribution to osmoregulation. Trehalose is unlikely to function as a signal of sucrose status. The abnormal inflorescence branching phenotype of the maize ramosa3 mutant might be linked to a decrease in trehalose levels in the inflorescence primordia or a downward shift in the trehalose:Tre6P ratio.

Purification and partial biochemical-genetic characterization of trehalose 6-phosphate synthase from muscles of adult female Ascaris suum

Trehalose 6-phosphate (T6P) synthase (TPS; EC 2.4.1.15) was isolated from muscles of Ascaris suum by ammonium sulphate fractionation, ion-exchange DEAE SEPHACEL(TM) anion exchanger column chromatography and Sepharose 6B gel filtration. On sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE), 265-fold purified TPS exhibited a molecular weight of 66 kDa. The optimum pH and temperature of the purified enzyme were 3.8-4.2 and 35°C, respectively. The isoelectric point (pI) of TPS was pH 5.4. The studied TPS was not absolutely substrate specific. Besides glucose 6-phosphate, the enzyme was able to use fructose 6-phosphate as an acceptor of glucose. TPS was activated by 10 mM MgCl2, 10 mM CaCl2 and 10 mM NaCl. In addition, it was inhibited by ethylenediaminetetra-acetic acid (EDTA), KCl, FeCl3 and ZnCl2. Two genes encoding TPS were isolated and sequenced from muscles of the parasite. Complete coding sequences for tps1 (JF412033.2) and tps2 (JF412034.2) were 3917 bp and 3976 bp, respectively. Translation products (AEX60788.1 and AEX60787.1) showed expression to the glucosyltransferase-GTB-type superfamily.

Genetic analysis of desiccation tolerance in Sachharomyces cerevisiae

Desiccation tolerance, the ability to survive nearly total dehydration, is a rare strategy for survival and reproduction observed in all taxa. However, the mechanism and regulation of this phenomenon are poorly understood. Correlations between desiccation tolerance and potential effectors have been reported in many species, but their physiological significance has not been established in vivo. Although the budding yeast Saccharomyces cerevisiae exhibits extreme desiccation tolerance, its usefulness has been hampered by an inability to reduce tolerance more than a few fold by physiological or genetic perturbations. Here we report that fewer than one in a million yeast cells from low-density logarithmic cultures survive desiccation, while 20-40% of cells from saturated cultures survive. Using this greatly expanded metric, we show that mutants defective in trehalose biosynthesis, hydrophilins, responses to hyperosmolarity, and hypersalinity, reactive oxygen species (ROS) scavenging and DNA damage repair nevertheless retain wild-type levels of desiccation tolerance, suggesting that this trait involves a unique constellation of stress factors. A genome-wide screen for mutants that render stationary cells as sensitive as log phase cells identifies only mutations that block respiration. Respiration as a prerequisite for acquiring desiccation tolerance is corroborated by respiration inhibition and by growth on nonfermentable carbon sources. Suppressors bypassing the respiration requirement for desiccation tolerance reveal at least two pathways, one of which, involving the Mediator transcription complex, is associated with the shift from fermentative to respiratory metabolism. Further study of these regulators and their targets should provide important clues to the sensors and effectors of desiccation tolerance.

Thermotropic phase behavior and headgroup interactions of the nonbilayer lipids phosphatidylethanolamine and monogalactosyldiacylglycerol in the dry state

BACKGROUND

Although biological membranes are organized as lipid bilayers, they contain a substantial fraction of lipids that have a strong tendency to adopt a nonlamellar, most often inverted hexagonal (HII) phase. The polymorphic phase behavior of such nonbilayer lipids has been studied previously with a variety of methods in the fully hydrated state or at different degrees of dehydration. Here, we present a study of the thermotropic phase behavior of the nonbilayer lipids egg phosphatidylethanolamine (EPE) and monogalactosyldiacylglycerol (MGDG) with a focus on interactions between the lipid molecules in the interfacial and headgroup regions.

RESULTS

Liposomes were investigated in the dry state by Fourier-transform Infrared (FTIR) spectroscopy and Differential Scanning Calorimetry (DSC). Dry EPE showed a gel to liquid-crystalline phase transition below 0°C and a liquid-crystalline to HII transition at 100°C. MGDG, on the other hand, was in the liquid-crystalline phase down to -30°C and showed a nonbilayer transition at about 85°C. Mixtures (1:1 by mass) with two different phosphatidylcholines (PC) formed bilayers with no evidence for nonbilayer transitions up to 120°C. FTIR spectroscopy revealed complex interactions between the nonbilayer lipids and PC. Strong H-bonding interactions occurred between the sugar headgroup of MGDG and the phosphate, carbonyl and choline groups of PC. Similarly, the ethanolamine moiety of EPE was H-bonded to the carbonyl and choline groups of PC and probably interacted through charge pairing with the phosphate group.

CONCLUSIONS

This study provides a comprehensive characterization of dry membranes containing the two most important nonbilayer lipids (PE and MGDG) in living cells. These data will be of particular relevance for the analysis of interactions between membranes and low molecular weight solutes or soluble proteins that are presumably involved in cellular protection during anhydrobiosis.

Coordination of frontline defense mechanisms under severe oxidative stress

Inference of an environmental and gene regulatory influence network (EGRIN_OS) by integrating transcriptional responses to H₂O₂ and paraquat (PQ) has revealed a multi-tiered oxidative stress (OS)-management program to transcriptionally coordinate three peroxidase/catalase enzymes, two superoxide dismutases, production of rhodopsins, carotenoids and gas vesicles, metal trafficking, and various other aspects of metabolism.

ChIP-chip, microarray, and survival assays have validated important architectural aspects of this network, identified novel defense mechanisms (including two evolutionarily distant peroxidase enxymes), and showed that general transcription factors of the transcription factor B family have an important function in coordinating the OS response (OSR) despite their inability to directly sense ROS.

A comparison of transcriptional responses to sub-lethal doses of H₂O₂ and PQ with predictions of these responses made by an EGRIN model generated earlier from responses to other environmental factors has confirmed that a significant fraction of the OSR is made up of a generalized component that is also observed in response to other stressors.

Analysis of active regulons within environment and gene regulatory influence network for OS (EGRIN_OS) across diverse environmental conditions has identified the specialized component of oxidative stress response (OSR) that is triggered by sub-lethal OS, but not by other stressors, including sub-inhibitory levels of redox-active metals, extreme changes in oxygen tension, and a sub-lethal dose of γ rays.

Reactive oxygen species (ROS), such as hydrogen peroxide (H₂O₂), superoxide (O₂⁻), and hydroxyl (OH⁻) radicals, are normal by-products of aerobic metabolism. Evolutionarily conserved mechanisms including detoxification enzymes (peroxidase/catalase and superoxide dismutase (SOD)) and free radical scavengers manage this endogenous production of ROS. OS is a condition reached when certain environmental stresses or genetic defects cause the production of ROS to exceed the management capacity. The damage to diverse cellular components including DNA, proteins, lipids, and carbohydrates resulting from OS (Imlay, 2003; Apel and Hirt, 2004; Perrone et al, 2008) is recognized as an important player in many diseases and in the aging process (Finkel, 2005).

We have applied a systems approach to characterize the OSR of an archaeal model organism, Halobacterium salinarum NRC-1. This haloarchaeon grows aerobically at 4.3 M salt concentration in which it routinely faces cycles of desiccation and rehydration, and increased ultraviolet radiation—both of which can increase the production of ROS (Farr and Kogoma, 1991; Oliver et al, 2001). We have reconstructed the physiological adjustments associated with management of excessive OS through the analysis of global transcriptional changes elicited by step exposure to growth sub-inhibitory and sub-lethal levels of H₂O₂ and PQ (a redox-cycling drug that produces O₂⁻; Hassan and Fridovich, 1979) as well as during subsequent recovery from these stresses. We have integrated all of these data into a unified model for OSR to discover conditional functional links between protective mechanisms and normal aspects of metabolism. Subsequent phenotypic analysis of gene deletion strains has verified the conditional detoxification functions of three putative peroxidase/catalase enzymes, two SODs, and the protective function of rhodopsins under increased levels of H₂O₂ and PQ. Similarly, we have also validated ROS scavenging by carotenoids and flotation by gas vesicles as secondary mechanisms that may minimize OS.

Given the ubiquitous nature of OS, it is not entirely surprising that most organisms have evolved similar multiple lines of defense—both passive and active. Although such mechanisms have been extensively characterized using other model organisms, our integrated systems approach has uncovered additional protective mechanisms in H. salinarum (e.g. two evolutionarily distant peroxidase/catalase enzymes) and revealed a structure and hierarchy to the OSR through conditional regulatory associations among various components of the response. We have validated some aspects of the architecture of the regulatory network for managing OS by confirming physical protein–DNA interactions of six transcription factors (TFs) with promoters of genes they were predicted to influence in EGRIN_OS. Furthermore, we have also shown the consequence of deleting two of these TFs on transcript levels of genes they control and survival rate under OS. It is notable that these TFs are not directly associated with sensing ROS, but, rather, they have a general function in coordinating the overall response. This insight would not have been possible without constructing EGRIN_OS through systems integration of diverse datasets.

Although it has been known that OS is a component of diverse environmental stress conditions, we quantitatively show for the first time that much of the transcriptional responses induced by the two treatments could indeed have been predicted using a model constructed from the analysis of transcriptional responses to changes in other environmental factors (UV and γ-radiation, light, oxygen, and six metals). However, using specific examples we also reveal the specific components of the OSR that are triggered only under severe OS. Notably, this model of OSR gives a unified perspective of the interconnections among all of these generalized and OS-specific regulatory mechanisms.

Complexity of cellular response to oxidative stress (OS) stems from its wide-ranging damage to nucleic acids, proteins, carbohydrates, and lipids. We have constructed a systems model of OS response (OSR) for Halobacterium salinarum NRC-1 in an attempt to understand the architecture of its regulatory network that coordinates this complex response. This has revealed a multi-tiered OS-management program to transcriptionally coordinate three peroxidase/catalase enzymes, two superoxide dismutases, production of rhodopsins, carotenoids and gas vesicles, metal trafficking, and various other aspects of metabolism. Through experimental validation of interactions within the OSR regulatory network, we show that despite their inability to directly sense reactive oxygen species, general transcription factors have an important function in coordinating this response. Remarkably, a significant fraction of this OSR was accurately recapitulated by a model that was earlier constructed from cellular responses to diverse environmental perturbations—this constitutes the general stress response component. Notwithstanding this observation, comparison of the two models has identified the coordination of frontline defense and repair systems by regulatory mechanisms that are triggered uniquely by severe OS and not by other environmental stressors, including sub-inhibitory levels of redox-active metals, extreme changes in oxygen tension, and a sub-lethal dose of γ rays.

Transcriptome survey of the anhydrobiotic tardigrade Milnesium tardigradum in comparison with Hypsibius dujardini and Richtersius coronifer

Background

The phenomenon of desiccation tolerance, also called anhydrobiosis, involves the ability of an organism to survive the loss of almost all cellular water without sustaining irreversible damage. Although there are several physiological, morphological and ecological studies on tardigrades, only limited DNA sequence information is available. Therefore, we explored the transcriptome in the active and anhydrobiotic state of the tardigrade Milnesium tardigradum which has extraordinary tolerance to desiccation and freezing. In this study, we present the first overview of the transcriptome of M. tardigradum and its response to desiccation and discuss potential parallels to stress responses in other organisms.

Results

We sequenced a total of 9984 expressed sequence tags (ESTs) from two cDNA libraries from the eutardigrade M. tardigradum in its active and inactive, anhydrobiotic (tun) stage. Assembly of these ESTs resulted in 3283 putative unique transcripts, whereof ~50% showed significant sequence similarity to known genes. The resulting unigenes were functionally annotated using the Gene Ontology (GO) vocabulary. A GO term enrichment analysis revealed several GOs that were significantly underrepresented in the inactive stage. Furthermore we compared the putative unigenes of M. tardigradum with ESTs from two other eutardigrade species that are available from public sequence databases, namely Richtersius coronifer and Hypsibius dujardini. The processed sequences of the three tardigrade species revealed similar functional content and the M. tardigradum dataset contained additional sequences from tardigrades not present in the other two.

Conclusions

This study describes novel sequence data from the tardigrade M. tardigradum, which significantly contributes to the available tardigrade sequence data and will help to establish this extraordinary tardigrade as a model for studying anhydrobiosis. Functional comparison of active and anhydrobiotic tardigrades revealed a differential distribution of Gene Ontology terms associated with chromatin structure and the translation machinery, which are underrepresented in the inactive animals. These findings imply a widespread metabolic response of the animals on dehydration. The collective tardigrade transcriptome data will serve as a reference for further studies and support the identification and characterization of genes involved in the anhydrobiotic response.

Antioxidant defences in hydrated and desiccated states of the tardigrade Paramacrobiotus richtersi

Reactive oxygen species (ROS) are formed in all aerobic organisms, potentially leading to oxidative damage of all biological molecules. A number of defence mechanisms have developed to protect the organism from attack by ROS. Desiccation tolerance is correlated with an increase in the antioxidant potential in several organisms, but the regulation of the antioxidant defence system is complex and its role in desiccation-tolerant organisms is not yet firmly established. To determine if anhydrobiotic tardigrades have an antioxidant defence system, capable of counteracting ROS, we compared the activity of several antioxidant enzymes, the fatty acid composition and Heat shock protein expression in two physiological states (desiccated vs. hydrated) of the tardigrade Paramacrobiotus richtersi. In hydrated tardigrades, superoxide dismutase and catalase show comparable activities, while in desiccated specimens the activity of superoxide dismutase increases. Both glutathione peroxidase and glutathione were induced by desiccation. The percentage of fatty acid composition of polyunsaturated fatty acids and the amount of thiobarbituric acid reactive substances are higher in desiccated animals than in hydrated ones. Lastly, desiccated tardigrades did not differ significantly from the hydrated ones in the relative levels of Hsp70 and Hsp90. These results indicate that the possession of antioxidant metabolism could represent a crucial strategy to avoid damages during desiccation in anhydrobiotic tardigrades.

Development of desiccation tolerance and vitrification by preculture treatment in suspension-cultured cells of the liverwort Marchantia polymorpha

Some cultured plant cells are able to acquire tolerance to various stresses when they are cultured under suitably controlled conditions. Induction of a high level of desiccation tolerance in suspension-cultured cells of the liverwort Marchantia polymorpha was examined for studying the mechanisms of desiccation tolerance and vitrification at the cellular level. Desiccation tolerance level of cells was very low and the survival rate was less than 10% after exposure to drying below 0.1 g H(2)O g(-1) dry weight (DW). Preculture treatment in 0.5 M sucrose medium was the most effective method for inducing a high level of desiccation tolerance in cells and the survival rate was 87% even after being desiccated to below 0.1 g H(2)O g(-1) DW. Preculture treatment caused alteration of cell structures and accumulation of a large amount of sucrose and newly synthesized proteins in cells. Abundant sucrose and preculture-induced proteins were necessary for full development of desiccation tolerance in the cells. When water content decreased to below 0.1 g H(2)O g(-1) DW, desiccation-tolerant cells that had been precultured were vitrified above 0 degrees C and maintained stable viability. We have succeeded in the induction of desiccation tolerance that allows formation of intracellular glass with cell viability at ambient temperatures by controlling culture conditions, and our results suggest that suspension-cultured cells of M. polymorpha are useful for studying cellular mechanisms for the development of desiccation tolerance and the stabilization of vitrified cells.

Application of functional genomics and proteomics to plant cryopreservation

Plant cryobiology has primarily emerged from the classical fields of cryobiology and plant stress physiology. Cryopreservation tools are now available to geneticists for germplasm preservation and the field itself is advancing significantly through the use of molecular techniques. Long-term preservation of vegetatively propagated tissues can minimize the risks of long-term maintenance under tissue culture or field conditions. Cells can be successfully cryopreserved when the adverse affects of ice crystal formation are mitigated by the removal of water or procedures to limit ice formation and crystal growth. The addition of cryoprotectant solutions to hydrated cells may improve the survival of microdissected shoot tips or embryonic axes. Recent discoveries in the genetic pathways leading to cold acclimation and freezing tolerance suggest the involvement of key cold-regulated genes in the acquisition of cold tolerance in plant tissues. Model systems of banana and Arabidopsis have revealed the involvement of genes and proteins in the glycolytic and other metabolic pathways, particularly processes involved in dehydration tolerance, osmoprotection, and membrane transport. Furthermore, successful recovery appears to be dependent upon the presence of antioxidant protection from reactive oxygen species. Characterization of specific genes and proteins will lead to significant advances in plant cryobiology research.

Survival and DNA degradation in anhydrobiotic tardigrades

Anhydrobiosis is a highly stable state of suspended animation in an organism due to its desiccation, which is followed by recovery after rehydration. Changes occurring during drying could damage molecules, including DNA. Using the anhydrobiotic tardigrade Paramacrobiotus richtersi as a model organism, we have evaluated the effects of environmental factors, such as temperature and air humidity level (RH), on the survival of desiccated animals and on the degradation of their DNA. Tardigrades naturally desiccated in leaf litter and tardigrades experimentally desiccated on blotting paper were considered. Replicates were kept at 37 degrees C and at different levels of RH for 21 days. RH values and temperature, as well as time of exposure to these environmental factors, have a negative effect on tardigrade survival and on the time required by animals to recover active life after desiccation. DNA damages (revealed as single strand breaks) occurred only in desiccated tardigrades kept for a long time at high RH values. These results indicate that during the anhydrobiotic state, damages take place and accumulate with time. Two hypotheses can be formulated to explain the results: (i) oxidative damages occur in desiccated specimens of P. richtersi, and (ii) high temperatures and high RH values change the state of the disaccharide trehalose, reducing its protective role.

Non-reducing sugar levels in beech (Fagus sylvatica) seeds as related to withstanding desiccation and storage

Levels of sucrose and raffinose family oligosaccharides (RFOs) (raffinose and stachyose) were determined in beech (Fagus sylvatica L.) seeds during development, maturation, desiccation and storage. An increase in RFOs and a marked decrease in the S:(R+St) ratio (i.e. mass ratio of sucrose to the sum of RFOs) were observed at the time of desiccation tolerance (DT) acquisition by seeds. In seeds stored at -10 degrees C through 1, 4, 7, and 12 years, changes in sucrose, raffinose and stachyose levels and in alpha-galactosidase activity were noted. The S/R+St ratio and alpha-galactosidase activity significantly increased in seeds after 7 and 12 years of storage, when a marked decrease in viability, measured as germination capacity, was recorded. Germination capacity was found to be strongly correlated with sucrose content, the S:(R+St) ratio, and alpha-galactosidase activity. A strong positive correlation was found between germination capacity and stachyose content. The results clearly indicated that the composition of RFOs in beech seeds is closely related to DT acquisition and seed viability during storage.

Fructan and its relationship to abiotic stress tolerance in plants

Numerous studies have been published that attempted to correlate fructan concentrations with freezing and drought tolerance. Studies investigating the effect of fructan on liposomes indicated that a direct interaction between membranes and fructan was possible. This new area of research began to move fructan and its association with stress beyond mere correlation by confirming that fructan has the capacity to stabilize membranes during drying by inserting at least part of the polysaccharide into the lipid headgroup region of the membrane. This helps prevent leakage when water is removed from the system either during freezing or drought. When plants were transformed with the ability to synthesize fructan, a concomitant increase in drought and/or freezing tolerance was confirmed. These experiments indicate that besides an indirect effect of supplying tissues with hexose sugars, fructan has a direct protective effect that can be demonstrated by both model systems and genetic transformation.

Effect of trehalose on a phospholipid membrane under mechanical stress

Explicit solvent molecular dynamics simulations were used to investigate at atomic resolution the effect of trehalose on a hydrated phospholipid bilayer under mechanical stress (stretching forces imposed in the form of negative lateral pressure). Simulations were performed in the absence or presence of trehalose at 325 K, and with different values for negative lateral pressure. In the concentration regime (2 molal) and range of lateral pressures (1 to -250 bar) investigated, trehalose was found to interact directly with the membrane, partially replacing water molecules in the formation of hydrogen bonds with the lipid headgroups. Similar to previous findings in the context of thermal stress, the number, degree of bridging, and reaching depth of these hydrogen bonds increased with the magnitude of perturbation. However, at the concentration considered, trehalose was not sufficient to preserve the integrity of the membrane structure and to prevent its extreme elongation (and possible disruption) under the effect of stretching forces.

The ectopic overexpression of a seed-specific transcription factor, HaHSFA9, confers tolerance to severe dehydration in vegetative organs

Most plant seeds tolerate desiccation, but vegetative tissues are intolerant to drastic dehydration, except in the case of resurrection plants. Therefore, changes in the regulation of genes normally expressed in seeds are thought to be responsible for the evolutionary origin of desiccation tolerance in resurrection plants. Here, we show that constitutive overexpression of the seed-specific HSFA9 transcription factor from sunflower is sufficient to confer tolerance to severe dehydration, outside of the developing seed context, to vegetative tissues of transgenic tobacco. Whole 3-week-old seedlings could survive severe dehydration. This was quantified as a water loss to 1.96 +/- 0.05% of the initial water content, which corresponds to a water potential of approximately -40 MPa. Survival depended on the water potential, from 40% survival at approximately -20 MPa to 6.5% survival at approximately -40 MPa. Whole-seedling survival was limited by the dehydration sensitivity of the roots. Survival correlated with the ectopic expression of a genetic program involving seed-specific, small heat-shock proteins, but not late embryogenesis abundant proteins. The accumulation of sucrose or raffinose family oligosaccharides was not altered by HSFA9. The observed tolerance was achieved without a reduction of growth and development. Our results strongly support the previously suggested contribution of small heat-shock proteins to the desiccation tolerance of seeds. We provide a successful system for analyzing tolerance to severe dehydration in all vegetative organs of seedlings. We propose that HSFA9 is a potential genetic switch involved in the evolution of tolerance to vegetative desiccation.

cAMP regulates respiration and oxidative stress during rehydration in Anabaena sp. PCC 7120

Cellular cAMP level increased dramatically upon rehydration following dehydration for 24h in Anabaena sp. PCC 7120, but not in disruptant of an adenylate cyclase gene, cyaC. Oxygen consumption in the cyaC disruptant upon rehydration was higher than that in wild-type strain. Determination of lipid peroxidation and protein carbonylation of the cells revealed greater oxidative stress in the cyaC disruptant than in the wild-type strain during rehydration. Addition of cAMP or KCN to the cyaC disruptant decreased cellular oxygen consumption upon rehydration and oxidative damage. These results suggest that respiration upon rehydration is regulated by cAMP and that the higher respiration activity results in more oxidative damage in cyaC disruptant.

LEA (late embryogenesis abundant) proteins and their encoding genes in Arabidopsis thaliana

BACKGROUND

LEA (late embryogenesis abundant) proteins have first been described about 25 years ago as accumulating late in plant seed development. They were later found in vegetative plant tissues following environmental stress and also in desiccation tolerant bacteria and invertebrates. Although they are widely assumed to play crucial roles in cellular dehydration tolerance, their physiological and biochemical functions are largely unknown.

RESULTS

We present a genome-wide analysis of LEA proteins and their encoding genes in Arabidopsis thaliana. We identified 51 LEA protein encoding genes in the Arabidopsis genome that could be classified into nine distinct groups. Expression studies were performed on all genes at different developmental stages, in different plant organs and under different stress and hormone treatments using quantitative RT-PCR. We found evidence of expression for all 51 genes. There was only little overlap between genes expressed in vegetative tissues and in seeds and expression levels were generally higher in seeds. Most genes encoding LEA proteins had abscisic acid response (ABRE) and/or low temperature response (LTRE) elements in their promoters and many genes containing the respective promoter elements were induced by abscisic acid, cold or drought. We also found that 33% of all Arabidopsis LEA protein encoding genes are arranged in tandem repeats and that 43% are part of homeologous pairs. The majority of LEA proteins were predicted to be highly hydrophilic and natively unstructured, but some were predicted to be folded.

CONCLUSION

The analyses indicate a wide range of sequence diversity, intracellular localizations, and expression patterns. The high fraction of retained duplicate genes and the inferred functional diversification indicate that they confer an evolutionary advantage for an organism under varying stressful environmental conditions. This comprehensive analysis will be an important starting point for future efforts to elucidate the functional role of these enigmatic proteins.

LEA (late embryogenesis abundant) proteins and their encoding genes in Arabidopsis thaliana

Background

LEA (late embryogenesis abundant) proteins have first been described about 25 years ago as accumulating late in plant seed development. They were later found in vegetative plant tissues following environmental stress and also in desiccation tolerant bacteria and invertebrates. Although they are widely assumed to play crucial roles in cellular dehydration tolerance, their physiological and biochemical functions are largely unknown.

Results

We present a genome-wide analysis of LEA proteins and their encoding genes in Arabidopsis thaliana. We identified 51 LEA protein encoding genes in the Arabidopsis genome that could be classified into nine distinct groups. Expression studies were performed on all genes at different developmental stages, in different plant organs and under different stress and hormone treatments using quantitative RT-PCR. We found evidence of expression for all 51 genes. There was only little overlap between genes expressed in vegetative tissues and in seeds and expression levels were generally higher in seeds. Most genes encoding LEA proteins had abscisic acid response (ABRE) and/or low temperature response (LTRE) elements in their promoters and many genes containing the respective promoter elements were induced by abscisic acid, cold or drought. We also found that 33% of all Arabidopsis LEA protein encoding genes are arranged in tandem repeats and that 43% are part of homeologous pairs. The majority of LEA proteins were predicted to be highly hydrophilic and natively unstructured, but some were predicted to be folded.

Conclusion

The analyses indicate a wide range of sequence diversity, intracellular localizations, and expression patterns. The high fraction of retained duplicate genes and the inferred functional diversification indicate that they confer an evolutionary advantage for an organism under varying stressful environmental conditions. This comprehensive analysis will be an important starting point for future efforts to elucidate the functional role of these enigmatic proteins.

LEA (late embryogenesis abundant) proteins and their encoding genes in Arabidopsis thaliana

BACKGROUND

LEA (late embryogenesis abundant) proteins have first been described about 25 years ago as accumulating late in plant seed development. They were later found in vegetative plant tissues following environmental stress and also in desiccation tolerant bacteria and invertebrates. Although they are widely assumed to play crucial roles in cellular dehydration tolerance, their physiological and biochemical functions are largely unknown.

RESULTS

We present a genome-wide analysis of LEA proteins and their encoding genes in Arabidopsis thaliana. We identified 51 LEA protein encoding genes in the Arabidopsis genome that could be classified into nine distinct groups. Expression studies were performed on all genes at different developmental stages, in different plant organs and under different stress and hormone treatments using quantitative RT-PCR. We found evidence of expression for all 51 genes. There was only little overlap between genes expressed in vegetative tissues and in seeds and expression levels were generally higher in seeds. Most genes encoding LEA proteins had abscisic acid response (ABRE) and/or low temperature response (LTRE) elements in their promoters and many genes containing the respective promoter elements were induced by abscisic acid, cold or drought. We also found that 33% of all Arabidopsis LEA protein encoding genes are arranged in tandem repeats and that 43% are part of homeologous pairs. The majority of LEA proteins were predicted to be highly hydrophilic and natively unstructured, but some were predicted to be folded.

CONCLUSION

The analyses indicate a wide range of sequence diversity, intracellular localizations, and expression patterns. The high fraction of retained duplicate genes and the inferred functional diversification indicate that they confer an evolutionary advantage for an organism under varying stressful environmental conditions. This comprehensive analysis will be an important starting point for future efforts to elucidate the functional role of these enigmatic proteins.

Protection of liposomes against fusion during drying by oligosaccharides is not predicted by the calorimetric glass transition temperatures of the dry sugars

Sugars play an important role in the desiccation tolerance of most anhydrobiotic organisms. It has been shown in previous studies that different structural families of oligosaccharides have different efficacies to interact with phospholipid headgroups and protect membranes from solute leakage during drying. Here, we have compared three families of linear oligosaccharides (fructans (inulins), malto-oligosaccharides, manno-oligosaccharides) for their chain-length dependent protection of egg phosphatidylcholine liposomes against membrane fusion. We found increased protection with chain length up to a degree of polymerization (DP) of 5 for malto-oligosaccharides, and a decrease for inulins and manno-oligosaccharides. Differential scanning calorimetry measurements showed that for all sugars the glass transition temperature (T_g) increased with DP, although to different degrees for the different oligosaccharide families. Higher T_g values resulted in reduced membrane fusion only for malto-oligosaccharides below DP5. Contrary to expectation, for inulins, manno-oligosaccharides and malto-oligosaccharides of a DP above five, fusion increased with increasing T_g, indicating that other physical parameters are more important in determining the ability of different sugars to protect membranes against fusion during drying. Further research will be necessary to experimentally define such parameters.

Oxidative stress and its effects during dehydration

Water is usually thought to be required for the living state, but several organisms are capable of surviving complete dehydration (anhydrobiotes). Elucidation of the mechanisms of tolerance against dehydration may lead to development of new methods for preserving biological materials that do not normally support drying, which is of enormous practical importance in industry, in clinical medicine as well as in agriculture. One of the molecular mechanisms of damage leading to death in desiccation-sensitive cells upon drying is free-radical attack to phospholipids, DNA and proteins. This review aims to summarize the strategies used by anhydrobiotes to cope with the danger of oxygen toxicity and to present our recent results about the importance of some antioxidant defense systems in the dehydration tolerance of Saccharomyces cerevisiae, a usual model in the study of stress response.

Constraints of tolerance: why are desiccation-tolerant organisms so small or rare?

Drying to equilibrium with the air kills nearly all animals and flowering plants, including livestock and crops. This makes drought a key ecological problem for terrestrial life and a major cause of human famine. However, the ability to tolerate complete desiccation is widespread in organisms that are either <5 mm long or found mainly where desiccation-sensitive organisms are scarce. This suggests that there is a trade-off between desiccation tolerance and growth. Recent molecular and biochemical research shows that organisms tolerate desiccation through a set of mechanisms, including sugars that replace water and form glasses, proteins that stabilize macromolecules and membranes, and anti-oxidants that counter damage by reactive oxygen species. These protections are often induced by drying, and some of the genes involved may be homologous in microbes, plants and animals. Understanding how mechanisms of desiccation tolerance may constrain growth might show how to undo the constraint in some economically important macroorganisms and elucidate the much-studied but elusive relationship between tolerance of stress and productivity.

Monosaccharide composition, chain length and linkage type influence the interactions of oligosaccharides with dry phosphatidylcholine membranes

Sugars play an important role in the desiccation tolerance of most anhydrobiotic organisms and disaccharides have been extensively investigated for their ability to stabilize model membranes in the dry state. Much less is known about the ability of oligosaccharides to protect dry membranes. However, it has been shown that different structural families of oligosaccharides have different efficacies to interact with and protect membranes during drying. Here, we have compared three families of linear oligosaccharides (fructans, malto-oligosaccharides, manno-oligosaccharides) for their chain-length dependent lyoprotective effect on egg phosphatidylcholine liposomes. We found increased protection with chain length for the fructans, a moderate decrease in protection with chain length for malto-oligosaccharides, and a strong decrease for manno-oligosaccharides. Using Fourier-transform infrared spectroscopy and differential scanning calorimetry, we show that the degree of lyoprotection of the different sugars is closely related to their influence on the gel to liquid-crystalline phase behavior of the dry membranes and to the extent of H-bonding to different groups (C=O, P=O, choline) in the lipids. Possible structural characteristics of the different oligosaccharides that may determine the extent to which they are able to interact with and protect membranes are discussed.

Effect of membrane lateral pressure on the expression of fructosyltransferases in Lactobacillus reuteri

The effect of environmental conditions on the production of homo-polysaccharides and oligosaccharides from sucrose and the regulation of glycosyltransferase genes responsible for biosynthesis of homo-polysaccharides was determined in Lactobacillus reuteri TMW1.106 (reutericyclin-producer) and LTH5448 (reutericyclin-negative). Strain L. reuteri TMW 1.106 harbours the glycosyltransferase genes gtfA and inu, strain LTH5448 harbours a fructosyltransferase, ftfA. Fructan and fructose-oligosaccharide (FOS) production in both strains was inducible by reutericyclin, trans-isohumulone, and nigericin at the levels of their minimum inhibitory concentrations (MIC) as well as phenylethanol (6mM) and elevated growth temperatures (45 degrees C), but not by nisin, CCCP or gramicidin. Elevated temperature (45 degrees C), reutericyclin or trans-isohumulone but not CCCP furthermore increased enhanced inu and ftfA transcription in L. reuteri TMW1.106 and LTH5448, respectively. Generally, effects of the various agents on fructosyltransferase transcription corresponded to their effect on formation of poly and oligosaccharides from sucrose. The effect of membrane-active agents on fructosyltransferase expression was compared to their effect on membrane biophysical parameters. The ability of chemical and physical agents to induce expression of fructosyltransferases correlated to their effect on the membrane lateral pressure as measured by pyrene-labelled phospholipids in membrane vesicles. Dextran, levan and fructose-oligosaccharides added at 50gL(-1) protected L. reuteri towards the membrane-active inhibitors nisin, reutericyclin, and CCCP. The induction of glycosyltransferases by membrane stress indicates a protective role of fructans and FOS to lactobacilli exposed to physical and chemical environmental stressors.

Extracellular homopolysaccharides and oligosaccharides from intestinal lactobacilli

AIMS

To characterize lactobacilli isolated from the intestines of ducks or pigs with respect to the production of extracellular homopolysaccharides (HoPS) and oligosaccharides.

METHODS AND RESULTS

Lactobacillus strains of duck or pig origin were screened for HoPS synthesis and >25% of the isolates produced fructans or glucans from sucrose. Glucan-forming strains were found within the species Lactobacillus reuteri and Lactobacillus animalis and fructan-forming strains were found within Lactobacillus mucosae, Lactobacillus crispatus and Lactobacillus acidophilus. The glucan-forming strains of L. reuteri but not L. animalis produced glucose-oligosaccharides in additon to the respective polymers, and two fructan-forming strains of L. acidophilus produced kestose. Genes coding for glycosyltransferases were detected by PCR and partially characterized by sequence analysis.

CONCLUSIONS

A large proportion of lactobacilli from intestinal habitats produce HoPS from sucrose and polysaccharide formation is generally associated with the formation of glucose- and fructose oligosaccharides.

SIGNIFICANCE AND IMPACT OF THE STUDY

The characterization of the metabolic potential of intestinal lactobacilli contributes to the understanding of the molecular basis of autochthony in intestinal habitats. Moreover, this is the first report of glucose-oligosaccharide production during growth of lactobacilli, and one novel fructosyltransferase and one novel glucansucrase were partially characterized on the genetic level.

The anhydrobiotic potential and molecular phylogenetics of species and strains of Panagrolaimus (Nematoda, Panagrolaimidae)

Members of the genus Panagrolaimus are bacterial-feeding nematodes that occupy a diversity of niches ranging from Antarctic and temperate soils to terrestrial mosses. Some members of this genus are able to survive extreme desiccation by entering into a state of suspended animation known as anhydrobiosis. We have assembled a collection of Panagrolaimus species and strains and have investigated their anhydrobiotic phenotypes. Our data show that within the genus Panagrolaimus there is a continuum of strains ranging from those unable to survive exposure to low relative humidity (RH) without prior preconditioning at high RH (slow desiccation strategists), through strains that have limited ability to survive rapid desiccation but whose anhydrobiotic ability improves upon preconditioning, to strains such as P. superbus that can readily survive immediate exposure to severe desiccation (fast desiccation strategists). Using this panel of nematodes we investigated the effect of preincubation at high RH on the accumulation of trehalose and on the nematodes' anhydrobiotic potential. We found that there is a strong correlation between trehalose induction and anhydrobiotic survival in Panagrolaimus. Furthermore, the high trehalose levels observed in fully hydrated P. superbus (10% dry mass) suggest that constitutive expression of trehalose pre-adapts this fast dehydration strategist to combat desiccation. All the strains observed, regardless of survival rates, undertook both coiling and clumping, which has the effect of reducing surface area and slowing the rate of water loss during desiccation. Phylogenetic analyses were carried out to investigate whether the observed anhydrobiotic phenotypes were the result of convergent evolution or represented a single phylogenetic lineage. These analyses, derived from alignments of the rDNA ITS and D3 sequences, indicate that the strongly anhydrobiotic strains of Panagrolaimus form a single phylogenetic lineage, which is separate from the weakly anhydrobiotic strains. The weakly anhydrobiotic strains are also phylogenetically divergent from each other. Our data indicate that Panagrolaimus has the potential to be an excellent model system for the investigation of molecular aspects of nematode anhydrobiosis.

Biopreservation of red blood cells: past, present, and future

Preservation and long-term storage of red blood cells (RBCs) is needed to ensure a readily available, safe blood supply for transfusion medicine. Effective preservation procedures are required at various steps in the production of a RBC product including testing, inventory, quality control, and product distribution. Biopreservation is the process of maintaining the integrity and functionality of cells held outside the native environment for extended storage times. The biopreservation of RBCs for clinical use can be categorized based on the techniques used to achieve biologic stability and ensure a viable state after long-term storage. This paper will review the history, science, current practices, and emerging technologies of current RBC biopreservation approaches: hypothermic storage, cryopreservation, and lyophilization.