State Of Anhydrobiosis Research Articles

Recovery from anhydrobiosis in the tardigrade Paramacrobiotus experimentalis: Better to be young than old and in a group than alone

Desiccation-tolerant organisms can survive dehydration in a state of anhydrobiosis. Tardigrades can recover from anhydrobiosis at any life stage and are considered among the toughest animals on Earth. However, the factors that influence recovery from anhydrobiosis are not well understood. The study aimed to evaluate the effect of sex, age, the presence of other individuals and the combination of the number and duration of anhydrobiosis episodes on the recovery of Paramacrobiotus experimentalis. The activity of 1200 individuals for up to 48 h after rehydration was evaluated using analysis of variance (ANOVA). Age was the main factor influencing return to activity, followed by the combination of number and duration of anhydrobiosis episodes, influence of the presence of other individuals, and sex. More individuals returned to activity after repeated short than repeated long anhydrobiosis episodes and older individuals were less likely to recover than younger individuals. In addition, when compared to single animals, the presence of other individuals resulted in higher number of active animals after dehydration and rehydration. The effect of sex was significant, but there was no general tendency for one sex to recover from anhydrobiosis better than the other one. The results contribute to a better understanding of the anhydrobiosis ability of Paramacrobiotus experimentalis and provide background for full explanation of molecular, cellular and environmental mechanisms of anhydrobiosis.

State of Cyanobacteria <i>Arthrospira platensis</i> and of Associated Microflora during Long-Term Storage in the State of Anhydrobiosis

Abstract—The biochemical composition of Arthrospira (Spirulina) platensis (Nordstedt) Gomont after long-term storage in the state of anhydrobiosis (4 years, 17 years) was determined by the standard methods. It was shown that protein content (55.3–61.2%) and total carbohydrates content (13.0–15.6%) in cyanobacterial cells were in agreement with the data known from the literature and with our results obtained at the onset of storage. The biomass had low content of free nucleotides (1.8–2.6%), lipids (1.3–11.0%), and especially pigments (0.5–1.3, 0.03–0.12, 1.4–2.0, 0.03–0.05% for chlorophyll a, carotenoids, C-phycocyanin, and allophycocyanin, respectively). The content of nucleic acids content was 3.1–24.0 and 0.11–0.16% for RNA and DNA, respectively. Microscopic examination of A. platensis (17 years of storage) showed high numbers of irreversibly damaged and dead cells (34.2 and 65.8%, respectively). To determine the quantitative and morphological parameters of associated microflora, a complex physicochemical treatment (methanol, ultrasound, and centrifugation) of the reactivated cyanobacterial suspension proved the most efficient. Three main groups were distinguished in the morphological structure of the microbiome (rod-shaped, rounded, and convoluted forms). The community was dominated by rod-shaped forms: large and small rods accounted for 60.5 and 14.4%, respectively. Mycelial forms (thin filaments), cocci, and convoluted forms were less common. On average, the volume of a bacterial cell was 0.27 ± 0.04 µm3. The contribution of bacteria to the biomass of A. platensis varied from 3.3 to 11.3% (8.3 ± 4.4% on average) of the dry weight of A. platensis. It has been suggested that the biochemical parameters and viability of cyanobacteria were affected by the accompanying microflora.

State of Cyanobacteria Arthrospira platensis and of Associated Microflora during Long-Term Storage in the State of Anhydrobiosis

State of Cyanobacteria Arthrospira platensis and of Associated Microflora during Long-Term Storage in the State of Anhydrobiosis

Anhydrobiosis in yeast: role of cortical endoplasmic reticulum protein Ist2 in Saccharomyces cerevisiae cells during dehydration and subsequent rehydration.

Two Saccharomyces cerevisiae strains, BY4741 and BY4741-derived strain lacking the IST2 gene (ist2Δ), were used to characterise the possible role of cortical endoplasmic reticulum (ER) protein Ist2 upon cell dehydration and subsequent rehydration. For the first time, we show that not only protein components of the plasma membrane (PM), but also at least one ER membrane protein (Ist2) play an important role in the maintenance of the viability of yeast cells during dehydration and subsequent rehydration. The low viability of the mutant strain ist2∆ upon dehydration-rehydration stress was related to the lack of Ist2 protein in the ER. We revealed that the PM of ist2∆ strain is not able to completely restore its molecular organisation during reactivation from the state of anhydrobiosis. As the result, the permeability of the PM remains high regardless of the type of reactivation (rapid or gradual rehydration). We conclude that ER protein Ist2 plays an important role in ensuring the stability of molecular organisation and functionality of the PM during dehydration-rehydration stress. These results indicate an important role of ER-PM interactions during cells transition into the state of anhydrobiosis and the subsequent restoration of their physiological activities.

Anhydrobiosis in yeasts: Psychrotolerant yeasts are highly resistant to dehydration.

Yeast cells are able to transition into a state of anhydrobiosis (temporary reversible suspension of metabolism) under conditions of desiccation. One of the most efficient approaches for understanding the mechanisms underlying resistance to dehydration-rehydration is to identify yeasts, which are stable under such treatments, and compare them with moderately resistant species and strains. In the current study, we investigated the resistance to dehydration-rehydration of six psychrotolerant yeast strains belonging to two species. All studied strains of Solicoccozyma terricola and Naganishia albida were found to be highly resistant to dehydration-rehydration. The viability of S.terricola strains was close to 100%. Such results have not been previously reported in studies of anhydrobiosis in yeasts. The plasma membrane changes, revealed by determining its permeability under various rehydration conditions, were also surprisingly minimal. Thus, the high level of resistance of psychrotolerant yeast strains might be related to the chemical composition and molecular organisation of their plasma membranes. Aside from plasma membrane characteristics, other important factors may also influence the maintenance of yeast cell viability under conditions of dehydration-rehydration.

Viability of Dunaliella Salina in the state of anhydrobiosis

In our manuscript we showed results of study of viability of Dunaliella salina in the state of dryness and in the state of anhydrobiosis.

Survival of root-lesion nematodes (Pratylenchus thornei) after wheat growth in a vertisol is influenced by rate of progressive soil desiccation

The root-lesion nematode (Pratylenchus thornei) is a major pathogen of wheat in the subtropical grain region of eastern Australia. Experiments were conducted to learn whether soil desiccation can account for the rapid fall in peak P. thornei population densities noted in the field after wheat matures. The decline in population densities of P. thornei after growth of wheat was measured on progressive desiccation of soil with roots by fast and slow drying methods. The vertisolic soil of initial moisture content 45% w/w (or matric potential of pF 3.3) was dried in 5% decrements to an air-dried gravimetric moisture content of 15% (pF 5.6) taking 10.7 h for fast drying and 91.5 h for slow drying. After drying, live nematodes were extracted with Whitehead trays for 2 and 7 days and counted in four life stages (adults and juvenile stages J2, J3 and J4). Fast drying resulted in a sigmoidal decline in total P. thornei with only 5% of the population alive in soil at 15% moisture content, but slow drying had no significant effect on the population density. The percentage of nematodes extracted at 2 days compared with the total extracted over 7 days in undried soil (∼89% of total) declined quadratically on desiccation to be 48% (fast drying) and 78% (slow drying) at 15% moisture content. With fast drying, the proportion of adults and J2 decreased whereas the proportion of J4 increased as the soil dried. With slow drying, the proportion of J2 and J3 stages decreased while the proportion of J4 increased. Thus the J4 or pre-adult was the life stage most tolerant of soil desiccation. Time is required for P. thornei to go into a state of anhydrobiosis as a soil dries and this information can be used to model P. thornei survival in the field based on environmental parameters.

Anhydrobiosis in yeast: cell wall mannoproteins are important for yeast Saccharomyces cerevisiae resistance to dehydration.

The state of anhydrobiosis is linked with the reversible delay of metabolism as a result of strong dehydration of cells, and is widely distributed in nature. A number of factors responsible for the maintenance of organisms' viability in these conditions have been revealed. This study was directed to understanding how changes in cell wall structure may influence the resistance of yeasts to dehydration-rehydration. Mutants lacking various cell wall mannoproteins were tested to address this issue. It was revealed that mutants lacking proteins belonging to two structurally and functionally unrelated groups (proteins non-covalently attached to the cell wall, and Pir proteins) possessed significantly lower cell resistance to dehydration-rehydration than the mother wild-type strain. At the same time, the absence of the GPI-anchored cell wall protein Ccw12 unexpectedly resulted in an increase of cell resistance to this treatment; this phenomenon is explained by the compensatory synthesis of chitin. The results clearly indicate that the cell wall structure/composition relates to parameters strongly influencing yeast viability during the processes of dehydration-rehydration, and that damage to cell wall proteins during yeast desiccation can be an important factor leading to cell death. Copyright © 2016 John Wiley & Sons, Ltd.

Molecular approaches for improving desiccation tolerance: insights from the brine shrimp Artemia franciscana.

We have evaluated the endogenous expression and molecular properties of selected Group 3 LEA proteins from Artemia franciscana , and the capacity of selected Groups 1 and 3 proteins transfected into various desiccation-sensitive cell lines to improve tolerance to drying. Organisms inhabiting both aquatic and terrestrial ecosystems frequently are confronted with the problem of water loss for multiple reasons--exposure to hypersalinity, evaporative water loss, and restriction of intracellular water due to freezing of extracellular fluids. Seasonal desiccation can become severe and lead to the production of tolerant propagules and entry into the state of anhydrobiosis at various stages of the life cycle. Such is the case for gastrula-stage embryos of the brine shrimp, Artemia franciscana. Physiological and biochemical responses to desiccation are central for survival and are multifaceted. This review will evaluate the impact of multiple late embryogenesis abundant proteins originating from A. franciscana, together with the non-reducing sugar trehalose, on prevention of desiccation damage at multiple levels of biological organization. Survivorship of desiccation-sensitive cells during water stress can be improved by use of the above protective agents, coupled to metabolic preconditioning and rapid cell drying. However, obtaining long-term stability of cells in the dried state at room temperature has not been accomplished and will require continued efforts on both the physicochemical and biological fronts.

The role of glycerol transporters in yeast cells in various physiological and stress conditions.

Small and uncharged glycerol is an important molecule for yeast metabolism and osmoadaptation. Using a series of S. cerevisiae BY4741-derived mutants lacking genes encoding a glycerol exporter (Fps1p) and/or importer (Stl1p) and/or the last kinase of the HOG pathway (Hog1p), we studied their phenotypes and various physiological characteristics with the aim of finding new roles for glycerol transporters. Though the triple mutant hog1Δ stl1Δ fps1Δ was viable, it was highly sensitive to various stresses. Our results showed that the function of both Stl1p and Fps1p transporters contributes to the cell ability to survive during the transfer into the state of anhydrobiosis, and that the deletion of FPS1 decreases the cell's tolerance of hyperosmotic stress. The deletion of STL1 results in a slight increase in cell size and in a substantial increase in intracellular pH. Taken together, our results suggest that the fluxes of glycerol in both directions across the plasma membrane exist in yeast cells simultaneously, and the export or import predominates according to the actual specific conditions.

Desiccation Induced Structural Alterations in a 66-Amino Acid Fragment of an Anhydrobiotic Nematode Late Embryogenesis Abundant (LEA) Protein

Late embryogenesis abundant (LEA) proteins have been found in a number of anhydrobiotic (i.e., a state of anhydrobiosis or life without water) organisms that are adapted to severe water deficit as a result of extreme drought and cold in nature. However, the precise mechanism by which LEA proteins protect the organisms in response to water depletion remains to be defined. Because protein functions are generally determined by its structure, molecular dynamics simulations were performed in this study to understand the structure and its stability of a 66-amino acid fragment of a group 3 LEA protein from an anhydrobiotic nematode during desiccation. It was found that, unlike the vast majority of proteins, the fully hydrated LEA protein in an aqueous solution is by and large unstructured (mainly in the form of random coils and turns). The protein gradually becomes folded into a hairpin-like, double-bundled, alpha-helical 3D conformation in response to the loss of water. Major structural formation was observed to occur only when the water content is less than about 20 wt %. It was further found the protein structure and its stability during desiccation are determined primarily by hydrogen bonding interactions followed by electrostatic interactions, both of which are a result of the extremely hydrophilic nature of the LEA protein. The Lennard-Jones interactions (van der Waals interactions) are the least important in determining the protein structure and its stability during water deficit.

Soil properties and their effect on water and mineral status of resurrection Ramonda serbica

The resurrection flowering plant Ramonda serbica inhabits the shallow organo-mineral soil that develops in crevices on northern-facing carbonate rocks in the gorges in the Balkan Peninsula. This type of soil represents a complex substrate whose physical and chemical properties were found to be well suited to the most important requirements for the growth and development of R. serbica as well as for the plant’s survival in the state of anhydrobiosis in periods of drought stress. Considerable amount of organic matter (39.4%) in the soil resulted in the high field capacity (134 ml/100 g soil) as well as the slow changes in the amount of its available water. The suitable soil hydric status, based on the organic remains, supports the slow dehydration of this poikilohydric plant, which is extremely important in allowing the activation of the plant’s protective mechanisms. The pH of the soil solution was slighty alkaline (7.7) mostly due to carbonates in its crystallographic structure. The large amount of incompletely decomposed organic debris resulted in a marked difference between total and available nutrient concentration in the soil. Still, the adequate content of nutrients in the leaves points to efficient mineral consumption by the plant roots. The sufficient bioavailability of nutrients and water was also improved by vesicular–arbuscular mycorrhiza detected in R. serbica roots.

The environmental physiology of Antarctic terrestrial nematodes: a review.

The environmental physiology of terrestrial Antarctic nematodes is reviewed with an emphasis on their cold-tolerance strategies. These nematodes are living in one of the most extreme environments on Earth and face a variety of stresses, including low temperatures and desiccation. Their diversity is low and declines with latitude. They show resistance adaptation, surviving freezing and desiccation in a dormant state but reproducing when conditions are favourable. At high freezing rates in the surrounding medium the Antarctic nematode Panagrolaimus davidi freezes by inoculative freezing but can survive intracellular freezing. At slow freezing rates this nematode does not freeze but undergoes cryoprotective dehydration. Cold tolerance may be aided by rapid freezing, the production of trehalose and by an ice-active protein that inhibits recrystallisation. P. davidi relies on slow rates of water loss from its habitat, and can survive in a state of anhydrobiosis, perhaps aided by the ability to synthesise trehalose. Teratocephalus tilbrooki and Ditylenchus parcevivens are fast-dehydration strategists. Little is known of the osmoregulatory mechanisms of Antarctic nematodes. Freezing rates are likely to vary with water content in Antarctic soils. Saturated soils may produce slow freezing rates and favour cryoprotective dehydration. As the soil dries freezing rates may become faster, favouring freezing tolerance. When the soil dries completely the nematodes survive anhydrobiotically. Terrestrial Antarctic nematodes thus have a variety of strategies that ensure their survival in a harsh and variable environment. We need to more fully understand the conditions to which they are exposed in Antarctic soils and to apply more natural rates of freezing and desiccation to our studies.

Survival of the cryptobiotic eutardigrade Adorybiotus coronifer during cooling to −196 °C: Effect of cooling rate, trehalose level, and short-term acclimation

The cryptobiotic eutardigrade Adorybiotus cornifer survives cooling to −196 °C in the hydrated state, showing decreasing viability with faster cooling rates. The dissaccharide trehalose may have some cryoprotective effect at low cooling rates during cooling of A. coronifer to −196 °C, whereas no effect of short-term acclimation (16 h at 0.5 °C) was observed. Cooling at 30 °C min −1 to an intermediate temperature greater than the ice crystallization temperature of the sample ( T c) before shock cooling to −196 °C is lethal, whereas cooling at a rate of 30 °C min −1 to an intermediate temperature less than T c before shock cooling to −196 °C achieved a survival of ca. 55%. This is similar to the survival of animals cooled to −196 °C at a constant rate of 30 °C min −1. The data support the hypothesis that the freeze tolerance exhibited by A. coronifer is closely related to its ability to be in the state of anhydrobiosis.

On the life history and functional morphology of Halipegus occidualis (Trematoda: Hemiuridae), with emphasis on the cystophorous cercaria stage

The cystophorous cercariae of Halipegus occidualis develop in rediae in the pulmonate snail, Helisoma anceps. Fully developed cercariae are shed from the snail and remain motionless on pond substrata. Manipulation of the caudal appendage by feeding microcrustaceans (copepods and ostracods) results in instantaneous eversion of the delivery tube within the cyst, through which the cercarial body is expelled into the crustacean hemocoel, wherein mesocercariae develop. Morphological and field evidence indicates that mesocercariae become metacercariae in the intestine of several species of larval odonate nymphs when they prey upon microcrustacea. The life cycle is completed when green frogs, Rana clamitans, ingest infected odonates. Phase contrast microscopy, scanning and transmission electron microscopy reveal that the tegument of the cercarial body is covered by microvilli, but internally lacks cellular and tissue differentiation. The apical portion of the delivery tube is covered by glandular papillae and the tip possesses a spined structure. Both represent modifications facilitating penetration and anchorage of the delivery tube through the crustacean intestine. While within the cyst, the body of the cercaria appears to be in a state of anhydrobiosis, an adaptation which presumably prolongs the life of this infective stage and enhances the temporal opportunity for transmission to microcrustacean hosts.

Faecal water content and egg survival of goat gastro-intestinal strongyles under dry tropical conditions in Guadeloupe

Faeces from naturally infected goats were deposited on a natural grassland during the dry season in Guadeloupe (French West Indies) at different times throughout the day. The grass was either 7 or 20-30 cm tall. After a period of between several hours and 7 days, the number of viable strongyle eggs and the faecal water content were measured. Faecal temperature was recorded continuously. Faecal temperature was greater than 40 degrees-45 degrees C at midday and dehydration was rapid between 8 a.m. and 2 p.m. Egg mortality was greater on short than on tall grass and higher in morning than in evening deposits. Minimal faecal water content during the first 36 h explained the 74%, 55% and 38% mortality rate for eggs of Oesophagostomum columbianum (OC), Haemonchus contortus (HC) and Trichostrongylus colubriformis (TC), respectively. In all, 5%-22% of the eggs of the latter species remained viable in a state of anhydrobiosis after 7 days on the ground. A delay of only 2 days between goat departure and irrigation would be sufficient to ensure that greater than 95% of O. columbianum and H. contortus eggs and 70% of T. colubriformis eggs are destroyed.

Treatments To Eliminate Root-Lesion Nematode (Pratylenchus Thornei Sher & Allen) From a Vertisol

Partial sterilization methods to eliminate root-lesion nematode (Pratylenchus thornei Sher & Allen) from a vertisol were investigated. Air-dried soil, with nematodes apparently in a state of anhydrobiosis, was treated with gamma irradiation (5, 7.5, 10 or 20 k Gy), aerated steam (50, 60, 70 or 80°C for 30 minutes), or methyl bromide fumigation, and motile nematodes were extracted in Whitehead trays. Approximately 1 % of P. thornei survived 5 k Gy of gamma irradiation but none survived 7.5 k Gy or more. Approximately 50% and 10% survived 50 and 60°C aerated steam treatment, respectively, but none survived 70 or 80°C or methyl bromide fumigation. P. thomei was no more tolerant of partial sterilization treatments than were saprobic nematodes present in the same soil.

Abiotic controls on the functional structure of soil food webs

The hypothesis that the trophic structure of soil food webs changes as a result of the abiotic environment was examined by reviewing studies of soil biota. In dry soils with a water potential below −1.5 MPa, most bacteria, protozoans, and many species of nematodes are not active. These taxa persist in the soil in a state of anhydrobiosis. Because soil fungi grow at soil water potentials of −6.0 to −8.0 MPa, soil food webs in dry environments appear to be fungal-based and fungal grazers in dry environments appear to be predominantly fungiphagous mites. There is indirect evidence that some species of fungiphagous mites remain inactive in dry soils in a state of “cryptobiosis”. In habitats where there is insufficient vegetative cover to shade and modify the soil surface, the functional soil food web consists of fungi and a few taxa of soil acari for extended periods of time.

Anhydrobiosis in Embryos of the Brine Shrimp Artemia: Characterization of Metabolic Arrest During Reductions in Cell-Associated Water

ABSTRACT Upon entry into the state of anhydrobiosis, trehalose-based energy metabolism is arrested in Artemia embryos (cysts). We have compared changes in the levels of trehalose, glycogen, some glycolytic intermediates and adenylate nucleotides in hydrated embryos observed under conditions of aerobic development with those occurring after transfer to 5·0mol 1−1 NaCl. This treatment is known to reduce cell-associated water into a range previously referred to as the ametabolic domain. The trehalose utilization and glycogen synthesis that occur during development of fully hydrated cysts are both blocked during desiccation. Upon return to 0·25 mol 1−1 NaCl both processes are resumed. Analysis of glycolytic intermediates suggests that the inhibition is localized at the trehalase, hexokinase and phosphofructokinase reactions. ATP level remains constant during the 6-h period of dehydration, as does the adenylate energy charge. An additional dehydration experiment was performed in 5·0moll−1 NaCl containing 50mmoll−1 ammonium chloride (pH9·0). The resulting level of gaseous ammonia in the medium has been shown to maintain an alkaline intracellular pH (pHi) in the embryos. The metabolic response to dehydration under these conditions was very similar to the previous dehydration series. Thus, these results are taken as strong evidence that the metabolic suppression observed during dehydration does not require cellular acidification, in contrast to the pronounced inhibitory role of low pHi during entry of hydrated embryos into the quiescent state of anaerobic dormancy. The arrest of carbohydrate metabolism seen during anhydrobiosis indeed appears to be a strict function of embryo water content.