Proteins under extreme physical conditions

Life on earth is ubiquitous within the limits from -5 to 110 degrees C for temperature, 0.1 to 120 MPa for hydrostatic pressure, 1.0 to 0.6 for water activity and pH 1 to 12. In general, mutative adaptation of proteins to changing environmental conditions tends to maintain 'corresponding states' regarding overall topology, flexibility and hydration. Due to the minute changes in the free energy of stabilization responsible for enhanced stability, nature provides a wide variety of different adaptative strategies. In the case of thermophilic proteins, improved packing densities are crucial. In halophilic proteins, decreased hydrophobicity and clustered surface charges serve to increase water and salt binding required for solubilization at high salt concentration. In the case of barophiles, high-pressure adaptation is expected to be less important than adaptation to low temperatures governing the deep sea. Nothing is known with respect to the mechanisms underlying psychrophilic and acidophilic/alkalophilic adaptation.     

Crenarchaeal biofilm formation under extreme conditions

Background

Biofilm formation has been studied in much detail for a variety of bacterial species, as it plays a major role in the pathogenicity of bacteria. However, only limited information is available for the development of archaeal communities that are frequently found in many natural environments.

Methodology

We have analyzed biofilm formation in three closely related hyperthermophilic crenarchaeotes: Sulfolobus acidocaldarius, S. solfataricus and S. tokodaii. We established a microtitre plate assay adapted to high temperatures to determine how pH and temperature influence biofilm formation in these organisms. Biofilm analysis by confocal laser scanning microscopy demonstrated that the three strains form very different communities ranging from simple carpet-like structures in S. solfataricus to high density tower-like structures in S. acidocaldarius in static systems. Lectin staining indicated that all three strains produced extracellular polysaccharides containing glucose, galactose, mannose and N-acetylglucosamine once biofilm formation was initiated. While flagella mutants had no phenotype in two days old static biofilms of S. solfataricus, a UV-induced pili deletion mutant showed decreased attachment of cells.

Conclusion

The study gives first insights into formation and development of crenarchaeal biofilms in extreme environments.     

The Sphagnum microbiome supports bog ecosystem functioning under extreme conditions

Sphagnum‐dominated bogs represent a unique yet widely distributed type of terrestrial ecosystem and strongly contribute to global biosphere functioning. Sphagnum is colonized by highly diverse microbial communities, but less is known about their function. We identified a high functional diversity within the Sphagnum microbiome applying an Illumina‐based metagenomic approach followed by de novo assembly and MG‐RAST annotation. An interenvironmental comparison revealed that the Sphagnum microbiome harbours specific genetic features that distinguish it significantly from microbiomes of higher plants and peat soils. The differential traits especially support ecosystem functioning by a symbiotic lifestyle under poikilohydric and ombrotrophic conditions. To realise a plasticity–stability balance, we found abundant subsystems responsible to cope with oxidative and drought stresses, to exchange (mobile) genetic elements, and genes that encode for resistance to detrimental environmental factors, repair and self‐controlling mechanisms. Multiple microbe–microbe and plant–microbe interactions were also found to play a crucial role as indicated by diverse genes necessary for biofilm formation, interaction via quorum sensing and nutrient exchange. A high proportion of genes involved in nitrogen cycle and recycling of organic material supported the role of bacteria for nutrient supply. 16S rDNA analysis indicated a higher structural diversity than that which had been previously detected using PCR‐dependent techniques. Altogether, the diverse Sphagnum microbiome has the ability to support the life of the host plant and the entire ecosystem under changing environmental conditions. Beyond this, the moss microbiome presents a promising bio‐resource for environmental biotechnology – with respect to novel enzymes or stress‐protecting bacteria.     

Bioenergetics and solute uptake under extreme conditions

The ion and particularly the proton and sodium ion permeabilities of cytoplasmic membranes play crucial roles in the bioenergetics of microorganisms. The proton and sodium permeabilities of membranes increase with temperature. Psychrophilic and mesophilic bacteria and mesophilic, (hyper)thermophilic, and halophilic archaea are capable of adjusting the lipid composition of their membranes in such a way that the proton permeability at the respective growth temperature remains constant (homeoproton permeability). Thermophilic bacteria are an exception. They rely on the less permeable sodium ions to generate a sodium motive force, which is subsequently used to drive energy-requiring membrane-bound processes. Transport of solutes across bacterial and archaeal membranes is mainly catalyzed by primary ATP-driven transport systems or by proton- or sodium-motive-force-driven secondary transport systems. Unlike most bacteria, hyperthermophilic bacteria and archaea prefer primary uptake systems. Several high-affinity ATP-binding cassette (ABC) transporters for sugars from hyperthermophiles have been identified and characterized. The activities of these ABC transporters allow these organisms to thrive in their nutrient-poor environments.     

Individual strategies of human adaptation under extreme conditions

Starting from the investigations of Sechenov, Pavlov, and Uchtomsky, the Russian psychophysiological school has been considering adaptation in connection with the biological and social origin of the person (human as a rational being) as an integrated, coordinated, and self-controlled system. On the basis of the problem of man and the environment, Medvedev added to the theory of human adaptation the activity paradigm that enables us to uncover the distinctive features of occupational activities under various environment conditions. The theoretical and practical investigations based on the activity methodology presented the opportunity to find new principles of interaction between man and the environment and of the strategy of adaptive behavior. From the investigations one could see that the main characteristic of the human-environment interaction is that the active factor is the human who could simulate different adaptation strategies.     

Structural stability of polypeptide nanofilms under extreme conditions

Self-assembly of designed peptides is a promising area of biomaterials research and development. Here, polypeptide nanofilms have been prepared by electrostatic layer-by-layer self-assembly (LBL) of cysteine (Cys)-containing 32mers designed to be oppositely charged at neutral pH, and structural stability of the films has been probed by subjecting them to various extreme physical and chemical conditions. The results suggest that although electrostatic attraction plays a key role in strengthening polypeptide films, stability is inversely related to absolute net charge of the supramolecular complex. This behavior is similar to the typical behavior of small globular proteins. Film structure is very stable in organic solvent and, when dehydrated, at extreme temperatures. Such stability is in marked contrast to the behavior of proteins, which tend to denature under comparable conditions. Similar to proteins, peptide nanofilms cross-linked by disulfide (S-S) bonds are considerably stronger than films stabilized by electrostatic, van der Waals, or hydrophobic interactions alone. This effect is particularly evident at extremes of pH and at elevated temperature when the film is hydrated. These results, the great variety of possible peptide structures, the inherent biocompatibility of l-amino acids, and current applications of thin films in commercial products together suggest that polypeptide films are promising for the development of new or enhanced products in food technology, drug delivery and medical device coatings, and biomaterials.     

Performance of Chlorella sorokiniana under simulated extreme winter conditions

High annual microalgae productivities can only be achieved if solar light is efficiently used through the different seasons. During winter the productivity is low because of the light and temperature conditions. The productivity and photosynthetic efficiency of Chlorella sorokiniana were assessed under the worst-case scenario found during winter time in Huelva, south of Spain. The maximum light intensity (800?μmol photons m^-2 s^-1) and temperature (20°C) during winter were simulated in a lab-scale photobioreactor with a short light-path of 14?mm. Chemostat conditions were applied and the results were compared with a temperature-controlled situation at 38°C (optimal growth temperature for C. sorokiniana). When temperature was optimal the highest productivity was found at a dilution rate of 0.18 h^-1 (P _v?=?0.28?g Kg^-1 h^-1), and the biomass yield on light energy was high (Y _x,E?=?1.2?g?mol^-1 photons supplied). However, at suboptimal temperature, the specific growth rate of C. sorokiniana was surprisingly low, not being able to support continuous operation at a dilution rate higher than 0.02 h^-1. The slow metabolism under suboptimal temperature resulted in a decline of the light energy requirements of the cells. Consequently, the maximum winter irradiance was experienced as excessive, leading to a low photosynthetic efficiency and productivity (Y _x,E?=?0.5?g mol^-1 photons supplied, P _v?=?0.1?g Kg^-1 h^-1). At suboptimal temperature a higher carotenoid-to-chlorophyll ratio was observed indicating the activation of light-dissipating processes. We conclude that temperature control and/or light dilution during winter time will enhance the productivity.     

The functional prognosis of physical working ability under conditions of extreme high altitude

The physical performance of climbers, those making high-altitude ascensions up to 8000 m, without additional oxygen was measured. Some functional criteria of the organism adaptation to exhausting physical loading at the high altitudes were selected. It was established that the forecasting of a successful ascension could be improved if the potential maximal oxygen uptake was added to the standard definition parameters of aerobic metabolism such as the maximal oxygen uptake and anaerobic threshold of oxygen uptake. The potential maximal oxygen uptake is considered to be the parameter of maximal oxygen uptake reserve growing in condition of realization of adaptive reaction to hypoxia.     

Charge transfer in TATB and HMX under extreme conditions

Charge transfer is usually accompanied by structural changes in materials under different conditions. However, the charge transfer in energetic materials that are subjected to extreme conditions has seldom been explored by researchers. In the work described here, the charge transfer in single molecules and unit cells of the explosives TATB and HMX under high temperatures and high pressures was investigated by performing static and dynamic calculations using three DFT methods, including the PWC functional of LDA, and the BLYP and PBE functionals of GGA. The results showed that negative charge is transferred from the nitro groups of molecular or crystalline TATB and HMX when they are heated. All DFT calculations for the compressed TATB unit cell indicate that, generally, negative charge transfer occurs to its nitro groups as the compression increases. PWC and PBE calculations for crystalline HMX show that negative charge is first transferred to the nitro groups but, as the compression increases, the negative charge is transferred from the nitro groups. However, the BLYP calculations indicated that there was gradual negative charge transfer to the nitro groups of HMX, similar to the case for TATB. The unrelaxed state of the uniformly compressed TATB causes negative charge to be transferred from its nitro groups, in contrast to what is seen in the relaxed state. Charge transfer in TATB is predicted to occur much more easily than in HMX.     

Study of visual perception under conditions of extreme light exposures

Neurophysiological processes of transduction and analysis of information concerning brightness of photostimuli and peculiarities of functioning of visual system under exposure to extra-bright light effects or extreme contrasting of visual objects are studied poorly and present significant interest for unraveling actual mechanisms of visual perception under extreme conditions. Conducting analysis of visual system in maximal broad range both in terms of adequate perception and reflection of light stimulus intensity and adaptive mechanisms to extra-strong illumination regimes is as well very important. The to-date obtained data indicate that under the extreme light effects pathology of the peripheral portion of visual analysator can be induced. The presented review does not pretend to comprise all present information concerning all achievements and results over this problem. Its goal concludes in maximal approaching to understanding the mechanisms of damaging and following recover of visual function under extreme effects of affecting light factors.     

Resilience under conditions of extreme stress: a multilevel perspective

Resilience has been conceptualized as a dynamic developmental process encompassing the attainment of positive adaptation within the context of significant threat, severe adversity, or trauma. Until the past decade, the empirical study of resilience predominantly focused on behavioral and psychosocial correlates of, and contributors to, the phenomenon and did not examine neurobiological or genetic correlates of and contributors to resilience. Technological advances in molecular genetics and neuroimaging, and in measuring other biological aspects of behavior, have made it more feasible to begin to conduct research on pathways to resilient functioning from a multilevel perspective. Child maltreatment constitutes a profound immersion in severe stress that challenges and frequently impairs development across diverse domains of biological and psychological functioning. Research on the determinants of resilience in maltreated children is presented as an illustration of empirical work that is moving from single-level to multilevel investigations of competent functioning in the face of adversity and trauma. These include studies of personality, neural, neuroendocrine, and molecular genetic contributors to resilient adaptation. Analogous to neural plasticity that takes place in response to brain injury, it is conjectured that it may be possible to conceptualize resilience as the ability of individuals to recover functioning after exposure to extreme stress. Multilevel randomized control prevention and intervention trials have substantial potential for facilitating the promotion of resilient functioning in diverse high-risk populations that have experienced significant adversity. Determining the multiple levels at which change is engendered through randomized control trials will provide insight into the mechanisms of change, the extent to which neural plasticity may be promoted, and the interrelations between biological and psychological processes in the development of maladaptation, psychopathology, and resilience.     

Principles of membrane stability and phase behavior under extreme conditions

Biological membranes consist of a complex assortment of lipids and proteins. The arrangement of the components, particularly in regard to their lateral disposition in the plane of the membrane under physiological conditions, is dependent on the phase behavior of the different membrane lipids and the way that this behavior is modified by interaction with other membrane components and electrolytes in the aqueous medium. Irreversible phase separation of components within the membrane may result from exposure to extreme environmental conditions including temperature, pressure, or electrolyte concentration. The principles underlying the phase-mixing behavior of model membrane systems can be used to provide useful information about the factors that determine the stability of biomembranes under physiological and non-physiological conditions. These data are reviewed and used to predict events that take place when membranes are exposed to environmental stress.     

The learning characteristics of rats under free-choice conditions]

The ability to organize a four-link operant food-procuring habit in a multiple alternative maze using the free-choice method was studied in albino rats. Three types of animals were observed which were different in the character of learning. The learning curve of 20% of rats had of exponential character (type I). Some animals (37%) acquired the skill through "insight" and the process of learning in these cases could be described by a logistic regression function (type II). The remaining rats (43%) refused from solving the intricate task and were able to acquire only the simplest form of a response, i.e., running to feeders. It is suggested that learning differences between the I and II types of animals may be associated with different strategies of problem solving: "procedural" (algorithmic) and "conceptual" (semantic).     

An archaeal tRNA-synthetase complex that enhances aminoacylation under extreme conditions

Aminoacyl-tRNA synthetases (aaRSs) play an integral role in protein synthesis, functioning to attach the correct amino acid with its cognate tRNA molecule. AaRSs are known to associate into higher-order multi-aminoacyl-tRNA synthetase complexes (MSC) involved in archaeal and eukaryotic translation, although the precise biological role remains largely unknown. To gain further insights into archaeal MSCs, possible protein-protein interactions with the atypical Methanothermobacter thermautotrophicus seryl-tRNA synthetase (MtSerRS) were investigated. Yeast two-hybrid analysis revealed arginyl-tRNA synthetase (MtArgRS) as an interacting partner of MtSerRS. Surface plasmon resonance confirmed stable complex formation, with a dissociation constant (K(D)) of 250 nM. Formation of the MtSerRS·MtArgRS complex was further supported by the ability of GST-MtArgRS to co-purify MtSerRS and by coelution of the two enzymes during gel filtration chromatography. The MtSerRS·MtArgRS complex also contained tRNA(Arg), consistent with the existence of a stable ribonucleoprotein complex active in aminoacylation. Steady-state kinetic analyses revealed that addition of MtArgRS to MtSerRS led to an almost 4-fold increase in the catalytic efficiency of serine attachment to tRNA, but had no effect on the activity of MtArgRS. Further, the most pronounced improvements in the aminoacylation activity of MtSerRS induced by MtArgRS were observed under conditions of elevated temperature and osmolarity. These data indicate that formation of a complex between MtSerRS and MtArgRS provides a means by which methanogenic archaea can optimize an early step in translation under a wide range of extreme environmental conditions.