Thermic Stresses Research Articles

Influence of tree residue retention in Mediterranean forest on soil microbial communities responses to frequent warming and drying events

In the coming decades, Mediterranean forests are likely to experience higher heat-wave frequency that may severely affect soil microbial functioning. Here, we studied the effects of warming intensification on soil microbial communities and tested whether certain types of Mediterranean plant residues favor soil biological resistance to frequent drying and warming events (FDW). To this aim, we set-up mesocosms in which soils originating from six Mediterranean forest stands (i.e, Quercus ilex and Q. pubescens and Pinus halepensis and P. sylvestris monospecific and mixed stands) were amended with corresponding coarse (crushed branches) and fine (crushed twigs with leaves/needles) woody debris. A quantity of residues corresponding to five-fold the equivalent of the quantity left on the floor after tree harvesting/logging (equivalent to 35 gC.kg−1 soil DW) was added to each pot, and mesocosms were laid out into a split-plot design and subjected to FDW. After nineteen months, soil physico-chemical properties and changes in microbial communities' diversity and structure, biomass and extracellular enzymatic activities were measured. We showed that FDW reduced the richness of the soil fungal community by ca. 11% and functional diversity by ca. 4% and increased bacterial richness by ca. 40%. We observed a drastic down-regulation of extracellular enzyme activities related with N and C cycles (respectively -44% for protease, -54% for cellulase and -31% for tyrosinase activities). We also found that residues inputs types (fine vs. coarse) only slightly mitigate those effects, while species origin did. Our study showed that residues retention could alleviate the consequences of hydric and thermic stresses on microbial communities by modulating communities’ resistance in specific stands. These results suggest that tree residues retention, in specific stands, could contribute to sustain soil biological properties in the context of Mediterranean climate intensification.

Probiogenomics of Lactobacillus delbrueckii subsp. lactis CIDCA 133: In Silico, In Vitro, and In Vivo Approaches.

Lactobacillus delbrueckii subsp. lactis CIDCA 133 (CIDCA 133) has been reported as a potential probiotic strain, presenting immunomodulatory properties. This study investigated the possible genes and molecular mechanism involved with a probiotic profile of CIDCA 133 through a genomic approach associated with in vitro and in vivo analysis. Genomic analysis corroborates the species identification carried out by the classical microbiological method. Phenotypic assays demonstrated that the CIDCA 133 strain could survive acidic, osmotic, and thermic stresses. In addition, this strain shows antibacterial activity against Salmonella Typhimurium and presents immunostimulatory properties capable of upregulating anti-inflammatory cytokines Il10 and Tgfb1 gene expression through inhibition of Nfkb1 gene expression. These reported effects can be associated with secreted, membrane/exposed to the surface and cytoplasmic proteins, and bacteriocins-encoding genes predicted in silico. Furthermore, our results showed the genes and the possible mechanisms used by CIDCA 133 to produce their beneficial host effects and highlight its use as a probiotic microorganism.

Влияние термической обработки на структуру и механические свойства дисперсионно-твердеющего элинварного сплава

This study presents experimental results of structural analysis, such as phase composition, grains size assessment, strength and hardness of Ni-SPAN-C alloy 902 after various heat treatment modes (hardening and aging for stress relaxation). A thermal treatment mode has been selected to obtain higher physical and mechanical properties of the elinvar alloy. It is shown that the improvement of the alloy structure in thermal treatment occurs due to the thermic stresses, as well as the formation and dissolution of intermetallides.

Kluyveromyces marxianus developing ethanol tolerance during adaptive evolution with significant improvements of multiple pathways

BackgroundKluyveromyces marxianus, the known fastest-growing eukaryote on the earth, has remarkable thermotolerance and capacity to utilize various agricultural residues to produce low-cost bioethanol, and hence is industrially important to resolve the imminent energy shortage crisis. Currently, the poor ethanol tolerance hinders its operable application in the industry, and it is necessary to improve K. marxianus’ ethanol resistance and unravel the underlying systematical mechanisms. However, this has been seldom reported to date.ResultsWe carried out a wild-type haploid K. marxianus FIM1 in adaptive evolution in 6% (v/v) ethanol. After 100-day evolution, the KM-100d population was obtained; its ethanol tolerance increased up to 10% (v/v). Interestingly, DNA analysis and RNA-seq analysis showed that KM-100d yeasts’ ethanol tolerance improvement was not due to ploidy change or meaningful mutations, but founded on transcriptional reprogramming in a genome-wide range. Even growth in an ethanol-free medium, many genes in KM-100d maintained their up-regulation. Especially, pathways of ethanol consumption, membrane lipid biosynthesis, anti-osmotic pressure, anti-oxidative stress, and protein folding were generally up-regulated in KM-100d to resist ethanol. Notably, enhancement of the secretory pathway may be the new strategy KM-100d developed to anti-osmotic pressure, instead of the traditional glycerol production way in S. cerevisiae. Inferred from the transcriptome data, besides ethanol tolerance, KM-100d may also develop the ability to resist osmotic, oxidative, and thermic stresses, and this was further confirmed by the cell viability test. Furthermore, under such environmental stresses, KM-100d greatly improved ethanol production than the original strain. In addition, we found that K. marxianus may adopt distinct routes to resist different ethanol concentrations. Trehalose biosynthesis was required for low ethanol, while sterol biosynthesis and the whole secretory pathway were activated for high ethanol.ConclusionsThis study reveals that ethanol-driven laboratory evolution could improve K. marxianus’ ethanol tolerance via significant up-regulation of multiple pathways including anti-osmotic, anti-oxidative, and anti-thermic processes, and indeed consequently raised ethanol yield in industrial high-temperature and high-ethanol circumstance. Our findings give genetic clues for further rational optimization of K. marxianus’ ethanol production, and also partly confirm the positively correlated relationship between yeast’s ethanol tolerance and production.

Translation of mitochondrial swinger RNAs according to tri-, tetra- and pentacodons

Transcriptomes and proteomes include RNA and protein fragments not matching regular transcription/translation. Some ‘non-canonical’ mitochondrial transcripts match mitogenomes after assuming one among 23 systematic exchanges between nucleotides, producing swinger RNAs (nine symmetric, X↔Y, example C↔T; 14 asymmetric, X→Y→Z→X, example A→T→G→A) in GenBank's EST database. Here, reanalyzes of (a) public human mitochondrial transcriptome data (Illumina: RNA-seq) allowed to detect mitochondrial swinger RNAs for all 23 exchanges and (b) independent public human mitochondrial trypsinized proteomic mass spectrometry data allowed to detect peptides predicted from translation of parts of swinger-transformed mitogenomes covered by detected swinger reads. RNA-seq and previous EST swinger transcript data converge. Swinger RNA translation frequently inserts various amino acids at stop codons. Swinger RNA-peptide associations exist also for peptides matching systematically frameshifting translation, peptides entirely coded by tetra- and pentacodons (regular codons expanded by silent mononucleotides at 4th, and silent dinucleotides at 4th and 5th position(s), respectively). Swinger peptides differ from regular mitochondrial proteins: not membrane embedded, reflect warmer, anaerobic, low resource conditions, reminding a free-living ancestor. Tetra- and pentacoded peptides associate with low, high GC contents, respectively, suggesting expanded codon translations associate with thermic stresses. Results confirm experimentally predicted swinger, tetra- and pentacoded mitochondrial peptides, increasing mitogenomic coding density.

Effects of drying–rewetting or freezing–thawing cycles on enzymatic activities of different Mediterranean soils

The aim of this study was to determine the impact of climatic stress scenarios on soil microbial functions. To this end, three Mediterranean soils (south exposed soil, S; north exposed soil, N; soil from riparian forest, R) were sampled and subjected to climatic stress events consisting of an increasing number of drying–rewetting (DRWc) or freezing–thawing (FTc) cycles (1, 2, 4, and 7 cycles) at −20, 20, and 40 °C. The microbial functions considered were: fluorescein diacetate hydrolase (FDAse), lipase, acid phosphomonoesterase (PhA), and β-glucosidase (β-glu). Results showed that the soils had different enzymatic patterns, the S soil being less active than the two others. Considering the climatic stresses, the repeated effects of hydric and thermic stresses resulted, in most cases, in enzymatic activity decreases. The soils with colder and moister conditions (i.e. R and N soils) had globally more vulnerable enzyme activities to DRWc, a phenomenon which was amplified by increased temperatures, 40 °C being the more deleterious temperature. On the contrary, the S soil appeared more resistant to climatic stresses and, in some cases, certain enzyme activities, namely β-glu and PhA, were unaffected by the various treatments. γ-irradiation was also used to assess the biotic and abiotic parts in soil FDAse response to stresses. Results showed that in soils devoid of active microbial biomass, the FDAse activity was very sensitive to DRWc at high temperature (40 °C), activity losses ranging from 90 to 95%. Moreover, comparison with unsterilized soils indicated that microbial communities were able to reload efficiently this activity between stresses.

Protected areas of Spain preserve the neutral genetic diversity of Quercus ilex L. irrespective of glacial refugia

Quercus ilex L. (holm oak) is a wind-pollinated, sclerophyllous tree that copes with the environmental variability of the Mediterranean climate and that displays flexible ecophysiological adaptability in relation to hydric and thermic stresses. The holm oak dominates Mediterranean woodlands on both acidic and calcareous soils and has been exposed to management (dehesas) for thousands of years. Both protected areas and glacial refugia are supposed to preserve a substantial fraction of the genetic diversity of Iberian species. Genetic diversity was examined for 68 populations sampled throughout Spain using ptDNA SNPs, ptDNA microsatellites, and primarily nuclear AFLPs. Protected populations did not significantly differ from nonprotected populations by any of the measures of levels of genetic diversity. The three-level hierarchical AMOVA indicated that a low number of protected populations harbor most of the species’ genetic diversity. In addition, we found no evidence from either ptDNA or AFLP variation to support that populations from putative glacial refugia are divergent genetic groups as expected during isolation. Outcrossing, anemophilous long-distance pollen dispersal, acorn transport by animals, tree reliance, and habitat availability in Spain probably played a primarily role in homogenizing allele frequency among populations. This result leads us to suggest that extensive gene flow has been prevalent across Spanish populations. We conclude that glacial refugia have not been essential to maintain the neutral genetic makeup of Q. ilex. Nevertheless, conservation of the holm oak in protected areas ensures protection of the species’ genetic diversity, the most widespread woodland ecosystem in Iberia and indirectly the four iconic, endangered animal species (black stork, cinereous vulture, Iberian lynx, western imperial eagle).

Gender Differences and Short-Term Exposure to Mechanical, Thermic, and Mechanical—Thermic Stress Conditions on Hemocyte Functional Characteristics andHSP70 Gene Expression in OysterCrassostrea corteziensis(Hertlein, 1951)

On sea farms, oysters are constantly submitted to mechanical manipulation through size sorting and cleaning of epibionts, and also are maintained out of seawater and exposed to air and sunlight radiation during cleaning and transport to marketplaces. Therefore, the aim of this work was to evaluate gender differences and short-term changes in the immune response, glucose plasma levels, and Hsp70 gene expression in oyster Crassostrea corteziensis exposed for 0 (control), 15, 30, 45, and 60 min to mechanical (agitated), thermic (sunlight), and a combination of both stressors. Variations in total hemocyte count (THC) and granulocyte count (GC), as well in functional characteristics [i.e., mortality of hemocytes, phagocytosis, and anion superoxide production (SOA)] of hemocytes, suggest that oysters seems well adapted to mechanical disturbance, because SOA values increased, phagocytic activity was not affected, and hemocyte counts and mortality were rapidly recovered. Contrary with prolonged exposure of oysters to thermic conditions, which exerted a constantly increase of THC, whereas both hemocyte mortality and phagocytic activity decreased, but oxidative capacity (i.e., SOA) decreased in male and increased in female oysters. Immune competence and Hsp70 gene expression were significantly diminished in oysters exposed for 30 min to a combination of both stressors (i.e., mechanical and thermic), indicating the most vulnerable stress conditions. Hsp70 gene expression showed that females were more susceptible than male oyster to short-term (i.e., 15–30 min) exposure to mechanical and thermic stresses, but prolonged (i.e., 60 min) exposure of combined stressors exerted a particular effect on male oysters. The immune responses assessed and glucose levels in plasma demonstrated that thermic and mechanical—thermic stress conditions were more stressful than mechanical disruption, and that females were more susceptible than male oysters to stress conditions assayed. These environmental and anthropogenic stressors should be considered for the cultivation of this oyster species, as well for further research related with immune response of C. corteziensis.

Can Cold or Heat Shock Improve Skeletal Myoblast Engraftment in Infarcted Myocardium?

Cell death remains a major limitation of skeletal myoblast (SM) transplantation but the patterns of cell survival and proliferation in heart and their potential modulation by thermic stresses like heat shock (HS) and cryopreservation (Cryo) are still incompletely characterized. To track SMs in situ, we developed a dual-marker system based on the semiconservative expression of the foreign soluble protein, beta-Galactosidase (beta-Gal) and the constitutive expression of the Y chromosome in a myocardial infarction model. Control medium or Lewis male rat SMs (fresh or subjected to Cryo or HS) were injected in Lewis female rats. There was a massive cell loss early after transplantation in the fresh group, which was only partially compensated for by a subsequent proliferation. Conversely, both Cryo and HS significantly improved early cell survival but blunted subsequent proliferation so that, at 15 days posttransplantation, the total number of engrafted donor-derived Y-positive cells did not differ significantly between the three groups. Most of them expressed a skeletal muscle phenotype. These data confirm the high death rate of in-scar transplanted myoblasts, demonstrate the ability of those that survive to proliferate and differentiate along the myogenic pathway but do not support the efficacy of either Cryo or HS for increasing the ultimate magnitude of myoblast engraftment.

Reinforcement of the radiative and thermic stresses of the grape vine. Repercussions on yeast surface microflora

<p>All along the ripening period, the radiative and thermic stresses of the grapevine may be reinforced by the use of a reflective soil cover (aluminized film). Such a treatment leads to repercussions on the berries, on the must composition and finally on the wine quality. During such a preliminary experiment, we demonstrated that the temperature increase and/or the reinforcement of the reflected ultraviolet radiations (measured at 254 nm) at the level of grape berries severely impaired the development of yeast cells at their surfaces. By means of an artificial inoculation of grapes at the beginning of the ripening period with a mixture of four different yeast genera (<em>Saccharomyces cerevisiae</em>, <em>Hanseniaspora uvarum</em>, <em>Pichiafermentans</em> and <em>Schizosaccharomyces pombe</em>), we demonstrated that the repartition of yeast genera amongst this population was affected by the treatment of stocks with the aluminized film: during the experiment presented in this paper, the <em>Saccharomyces</em> genus was favoured. One may consider by extension similar effects resulting from the reflective properties of some natural soils. Such effects may considerably influence the distribution of wild yeast flora during the spontaneous fermentation of musts. If such an hypothesis is confirmed at a local or regional level, it will represent a first significant piece of the definition of one of the aspects of the" terroir" effect on the characteristics of wines.</p>