Temperature Limit For Growth Research Articles

Climate acts as an environmental filter to plant pathogens.

Climate shapes the distribution of plant-associated microbes such as mycorrhizal and endophytic fungi. However, the role of climate in plant pathogen community assembly is less understood. Here, we explored the role of climate in the assembly of Phytophthora communities at >250 sites along a latitudinal gradient from Spain to northern Sweden and an altitudinal gradient from the Spanish Pyrenees to lowland areas. Communities were detected by ITS sequencing of river filtrates. Mediation analysis supported the role of climate in the biogeography of Phytophthora and ruled out other environmental factors such as geography or tree diversity. Comparisons of functional and species diversity showed that environmental filtering dominated over competitive exclusion in Europe. Temperature and precipitation acted as environmental filters at different extremes of the gradients. In northern regions, winter temperatures acted as an environmental filter on Phytophthora community assembly, selecting species adapted to survive low minimum temperatures. In southern latitudes, a hot dry climate was the main environmental filter, resulting in communities dominated by drought-tolerant Phytophthora species with thick oospore walls, a high optimum temperature for growth, and a high maximum temperature limit for growth. By taking a community ecology approach, we show that the establishment of Phytophthora plant pathogens in Europe is mainly restricted by cold temperatures.

Effect of Low Temperature on Photosynthetic Characteristics, Senescence Characteristics, and Endogenous Hormones of Winter Wheat “Ji Mai 22” during the Jointing Stage

To investigate the effects of low-temperature (LT) stress on photosynthetic properties and senescence characteristics of winter wheat leaves during the jointing stage, an environmental temperature control experiment was designed at Nanjing University of Information Science and Technology in 2023, using Triticum aestivum L. cv. “Ji Mai 22” as the test material. Four different temperature levels were set: 18 °C/8 °C (daily maximum/daily minimum temperature; CK), 13 °C/3 °C, 10 °C/0 °C, and 7 °C/3 °C. The duration of each treatment was 2, 4, and 6 days, respectively. The experimental findings reveal that the changes in physiological parameters of winter wheat leaves under low-temperature stress treatments are nonlinear. Under the 3 °C LT treatment, the photosynthetic parameters and endogenous hormone levels of wheat leaves significantly decrease after 6 days of stress. Under the 0 °C LT treatment, the photosynthetic parameters, leaf pigment content, and endogenous hormones of wheat decrease significantly, while under the −3 °C LT treatment, all the parameters of winter wheat leaves show a significant decline. Generally, the “Ji Mai22” wheat cultivar has a lower growth temperature limit of −3 °C during the jointing stage.

Potentials and limitations of cold-adapted hydrogen producing bacteria: A mini review

Low-temperature bacteria have potential to produce biohydrogen and are often considered a potential renewable energy generator for the future. However, the bacteria have presented poor hydrogen yield due to slow metabolic rate and prolonged lag phase often caused by their restricted growth temperature limit. The ineffective search for new biocatalysts from cold environments and the application of modification techniques almost jeopardize the economic viability of these strains in the biohydrogen production research. This article examined cold genetic and enzymatic adaptation potentials that led to the continuous expression of novel biocatalysts of biotechnological importance under the following headings; cold-adapted bacteria, biohydrogen-producing bacteria, strategies for adapting to stress in low temperatures, performance of cold-adapted bacteria in biohydrogen production, challenges of cold-adapted bacteria in biohydrogen production and future prospect. Finding new strains and studying their unique properties can improve the efficiency of hydrogen production by cold-adapted bacteria, as this new area has not yet been extensively studied.

Comparative experimental evolution reveals species-specific idiosyncrasies in marine phytoplankton adaptation to warming.

A number of experimental studies have demonstrated that phytoplankton can display rapid thermal adaptation in response to warmed environments. While these studies provide insight into the evolutionary responses of single species, they tend to employ different experimental techniques. Consequently, our ability to compare the potential for thermal adaptation across different, ecologically relevant, species remains limited. Here, we address this limitation by conducting simultaneous long-term warming experiments with the same experimental design on clonal isolates of three phylogenetically diverse species of marine phytoplankton; the cyanobacterium Synechococcus sp., the prasinophyte Ostreococcus tauri and the diatom Phaeodoactylum tricornutum. Over the same experimental time period, we observed differing levels of thermal adaptation in response to stressful supra-optimal temperatures. Synechococcus sp. displayed the greatest improvement in fitness (i.e., growth rate) and thermal tolerance (i.e., temperature limits of growth). Ostreococcus tauri was able to improve fitness and thermal tolerance, but to a lesser extent. Finally, Phaeodoactylum tricornutum showed no signs of adaptation. These findings could help us understand how the structure of phytoplankton communities may change in response to warming, and possible biogeochemical implications, as some species show relatively more rapid adaptive shifts in their thermal tolerance.

Manipulating Fermentation Pathways in the Hyperthermophilic Archaeon Pyrococcus furiosus for Ethanol Production up to 95°C Driven by Carbon Monoxide Oxidation.

Genetic engineering of hyperthermophilic organisms for the production of fuels and other useful chemicals is an emerging biotechnological opportunity. In particular, for volatile organic compounds such as ethanol, fermentation at high temperatures could allow for straightforward separation by direct distillation. Currently, the upper growth temperature limit for native ethanol producers is 72°C in the bacterium Thermoanaerobacter ethanolicus JW200, and the highest temperature for heterologously-engineered bioethanol production was recently demonstrated at 85°C in the archaeon Pyrococcus furiosus. Here, we describe an engineered strain of P. furiosus that synthesizes ethanol at 95°C, utilizing a homologously-expressed native alcohol dehydrogenase, termed AdhF. Ethanol biosynthesis was compared at 75°C and 95°C with various engineered strains. At lower temperatures, the acetaldehyde substrate for AdhF is most likely produced from acetate by aldehyde ferredoxin oxidoreductase (AOR). At higher temperatures, the effect of AOR on ethanol production is negligible, suggesting that acetaldehyde is produced by pyruvate ferredoxin oxidoreductase (POR) via oxidative decarboxylation of pyruvate, a reaction known to occur only at higher temperatures. Heterologous expression of a carbon monoxide dehydrogenase complex in the AdhF overexpression strain enabled it to use CO as a source of energy, leading to increased ethanol production. A genome reconstruction model for P. furiosus was developed to guide metabolic engineering strategies and understand outcomes. This work opens the door to the potential for 'bioreactive distillation' since fermentation can be performed well above the normal boiling point of ethanol. IMPORTANCE Previously, the highest temperature for biological ethanol production was 85°C. Here, we have engineered ethanol production at 95°C by the hyperthermophilic archaeon Pyrococcus furiosus. Using mutant strains, we showed that ethanol production occurs by different pathways at 75°C and 95°C. In addition, by heterologous expression of a carbon monoxide dehydrogenase complex, ethanol production by this organism was driven by the oxidation of carbon monoxide. A genome reconstruction model for P. furiosus was developed to guide metabolic engineering strategies and understand outcomes.

Microbial maintenance energy quantified and modeled with microcalorimetry

Refining the energetic costs of cellular maintenance is essential for predicting microbial growth and survival in the environment. Here, we evaluate a simple batch culture method to quantify energy partitioning between growth and maintenance using microcalorimetry and thermodynamic modeling. The constants derived from the batch culture system were comparable to those that have been reported from meta-analyses of data derived from chemostat studies. The model accurately predicted temperature-dependent biomass yield and the upper temperature limit of growth for Desulfovibrio alaskensis G20, suggesting the method may have broad application. An Arrhenius temperature dependence for the specific energy consumption rate, inferred from substrate consumption and heat evolution, was observed over the entire viable temperature range. By combining this relationship for specific energy consumption rates and observed specific growth rates, the model describes an increase in nongrowth associated maintenance at higher temperatures and the corresponding decrease in energy available for growth. This analytical and thermodynamic formulation suggests that simply monitoring heat evolution in batch culture could be a useful complement to the recognized limitations of estimating maintenance using extrapolation to zero growth in chemostats.

Requirement of de novo synthesis of pyruvate carboxylase in long-term succinic acid production in Corynebacterium glutamicum.

Protein turnover through de novo synthesis is critical for sustainable cellular functions. We previously found that glucose consumption rate in Corynebacterium glutamicum under anaerobic conditions increased at temperature higher than the upper limit of growth temperature. Here, we showed that production of lactic and succinic acids increased at higher temperature for long-term (48h) anaerobic reaction in metabolically engineered strains. At 42°C, beyond the upper limit of growth temperature range, biomass-specific lactic acid production rate was 8% higher than that at 30°C, the optimal growth temperature. In contrast, biomass-specific succinic acid production rate was highest at 36°C, 28% higher than that at 30°C, although the production at 42°C was still 23% higher than that at 30°C. As enzymes are usually unstable at high temperatures, we investigated whether protein turnover of metabolic enzymes is required for the production of lactic and succinic acids under these conditions. Interestingly, when de novo protein synthesis was inhibited by addition of chloramphenicol, after 6h, only succinic acid production was inhibited. Because glycolytic enzymes are involved in both lactic and succinic acids synthesis, enzymes in the anaplerotic pathway and the tricarboxylic acid (TCA) cycle leading to succinic acid synthesis were likely to be responsible for its decreased production. Among the five enzymes examined, the specific activity of only pyruvate carboxylase was drastically decreased after 48h at 42°C. Thus, the de novo synthesis of pyruvate carboxylase is required for long-term production of succinic acid. Graphical abstract KEY POINTS: • Long-term reaction for organic acids can be improved at temperature beyond ideal growth conditions. • De novo synthesis of pyruvate carboxylase is required for long-term succinic acid production.

Temperature effects on growth rates and fatty acid content in freshwater algae and cyanobacteria

Mass cultivation of algae for biofuel and other bioproduct production in outdoor, open raceway ponds has some considerable economic advantages. However, these systems would be subject to fluctuations in temperature (among other environmental factors), which can have dramatic effects on the growth rates of algal species and impact the overall productivity and quality of targeted algal crops. This study sought to elucidate the effects of temperature on algal growth rates, biomass accumulation, fatty acid production and composition. We surveyed 26 algal species from 5 different functional groups, growing them at 6 different temperatures between 9 and 32 °C. For each surveyed species, we collected eco-physiological trait data including maximum growth rate, thermal optimum (Topt), thermal niche width, and lower and upper temperature limits for growth (CTmin and CTmax, respectively); these data were also pooled for analysis at the functional group level. Responses to temperature varied among species, but at the functional group level we determined that the cyanobacteria have the highest thermal optimum (30.6 ± 2.3 °C), followed by chlorophytes (25.7 ± 0.1 °C) and diatoms (24.0 ± 0.4 °C). Temperature-specific fatty acid (FA) production was mostly controlled by growth rates, though some change in production was attributable to modification of intracellular FA stores. Temperature affected FA profiles in diverse ways, with no consistent trends across species or functional groups. In sum, temperature significantly impacts the overall productivity of algal biofuel systems by influencing species growth rates and fatty acid production. While algal growth rates varied predictably with temperature, we did not find the generalizable trends in temperature dependence of FA composition, suggesting that some aspects of algal cultivation for bioproducts in outdoor, open-air systems may be less predictable. However, a compilation of algal growth and FA composition responses to temperature, such as ours, may be useful for choosing appropriate species for given temperature regimes.

Spirosoma terrae sp. nov., Isolated from Soil from Jeju Island, Korea

The taxonomic position of bacterial strain, designated 15J9-4T, recovered from a beach soil sample on Jeju Island, South Korea, was established using a polyphasic approach. Strain 15J9-4T was assigned to phylum Bacteroidetes within the family Cytophagaceae based on 16S rRNA gene similarities. The closest phylogenetic relatives with validly published names were Spirosoma panaciterrae Gsoil 1519T (94.2% similarity) and Spirosoma luteolum 16F6ET (94.1%). Cells were rod-shaped, Gram-stain-negative, and non-motile. The isolate grew on NA, R2A, TSA, and LB agar. The temperature limits for growth were 10 and 30°C with an optimum at 25°C and the pH range was 7-8. Menaquinone MK-7 was the predominant respiratory quinone. The major cellular fatty acids comprised summed feature 3 (C16:1 ω6c/C16:1 ω7c, 30.2%), C16:1 ω5c (22.2%), iso C15:0 (12.9%), and C16:0 (8.8%). Phosphatidylethanolamine was identified as the major polar lipid. The G+C content of the genomic DNA was 48.4mol%. The results obtained from the polyphasic analyses allowed for the genotypic and phenotypic differentiation of strain 15J9-4T from recognized Spirosoma species. Therefore, the isolate is considered to represent a novel species in the genus Spirosoma, for which the name Spirosoma terrae sp. nov. is proposed. The type strain is 15J9-4T (= KCTC 52035T = JCM 31994T).

Low temperature limits for root growth in alpine species are set by cell differentiation.

Plant growth in cold climates is not limited by carbon assimilation (source activity) but rather by reduced carbon investment into new tissues (sink limitation). It has been hypothesized that all cold-adapted plants face similar growth constraints at low temperature mainly associated with the formation of new tissues. To explore the thermal limitation of plant tissue formation, we studied root growth and anatomical root tissue characteristics in four cold-adapted alpine species (Ranunculus glacialis, Rumex alpinus, Tussilago farfara, Poa alpina), grown in thermostated soils with a vertical temperature gradient approaching 1 °C. Above-ground plant organs were exposed to typical alpine climate conditions (high solar radiation and cool nights) at 2440 m a.s.l. in the Swiss Alps to assure continuous source activity. Image-based measurements of root growth (root elongation rates at 12-h intervals, RERs) were combined with anatomical examinations in thermally constrained root tips as well as with a functional growth analysis of entire plants. Temperatures in the range 0.8 to 1.4 °C were denoted as critically low temperature thresholds for root formation across the four species. The RERs per 12 h revealed that roots kept extending at low rates at 0.7-1.2 °C but cell elongation and xylem lignification were clearly inhibited in the terminal zones of root tips. Roots exposed to temperatures between 1 and 5 °C showed strongly reduced elongation rates so that these roots contributed very little to the entire root system compared to control roots grown at 10 °C. Hardly any secondary roots were formed at temperatures below 5 °C and total root mass was substantially lower (74 % reduction in comparison to control), also the above-ground biomass was reduced by 23 %. Cell elongation and differentiation rather than cell division control length and shape of root cells at the low temperature limit of growth. Lignification of root xylem is clearly constrained at temperatures below 3 °C.

Desulfobulbus aggregans sp. nov., a Novel Sulfate Reducing Bacterium Isolated from Marine Sediment from the Gulf of Gabes.

Three sulfate-reducing bacterial strains designated SM40T, SM41, and SM43 were isolated from marine sediment in the region of Skhira located in the Gulf of Gabes (Tunisia). These strains grew in anaerobic media with phosphogypsum as a sulfate source and sodium lactate as an electron and carbon source. One of them, strain SM40T, was characterized by phenotypic and phylogenetic methods. Cells were ovoid, Gram-stain-negative and non-motile. The temperature limits for growth were 10 and 55 °C with an optimum at 35 °C and the pH range was 6.5-8.1 with an optimum at pH 7.5. Growth was observed at salinities ranging from 10 to 80g NaCl l-1 with an optimum at 30g NaCl l-1. Strain SM40T was able to utilize butanol, ethanol, formate, L-glucose, glycerol, lactate, propanol, propionate, and pyruvate as electron donors for the reduction of sulfate, sulfite, or thiosulfate to H2S. Without electron acceptors, strain SM40T fermented butanol and pyruvate. The DNA G+C content of strain SM40T was 52.6mol %. Phylogenetic analysis based on the 16S rRNA gene sequence of the isolate revealed that strain SM40T was closely related to the species in the genus Desulfobulbus of the family Desulfobulbaceae. The sequence similarity between strain SM40 and Desulfobulbus marinus was 95.4%. The phylogenetic analysis, DNA G+C content, and differences in substrate utilization suggested that strain SM40 represents a new species of the genus Desulfobulbus, D. aggregans sp. nov. The type strain is strain SM40T (=DSM 28693T = JCM 19994T).

A theoretical examination of environmental effects on the life cycle schedule and range limits of the invasive seaweed Undaria pinnatifida

Invasive macroalgae form a substantial component of marine invaders at a global level. However, it is poorly understood how the complex interactions between local environmental conditions and life cycle dynamics contribute to invasion success from a mechanistic viewpoint. The aim of this study was to use a model (UndariaGEN) that incorporates a detailed representation of the individual heteromorphic life history stages (sporophytes and gametophytes) of the species in order to explore how interactions between these components contribute to the overall population dynamics. The latest version of the model was validated against field data from a real-life population in Brittany, France. This was followed by an assessment of the role of temperature limitations in determining its potential global range and then a more detailed examination of how environmental factors affect the life cycle dynamics of U. pinnatifida across a range of conditions characteristic of European populations. In terms of both relative abundance and recruitment, the model matches closely the patterns observed from field studies in Brittany, France (R2 = 0.98 respectively). Furthermore, the model predicted theoretical temperature limits for growth (9.1–22.5 °C) match closely the actual current global range limits for the species (9.5–22.4 °C) reported in the literature. In addition, the size of the species’ ecological niche is shown to be directly related to the amplitude in seasonal variation of temperature. This demonstrates that U. pinnatifida has a wider ecological niche in conditions of high seasonality; this finding is consistent with theories that propose the heteromorphic life cycle may have evolved as an optimal growth strategy for highly seasonal environments.

Tri-halide vapor phase epitaxy of thick GaN using gaseous GaCl3 precursor

Tri-halide vapor phase epitaxy (THVPE) of thick GaN using GaCl3 was investigated for fabricating low-cost, high-crystalline-quality GaN substrates instead of the conventional manufacturing method of GaCl-based hydride vapor phase epitaxy (HVPE). The growth rate and upper growth temperature limit of GaN using THVPE were found to be much higher than those obtained using conventional HVPE under the same growth conditions. Drastic reduction in the number of dark spots measured by cathodoluminescence at room temperature was observed for the high-temperature-grown GaN layer on the (000-1) GaN/sapphire template due to the enhancement of precursor migration on the growing surface. It was found that the incorporation of impurities such as O, C, and Cl can be reduced even on the N-polarity GaN by increasing the growth temperature. The possibility of enlargement of the crystal diameter by growing the N-polarity GaN layer using THVPE was also proposed.

Thermal and solvent stress cross-tolerance conferred to Corynebacterium glutamicum by adaptive laboratory evolution.

Reinforcing microbial thermotolerance is a strategy to enable fermentation with flexible temperature settings and thereby to save cooling costs. Here, we report on adaptive laboratory evolution (ALE) of the amino acid-producing bacterium Corynebacterium glutamicum under thermal stress. After 65 days of serial passage of the transgenic strain GLY3, in which the glycolytic pathway is optimized for alanine production under oxygen deprivation, three strains adapted to supraoptimal temperatures were isolated, and all the mutations they acquired were identified by whole-genome resequencing. Of the 21 mutations common to the three strains, one large deletion and two missense mutations were found to promote growth of the parental strain under thermal stress. Additive effects on thermotolerance were observed among these mutations, and the combination of the deletion with the missense mutation on otsA, encoding a trehalose-6-phosphate synthase, allowed the parental strain to overcome the upper limit of growth temperature. Surprisingly, the three evolved strains acquired cross-tolerance for isobutanol, which turned out to be partly attributable to the genomic deletion associated with the enhanced thermotolerance. The deletion involved loss of two transgenes, pfk and pyk, encoding the glycolytic enzymes, in addition to six native genes, and elimination of the transgenes, but not the native genes, was shown to account for the positive effects on thermal and solvent stress tolerance, implying a link between energy-producing metabolism and bacterial stress tolerance. Overall, the present study provides evidence that ALE can be a powerful tool to refine the phenotype of C. glutamicum and to investigate the molecular bases of stress tolerance.

Diversity and Bioprospective Potential (Cold-Active Enzymes) of Cultivable Marine Bacteria from the Subarctic Glacial Fjord, Kongsfjorden

The diversity and abundance of culturable bacteria in Kongsfjorden water (15 stations) and sediments (12 stations) were studied. Viable numbers ranged between 105–106 CFU l−1 in water and 102–104 CFU g−1 in the sediments. A total of 291 and 43 bacterial isolates were retrieved from the water (KJF) and sediments (FS), respectively. Based on 16S rRNA gene sequence similarities, the KJF and FS isolates were grouped into 49 and 23 phylotypes, respectively. The KJF and FS phylotypes represented three phyla namely, Actinobacteria, Bacteroidetes, and Proteobacteria. At the genus level, Flavobacterium and Shewanella and at the species level, Pseudoaltermonas arctica and Colwellia psychrerythraea were dominant in the water and sediments, respectively. Most phylotypes were psychrotolerant with upper growth temperature limit of 25–37 °C and tolerated 0.3–2.5 M NaCl and pH values of 5.0–11.0. Majority of the phylotypes produced one or more of the extracellular hydrolytic enzymes amylase, lipase, caseinase, urease, gelatinase, and DNase at 4 and 18 °C, while none were chitinolytic. Few of the FS phylotypes exhibited extracellular activity only at 4 or 18 °C. Nine FS and 21 KJF isolates were pigmented. The predominant cellular fatty acids were unsaturated, branched, and modified fatty acids, which are unique to cold-adapted bacteria.

Reduced threading dislocation densities in high-T/N-rich grown InN films by plasma-assisted molecular beam epitaxy

We explore the effect of growth kinetics on the structural properties of In-polar InN films on GaN templates grown near the thermal dissociation limit by plasma-assisted molecular beam epitaxy. Unlike the common growth temperature limit (T ≈ 500 °C) for In-polar InN grown under In-rich conditions, slightly N-rich conditions are demonstrated to shift the available growth temperature window to much higher temperatures (by >50 °C). InN films grown in this high-T/N-rich regime show significantly reduced off-axis X-ray diffraction rocking curve peak widths and record low threading dislocation densities (TDD ∼ 4 × 109 cm−2) even for film thicknesses <1 μm, as compared to state of the art In-rich growth. The reduction of TDD is attributed to more effective TD inclination and annihilation under N-rich growth, delineating prospective routes for improved InN-based materials.

Isolation and characterization of bacteria from ancient siberian permafrost sediment.

In this study, we isolated and characterized bacterial strains from ancient (Neogene) permafrost sediment that was permanently frozen for 3.5 million years. The sampling site was located at Mammoth Mountain in the Aldan river valley in Central Yakutia in Eastern Siberia. Analysis of phospolipid fatty acids (PLFA) demonstrated the dominance of bacteria over fungi; the analysis of fatty acids specific for Gram-positive and Gram-negative bacteria revealed an approximately twofold higher amount of Gram-negative bacteria compared to Gram-positive bacteria. Direct microbial counts after natural permafrost enrichment showed the presence of (4.7 ± 1.5) × 108 cells g−1 sediment dry mass. Viable heterotrophic bacteria were found at 0 °C, 10 °C and 25 °C, but not at 37 °C. Spore-forming bacteria were not detected. Numbers of viable fungi were low and were only detected at 0 °C and 10 °C. Selected culturable bacterial isolates were identified as representatives of Arthrobacter phenanthrenivorans, Subtercola frigoramans and Glaciimonas immobilis. Representatives of each of these species were characterized with regard to their growth temperature range, their ability to grow on different media, to produce enzymes, to grow in the presence of NaCl, antibiotics, and heavy metals, and to degrade hydrocarbons. All strains could grow at −5 °C; the upper temperature limit for growth in liquid culture was 25 °C or 30 °C. Sensitivity to rich media, antibiotics, heavy metals, and salt increased when temperature decreased (20 °C > 10 °C > 1 °C). In spite of the ligninolytic activity of some strains, no biodegradation activity was detected.

Climatic and hydrologic variability in the East China Sea during the last 7000 years based on oxygen isotope records of the submarine cavernicolous micro-bivalve Carditella iejimensis

The micro-bivalve Carditella iejimensis inhabits the sediment surface within submarine caves at Ie Island, Okinawa, Japan. A comparison of the δ 18O values ( δ 18O aragonite) of empty and living shells indicates that the shell is formed over several seasons, and that the main cause of mortality is low water temperature. According to this hypothesis, it is likely that the shells with heaviest δ 18O aragonite values (− 0.4‰) among the recent dataset formed under or close to the lower limit of growth temperature for the species. Assuming an unchanging temperature tolerance of the species during the Holocene, samples with δ 18O aragonite values heavier than − 0.4‰ indicate unusually low temperatures and enrichment of δ 18O of sea water ( δ 18O seawater). The δ 18O aragonite record of C. iejimensis from sediment cores recovered from Daidokutsu cave shows no clear long-term trend in sea surface temperature or δ 18O seawater in the East China Sea during the past 7000 years, and indicates anomalously cool and dry events (enrichment in δ 18O seawater) at around 6300 and 5550 cal. years BP. These events may have been related to changes in the activity of the East Asian monsoon, related in turn to weakening solar activity. In contrast, these anomalies appear to be obscured during the last 1000 years, including a weak Asian summer monsoon event during the Little Ice Age, thereby indicating that the mode of the East China Sea climatic and hydrologic response to decadal- to centennial-scale variability in the intensity of East Asian monsoon has varied over the past 7000 years.

Characterisation of a thermotolerant yeast, Kluyveromyces marxianus CBS712

Fermentation at high temperature with application of thermotolerant microorganisms is a technological advantage in bioethanol production. Among the yeasts, K. marxianus has outstanding thermotolarance. The industrial application of the IMB3 strain occurs usually at 45C. The final aim of our project is the genetic modification of the K. marxianus CBS712 strain in order to achieve ethanol production at higher temperature than the currently applied. This requires the characterization of the CBS712 strain, with special attention to the determination of the temperature limit of its growth and the amount of the ethanol produced. The temperature limit of growth was 48C in YPD medium. Elevation of the temperature above 45C led to an exponential drop of the cell viability. Ethanol production was tested in shaking flasks, in MYFM medium, under oxigene limited conditions, applying variable concentrations of glucose (12–20%) and different temperatures (45–47 ºC). Preliminary results have revealed that the elevation of glucose concentration increased the amount of ethanol produced. The amount of ethanol (appr. 5%)+ produced at the highest glucose concentration was not different at the tested temperatures (45, 46 and 47 ºC). The observation indicates the potential in raising the thermotolerance of the strain.

Algal communities at Gouqi Island in the Zhoushan archipelago, China

The kelp bed of Gouqi Island lies in the east of the East China Sea, in the Shengsi Archipelago. It is a key component of the island-reef ecosystem. This study evaluated kelp beds on intertidal and subtidal zones from 2004 to 2006. We evaluated seasonal variations in the community structure of macroalgae, and their relationship with water temperature, nitrogen and phytoplankton. The Gouqi Island kelp bed consists mainly of species of Sargassum. Sargassum horneri was the dominant species in subtidal zones, representing 90% of the total biomass. The dominant species in intertidal zones were S. fusiforme, S. horneri, S. thunbergii and Undaria pinnatifida. Fifty-four phytoplankton species were found in the Gouqi Island kelp bed, of which 51 species were found inside the kelp beds, 43 species outside the kelp beds, and 40 species were present both inside and outside the kelp beds. Diatoms were dominant both inside and outside the kelp beds. Except in winter, Skeletonema costatum was dominant, and its abundance in autumn was over 98% of the total abundance. Water temperature was found to be the primary factor influencing the growth of S. horneri in the Gouqi Island kelp bed. S. horneri grew slowly from November to March, and rapidly from March to June. The upper temperature limit for growth of S. horneri was about 18°C. Higher water temperatures can result in a decline in the kelp bed. Nitrogen seemed to be a limiting factor for macroalgal growth. This was particularly true for S. horneri and phytoplankton. Since nitrate is the primary nutrient for S. horneri, its absorption by S. horneri resulted in seasonal changes of nitrate in the ecosystem.