Characterization of spatial scaling relationships between vegetation pattern and topography at different directions in Gurbantunggut desert,China

Vegetation striped pattern is a common feature in semiarid and arid landscapes, which is seen as mosaics including vegetated and non-vegetated patches. Identifying scales of pattern in ecological systems and referring patterns to multi-scaled processes that create them are ongoing challenges. The aim of this paper is to study the vegetation patterns and their across-scale relationships between the vegetation and anisotropic topography (W–E and N–S) in 12 transects at Gurbantunggut desert. We used wavelet-based across-scale analysis for extracting information on scales of pattern for those transect data, evaluating their inherent structure, and inferring characteristics of the processes that imposed those patterns at across scales. The results show that, in W–E direction, the scales of vegetation pattern (C. ewersmanniana is at the scale 40 m, H. ammodendron, at 35 m) correspond to the dune ridge/dune valley sequences (appearing at distance of 40 m), and vegetation on mesoscale and large scale are significant cross-scale correlation with topography on mesoscale and large scale in all W–E transects. In N–S direction, there is an irregular pattern of vegetation along the N–S irregular topography, and no unified cross-scale relationships between topography and vegetation on different scales in different transects. Moreover, cross-scale correlation analysis between topography and vegetation provides further detail on hierarchical structure and specific scales in space that strongly influenced the larger patterns. Knowledge of the cross-scale relationships between topography and vegetation could lead to better understanding and management of biological resources in that region.     

Heat coma temperature,relative contents of saturated/unsaturated fatty acids and reproductive maturation in the oceanic sea skaters Halobates micans

This study was performed to clarify how the relative volume of saturated/unsaturated lipid and reproductive maturation relate to resistance to high temperature in the oceanic sea skaters, Halobates micans. Heat coma temperature (HCT) was measured in H. micans adults collected from a fixed sampling location (12°00′N, 135°00′E) in the western tropical Pacific Ocean. After measuring HCT, the specimen were dissected to measure the testes size and to determine the presence and number of oocytes in females. Bodies of the specimen were assessed by lipid analysis to evaluate saturated and unsaturated lipid content. A negative trend was seen between heat coma temperature and percentage of a saturated fatty acid, myristic acid (ratio of carbon number to number of double bonds = 14:0) (Pearson's correlation test: r = − 0.520, p = 0.101). In contrast, a positive trend was detected between heat coma temperature and percentage of an unsaturated fatty acid, palmitoleic acid (16:1) (r = 478, p = 0.137). Young males with small testes showed lower heat coma temperatures, whereas females that showed relatively high heat coma temperatures of 36–40 °C tended to have fewer mature oocytes in their ovaries than those that showed low heat coma temperatures of 30–34 °C. As Halobates appears to exhibit embryonic diapause rather than adult diapause, males of H. micans may develop both testes and resistance to high temperature in the parallel as they grow. In females, a trade-off may occur between heat tolerance function and oogenesis in the oceanic sea skaters.     

Spontaneously reduced body temperature and gasping ability as a mechanism of extreme tolerance to asphyxia in neonatal rats

The aim of the investigation was to verify our hypothesis that extreme tolerance of newborn rodents to anoxia is determined by their ability to maintain reduced body temperature and to keep on gasping.Newborn Wistar rats were used. In separate experiments we checked (1) effect of extreme thermal conditions on rectal temperature (T_re) of the newborns in their nests; (2) effect of ambient temperature (T_a) on oxygen consumption; (3) effects of controlled changes in T_re on thermoregulatory and respiratory responses to anoxia and on anoxia tolerance.In their nests rat pups controlled T_re at 32–36 °C while the T_re–T_a difference changed within a range of 1–20 °C. The lowest oxygen consumption of ∼24 ml O₂ kg⁻¹ min⁻¹ was recorded at T_a of 32 °C. Pups, exposed to anoxia at their normal T_re of 33 °C, were able to decrease T_re by another 1.7 °C and they kept on extremely slow and quiescent gasping for scheduled 25 min. In contrast, rats at T_re of 37 °C and 39 °C reached a critical phase of accelerated and shallow gasping after 14.95±0.40 min and 9.25±0.30 min, respectively.In conclusion, reduced T_re and unique gasping ability make newborn rats extremely tolerant to asphyxia.     

Variability of sea-surface temperature and sea-ice cover in the Fram Strait over the last two millennia

A sediment core located on the West Spitzbergen margin in the Fram Strait (78°54.931′N, 6°46.005′E, water depth: 1497 m) was analyzed for its dinocyst content in order to reconstruct hydroclimatic variations of the last 2500 years. The relative abundance of dinocyst taxa and principal component analysis show a major transition at about 300 cal. years BP. It is characterized by the disappearance of thermophilic taxa Spiniferites mirabilis-hyperacanthus and Impagidinium sphaericum and the increase of polar–subpolar taxa Impagidinium pallidum and Pentapharsodinium dalei. Sea-surface temperature (SST) estimates suggest warmer conditions than present (anomaly～+2 °C) averaging at 7 °C in summer until 300 cal. years BP, although cooling pulses are recorded around 1700, 1500, 1200 and 800 cal. years BP. The last 300 years were marked by a cooling from 7.6 to 3.5 °C and sea-ice cover increasing up to 7 months/yr. The results demonstrate that the Fram Strait area is sensitive to hydroclimatic variations, notably with respect to sea-ice and SSTs, which are linked to the relative strength of northward flow of North Atlantic waters to the East and southward outflow of cold and fresh waters from the Arctic Ocean. Based on our data, the warmest part of our record around 1320 cal. years BP is the only interval of the last 2500 years that provides a possible analogue for the modern post-AD 2000 interval, which is characterized by sea-ice free conditions.     

Structures,magnetic properties,and XPS of cyanide-bridged NdIII/SmIII/GdIII–CrIII complexes

Synthesis, structural characterization, and spectroscopic and magnetic properties of three new cyano-bridged 3d–4f bimetallic complexes, Ln^III(DMF)₄(H₂O)₃Cr^III (CN)₆ · nH₂O (Ln = Nd, Sm, Gd), have been described. The Nd–Cr complex crystallizes in the monoclinic P2₁/n space group with the following unit cell parameters: a = 20.063(7) Å, b = 8.967(4) Å, c = 18.023(6) Å, b = 96.12(3)°, V = 3224(2) Å³, and Z = 4. The neodymium (III) ion, which adopts anti-prism eight-coordination environment, is linked to the [Cr^III(CN)₆]³⁻ moiety through a bridging cyanide ligand with Nd–N = 2.550(4) Å and Nd–N–C = 164.4(4)°. The variable-temperature (0.5 T at 2–300 K) and variable-field (0–5 T at 2 and 5 K) magnetic measurements reveal that the weak interaction of Gd–Cr complexes differs from that of Nd–Cr and Sm–Cr ones mainly because of the lack of orbital angular momentum. The XPS and diffuse reflectance electronic spectra were also measured to discuss charge transfer transitions concerning π-backdonation from the viewpoint of magneto-optical functions.     

Comparison of thermotolerance of sun-exposed peel and shaded peel of ‘Fuji’ apple

The thermotolerance of the sun-exposed peel and the shaded peel of ‘Fuji’ apple (Malus domestica Borkh.) fruit was evaluated by measuring pigments, chlorophyll a fluorescence transients and O₂ evolution or uptake after exposure to 25, 35, 40, 42, 44, 46 or 48 °C for 30 min in the dark. A major effect of heat stress at 46–48 °C on the chlorophyll a fluorescence transients was the appearance of a very clear K step at 200–300 μs for both peel types. The K step was slightly more pronounced in the sun-exposed peel than in the shaded peel, suggesting that the resistance of oxygen-evolving complex to heat stress is slightly lower in the sun-exposed peel than in the shaded peel. Minimal fluorescence (F_O), relative to the value at 25 °C, increased to a greater extent in the shaded peel than in the sun-exposed peel after exposure to 46–48 °C, but the temperature dependencies of F_O changes were similar for both peel types. Maximum quantum yield of PSII (F_V/F_M) decreased to a similar extent in the sun-exposed peel and the shaded peel as temperature rose from 25 to 44 °C, but the sun-exposed peel reached slightly lower values at 46–48 °C. Correspondingly, gross O₂ evolution rate, relative to that at 25 °C, was also slightly lower in the sun-exposed peel than in the shaded peel at 46–48 °C. In response to heat stress, the ratio of Q_A-reducing reaction centers (RCs) to total RCs and the ratio of Q_B-reducing RCs to Q_A-reducing RCs decreased, but both of them decreased to lower values in the sun-exposed peel than in the shaded peel at 46–48 °C, indicating that the capacity of electron transfer between P₆₈₀⁺ and Q_B via Q_A was damaged to a greater extent in the sun-exposed peel than in the shaded peel. At each given temperature, dark respiration was similar between the two peel types. Overall, it appears that the exposure to higher surface temperature under high light does not make the sun-exposed peel more tolerant of heat stress than the shaded peel of apple fruit.     

Partial nitrification under limited dissolved oxygen conditions

Partial nitrification to nitrite is technically feasible and economically favourable, especially when wastewaters contained high ammonium concentrations or low C/N ratios. Partial nitrification can be obtained by selectively inhibiting nitrite-oxidizing bacteria (NOB) through appropriate regulation of the pH, temperature and dissolved oxygen (DO) concentrations. The effect of pH, DO levels and temperature on ammonia oxidation rate and nitrite accumulation was investigated in order to determine the optimal conditions for partial nitrification of synthetic wastewater with high ammonia concentration. The experiments performed at low DO levels to lower the total oxygen needed in the nitrification step, which means great saving in aeration. During the start-up stage pH and DO were set at 7.0–7.4 and 0.5 mg/l, respectively. The reactor was operated until complete partial nitrification was achieved. The effect of pH, DO on partial nitrification was studied, as pH was kept at 6.5, 7.5, 8.5, 9.5 and DO at 0.5±0.2, 1.5±0.2 and 2.5±0.2 mg/l, and temperature at 30 °C. The influence of temperature on k_a value was studied by keeping pH=7.5, DO=1.5 mg/l and temperature was controlled at 12, 20 and 30 °C, respectively. The results showed that partial nitrification to nitrite was steadily obtained and the optimal operational parameters were pH=7.5, DO=1.5 mg/l, T=30 °C based on ammonia oxidation rate and nitrite accumulation rate. The maximum k_a was achieved and to be 115.1×10⁻³ mg NH₄⁺–N (mg VSS h)⁻¹ under this condition.     

Pulleniatina Minimum Events in the Andaman Sea (NE Indian Ocean): Implications for winter monsoon and thermocline changes

The late Quaternary record of Pulleniatina obliquiloculata was investigated from two well dated sediment cores from the Andaman Sea (NE Indian Ocean) to examine its paleoceanographic significance and the presence of the Pulleniatina Minimum Events (PME) in the western North Pacific. As in the Pacific, our study shows that PMEs exist in the Indian Ocean albeit with a lower intensity. The Holocene PME occurs between 4.5 and 3.0 cal ka BP with a considerable reduction in P. obliquiloculata abundance, and which matches well with the Pacific records influenced by the Kuroshio Current. Additionally, two significant minimum events of P. obliquiloculata are also seen during the Younger Dryas (YD) and late Last Glacial Maximum (LGM, 20–18 cal ka BP). Overall, the PMEs of the Andaman Sea are not current driven events like in the western Pacific margin either by the weakening of the Kuroshio Current or reduced winter SSTs. The PMEs of the Andaman Sea are characterised by lower abundances of thermocline species indicating the increased depth of the thermocline (DOT) and reduced winter SSTs mainly during the minimum events of the YD and late LGM. The high SSTs during the Holocene PME make this event a mystery. However, the presence of PMEs in the Andaman Sea suggests that these events are not confined to areas influenced by the Kuroshio Current but may be responding to a broad scale oceanographic–climatic process or mechanism which needs to be explored with a detailed study.     

Germination response and viability of an endangered tropical conifer Widdringtonia whytei seeds to temperature and light

The tropical conifer Widdringtonia whytei Rendle is an endangered species endemic to Mulanje Mountain in Malawi. A study was conducted for the first time under controlled conditions in order to assess the effects of temperature and light on germination and viability of W. whytei seeds. Seeds incubated at a constant temperature of 20 °C attained the highest cumulative germination percentage (100%) followed by 87% germination under fluctuating temperatures of 15 °C night/25 °C day. No seed germination occurred at temperatures below 15 °C. Seeds that failed to germinate at temperatures below 15 °C showed the highest (> 90%) viability compared to the seeds incubated at 25 °C (60%). Across temperature regimes, germination was significantly higher under light (44.7%) than dark (35.6%) conditions. It is concluded that temperature is one of the critical factors for germination of W. whytei seed. The ability of W. whytei seeds to germinate both in light and darkness implies that the species would unlikely form a persistent soil seed bank, an attribute which is common in species that survive in habitats frequently disturbed by fires.     

Diatom taxa and assemblages for establishing nutrient criteria of lakes with anthropogenic hydrologic alteration

Stressor-response models offer guidance for concentration-based nutrient criteria in lakes under human intervention. Diatom-based statistics from biological responses were incorporated to derive taxon-specific and community-level change points (thresholds) of phosphorous and nitrogen in 77 Yangtze floodplain lakes. Diatom metrics relating with conductivity were adopted as response variables, since conductivity explained the maximum variation (38.1%) in diatom assemblages via Bootstrapped regression trees. Nonparametric change-point analysis and Threshold Indicator Taxa ANalysis showed threshold responses of diatom community structure at 0.05–0.08 mg TP/L in connected lakes and 0.02–0.04 mg TP/L in isolated lakes. Distinct community change points of sensitive diatoms occurred at 0.96–1.63 mg TN/L in connected lakes and 0.52–0.63 mg TN/L in isolated lakes. Diatom community structures of tolerant taxa were substantially altered beyond 0.22–0.23 mg/L in connected lakes and 0.52–0.69 mg NO_x/L in isolated lakes. Hydrological river-lake connectivity differed significantly in ecological nutrient criteria with more TN/TP criteria and less NO_x criteria in connected lakes. Given the ecological significance and biological integrity, diatom-based statistics can provide more reliable change points (thresholds) for nutrient criteria than Chl a-nutrient relationships.     

Warneckea parvifolia (Melastomataceae–Olisbeoideae), a new “sand-forest” endemic from northeastern KwaZulu-Natal (South Africa) and southernmost Mozambique,and a phylogenetic analysis of eastern and southern African representatives of W. section Warneckea

Warneckea populations from “sand-forest” or “sand-thicket” habitats in Tembe Elephant Park, South Africa, and Licuati Forest Reserve in adjacent southern Mozambique were previously thought to be a small-leaved form of W. sousae, which typically includes larger-leaved plants ranging from central Mozambique northward to Tanzania. We examine this hypothesis using molecular and morphological evidence. Maximum-likelihood phylogenetic analysis of combined nrDNA ETS and ITS sequence data failed to resolve W. sousae and the Maputaland populations as an exclusively monophyletic group. Instead, the Kenyan endemic W. mouririifolia was strongly supported as the sister species of W. sousae, and the Maputaland plants were resolved in a separate, strongly supported clade together with populations of an as-yet undetermined Warneckea species from northern Mozambique. A hypothesis of exclusive monophyly for the plants from Tembe and Licuati had moderate support in separate ETS and ITS1 analyses (bootstrap proportions of 88% and 81%, respectively). Statistically significant differences in leaf dimensions and internode length were found between the Maputaland plants and typical W. sousae. We conclude that the populations from Tembe and Licuati represent a distinct species, which we describe as W. parvifolia. The species differs from W. sousae in having shorter internodes (mostly 5–25 mm not 10–60 mm long), smaller leaves (mostly 14–32 × 8–19 mm not 40–76 × 22–52 mm), shorter petioles (mostly 1–1.5 mm not 1.5–6 mm long), smaller flowers (hypanthium 1 × 1.5–1.75 mm not 1.5–2 × 2 mm; calyx lobes 0.5 mm not 0.75 mm long; staminal filaments 3–4 mm not 5 mm long; style 4–5 mm not 9 mm long), and globose fruit (not obovoid). An IUCN conservation status of Endangered (EN) B1a, b(ii, iii) is indicated for W. parvifolia, due to its limited distribution and projected declines in its habitat quality and area of occupancy.     

Estimation of the core temperature control during ambient temperature changes and the influence of circadian rhythm and metabolic conditions in mice

It has been speculated that the control of core temperature is modulated by physiological demands. We could not prove the modulation because we did not have a good method to evaluate the control. In the present study, the control of core temperature in mice was assessed by exposing them to various ambient temperatures (T_a), and the influence of circadian rhythm and feeding condition was evaluated. Male ICR mice (n=20) were placed in a box where T_a was increased or decreased from 27 °C to 40 °C or to −4 °C (0.15 °C/min) at 0800 and 2000 (daytime and nighttime, respectively). Intra-abdominal temperature (T_core) was monitored by telemetry. The relationship between T_core and T_a was assessed. The range of T_a where T_core was relatively stable (range of normothermia, RNT) and T_core corresponding to the RNT median (regulated T_core) were estimated by model analysis. In fed mice, the regression slope within the RNT was smaller in the nighttime than in the daytime (0.02 and 0.06, respectively), and the regulated T_core was higher in the nighttime than in the daytime (37.5 °C and 36.0 °C, respectively). In the fasted mice, the slope remained unchanged, and the regulated T_core decreased in the nighttime (0.05 and 35.9 °C, respectively), while the slopes in the daytime became greater (0.13). Without the estimating individual thermoregulatory response such as metabolic heat production and skin vasodilation, the analysis of the T_a–T_core relationship could describe the character of the core temperature control. The present results show that the character of the system changes depending on time of day and feeding conditions.     

Multi-channel electromyography during maximal isometric and dynamic contractions

Motor unit behavior differs between contraction types at submaximal contraction levels, however is challenging to study during maximal voluntary contractions (MVCs). With multi-channel surface electromyography (sEMG), mean physiological characteristics of the active motor units can be extracted. Two 8-electrode sEMG arrays were attached on biceps brachii muscle (one on each head) to examine behavior of sEMG variables during isometric, eccentric and concentric MVCs of elbow flexors in 36 volunteers.On average, isometric (364 ± 88 N) and eccentric (353 ± 74 N) MVCs were higher than concentric (290 ± 73 N) MVC (p < 0.001). Mean muscle fiber conduction velocity (CV) was highest during eccentric MVC (4.42 ± 0.49 m/s) than concentric (4.25 ± 0.49 m/s, p < 0.01) and isometric (4.14 ± 0.45 m/s, p < 0.001) MVCs. Furthermore, eccentric MVC showed lower sEMG amplitude at the largest elbow joint angles (120–170°) and higher CV at the smallest (70–150°) elbow joint angles (p < 0.05–0.001) than concentric MVC.The differences in CV and sEMG amplitude between the MVCs suggest that the control strategy of motor units differs between the contraction types during MVCs, and is dependent on the muscle length between the dynamic MVCs.     

The last occurrence of Proboscia curvirostris in the North Atlantic marine isotope stages 9-8

Well-preserved diatoms are present in high sedimentation rate Pleistocene cores retrieved on Ocean Drilling Program (ODP) Legs 151, 152, 162 and IMAGES cruises of R/V Marion Dufresne from the North Atlantic. Investigation of the stratigraphic occurrence of diatom species shows that the youngest diatom event observed in the area is the last occurrence (LO) of Proboscia curvirostris (Jousé) Jordan and Priddle. P. curvirostris is a robust species that can easily be identified in the sediments, and therefore can be a practical biostratigraphic tool. We have mapped its areal distribution, and found that it stretches from 40°N to 80°N in the North Atlantic. Further, we have correlated the LO P. curvirostris to the oxygen isotope records of six cores to refine the age of this biostratigraphic event. The extinction of P. curvirostris is latitudinally diachronous through Marine Isotope Stages (MIS) 9 to 8 within the North Atlantic. This is closely related to the paleoceanography of the area. P. curvirostris first disappeared within interglacial MIS 9 (324 ka) from the northern areas that are most sensitive to climatic forcing, like the East Greenland current and the sea–ice margin. It survived in mid-North Atlantic until the conditions of the MIS 8 (glaciation) became too severe (260 ka). In the North Pacific at ODP Site 883 the LO P. curvirostris falls within MIS 8. The observed overlap in age between the North Atlantic and the North Pacific strongly suggests that the extinction of P. curvirostris is synchronous between these oceans.     

Impact of fluctuating temperatures on development of the koinobiont endoparasitoid Venturia canescens

The effect of temperature on the biology of Venturia canescens (Gravenhorst) (Hymenoptera: Ichneumonidae) is well understood under constant temperature conditions, but less so under more natural, fluctuating conditions. Herein we studied the influence of fluctuating temperatures on biological parameters of V. canescens. Parasitized fifth-instar larvae of Ephestia kuehniella Zeller (Lepidoptera: Pyralidae) were reared individually in incubators at six fluctuating temperature regimes (15–19.5 °C with a mean of 17.6 °C, 17.5–22.5 °C with a mean of 19.8 °C, 20–30 °C with a mean of 22.7 °C, 22.5–27.5 °C with a mean of 25 °C, 25.5-32.5 °C with a mean of 28.3 °C and 28.5–33 °C with a mean of 30 °C) until emergence and death of V. canescens adults. Developmental time from parasitism to adult eclosion, adult longevity and survival were recorded at each fluctuating temperature regime. In principle, developmental time decreased with an increase of the mean temperature of the fluctuating temperature regime. Upper and lower threshold temperatures for total development were estimated at 34.9 and 6.7 °C, respectively. Optimum temperature for development and thermal constant were 28.6 °C and 526.3 degree days, respectively. Adult longevity was also affected by fluctuating temperature, as it was significantly reduced at the highest mean temperature (7.0 days at 30 °C) compared to the lowest one (29.4 days at 17.6 °C). Survival was low at all tested fluctuating temperatures, apart from mean fluctuating temperature of 25 °C (37%). Understanding the thermal biology of V. canescens under more natural conditions is of critical importance in applied contexts. Thus, predictions of biological responses to fluctuating temperatures may be used in population forecasting models which potentially influence decision-making in IPM programs.     

Toxic strains of the Alexandrium ostenfeldii complex in southern South America (Beagle Channel,Argentina)

During phytoplankton monitoring in the Beagle Channel (≈54°52′ S, 67°32′ W) a previously undetected Alexandrium species was observed in coincidence with mouse bioassay toxicity. Detailed thecal plates analysis using epifluorescence and scanning electron microscopy revealed the presence of the Alexandrium ostenfeldii species complex, showing a mixture of the diagnostic features usually used to discriminate between the morphospecies A. ostenfeldii and A. peruvianum. Cells of the A. ostenfeldii complex were commonly observed during spring after the main annual diatom bloom, when temperatures and salinities were respectively around 7.5–10 °C and 30–30.5 psu, and nutrients showed a seasonal decrease. Toxin analysis by liquid chromatography–mass spectrometry revealed the production of 13-desmethyl spirolide C and 20-methyl spirolide G in cell cultures. The cellular contain of spirolides during exponential phase growth was 0.5906 ± 0.0032 and 0.1577 ± 0.0023 pg cell⁻¹ for 13-desMe-C and 20-Me-G, respectively. A third unknown compound, with a structure resembling that of spirolides was also detected in culture. Moreover, an additional compound with a similar m/z (692) than that of 13-desMe-C but presenting a higher retention time (Rt = 40.5 min) was found in high proportions in mussel samples. PSP toxins were present at low concentration in mussels but were not detected in cultures. These results extend the world-wide distribution of toxic strains of the A. ostenfeldii complex to the Beagle Channel (southern South America), where toxic events have been traditionally linked to the presence of Alexandrium catenella. This is the first confirmed occurrence of spirolides in mussels and plankton from Argentina, which highlights the importance of monitoring these toxins and their producing organisms to protect public health and improve the management of shellfish resources.     

Development response of Spodoptera exigua to eight constant temperatures: Linear and nonlinear modeling

Temperature-dependent development of Spodoptera exigua (Hübner) were evaluated at eight constant temperatures of 12, 15, 20, 25, 30, 33, 34 and 36 °C with a variation of 0.5 °C on sugar beet leaves. No development occurred at 12 °C and 36 °C. Total developmental time varied from 120.50 days at 15 °C to 14.50 days at 33 °C. As temperature increased from 15 °C to 33 °C, developmental rate (1/developmental time) of S. exigua increased but declined at 34 °C. The lower temperature threshold (T_min) was estimated to be 12.98 °C and 12.45 °C, and the thermal constant (K) was 294.99 DD and 311.76 DD, using the traditional and Ikemoto–Takai linear models, respectively. The slopes of the Ikemoto–Takai linear model for different immature stages were different, violating the assumption of rate isomorphy. Data were fitted to three nonlinear models to predict the developmental rate and estimate the critical temperatures. The T_min values estimated by Lactin-2 (12.90 °C) and SSI (13.35 °C) were higher than the value estimated by Briere-2 (8.67 °C). The estimated fastest development temperatures (T_fast) by the Briere-2, Lactin-2 and SSI models for overall immature stages development of S. exigua were 33.4 °C, 33.9 °C and 32.4 °C, respectively. The intrinsic optimum temperature (T_Φ) estimated from the SSI model was 28.5 °C, in which the probability of enzyme being in its native state is maximal. The upper temperature threshold (T_max) values estimated by these three nonlinear models varied from 34.00 °C to 34.69 °C. These findings on thermal requirements can be used to predict the occurrence, number of generations and population dynamics of S. exigua.     

Improved high thermal stability of pullulanase from a newly isolated thermophilic Bacillus sp. AN-7

A thermophilic Bacillus sp. strain AN-7, isolated from a soil in India, produced an extracellular pullulanase upon growth on starch–peptone medium. The enzyme was purified to homogeneity by ammonium sulfate precipitation, anion exchange and gel filtration chromatography. The optimum temperature and pH for activity was 90 °C and 6.0. With half-life time longer than one day at 80 °C the enzyme proves to be thermostable in the pH range 4.5–7.0. The pullulanase from Bacillus strain lost activity rapidly when incubated at temperature higher than 105 °C or at pH lower than 4.5. Pullulanase was completely inhibited by the Hg²⁺ ions. Ca²⁺, dithiothreitol, and Mn²⁺ stimulated the pullulanase activity. Kinetic experiments at 80 °C and pH 6.0 gave V_max and K_m values of 154 U mg⁻¹ and 1.3 mg ml⁻¹. The products of pullulan were maltotriose and maltose. This proved that the purified pullulanase (pullulan-6-glucanohydrolase, EC 3.2.1.41) from Bacillus sp. AN-7 is classified under pullulanase type I. To our knowledge, this Bacillus pullulanase is the most highly thermostable type I pullulanase known to date.     

Copper,zinc superoxide dismutase of Curcuma aromatica is a kinetically stable protein

This study details on cloning and characterization of Cu,Zn superoxide dismutase (Ca–Cu,Zn SOD) from a medicinally important plant species Curcuma aromatica. Ca–Cu,Zn SOD was 692 bp with an open reading frame of 459 bp. Expression of the gene in Escherichia coli cells followed by purification yielded the enzyme with K_m of 0.047 ± 0.008 μM and V_max of 1250 ± 24 units/mg of protein. The enzyme functioned (i) across a temperature range of −10 to +80 °C with temperature optima at 20 °C; and (ii) at pH range of 6–9 with optimum activity at pH 7.8. Ca–Cu,Zn SOD retained 50% of the maximum activity after autoclaving, and was stable at a wide storage pH ranging from 3 to 10. The enzyme tolerated varying concentrations of denaturating agent, reductants, inhibitors, trypsin, was fairly resistant to inactivation at 80 °C for 180 min (k_d, 6.54 ± 0.17 × 10⁻³ min⁻¹; t_1/2, 106.07 ± 2.68 min), and had midpoint of thermal transition (T_m) of 70.45 °C. The results suggested Ca–Cu,Zn SOD to be a kinetically stable protein that could be used for various industrial applications.