Heat tolerance, behavioural temperature selection and temperature-dependent respiration in larval Octopus huttoni

This study reports temperature effects on paralarvae from a benthic octopus species, Octopus huttoni, found throughout New Zealand and temperate Australia. We quantified the thermal tolerance, thermal preference and temperature-dependent respiration rates in 1-5 days old paralarvae. Thermal stress (1 °C increase h⁻¹) and thermal selection (∼10-24 °C vertical gradient) experiments were conducted with paralarvae reared for 4 days at 16 °C. In addition, measurement of oxygen consumption at 10, 15, 20 and 25 °C was made for paralarvae aged 1, 4 and 5 days using microrespirometry. Onset of spasms, rigour (CT_max) and mortality (upper lethal limit) occurred for 50% of experimental animals at, respectively, 26.0±0.2 °C, 27.8±0.2 °C and 31.4±0.1 °C. The upper, 23.1±0.2 °C, and lower, 15.0±1.7 °C, temperatures actively avoided by paralarvae correspond with the temperature range over which normal behaviours were observed in the thermal stress experiments. Over the temperature range of 10 °C-25 °C, respiration rates, standardized for an individual larva, increased with age, from 54.0 to 165.2 nmol larvae⁻¹ h⁻¹ in one-day old larvae to 40.1-99.4 nmol h⁻¹ at five days. Older larvae showed a lesser response to increased temperature: the effect of increasing temperature from 20 to 25 °C (Q₁₀) on 5 days old larvae (Q₁₀=1.35) was lower when compared with the 1 day old larvae (Q₁₀=1.68). The lower Q₁₀ in older larvae may reflect age-related changes in metabolic processes or a greater scope of older larvae to respond to thermal stress such as by reducing activity. Collectively, our data indicate that temperatures >25 °C may be a critical temperature. Further studies on the population-level variation in thermal tolerance in this species are warranted to predict how continued increases in ocean temperature will limit O. huttoni at early larval stages across the range of this species.     

Extracellular expression and biochemical characterization of α-cyclodextrin glycosyltransferase from Paenibacillus macerans

The cgt gene encoding α-cyclodextrin glycosyltransferase (α-CGTase) from Paenibacillus macerans strain JFB05-01 was expressed in Escherichia coli as a C-terminal His-tagged protein. After 90 h of induction, the activity of α-CGTase in the culture medium reached 22.5 U/mL, which was approximately 42-fold higher than that from the parent strain. The recombinant α-CGTase was purified to homogeneity through either nickel affinity chromatography or a combination of ion-exchange and hydrophobic interaction chromatography. Then, the purified enzyme was characterized in detail with respect to its cyclization activity. It is a monomer in solution. Its optimum reaction temperature is 45 °C, and half-lives are approximately 8 h at 40 °C, 1.25 h at 45 °C and 0.5 h at 50 °C. The recombinant α-CGTase has an optimum pH of 5.5 with broad pH stability between pH 6 and 9.5. It is activated by Ca²⁺, Ba²⁺, and Zn²⁺ in a concentration-dependent manner, while it is dramatically inhibited by Hg²⁺. The kinetics of the α-CGTase-catalyzed cyclization reaction could be fairly well described by the Hill equation.     

Purification and characterisation of a bifunctional alginate lyase from novel Isoptericola halotolerans CGMCC 5336

A novel halophilic alginate-degrading microorganism was isolated from rotten seaweed and identified as Isoptericola halotolerans CGMCC5336. The lyase from the strain was purified to homogeneity by combining of ammonium sulfate fractionation and anion-exchange chromatography with a specific activity of 8409.19 U/ml and a recovery of 25.07%. This enzyme was a monomer with a molecular mass of approximately 28 kDa. The optimal temperature and pH were 50 °C and pH 7.0, respectively. The lyase maintained stability at neutral pH (7.0–8.0) and temperatures below 50 °C. Metal ions including Na⁺, Mg²⁺, Mn²⁺, and Ca²⁺ notably increased the activity of the enzyme. With sodium alginate as the substrate, the K_m and V_max were 0.26 mg/ml and 1.31 mg/ml min, respectively. The alginate lyase had substrate specificity for polyguluronate and polymannuronate units in alginate molecules, indicating its bifunctionality. These excellent characteristics demonstrated the potential applications in alginate oligosaccharides production with low polymerisation degrees.     

A kinetic evaluation of anaerobic treatment of swine wastewater at two temperatures in a temperate climate zone

A static granular bed reactor (SGBR) was used to treat swine wastewater at 24 and 16 °C. At 24 °C, the organic loading rate (OLR) was 0.7-5.4 kg COD/m³ day and the average chemical oxygen demand (COD) removal efficiency was 88.5%, respectively. Meanwhile, at 16 °C, the OLR was 1.6-4.0 kg COD/m³ day and the average COD removal efficiency was 68.0%, respectively. The SGBR acted as a bioreactor as well as a biofilter. After backwashing, the recovery of COD removal was not a function of an OLR but recovery time, while that of TSS removal was not a function of either recovery time or the OLR. The maximum substrate utilization rate (k_max) ratio was 1.89 between 24 and 16 °C, and the half velocity constant (K_s) ratio was 1.22, and the maximum specific growth rate (μ_max) ratio was 4.71. In addition, the temperature-activity coefficient in this study was determined to be 1.09.     

Rapid thermal responses and thermal tolerance in adult codling moth Cydia pomonella (Lepidoptera: Tortricidae)

In order to preserve key activities or improve survival, insects facing variable and unfavourable thermal environments may employ physiological adjustments on a daily basis. Here, we investigate the survival of laboratory-reared adult Cydia pomonella at high or low temperatures and their responses to pre-treatments at sub-lethal temperatures over short time-scales. We also determined critical thermal limits (CTLs) of activity of C. pomonella and the effect of different rates of cooling or heating on CTLs to complement the survival assays. Temperature and duration of exposure significantly affected adult C. pomonella survival with more extreme temperatures and/or longer durations proving to be more lethal. Lethal temperatures, explored between −20 °C to −5 °C and 32 °C to 47 °C over 0.5, 1, 2, 3 and 4 h exposures, for 50% of the population of adult C. pomonella were −12 °C for 2 h and 44 °C for 2 h. Investigation of rapid thermal responses (i.e. hardening) found limited low temperature responses but more pronounced high temperature responses. For example, C. pomonella pre-treated for 2 h at 5 °C improved survival at −9 °C for 2 h from 50% to 90% (p < 0.001). At high temperatures, pre-treatment at 37 °C for 1 h markedly improved survival at 43 °C for 2 h from 20% to 90% (p < 0.0001). We also examined cross-tolerance of thermal stressors. Here, low temperature pre-treatments did not improve high temperature survival, while high temperature pre-treatment (37 °C for 1 h) significantly improved low temperature survival (−9 °C for 2 h). Inducible cross-tolerance implicates a heat shock protein response. Critical thermal minima (CTmin) were not significantly affected by cooling at rates of 0.06, 0.12 and 0.25 °C min⁻¹ (CTmin range: 0.3-1.3 °C). By contrast, critical thermal maxima (CTmax) were significantly affected by heating at these rates and ranged from 42.5 to 44.9 °C. In sum, these results suggest pronounced plasticity of acute high temperature tolerance in adult C. pomonella, but limited acute low temperature responses. We discuss these results in the context of local agroecosystem microclimate recordings. These responses are significant to pest control programmes presently underway and have implications for understanding the evolution of thermal tolerance in these and other insects.     

Thermal tolerance of Litopenaeus vannamei (Crustacea: Penaeidae) acclimated to four temperatures

Critical thermal minima (CTMin) and maxima (CTMax) values were determined for the Pacific white shrimp Litopenaeus vannamei post-larvae and juveniles at four different acclimation temperatures (15, 20, 25, and 30 °C). The CTMin of shrimp at these acclimation temperatures were 7.82, 8.95, 9.80, and 10.96 °C for post-larvae and 7.50, 8.20, 10.20, and 10.80 °C for juveniles, respectively, at 1 °C h⁻¹ cooling rate. The CTMax values were 35.65, 38.13, 39.91, and 42.00 °C for post-larvae and 35.94, 38.65, 40.30, and 42.20 °C for juveniles at the respective acclimation temperatures. Both acclimation temperature and size of the shrimp affected CTMin values of L. vannamei (P<0.01). Overall, juveniles displayed significantly lower CTMin values than the post-larvae (P<0.0001). However, the CTMax response by post-larvae and juveniles were not significantly different from each other and no interaction was determined between the acclimation temperature and development stage (P>0.01). The area of the thermal tolerance polygon over four acclimation temperatures (15, 20, 25, and 30 °C) for the post-larvae of L. vannamei was calculated to be 434.94 °C². The acclimation response ratio (ARR) values were high ranging from 0.35 to 0.44 for both post-larvae and juveniles. L. vannamei appears to be more sensitive to low temperatures than other penaeid species and its cold tolerance zone ranged from 7.5 to 11 °C. In successful aquaculture temperature must never fall below 12 °C to prevent mortalities. Upper thermal tolerance is less of a problem as in most subtropical regions maximum water temperature rarely exceeds 34 °C, but care should be given if shallow ponds with low water renewal rate are being used.     

Seed germination of Lasia spinosa as a function of temperature,light, desiccation,and storage

Lasia spinosa seeds were not dormant at maturity in early spring. The most favorable temperatures for germination were between 25 and 30 °C, and final percentage and rate of germination decreased with an increase or decrease in temperature. When L. spinosa seeds were transferred to 25 °C, after 60 days at 10 °C (where none of the seeds germinated), final germination increased from 0% to 78%. Seeds germinated to high percentage both in light and in dark, although dark germination took more than twice as long as in the light. During desiccation of seeds at 15 °C and 45% relatively humidity, moisture loss decreased exponentially from 2.02 to 0.13 g H₂O g⁻¹ dry wt within 16 days, and only a few seeds (12%) survived 0.13 g H₂O g⁻¹ dry wt moisture content. Seeds stored at 0.58 g H₂O g⁻¹ dry wt moisture content at four constant temperatures (4, 10, 15, and −18 °C) for up to 6 months exhibited a well-defined trend of decreasing viability with decreasing temperature. Thus, we concluded that freshly harvested L. spinosa seeds are non-dormant and recalcitrant. Also, the seeds with 0.58 g H₂O g⁻¹ dry wt moisture content could be effectively stored for a few months between 10 and 15 °C although the most appropriate temperature for wet storage appears to be 10 °C, as it is close to the minimum temperature for germination and so there will be less pre-sprouting compared to 15 °C.     

Seasonal acclimation in resting metabolism of the skink, Mabuya brevicollis (Reptilia: Scincidae) from southwestern Saudi Arabia

The resting metabolic rate (RMR) of seasonally-acclimated Mabuya brevicollis of various body masses was determined at 20, 25, 30, 35 and 40 °C, using open-flow respirometry. RMR (ml g⁻¹ h⁻¹) decreased with increasing mass at each temperature. RMRs increaProd. Type: FTPsed as temperature increased. The highest and lowest Q₁₀ values were obtained for the temperature ranges 20–25 °C and 30–35 °C for the summer-acclimated lizards. The exponent of mass “b” in the metabolism-body mass relation ranged from 0.41 to 0.61. b values were lower in the autumn and winter-acclimated lizards than in spring and summer-acclimated lizards. Seasonal acclimation effects were evident at all temperatures (20–40 °C) for M. brevicollis. Winter-acclimated skinks had the lowest metabolic rates at different temperatures. The pattern of acclimation exhibited by M. brevicollis may represent a useful adaptation for lizards inhabiting subtropical deserts to promote activity during their active seasons.     

Genomics and simulated laboratory studies reveal Thermococcus sp. 101C5 as a novel hyperthermophilic archaeon possessing a specialized metabolic arsenal for enhanced oil recovery

Laboratory evaluation of hyperthermophiles with the potential for Enhanced Oil Recovery (EOR) is often hampered by the difficulties in replicating the in situ growth conditions in the laboratory. In the present investigation, genome analysis was used to gain insights into the metabolic potential of a hyperthermophile to mobilize the residual oil from depleting high-temperature oil reservoirs. Here, we report the 1.9 Mb draft genome sequence of a hyperthermophilic anaerobic archaeon, Thermococcus sp. 101C5, with a GC content of 44%, isolated from a high-temperature oil reservoir of Gujarat, India. 101C5 possessed the genetic arsenal required for adaptation to harsh oil reservoir conditions, such as various heat shock proteins for thermo-adaptation, Trk potassium uptake system proteins for osmo-adaptation, and superoxide reductases against oxidative stress. Microbial Enhanced Oil Recovery (MEOR) potential of the strain was established by ascertaining the presence of genes encoding enzymes involved in the production of the metabolites such as hydrogen, bio-emulsifier, acetate, exopolysaccharide, etc. Production of these metabolites which pressurize the reservoir, emulsify the crude oil, lower the viscosity and reduce the drag, thus facilitating mobilization of the residual oil was experimentally confirmed. Also, the presence of crude oil degradative genes highlighted the ability of the strain to mobilize heavy residual oil, which was confirmed under simulated conditions in sand-pack studies. The obtained results demonstrated additional oil recoveries of 42.1% and 56.5% at 96 °C and 101 °C, respectively, by the strain 101C5, illustrating its potential for application in high-temperature oil reservoirs. To our best knowledge, this is the first report of genome analysis of any microbe assessed for its suitability for MEOR from the high-temperature oil reservoir.

     

Effect of lignocellulosic inhibitory compounds on growth and ethanol fermentation of newly-isolated thermotolerant Issatchenkia orientalis

A newly isolated thermotolerant ethanologenic yeast strain, Issatchenkia orientalis IPE 100, was able to produce ethanol with a theoretical yield of 85% per g of glucose at 42 °C. Ethanol production was inhibited by furfural, hydroxymethylfurfural and vanillin concentrations above 5.56 g L⁻¹, 7.81 g L⁻¹, and 3.17 g L⁻¹, respectively, but the strain was able to produce ethanol from enzymatically hydrolyzed steam-exploded cornstalk with 93.8% of theoretical yield and 0.91 g L⁻¹ h⁻¹ of productivity at 42 °C. Therefore, I. orientalis IPE 100 is a potential candidate for commercial lignocelluloses-to-ethanol production.     

Maximization of bioconversion of castor oil into ricinoleic acid by response surface methodology

In this study, response surface methodology was applied to optimize process variables like temperature, pH, enzyme concentration (mg/g oil), and buffer concentration (g/g oil) for hydrolysis of castor oil using Candida rugosa lipase. A 2⁴ full factorial central composite design was used to develop the quadratic model that was subsequently optimized and the optimal conditions were as follows: temperature 40 °C, pH 7.72, enzyme concentration 5.28 mg/g oil, buffer concentration 1 g/g oil and there was 65.5% conversion in 6 h. These predicted optimal conditions agreed well with the experimental results. This is the first report on the application of response surface methodology in castor oil hydrolysis using C. rugosa lipase with higher percentage conversion in 6 h.     

Gelation of high-methoxy pectin by enzymic de-esterification in the presence of calcium ions: a preliminary evaluation

Cohesive gels have been obtained by de-esterification of 1.0 wt % high-methoxy citrus pectin (degree of esterification ≈ 68%) in the presence of Ca²⁺ cations, using a commercial preparation (NovoShape) of fungal methyl esterase cloned from Aspergillus aculeatus. A convenient rate of network formation (gelation within ∼30 min) was achieved at an enzyme concentration of 0.2 PEU/g pectin. At a Ca²⁺-concentration of 40 mM and incubation temperature of 20 °C, severe syneresis (>7% of sample mass) was observed, but release of fluid decreased with decreasing concentration of Ca²⁺ and increasing temperature of incubation, becoming undetectable for 10 mM Ca²⁺ at 30 °C. Under these conditions, progressive development of solid-like character (storage modulus, G′) was observed during 160 min of enzymic de-esterification, and the mechanical spectrum recorded at the end of the incubation period had the form typical of a biopolymer gel. On subsequent heating to 70 °C, dissociation of the gel network (sigmoidal reduction in G′ and G″) was observed. At or above the midpoint temperature of this melting process (∼50 °C), there was no indication of gel formation on enzymic de-esterification (at 50 or 60 °C). At lower temperatures (20, 30 and 40 °C), the rate of gelation (assessed visually) showed no systematic increase as the incubation temperature was increased towards the temperature-optimum of the enzyme (∼50 °C). This unexpected behaviour is attributed to competition between faster de-esterification and slower formation of Ca²⁺-induced ‘egg-box’ junctions.     

Mycosporine-like amino acids in azooxanthellate and zooxanthellate early developmental stages of the soft coral Heteroxenia fuscescens

The ontogenetic changes of MAAs in the soft coral Heteroxenia fuscescens was studied in relation to their symbiotic state (azooxanthellate vs. zooxanthellate) under different temperature conditions in the Gulf of Eilat, northern Red Sea. The HPLC chromatograms for extracts of the planulae, azoo- and zooxanthellate primary polyps of H. fuscescens from all dates of collection yielded a single peak at 320 nm that has been identified as the compound palythine. Concentration of palythine in planulae at 23 °C was 7.57 ± 1 nmol mg^− 1 protein and at 28 °C reached 17.29 ± 1 nmol × mg^− 1 protein. Concentration of palythine in azooxanthellate primary polyps was 16.4 ± 3 nmol × mg^− 1 protein and 28.37 ± 2.8 nmol × mg^− 1 protein at 23 °C and 28 °C respectively. The palythine concentration for zooxanthellate primary polyps at 23 °C was 13 ± 3 nmol × mg^− 1 protein and at 28 °C 32.7 ± 2 nmol mg^− 1 protein. Palythine concentrations were significantly higher at 28 °C in the different animal groups and correlated linearly with the ambient collection temperature. This study shows for the first time that UVR and temperature act synergistically and affect the MAA levels of early life-history stages of soft corals.     

Longevity and temperature response of pollen as affected by elevated growth temperature and carbon dioxide in peanut and grain sorghum

It is important to understand the effects of environmental conditions during plant growth on longevity and temperature response of pollen. Objectives of this study were to determine the influence of growth temperature and/or carbon dioxide (CO₂) concentration on pollen longevity and temperature response of peanut and grain sorghum pollen. Plants were grown at daytime maximum/nighttime minimum temperatures of 32/22, 36/26, 40/30 and 44/34 °C at ambient (350 μmol mol⁻¹) and at elevated (700 μmol mol⁻¹) CO₂ from emergence to maturity. At flowering, pollen longevity was estimated by measuring in vitro pollen germination at different time intervals after anther dehiscence. Temperature response of pollen was measured by germinating pollen on artificial growth medium at temperatures ranging from 12 to 48 °C in incubators at 4 °C intervals. Elevated growth temperature decreased pollen germination percentage in both crop species. Sorghum pollen had shorter longevity than peanut pollen. There was no influence of CO₂ on pollen longevity. Pollen longevity of sorghum at 36/26 °C was about 2 h shorter than at 32/22 °C. There was no effect of growth temperature or CO₂ on cardinal temperatures (T_min, T_opt, and T_max) of pollen in both crop species. The T_min, T_opt, and T_max identified at different growth temperatures and CO₂ levels were similar at 14.9, 30.1, and 45.6 °C, respectively for peanut pollen. The corresponding values for sorghum pollen were 17.2, 29.4, and 41.7 °C. In conclusion, pollen longevity and pollen germination percentage was decreased by growth at elevated temperature, and pollen developed at elevated temperature and/or elevated CO₂ did not have greater temperature tolerance.     

Combined effects of temperature and salinity on critical thermal minima of pacific white shrimp Litopenaeus vannamei (Crustacea: Penaeidae)

Critical thermal minima (CTMin) were determined for the Pacific white shrimp Litopenaeus vannamei juveniles from four different acclimation temperatures (15, 20, 25, and 30 °C) and salinities (10‰, 20‰, 30‰, and 40‰). The lowest and highest CTMin of shrimp ranged between 7.2 °C at 15 °C/30‰ and 11.44 °C at 30 °C/20‰ at the cooling rate of 1 °C h⁻¹. Acclimation temperature and salinity, as well as the interaction of both parameters, had significant effects on the CTMin values of L. vannamei (P<0.01). Yet, the results showed a much more profound effect of temperature on low thermal tolerance of juveniles. Only 40‰ salinity had an influence on the CTMin values (P<0.01). As the acclimation temperature was lowered from 30 to 15 °C thermal tolerance of the shrimp significantly increased by 3.25–4.14 °C. The acclimation response ratio (ARR) of the Pacific white shrimp exposed to different combinations of salinity and temperature ranged between 0.25 and 0.27. When this species is farmed in sub-tropical regions, its pond water temperature in the over-wintering facilities (regardless of the water salinity level) must never fall below 12 °C throughout the cold season to prevent mortalities.     

Cold stress causes rapid but differential changes in properties of plasma membrane H-ATPase of camelina and rapeseed

Camelina (Camelina sativa) and rapeseed (Brassica napus) are well-established oil-seed crops with great promise also for biofuels. Both are cold-tolerant, and camelina is regarded to be especially appropriate for production on marginal lands. We examined physiological and biochemical alterations in both species during cold stress treatment for 3 days and subsequent recovery at the temperature of 25 °C for 0, 0.25, 0.5, 1, 2, 6, and 24 h, with particular emphasis on the post-translational regulation of the plasma membrane (PM) H⁺-ATPase (EC3.6.3.14). The activity and translation of the PM H⁺-ATPase, as well as 14-3-3 proteins, increased after 3 days of cold stress in both species but recovery under normal conditions proceeded differently. The increase in H⁺-ATPase activity was the most dramatic in camelina roots after recovery for 2 h at 25 °C, followed by decay to background levels within 24 h. In rapeseed, the change in H⁺-ATPase activity during the recovery period was less pronounced. Furthermore, H⁺-pumping increased in both species after 15 min recovery, but to twice the level in camelina roots compared to rapeseed. Protein gel blot analysis with phospho-threonine anti-bodies showed that an increase in phosphorylation levels paralleled the increase in H⁺-transport rate. Thus our results suggest that cold stress and recovery in camelina and rapeseed are associated with PM H⁺-fluxes that may be regulated by specific translational and post-translational modifications.     

Effects of acclimation temperature on thermal tolerance, locomotion performance and respiratory metabolism in Acheta domesticus L. (Orthoptera: Gryllidae)

The effects of acclimation temperature on insect thermal performance curves are generally poorly understood but significant for understanding responses to future climate variation and the evolution of these reaction norms. Here, in Acheta domesticus, we examine the physiological effects of 7-9 days acclimation to temperatures 4 °C above and below optimum growth temperature of 29 °C (i.e. 25, 29, 33 °C) for traits of resistance to thermal extremes, temperature-dependence of locomotion performance (jumping distance and running speed) and temperature-dependence of respiratory metabolism. We also examine the effects of acclimation on mitochondrial cytochrome c oxidase (CCO) enzyme activity. Chill coma recovery time (CRRT) was significantly reduced from 38 to 13 min with acclimation at 33-25 °C, respectively. Heat knockdown resistance was less responsive than CCRT to acclimation, with no significant effects of acclimation detected for heat knockdown times (25 °C: 18.25, 29 °C: 18.07, 33 °C: 25.5 min). Thermal optima for running speed were higher (39.4-40.6 °C) than those for jumping performance (25.6-30.9 °C). Acclimation temperature affected jumping distance but not running speed (general linear model, p = 0.0075) although maximum performance (U_MAX) and optimum temperature (T_OPT) of the performance curves showed small or insignificant effects of acclimation temperature. However, these effects were sensitive to the method of analysis since analyses of T_OPT, U_MAX and the temperature breadth (T_BR) derived from non-linear curve-fitting approaches produced high inter-individual variation within acclimation groups and reduced variation between acclimation groups. Standard metabolic rate (SMR) was positively related to body mass and test temperature. Acclimation temperature significantly influenced the slope of the SMR-temperature reaction norms, whereas no variation in the intercept was found. The CCO enzyme activity remained unaffected by thermal acclimation. Finally, high temperature acclimation resulted in significant increases in mortality (60-70% at 33 °C vs. 20-30% at 25 and 29 °C). These results suggest that although A. domesticus may be able to cope with low temperature extremes to some degree through phenotypic plasticity, population declines with warmer mean temperatures of only a few degrees are likely owing to the limited plasticity of their performance curves.     

Effect of temperature on chitin and astaxanthin recoveries from shrimp waste using lactic acid bacteria

The chitin and astaxanthin recoveries by lactic acid fermentation of shrimp wastes (Litopenaeus sp) were conducted in bed-column reactors at 15, 20, 25, 30, 35, 40 and 45 °C. The response surface methodology showed that the fermentations carried out in the 27–36 °C temperature range with lactic acid above 0.319 mmol/g resulted in the highest demineralization. The maximal deproteinizations were attained from 30 to 40 °C. The extraction of free-astaxanthin did not present significant differences between 20 and 35 °C and the proportion of cis-stereoisomer forms increased with temperature. The growth rates of Lactobacillus plantarum were estimated in the 15–45 °C range and analyzed by Arrhenius and square root models. The cardinal values were 3.94 and 51.7 °C for minimum and maximum temperatures, respectively, with activation energy of 43.38 Jmol⁻¹.     

Temperature dependence of structure, bending rigidity, and bilayer interactions of dioleoylphosphatidylcholine bilayers

X-ray diffuse scattering was measured from oriented stacks and unilamellar vesicles of dioleoylphosphatidylcholine lipid bilayers to obtain the temperature dependence of the structure and of the material properties. The area/molecule, A, was 75.5 Å² at 45°C, 72.4 Å² at 30°C, and 69.1 Å² at 15°C, which gives the area expansivity α_A = 0.0029/deg at 30°C, and we show that this value is in excellent agreement with the polymer brush theory. The bilayer becomes thinner with increasing temperature; the contractivity of the hydrocarbon portion was α_Dc = 0.0019/deg; the difference between α_A and α_Dc is consistent with the previously measured volume expansivity α_Vc = 0.0010/deg. The bending modulus K_C decreased as exp(455/T) with increasing T (K). Our area compressibility modulus K_A decreased with increasing temperature by 5%, the same as the surface tension of dodecane/water, in agreement again with the polymer brush theory. Regarding interactions between bilayers, the compression modulus B as a function of interbilayer water spacing D′_W was found to be nearly independent of temperature. The repulsive fluctuation pressure calculated from B and K_C increased with temperature, and the Hamaker parameter for the van der Waals interaction was nearly independent of temperature; this explains why the fully hydrated water spacing, D′_W, that we obtain from our structural results increases with temperature.     

Ambient temperature modulates the magnitude of LPS-induced fevers in Pekin ducks

The consequences of variations in environmental temperature on innate immune responses in birds are by and large not known. We investigated the influence of ambient temperature on the febrile response in female Pekin ducks (Anas platyrhynchos). Ducks, implanted with temperature data loggers to measure body temperature, were injected with lipopolysaccharide (100 μg kg⁻¹) to evoke febrile responses and kept at ambient temperatures higher, within, and lower than their thermoneutral zone (n=10), and in conditions that simulated one day of a heat wave (n=6). Compared to the febrile response at thermoneutrality, at low temperatures, febrile responses were significantly attenuated; fevers reached lower magnitudes (from basal body temperature of 41.2±0.3 °C to a peak of 42.0±0.3 °C). In contrast, at high ambient temperatures, ducks rapidly developed significantly enhanced fevers, which reached markedly higher febrile peaks (from basal body temperature of 41.6 °C to a peak of 44.0 °C in a simulated heat wave when ambient temperature reached 40 °C). These results indicate that ambient temperature affects the febrile response in female Pekin ducks. Our findings reveal a key difference in febrile mediation between ducks and mammals, and have implications for avian survival because high environmental temperatures during febrile mediation could lead to febrile responses becoming physiologically deleterious.