Temperature × light interaction and tolerance of high water temperature in the planktonic freshwater flagellates Cryptomonas (Cryptophyceae) and Dinobryon (Chrysophyceae)

Using microcosm experiments, we investigated the interactive effects of temperature and light on specific growth rates of three species each of the phytoplanktonic genera Cryptomonas and Dinobryon. Several species of these genera play important roles in the food web of lakes and seem to be sensitive to high water temperature. We measured growth rates at three to four photon flux densities ranging from 10 to 240 μmol photon · m^?2 · s^?1 and at 4–5 temperatures ranging from 10°C to 28°C. The temperature × light interaction was generally strong, species specific, and also genus specific. Five of the six species studied tolerated 25°C when light availability was high; however, low light reduced tolerance of high temperatures. Growth rates of all six species were unaffected by temperature in the 10°C–15°C range at light levels ≤50 μmol photon · m^?2 · s^?1. At high light, growth rates of Cryptomonas spp. increased with temperature until the temperature optimum was reached and then declined. The Dinobryon species were less sensitive than Cryptomonas spp. to photon flux densities of 40 μmol photon · m^?2 · s^?1 and 200 μmol photon · m^?2 · s^?1 over the entire temperature range but did not grow under a combination of very low light (10 μmol photon · m^?2 · s^?1) and high temperature (≥20°C). Among the three Cryptomonas species, cell volume declined with temperature and the maximum temperature tolerated was negatively related to cell size. Since Cryptomonas is important food for microzooplankton, these trends may affect the pelagic carbon flow if lake warming continues.     

Thermoanaerobacterium thermostercus sp. nov., a new anaerobic thermophilic hydrogen-producing bacterium from buffalo-dung

A novel thermophilic, anaerobic, rod-shaped bacterium strain, designated Buff, was isolated from buffalo-dung samples collected from a buffalo-farm located in Caserta (Campania, south of Italy). Strain Buff was Gram-positive, motile and no spore-forming. The growth temperature range was 40–65°C with an optimum at 60°C, while pH growth range at 60°C was 5.5–8.0 with an optimum at about pH 6.5. NaCl growth concentration ranged from 0 to 2.0% with an optimum at 0.5% (w/v); no growth was observed with the presence of NaCl 3.0% (w/v). The strain produced ethanol, acetate, lactate, H₂, H₂S and CO₂ by glucose fermentation. The DNA G + C content was 34.4 mol%. As determined by 16S rRNA sequence analysis, this organism belonged to the genus Thermoanaerobacterium. On the basis of the physiological and molecular properties, we propose for strain Buff the new species designation Thermoanaerobacterium thermostercus sp. nov. This novel organism represents the first species of the genus Thermoanaerobacterium isolated from buffalo-dung. The type strain is Buff (=DSM 22141 = ATCC BAA-1776).     

Life tables and development of <Emphasis Type="Italic">Amblyseius swirskii</Emphasis> (Acari: Phytoseiidae) at different temperatures

Development time, reproduction, survival and sex ratio were determined for the omnivorous mite Amblyseius swirskii at nine constant temperatures (13, 15, 18, 20, 25, 30, 32, 34 and 36°C) on pepper leaf disks with cattail, Typha latifolia, pollen for food. These data were used to derive life table parameters at these constant temperatures. No development was observed at 13°C. The lower development threshold, based on the fit to the linear portion of the development curve, was 11.3°C. The upper development threshold was 37.4 ± 1.12°C, and the optimum temperature was calculated to be 31.5°C. Average lifetime fecundity ranged from a low of 1.3 ± 0.24 eggs/female at 15°C to a high of 16.1 ± 0.34 eggs/female at 25°C, and r _m was greatest at 32°C. Non-linear regression of the relationship between temperature and r _m produced an estimate of 15.49 ± 0.905°C for the lower threshold for population growth and 36.99 ± 0.816°C for the upper threshold for population growth, and an optimum temperature of 30.1°C. These values suggest that A. swiskii populations should grow quickly in response to food availability (pollen or prey) between 20 and 32°C, but that, especially below 20°C, population growth could be slow and impacts on prey populations should be monitored carefully.     

Direct ethanol production from cellulosic materials at high temperature using the thermotolerant yeast Kluyveromyces marxianus displaying cellulolytic enzymes

To exploit cellulosic materials for fuel ethanol production, a microorganism capable of high temperature and simultaneous saccharification–fermentation has been required. However, a major drawback is the optimum temperature for the saccharification and fermentation. Most ethanol-fermenting microbes have an optimum temperature for ethanol fermentation ranging between 28 °C and 37 °C, while the activity of cellulolytic enzymes is highest at around 50 °C and significantly decreases with a decrease in temperature. Therefore, in the present study, a thermotolerant yeast, Kluyveromyces marxianus, which has high growth and fermentation at elevated temperatures, was used as a producer of ethanol from cellulose. The strain was genetically engineered to display Trichoderma reesei endoglucanase and Aspergillus aculeatus β-glucosidase on the cell surface, which successfully converts a cellulosic β-glucan to ethanol directly at 48 °C with a yield of 4.24 g/l from 10 g/l within 12 h. The yield (in grams of ethanol produced per gram of β-glucan consumed) was 0.47 g/g, which corresponds to 92.2% of the theoretical yield. This indicates that high-temperature cellulose fermentation to ethanol can be efficiently accomplished using a recombinant K. marxianus strain displaying thermostable cellulolytic enzymes on the cell surface.     

Temperature‐dependent development of the double‐spined spruce bark beetle Ips duplicatus (Sahlberg, 1836) (Coleoptera; Curculionidae)

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Effects of high-temperature treatments on development,viability, and heat-shock response in a temperature-sensitive cell-lethal mutant of Drosophila melanogaster

Pulses of various durations at temperatures between 29 and 38°C were applied to developing larvae of Drosophila melanogaster carrying the temperature-sensitive cell-lethal mutation 1 (1)ts726. The results show that it is not possible to reduce the time required for the induction of abnormalities in the mutant by treating larvae with heat pulses at temperatures higher than 29°C. Instead, treatment with high temperature leads to fewer abnormalities than 29°C treatments. Furthermore with high temperature treatments, the mutation has less effect on viability than is seen at 29°C. It is suggested that 1 (1)ts726 leads to abnormalities and death by a temperature-induced imbalance between different physiological or development events, rather than by interfering with the ability of the cell or the organism to withstand high temperature in general.     

Screening Escherichia coli, Enterococcus faecalis, and Clostridium perfringens as Indicator Organisms in Evaluating Pathogen-Reducing Capacity in Biogas Plants

This study was conducted to identify an indicator organism(s) in evaluating the pathogen-reducing capacity of biogas plants. Fresh cow manure containing 10⁴ to 10⁵ colony forming unit (CFU) per milliliter of Escherichia coli and Enterococcus faecalis along with an inoculated Clostridium perfringens strain were exposed to 37°C for 15 days, 55°C for 48 h, and 70°C for 24 h. C. perfringens was the most heat-resistant organism followed by E. faecalis, while E. coli was the most heat-sensitive organism. E. coli was reduced below detection limit at all temperatures with log₁₀ reductions of 4.94 (10 s), 4.37 (40 min), and 2.6 (5 days) at 70°C, 55°C, and 37°C, respectively. Maximum log₁₀ reductions for E. faecalis were 1.77 at 70°C (1 day), 1.7 at 55°C (2 days) and 3.13 at 37°C (15 days). For C. perfringens, maximum log₁₀ reduction at 37°C was 1.35 log₁₀ units (15 days) compared to less than 1 unit at 55 and 70°C. Modeling results showed that E. faecalis and C. perfringens had higher amount of heat-resistant fraction than E. coli. Thus, E. faecalis and C. perfringens can be used as indicator organisms to evaluate pathogen-reducing capacity in biogas plants at high temperatures of 55°C and 70°C while at 37°C E. coli could also be included as indicator organism.     

The Influence of <Emphasis Type="Italic">P. fluorescens</Emphasis> Cell Morphology on the Lytic Performance and Production of Phage ϕIBB-PF7A

This study aims at assessing the influence of Pseudomonas fluorescence cell morphology on the effectiveness and production of the lytic bacteriophage ϕIBB-PF7A. P. fluorescens were cultured as rods or as elongated cells by varying the temperature and rotary agitation conditions. Cells presented rod shape when grown at temperatures up to 25°C and also at 30°C under static conditions, and elongated morphology only at 30°C when cultures were grown under agitation. Elongated cells were 0.4 up to 27.9 μm longer than rod cells. Rod-shaped hosts were best infected by phages at 25°C which resulted in an 82% cell density reduction. Phage infection of elongated cells was successful, and the cell density reductions achieved was statistically similar (P > 0.05) to those obtained at the optimum growth temperature of P. fluorescens. Phage burst size varied with the cell growth conditions and was approximately 58 and 153 PFU per infected rod and elongated cells, grown at 160 rpm, at 25°C (the optimal temperature) and 30°C, respectively. Phage adsorption was faster to elongated cells, most likely due to the longer length of the host. The surface composition of rod and elongated cells is similar in terms of outer membrane proteins and lipopolysaccharide profiles. The results of this study suggest that the change of rod cells to an elongated morphology does not prevent cells from being attacked by phages and also does not impair the phage infection.     

Temperature dependence for development of the whitefly predator <Emphasis Type="Italic">Clitostethus arcuatus</Emphasis> (Rossi)

This work aimed to study the biology of Clitostethus arcuatus (Rossi) (Coleoptera: Coccinellidae) under different temperatures and evaluate the optimum temperature for its mass rearing. Studies were carried out in the laboratory at four constant temperatures (15°C, 20°C, 25°C and 30°C), 75 ± 5% relative humidity and a photoperiod of 16 h light:8 h dark, in which C. arcuatus was fed ad libitum with nymphs of all instar of Aleyrodes proletella L. (Homoptera: Aleyrodidae) on Brassicae oleracea L. (var. Costata). The following biological parameters were evaluated: development time and survival rates of pre-imaginal stages, adult longevity (female and male), length of the pre-oviposition and oviposition periods, fecundity, fertility and percentage of egg hatching. Population growth parameters, the lower development threshold and the sum of effective temperatures were estimated. Temperatures ranging from 20°C to 30°C were suitable for the development of C. arcuatus, suggesting that this species is well adapted to the temperatures usually found inside greenhouses or in open fields in temperate regions. Although the intrinsic rate of natural increase and doubling time were similar at 25°C and 30°C, the temperature of 25°C was shown to be the most suitable for mass rearing and development of populations under field conditions, since the percentage of egg hatching and the accumulated survival rates of the pre-imaginal stages were the highest. Considering the estimated lower threshold for pre-imaginal development (7.9°C) and the sum of effective temperatures [293.6 degree-days (°D)], it is predicted for Ponta Delgada (Azores, Portugal) that the first adults of C. arcuatus should emerge by the first fortnight of February and that up to 12 generations per year can occur.     

Improvement of l-valine production at high temperature in Brevibacterium flavum by overexpressing ilvEBNrC genes

Brevibacterium flavum ATCC14067 was engineered for l-valine production by overexpression of different ilv genes; the ilvEBN^rC genes from B. flavum NV128 provided the best candidate for l-valine production. In traditional fermentation, l-valine production reached 30.08 ± 0.92 g/L at 31°C in 72 h with a low conversion efficiency of 0.129 g/g. To further improve the l-valine production and conversion efficiency based on the optimum temperatures of l-valine biosynthesis enzymes (above 35°C) and the thermotolerance of B. flavum, the fermentation temperature was increased to 34, 37, and 40°C. As a result, higher metabolic rate and l-valine biosynthesis enzymes activity were obtained at high temperature, and the maximum l-valine production, conversion efficiency, and specific l-valine production rate reached 38.08 ± 1.32 g/L, 0.241 g/g, and 0.133 g g⁻¹ h⁻¹, respectively, at 37°C in 48 h fermentation. The strategy for enhancing l-valine production by overexpression of key enzymes in thermotolerant strains may provide an alternative approach to enhance branched-chain amino acids production with other strains.     

Temperature-dependent phosphate solubilization by cold- and pH-tolerant species of Aspergillus isolated from Himalayan soil

Ten species of Aspergillus isolated from soil samples collected from different locations in the Indian Himalayan region have been studied for their growth requirements and tricalcium phosphate solubilization at different temperatures. The Aspergillus species could grow at low temperature and tolerated a wide range of pH. Phosphate solubilization by various Aspergillus species ranged between 374 μg/ml (A. candidus) to 1394 μg/ml (A. niger) at 28°C, 33 μg/ml (A. fumigatus) to 2354 μg/ml (A. niger) at 21°C, 93 μg/ml (A. fumigatus) to 1452 μg/ml (A. niger) at 14°C, and 21 μg/ml (A. wentii) to 83 μg/ml (A. niger) at 9°C. At 21 and 28°C, phosphate solubilization showed a decrease within 4 weeks of incubation, whereas at 9°C and 14°C, it continued further up to 6 weeks of incubation. In general, phosphate solubilization by different Aspergillus species was recorded at a maximum of 28°C or 21°C; biomass production was favored at 21°C or 14°C. Conversely, A. nidulans and A. sydowii exhibited maximum phosphate solubilization at 14°C and produced maximum biomass at 21°C. Data suggest that suboptimal conditions (higher or lower temperature) for fungal growth and biomass production were optimal for the production of metabolites involved in phosphate solubilization. Significant negative correlations were obtained between pH and phosphate solubilization for eight species at 28°C, for seven at 21°C, and for nine at 14°C. Extracellular phosphatase activity was exhibited only in case of A. niger, whreas intracellular phosphatase activity was detected in all species, the maximum being in A. niger. Statistically significant positive or negative correlations were obtained between phosphate solubilization and other parameters in most cases at different temperatures.     

Effects of four constant temperatures on the development of two Bradysia (Diptera: Sciaridae) species

In this study, the effects of temperature on the growth, development, survival, fecundity and other population parameters of two local Bradysia species B. odoriphaga and B. impatiens were studied at four constant temperatures (25, 28, 31 and 34°C). The results show that 25°C is the optimum temperature for the growth and development of B. odoriphaga, while 28°C is more favourable for B. impatiens. The temperature of 31°C restricted the growth and development, while the temperature of 34°C inhibited the eggs hatching in both species, resulting in no egg survival and no subsequent development. High temperatures (>28°C) prolonged the 4th larval stage duration, mean generation time (T) and population doubling time (Dt) of both species. The high temperature of 31°C greatly shortened the female longevity, weakened the oviposition and reduced the survival of both species. Moreover, the life table parameters R₀, r_m and λ were also suppressed by this high temperature. However, the high temperature of 31°C had little impact on the egg survival, pupal weight and male longevity. In addition, at 31°C, the values of R₀, r_m and λ of B. odoriphaga were higher than those of B. impatiens, suggesting that B. odoriphaga is more tolerant to high temperature than B. impatiens. The differences between two Bradydsia species seem determined genetically. Our findings are important for better understanding their biological characteristics at a certain constant temperature and demonstrate the possibility to control and manage those two Bradysia species by increasing ambient temperature.     

Genome-wide screen for temperature-regulated genes of the obligate intracellular bacterium, <Emphasis Type="Italic">Rickettsia typhi</Emphasis>

Background  

The ability of rickettsiae to survive in multiple eukaryotic host environments provides a good model for studying pathogen-host molecular interactions. Rickettsia typhi, the etiologic agent of murine typhus, is a strictly intracellular gram negative α-proteobacterium, which is transmitted to humans by its arthropod vector, the oriental rat flea, Xenopsylla cheopis. Thus, R. typhi must cycle between mammalian and flea hosts, two drastically different environments. We hypothesize that temperature plays a role in regulating host-specific gene expression, allowing R. typhi to survive in mammalian and arthropod hosts. In this study, we used Affymetrix microarrays to screen for temperature-induced genes upon a temperature shift from 37°C to 25°C, mimicking the two different host temperatures in vitro.     

Photosynthetic characteristics and physiological plasticity of an Aphanizomenon flos-aquae (Cyanobacteria, Nostocaceae) winter bloom in a deep oligo-mesotrophic lake (Lake Stechlin, Germany)

In winter of 2009/2010, Aphanizomenon flos-aquae bloomed in the ice and snow covered oligo-mesotrophic Lake Stechlin, Germany. The photosynthesis of the natural population was measured at eight temperatures in the range of 2–35°C, at nine different irradiance levels in the range of 0–1,320 μmol m⁻² s⁻¹ PAR at each applied temperature. The photoadaptation parameter (I _k) and the maximum photosynthetic rate (P _max) correlated positively with the temperature between 2 and 30°C, and there was a remarkable drop in both parameters at 35°C. The low I _k at low temperatures enabled the active photosynthesis of overwintering populations at low irradiance levels under ice and snow cover. The optimum of the photosynthesis was above 20°C at irradiances above 150 μmol m⁻² s⁻¹. At lower irradiance levels (7.5–30 μmol m⁻² s⁻¹), the photosynthesis was the most intensive in the temperature range of 2–5°C. The interaction between light and temperature allowed the proliferation of A. flos-aquae in Lake Stechlin resulting in winter water bloom in this oligo-mesotrophic lake. The applied 2°C is the lowest experimental temperature ever in the photosynthesis/growth studies of A. flos-aquae, and the results of the P–I and P–T measurements provide novel information about the tolerance and physiological plasticity of this species.     

Physiological constraints on the life cycle and distribution of the Antarctic fairy shrimp <Emphasis Type="Italic">Branchinecta gaini</Emphasis>

Maturation to adulthood and successful reproduction in the Antarctic fairy shrimp, Branchinecta gaini, must be completed within a physiologically challenging temporal window of ca. 2.5 months in the southern Antarctic Peninsula. Although adults show considerable metabolic opportunism at positive temperatures, little is known of their tolerance of two physiological insults potentially typical to pool life in the maritime Antarctic: sub-zero temperatures and salinity. B. gaini are freeze-avoiding crustaceans with temperatures of crystallisation (T _cs) of −5°C. No antifreeze proteins were detected in the haemolymph. Adults osmoregulate in relation to temperature, but rapid mortality in saline solutions of even low concentration, indicate they cannot osmoregulate in relation to salinity. Survival of ice encasement at temperatures above their T _c was found to be pressure but not time dependent: at severe inoculative ice pressures, there was little immediate survival and none survived after 48 h below −2°C; at mild inoculative ice pressures, immediate survival was ca. 100% at −3°C, but <20% after 48 h. There was no significant difference in survival after 1 and 6 h encasement at −3°C. Observations of ventilation suggest that it is not low temperature per se, but ice that represents the primary cryo-stress, with ventilatory appendages physically handcuffed below the freezing point of pool water. Both sub-zero temperatures and salinity represent real physiological constraints on adult fairy shrimp.     

The neotropical shrub Lupinus elegans,from temperate forests,may not adapt to climate change

Considering that their distribution is limited to altitudinal gradients along mountains that are likely to become warmer and drier, climate change poses an increased threat to temperate forest species from tropical regions. We studied whether the understorey shrub Lupinus elegans, endemic to temperate forests of west‐central Mexico, will be able to withstand the projected temperature increase under seven climate change scenarios. Seeds were collected along an altitudinal gradient and grown in a shade‐house over 7 months before determining their temperature tolerance as electrolyte leakage. The plants from colder sites tolerated lower temperatures, i.e. the temperature at which half of the maximum electrolyte leakage occurred (LT₅₀), ranged from −6.4 ± 0.7 to −2.4 ± 0.3 °C. In contrast, no pattern was found for tolerance to high temperature (LT₅₀ average 42.8 ± 0.3 °C). The climate change scenarios considered here consistently estimated an increase in air temperature during the present century that was higher for the maximum air temperature than for the mean or minimum. In particular, the anomaly from the normal maximum air temperature at the study region ranged from 2.8 °C by 2030 to 5.8 °C by 2090. In this respect, the inability of L. elegans to adapt to increasingly higher temperatures found here, in addition to a possible inhibition of reproduction caused by warmer winters, may limit its future distribution.     

Seed ecology of the geophyte Conopodium majus (Apiaceae), indicator species of ancient woodland understories and oligotrophic meadows

• Conopodium majus is a geophyte with pseudomonocotyly, distributed in Atlantic Europe. It is an indicator of two declining European habitats: ancient woodland understories and oligotrophic hay meadows. Attempts to reintroduce it by seed have been hindered by scarce seedling emergence and limited knowledge of its seed biology.
• Micro‐CT scanning was used to assess pseudomonocotyly. Embryo growth and germination were studied in the laboratory and the field, using dissection and image analysis. The effects of temperature, light, nitrate and GA₃ on germination were tested. Seed desiccation tolerance was investigated by storage at different RHs and by drying seeds at different stages of embryo growth.
• Seeds possess morphological but not physiological dormancy. Embryo growth and germination were promoted by temperatures between 0 and 5 °C, arrested above 10 °C, and indifferent to alternating temperatures, light, nitrate and GA₃. Pseudomonocotyly appears to result from cotyledon fusion. While seeds tolerated drying to 15% RH and storage for 1 year at 20 °C, viability was lost when storage was at 60% RH. Seeds imbibed at 5 °C for 84 days had significant internal embryo growth but were still able to tolerate drying to 15% RH.
• Reproduction by seed in C. majus follows a strategy shared by geophytes adapted to deciduous temperate forests. The evolution of fused cotyledons may enable the radicle and the hypocotyl to reach deeper into the soil where a tuber can develop. The embryo is capable of growth within the seed at low temperatures so that germination is timed for early spring.

     

Biology of Doryctobracon brasiliensis at different temperatures: development of life table and determining thermal requirements

Doryctobracon brasiliensis (Szépligeti) is a parasitoid larval–pupal of fruit flies and has great potential to be used in biological control programmes as it feeds on other Anastrepha species in addition to Anastrepha fraterculus (Wiedemann). This study investigated the biology of D. brasiliensis at different temperatures to design a life fertility table and determine thermal requirements. The parasitoids were multiplied in larvae of A. fraterculus in air‐conditioned chambers at 15, 18, 20, 22, 25, 28 and 30°C, 70 ± 20% RH and photophase of 12 h. We determined the number of offspring, sex ratio, longevity of males and females and duration of egg–adult period. The temperature range 18–22°C ensures higher fecundity and at 20°C, and the average number of offspring per female was 152.77 parasitoids. The sex ratio of offspring produced was reduced with increasing temperatures. Longevity of males and females of D. brasiliensis was reduced by increasing temperatures. At 15, 28 and 30°C, there was no development of immature stages. For the temperature range 18–25°C, the duration of egg–adult period of D. brasiliensis was inversely proportional to temperature. At 20 and 22°C, we observed the highest values of net reproduction rate (Ro) and finite reason of increase (λ), meaning that at the estimated optimum temperature (21°C), the population of D. brasiliensis increased 47 times each generation. The lower temperature threshold for development was 10.01°C and the thermal constant (K) 303.21 degree/days. This information confirms that D. brasiliensis is better suited to temperate environments, which implies a significant potential for the use of D. brasiliensis in the control of A. fraterculus, because most areas occupied by this pest are in temperate regions. In addition, D. brasiliensis is useful in mass rearing systems in laboratory.