Spatio-temporal patterns of gene flow and dispersal under temperature increase

Recent data show that the Earth climate is undergoing a change at a rate which is outstanding in geologic history. Temperature is one of the major driving forces of gene flow and dispersal. In this paper the spatial dynamics of genetic dispersal is studied under the auspices of temperature increase by means of a mathematical model. The main elements genetics, competition and dispersal are combined in a coherent approach by a system of coupled partial differential equations with non-linear reaction terms describing population dynamics, genetic exchange and competition. Temperature reaction norms are conferred by a two allele system. The non-linearities of the interaction terms give rise to a richness of spatio-temporal dynamic patterns. Here we show how invasion processes in form of travelling waves are initiated by a temperature rise.     

Probing the archaeal diversity of a mixed thermophilic bioleaching culture by TGGE and FISH

The archaeal community present in a sample of Mixed Thermophilic Culture-B (MTC-B) from a laboratory-scale thermophilic bioleaching reactor was investigated by temperature gradient gel electrophoresis (TGGE) and fluorescence in situ hybridisation (FISH). Both techniques were specifically adapted for use on native state bioleaching samples, with a view to establishing convenient means for monitoring culture composition. Using the TGGE protocol developed, the relative species composition of the thermophilic bioleaching sample was analysed, and included four phylotypes belonging to the Sulfolobales, which were related to Stygiolobus azoricus, Metallosphaera sp. J1, Acidianus infernus and Sulfurisphaera ohwakuensis. However, the St. azoricus-like phylotype was difficult to resolve and some micro-heterogeneity was observed within this phylotype. Specific FISH probes were designed to qualitatively assess the presence of the phylotypes in MTC-B. The sample was dominated by Sf. ohwakuensis-like Archaea. In addition, the St. azoricus-like, Metallosphaera species-like and Acidianus species-like cells appeared in similar low abundance in the community. Most strikingly, FISH identified Sulfolobus shibatae-like cells present in low numbers in the sample even though these were not detected by PCR-dependent TGGE. These results highlight the importance of using more than one molecular technique when investigating the archaeal diversity of complex bioleaching reactor samples.     

Comparison of angiotensin converting enzyme-like activity in the Antarctic teleosts <Emphasis Type="Italic">Trematomus bernacchii</Emphasis> and <Emphasis Type="Italic">Chionodraco hamatus</Emphasis>

Biochemical parameters of the angiotensin converting enzyme-like activity (ACELA) in the gills of two Antarctic teleosts, Chionodraco hamatus and Trematomus bernacchii were characterized. Enzymatic activity was revealed following hydrolysis of a specific substrate of angiotensin-converting enzyme N-[3-(2-furyl)acryloyl]l-phenylalanyl-glycyl-glycine (FAPGG) and metabolites were separated by reverse phase HPLC analysis. The results showed similar Km values for the substrate FAPGG at 5°C for the two species with an increase of Km value for T. bernacchii at 25°C. The optimum pH value was 8.5 at 25°C and optimum chloride concentrations were about 300 mM. In T. bernacchii the optimum temperature for maximum enzyme activity was 50°C, while maximum activity in C. hamatus occurred at 35°C. Lisinopril was more efficient in inhibiting ACELA in C. hamatus with an I ₅₀ value of 16.83 ± 5.11 nM, compared to an I ₅₀ value of 30.66 ± 5.19 nM in T. bernacchii. In conclusion, it appears that some biochemical parameters of ACELA in C. hamatus differ from those in T. bernacchii, probably due to different ways that the enzyme adapts to the constantly cold temperatures of the animal’s environment.     

Effects of the multiple stressors high temperature and reduced salinity on the photosynthesis of the hermatypic coral Galaxea fascicularis

This study investigates the physiological responses in the hermatypic coral Galaxea fascicularis exposed to salinity stress (from 37 ppt to 15 ppt) for 12 h, combined effects of reduced salinity (from 37 ppt to 20 ppt) and two temperatures (26 °C and 32 °C) for 12 h and combined effects of reduced salinity (from 37 ppt to 25 ppt) and two temperatures (26 °C and 29.5 °C) for 10 d. The results demonstrate that the coral is tolerant to 12 h exposure to extremely low salinity (15 ppt). The study also shows that combined effects of temperature and low salinity aggravate the damage on the photosynthesis of the symbiotic dinoflagellates in 12 h exposure to 20 ppt sea water. This study suggests that high temperature (29.5 °C) aggravates the damage of trivially low salinity (30 ppt) on the holobiont (the coral and its symbiotic dinoflagellates) in 10 d exposure. However, high temperature (29.5 °C) may have an antagonistic effect between temperature and low salinity (25 ppt) on metabolism of the holobiont. Based on the above results, we suggest that (1) the true mechanism of corals exposed to combined effects of low salinity and high temperature is complicated. This calls for more studies on different corals. Future studies should aim at investigating long-term low-level stress in order to simulate in situ conditions more accurately; (2) when corals exposed to extremely severe combined stressors for short-term or trivially severe stressors for relative long-term, the combined effects of two stressors (such as low salinity and high temperature) may be negative, otherwise, the effects may be additive.     

Physiological characteristics of 13 common fungal species in bathrooms

To clarify the factors affecting fungal contamination in bathrooms, the growth of 13 common fungal species (13 isolates) in bathrooms was studied under various environmental conditions. Most of the fungi examined grew on media of 0.01% and 0.05% sodium fatty acid and on media of 0.01% anion surfactant. On media of non-ion surfactant, however, growth varied from species to species. Fungi found commonly in bathrooms can be divided into two groups. The first group, including six species — Cladophialophora boppii, Exophiala spinifera, E. salmonis, Phialophora europaea, Phoma herbarum, and Scolecobasidium constrictum — grew on media of 0.01%, 0.05%, and 0.25% non-ion surfactant, with the latter five species also growing on alkali medium. Most of them did not grow at 33°C, or on media with 10% NaCl, however. Fungi of these six species, identified using DNA and morphological analysis, were common in bathrooms, but not in other indoor environments, for example, in house dust or on windows. The second group contained seven species including Aureobasidium sp., Cladosporium cladosporioides, and Fusarium sp., which were common both in house dust and in bathrooms; they did not grow on media of 0.05% or 0.25% non-ion surfactant, but most grew comparatively fast on normal medium (1/4 PDA), and were able to grow on media with 10% NaCl and also at 33°C. The characteristic fungi found in bathrooms were able to exploit surfactant but were unable to grow well under comparatively dry or high-temperature conditions.     

Clearance rates of the bdelloid rotifer, <Emphasis Type="Italic">Habrotrocha thienemanni</Emphasis>, a tree-hole inhabitant

Bdelloid rotifers are basal consumers in aquatic and limnoterrestrial communities that feed primarily on small bacteria. Unfortunately, we know only a little of the role they play in the trophic dynamics in some unusual habitats they inhabit. Habrotrocha thienemanni is a typical example; it is a typical tree-hole inhabitant, commonly achieving dense populations. Filtering rates of H. thienemanni were estimated using fluorescent microspheres of a size close to natural bacterial community (0.5 μm in diameter) at two temperatures (15 and 20°C). This microspheres artificial food had been coated with BSA protein. Mean clearance rates of this rotifer varied between 1.65 and 3.79 μl ind⁻¹ h⁻¹ under different temperatures. Uptake of particles coated with protein was significantly higher than that on uncoated particles (t = 2.85; P = 0.005). Particle uptake also was correlated to the body size of the animal (r = 0.44; P = 0.004,). The clearance rate of the natural H. thienemanni population (56,800 ind l⁻¹) ranged from 981 to 5170 ml l⁻¹ d⁻¹.     

Fitness and life history parameters of <Emphasis Type="Italic">Leptomastix epona</Emphasis> and <Emphasis Type="Italic">Pseudaphycus flavidulus</Emphasis>, two parasitoids of the obscure mealybug <Emphasis Type="Italic">Pseudococcus viburni</Emphasis>

Fitness and life table parameters of two endoparasitoids of the obscure mealybug Pseudococcus viburni (Signoret), the solitary Leptomastix epona (Walker) and the gregarious Pseudaphycus flavidulus (Brèthes), were examined in relation to temperature and host size with a view to determine the efficacy of the parasitoids as biocontrol agents of the pest. Three temperature levels (21°C, 26°C and 31°C) and two host sizes classes (small, which mostly comprised third instar nymphs and large, which consisted of female adults) were studied. The lower developmental threshold and thermal constant of the host and the parasitoids were found similar so the coincidence of pest and parasitoids is likely. The rate of development of the parasitoids increased with a linear trend as the temperature increased from 21°C to 31°C. Temperature had a significant effect on mummification in both parasitoid species and on successful parasitism by P. flavidulus. Host size had a significant effect on the mummification caused by L. epona and on the proportion of the male offspring which emerged as well as on the successful parasitism by P. flavidulus. Life table parameters of the parasitoids were estimated in small and large hosts at 26°C in the laboratory. Both parasitoids achieved a greater intrinsic rate of natural increase and gross reproductive rate in addition to a shorter generation and doubling time in large mealybugs compared with small ones. Consequently, large hosts are expected to have a higher impact on the rise of the parasitoids population and the potential of the parasitoids to control the mealybug population improves with the increase of host size. Handling Editor: Torsen Meiners.     

Thermal Sensitivity of Mitochondrial Respiration Efficiency and Protein Phosphorylation in the Clam Mercenaria mercenaria

The mitochondria of intertidal invertebrates continue to function when organisms are exposed to rapid substantial shifts in temperature. To test if mitochondrial physiology of the clam Mercenaria mercenaria is compromised under elevated temperatures, we measured mitochondrial respiration efficiency at 15°C, 18°C, and 21°C using a novel, high-throughput, microplate respirometry methodology developed for this study. Though phosphorylating (state 3) and resting (state 4) respiration rates were unaffected over this temperature range, respiratory control ratios (RCRs: ratio of state 3 to state 4 respiration rates) decreased significantly above 18°C (p < 0.05). The drop in RCR was not associated with reduction of phosphorylation efficiency, suggesting that, while aerobic scope of mitochondrial respiration is limited at elevated temperatures, mitochondria continue to efficiently produce adenosine triphosphate. We further investigated the response of clam mitochondria to elevated temperatures by monitoring phosphorylation of mitochondrial protein. Three proteins clearly demonstrated significant time- and temperature-specific phosphorylation patterns. The protein-specific patterns of phosphorylation may suggest that a suite of protein kinases and phosphatases regulate mitochondrial physiology in response to temperature. Thus, while aerobic scope of clam mitochondrial respiration is reduced at moderate temperatures, specific protein phosphorylation responses reflect large shifts in function that are initiated within the organelle at higher temperatures.     

The effect of temperature on protein refolding at high pressure: Enhanced green fluorescent protein as a model

The application of high hydrostatic pressure (HHP) impairs electrostatic and hydrophobic intermolecular interactions, promoting the dissociation of recombinant inclusion bodies (IBs) under mild conditions that favor subsequent protein refolding. We demonstrated that IBs of a mutant version of green fluorescent protein (eGFP F64L/S65T), produced at 37 °C, present native-like secondary and tertiary structures that are progressively lost with an increase in bacterial cultivation temperature. The IBs produced at 37 °C are more efficiently dissociated at 2.4 kbar than those produced at 47 °C, yielding 25 times more soluble, functional eGFP after the lower pressure (0.69 kbar) refolding step. The association of a negative temperature (−9 °C) with HHP enhances the efficiency of solubilization of IBs and of eGFP refolding. The rate of refolding of eGFP as temperature increases from 10 °C to 50 °C is proportional to the temperature, and a higher yield was obtained at 20 °C. High level refolding yield (92%) was obtained by adjusting the temperatures of expression of IBs (37 °C), of their dissociation at HHP (−9 °C) and of eGFP refolding (20 °C). Our data highlight new prospects for the refolding of proteins, a process of fundamental interest in modern biotechnology.     

Factors supporting harmful macroalgal blooms in flowing waters: A 2-year study in the Lower Ain River,France

A two-year study was conducted to explore summer development of macroalgae and their total phosphorus and nitrogen content at three stations in a broad and clear French carbonate river. Water discharge, temperature and insolation, each with a different time lag, as well as substrates and nutrients were examined in order to explain macroalgal biomass variability. Twenty-four macroalgae genera were recorded with Spirogyra, Cladophora, Vaucheria and Oedogonium as abundant. Through redundancy analysis the macroalgal community composition exhibited significant differences, between the sampling sites and also from one year to the next. Water discharge (time-lag = 5 days) and temperature (time-lag = 20 days) both significantly explained macroalgal biomass variability, highlighting differences in the time lag of the macroalgal community's ecological response to environmental changes. Spatial segregation was observed within the wide riverbed due to habitat variability, allowing co-occurrence in the development of ecologically different taxa within each sampling site. The high nitrate concentrations as compared with the particular low phosphorus concentrations led to especially high DIN/SRP ratios (248 ± 103, n = 18). The N/P ratios in algal tissues were high (25 ± 16, n = 26) and indicated P-limitation. The differences in DIN/SRP and N/P ratios suggest additional nutrient sources than open water such as groundwater inputs.