Effects of microwave exposure and temperature on survival of mice infected with Streptococcus pneumoniae

Female CD-1 mice were injected with an LD₅₀ dose of Streptococcus pneumoniae and then exposed to 2.45 GHz (CW) microwave radiation at an incident power density of 10 mW/cm² (SAR = 6.8 W/kg), 4 h/d for 5 d at ambient temperatures of 19 °C, 22 °C, 25 °C, 28 °C, 31 °C, 34 °C, 37 °C and 40 °C. Four groups of 25 animals were exposed at each temperature with an equal number of animals concurrently sham-exposed. Survival was observed for a 10-d period after infection. Survival of the sham-exposed animals increased as ambient temperature increased from 19 °C–34 °C. At ambient temperatures at or above 37 °C the heat induced in the body exceeded the thermoregulatory capacity of the animals and deaths from hyperthermia occurred. Survival of the microwave-exposed animals was significantly greater than the shams (～20%) at each ambient temperature below 34 °C. Based on an analysis of the data it appears that the hyperthermia induced by microwave exposure may be more effective in increasing survival in infected mice than hyperthermia produced by conventional methods (ie, high ambient temperature). Microwave radiation may be beneficial to infected animals at low and moderate ambient temperatures, but it is detrimental when combined with high ambient temperatures.     

The influence of internal and skin temperatures on active cutaneous vasodilation under different levels of exercise and ambient temperatures in humans

To clarify the influence of internal and skin temperature on the active cutaneous vasodilation during exercise, the body temperature thresholds for the onset of active vasodilation during light or moderate exercise under different ambient temperature conditions were compared. Seven male subjects performed 30 min of a cycling exercise at 20 % or 50 % of peak oxygen uptake in a room maintained at 20, 24, or 28 °C. Esophageal (Tes) and mean skin temperature (Tsk) as measured by a thermocouple, deep thigh temperature (Tdt) by the zero-heat-flow (ZHF) method, and forearm skin blood flow by laser-Doppler flowmetry (LDF) were monitored. The mean arterial pressure (MAP) was also monitored non-invasively, and the cutaneous vascular conductance (CVC) was calculated as the LDF/MAP. Throughout the experiment, the Tsk at ambient temperatures of 20, 24, and 28 °C were approximately 30, 32, and 34 °C, respectively, for both 20 % and 50 % exercise. During 50 % exercise, the Tes or Tdt thresholds for the onset of the increase in CVC were observed to be similar among the 20, 24, and 28 °C ambient conditions. During 20 % exercise, the increase in Tes and Tdt was significantly lower than those found at 50 %, and the onset of the increase in CVC was only observed at 28 °C. These results suggest that the onset of active vasodilation was affected more strongly by the internal or exercising tissue temperatures than by the skin temperatures during exercise performed at a moderate load in comparison to a light load under Tsk variations ranging from 30 °C to 34 °C. Therefore, the modification by skin temperature of the central control on cutaneous vasomotor tone during exercise may differ between different exercise loads.     

Der Einfluß der Umgebungstemperatur auf Motilität,Körpertemperatur und Sauerstoffverbrauch von normalen und Pervitin-behandelten Mäusen

Single mice were kept in various ambient temperatures (15° to 35° C) and motility, oxygen consumption, and body temperature were recorded. Untreated animals: Motility was least at 25° C room temperature. Relations between motility and body temperature were linear at all ambient temperatures. The body temperatures of very agile mice did not vary at ambient temperatures from 15° to 30° C whereas that of quiet mice was strongly influenced by the milieu. The relations between oxygen consumption and body weight were also linear at all ambient temperatures; the corresponding regression coefficients decreased progressively with rising ambient temperatures. Oxygen consumption increased at a constant rate with motility, independent of ambient temperatures. Animals treated with methamphetamine: The LD₅₀ of methamphetamine decreased considerably with rising ambient temperature. The influence on body temperature of methamphetamine was very variable and depended on both dose and ambient temperature. Toxic doses of methamphetamine induced hyperthermia in warm surroundings and hypothermia in a cool milieu. Under the influence of methamphetamine, oxygen consumption increased or decreased considerably with the body temperature. Ambient temperatures exerted an essential influence on the cause of death after toxic doses of methamphetamine.     

Thin-blooded Antarctic fishes: a rheological comparison of the haemoglobin-free icefishes Chionodraco kathleenae and Cryodraco antarcticus with a red-blooded nototheniid, Pagothenia bernacchii

The icefishes (family Channichthyidae) comprise a unique group of teleost fishes endemic to Antarctic and sub-antarctic seas. All members of the family totally lack haemoglobin. Haematological parameters and viscosity were determined for blood from 11 specimens of two channichthyid species (Chionodraco kathleenae Regan, 1914; Cryodraco antarcticus Dollo, 1900), and 14 specimens of a red-blood Antarctic nototheniid species (Pagothenia bernacchii (Boulenger, 1902)), captured near the Italian research station at Terra Nova Bay, Ross Sea, Antarctica. Channichthyid blood contained only a small number of non-pigmented cells (10 000-40 000 cells μI^?1, depending on species) in contrast to nototheniid blood (360 000-450 000 cells μI^?1 in unstressed specimens). Blood viscosity was measured by cone plate viscometry over a range of shear rates (11.3-450s ^?1), at six temperatures between – 1.8°C and + 15°C. At the ambient Antarctic seawater temperature of – 1.8° C, and at low shear rate (22.5 s^?1), the viscosity of channichthyid blood was relatively low (3.99 ± 0.40 cP) compared with blood taken from unstressed P. bernacchii, which was about 25% more viscous (4.91 ± 0.59 cP). The viscosity of channichthyid blood was almost independent of shear rate, approximating an ideal Newtonian fluid, while the viscosity of nototheniid blood was much more dependent upon both shear rate and temperature, increasing sharply at low shear rates and low temperatures. Viscosity of nototheniid blood varied with haematocrit, which was in turn strongly influenced by stress. Blood samples taken from P. bernacchii under moderate stress induced by handling during acute caudal venepuncture had haematocrit values in the range 15–20% and viscosities of 8-l0cP, while undisturbed specimens sampled through a venous cannula yielded haematocrits of 8–10%. The viscosity of nototheniid plasma did not differ significantly from that of channichthyid whole blood or channichthyid plasma. The higher viscosity of nototheniid blood is attributable to cell content, and in stressed specimens possibly also to adrenergic swelling of erythrocytes. The absence of erythrocytes in channichthyid blood avoids the great increases in viscosity which are induced in corpusculate blood by sub-zero seawater temperatures.     

Acclimation of chlorophyll biosynthetic reactions to temperature stress in cucumber (Cucumis sativus L.)

The adaptive responses of the greening process of plants to temperature stress were studied in cucumber (Cucumis sativus L. cv. Poinsette) seedlings grown at ambient (25 °C), low (7 °C) and high (42 °C) temperatures. Plastids isolated from these seedlings were incubated at different temperatures and the net syntheses of various tetrapyrroles were monitored. In plastids isolated from control seedlings grown at 25 °C, the optimum temperature for synthesis of Mg-protoporphyrin IX monoester or protochlorophyllide was 35 °C. Temperature maxima for Mg-protoporphyrin IX monoester and protochlorophyllide syntheses were shifted to 30 °C in chill-stressed seedlings. The net synthesis of total tetrapyrroles was severely reduced in heat-stressed seedlings and the optimum temperature for Mg-protoporphyrin IX monoester or protochlorophyllide synthesis shifted slightly towards higher temperatures, i.e. a broader peak was observed. To further study the temperature acclimation of seedlings with respect to the greening process, tetrapyrrole biosynthesis was monitored at 25 °C after pre-heating the plastids (28–70 °C) isolated from control, chill- and heat-stressed seedlings. In comparison to 28 °C-pre-heated plastids the percent inhibition of protochlorophyllide synthesis in 40 °C-pre-heated plastids was higher than for the control (25 °C-grown) in chill-stressed seedlings and lower than for the control in heat-stressed seedlings. Maximum synthesis of total tetrapyrroles and protoporphyrin IX was observed when chloroplasts were heated at 50 °C, which was probably due to heat-induced activation of the enzymes involved in protoporphyrin IX synthesis. Prominent shoulders towards lower or higher temperatures were seen in chill-stressed or heat-stressed seedlings, respectively. The shift in optimum temperature for tetrapyrrole biosynthesis in chill- and heat-stressed seedlings was probably due to acclimation of membranes possibly undergoing desaturation or saturation of membrane lipids. Proteins synthesized in response to temperature-stress may also play an important role in conferring stress-tolerance in plants. Received: 8 October 1998 / Accepted: 19 November 1998     

The influence of increasing growth temperature and CO2 concentration on the ratio of respiration to photosynthesis in soybean seedlings

Using controlled environmental growth chambers, whole plants of soybean, cv. ‘Clark’, were examined during early development (7–20 days after sowing) at both ambient (≈ 350 μL L^–1) and elevated (≈ 700 μL L^–1) carbon dioxide and a range of air temperatures (20, 25, 30, and 35 °C) to determine if future climatic change (temperature or CO₂ concentration) could alter the ratio of carbon lost by dark respiration to that gained via photosynthesis. Although whole-plant respiration increased with short-term increases in the measurement temperature, respiration acclimated to increasing growth temperature. Respiration, on a dry weight basis, was either unchanged or lower for the elevated CO₂ grown plants, relative to ambient CO₂ concentration, over the range of growth temperatures. Levels of both starch and sucrose increased with elevated CO₂ concentration, but no interaction between CO₂ and growth temperature was observed. Relative growth rate increased with elevated CO₂ concentration up to a growth temperature of 35 °C. The ratio of respiration to photosynthesis rate over a 24-h period during early development was not altered over the growth temperatures (20–35 °C) and was consistently less at the elevated relative to the ambient CO₂ concentration. The current experiment does not support the proposition that global increases in carbon dioxide and temperature will increase the ratio of respiration to photosynthesis; rather, the data suggest that some plant species may continue to act as a sink for carbon even if carbon dioxide and temperature increase simultaneously.     

Effect of varying environmental temperature on heat output and finger skin temperature

Heat output from the right hand was estimated on six healthy young men at varying ambient temperatures, in a temperature-controlled room maintained at 5°, 10°, 15°, 20°, 25°, 30° and 35°C at weekly intervals. The skintemperature of the index finger of both the hands, wrist vein of the right hand and oral temperature, were also recorded during the study. Results indicate that the heat output varies significantly with the changes in ambient temperatures, at higher ranges only. This variation is negligible at lower ambient temperatures. Other parameters supported this observation.     

Effects of temperature on growth and efficiency of food utilization in fifth-instar caterpillars of the tobacco hornworm, Manduca sexta

Fifth-instar larvae of Manduca sexta were reared from hatching on artificial diet at 15, 20, 25, 30 and 35°C. Total development time decreased with increasing temperature. Very few larvae (12%) survived at 15°C, so this temperature was not considered further. There was some mortality at 30°C (11%), and at 35°C (50%).The absolute rate of growth in the fifth instar was faster at 25 than at 20°C, but was similar at 25, 30 and 35°C. This was true both for caterpillars that were chronically exposed to experimental temperatures (i.e. since hatching) and for those acutely exposed (i.e. reared up to fifth instar at 25°C).There was a progressive decrease with higher rearing temperatures in both the initial and final sizes of chronically exposed fifth-instar larvae. Acutely exposed caterpillars matched for initial size showed smaller temperature related differences in final size. Because of these size differences there were differences in relative growth rate which did not reflect true differences in absolute growth rate.Total food consumed by chronically exposed caterpillars was greatest at the lowest temperature (20°C), and decreased progressively with increasing temperature. The absolute rate of food consumption increased from 20 to 25°C, but did not vary significantly between 25 and 35°C. Differences in the sizes of the insects at the different temperatures meant that there were differences among relative measures of consumption that did not reflect absolute food consumption.For chronically exposed caterpillars, none of the three usual indices of food conversion efficiency (AD, ECI and ECD) varied significantly with temperature between 20 and 35°C. This implies that the effects of temperature on metabolic costs are closely matched to food consumption.Oxygen consumption increased with temperature between 20 and 25°C but was temperature compensated between 25 and 35°C.These findings are discussed in terms of their implications for the optimal temperature for growth in Manduca.     

Heat-Resistance and Heat-Shock Response in the Nosocomial Pathogen <Emphasis Type="Italic">Enterococcus faecium</Emphasis>

We have characterized the heat-shock response of the nosocomial pathogen Enterococcus faecium. The growth of E. faecium cells was analyzed at different temperatures; little growth was observed at 50°C, and no growth at 52°C or 55°C. In agreement, a marked decrease of general protein synthesis was observed at 52°C, and very light synthesis was detected at 55°C. The heat resistance of E. faecium cells was analyzed by measuring the survival at temperatures higher than 52°C and, after 2 h of incubation, viable cells were still observed at 70°C. By Western blot analysis, two heat-induced proteins were identified as GroEL (65 kDa) and DnaK (75 kDa). Only one isoform for either GroEL or DnaK was found. The gene expression of these heat-shock proteins was also analyzed by pulsed-labeled experiments. The heat-induced proteins showed an increased rate of synthesis during the first 5 min, reaching the highest level of induction after 10 min and returning to the steady-state level after 20 min of heat treatment. Received: 29 March 2002 / Accepted: 5 July 2002     

Thermoregulation dynamics in commercially reared colonies of the bumblebee Bombus terrestris

Thermoregulation, that is, the active control of temperature, is key to ensure proper brood development in both wild and captive bumblebee nests. In this study, thermoregulation dynamics were assessed relative to colony age and ambient temperature using commercially reared Bombus terrestris L. (Hymenoptera, Apidae, Bombus) colonies. We observed a positive relationship between brood and nest temperatures in response to ambient temperature. Thermoregulation investment (by either brooding or fanning) was lowest at brood surface temperatures between 33 and 34 °C and ambient temperatures between 28 and 32 °C. Brood temperature was less stable and thermoregulation investment higher in younger colonies, especially at lower ambient temperatures. Furthermore, queens initiated colonies sooner and colonies developed faster when kept at an ambient temperature of 29 °C as compared to 24 °C. Our results suggest that ambient temperatures are ideally kept between 29 and 31 °C.     

Water Temperature Affects Susceptibility to Ranavirus

The occurrence of emerging infectious diseases in wildlife populations is increasing, and changes in environmental conditions have been hypothesized as a potential driver. For example, warmer ambient temperatures might favor pathogens by providing more ideal conditions for propagation or by stressing hosts. Our objective was to determine if water temperature played a role in the pathogenicity of an emerging pathogen (ranavirus) that infects ectothermic vertebrate species. We exposed larvae of four amphibian species to a Frog Virus 3 (FV3)-like ranavirus at two temperatures (10 and 25°C). We found that FV3 copies in tissues and mortality due to ranaviral disease were greater at 25°C than at 10°C for all species. In a second experiment with wood frogs (Lithobates sylvaticus), we found that a 2°C change (10 vs. 12°C) affected ranaviral disease outcomes, with greater infection and mortality at 12°C. There was evidence that 10°C stressed Cope’s gray tree frog (Hyla chrysoscelis) larvae, which is a species that breeds during summer—all individuals died at this temperature, but only 10% tested positive for FV3 infection. The greater pathogenicity of FV3 at 25°C might be related to faster viral replication, which in vitro studies have reported previously. Colder temperatures also may decrease systemic infection by reducing blood circulation and the proportion of phagocytes, which are known to disseminate FV3 through the body. Collectively, our results indicate that water temperature during larval development may play a role in the emergence of ranaviruses.     

Environmental induction of larval diapause and life-history consequences of post-diapause development in the Large Copper butterfly,Lycaena dispar (Lepidoptera: Lycaenidae)

Many insects in temperate zones withstand the adverse conditions of winter through entering diapause and the two most important environmental stimuli that induce diapause are photoperiod and ambient temperature. The Large Copper butterfly, Lycaena dispar Haworth (Lepidoptera: Lycaenidae), is a Palearctic butterfly that hibernates as larvae. Since this butterfly is a near threatened species in some regions, there has been a growing need for a standardized protocol for mass rearing of this butterfly based on the adequate knowledge of its ecology. In the present study, we first identified that L. dispar larvae were sensitive to the photoperiodic induction of diapause during their first larval instar. We then investigated to what extent the diapause-inducing effects of photoperiod could be modified by ambient temperatures in L. dispar larvae by exposing them to the range of day-lengths (L:D 14:10, 12:12, 10:14 and 8:16) at three different temperatures (15, 20 and 25 °C). All larvae were induced to enter diapause at low ambient temperature (15 °C) regardless of photoperiod, whereas most of them (86 %) exhibited direct development when temperature was high (25 °C). The photoperiodic induction of diapause was evident when day-length was shorter than 14 h at intermediate temperature (20 °C). Pre-diapause development was prolonged at low temperatures. Finally, we found that post-diapause development of L. dispar larvae was determined by both the chilling temperature experienced by diapausing larvae and the duration of larval diapause. Adult emergence was enhanced when larvae were chilled at 8 °C and when they had been under the state of diapause for 20 days before they were treated to terminate diapause.     

Root–shoot communication of the seedlings of Japanese larch and a hybrid species grown in different soil-temperature regimes

We studied the effects of soil temperature (7, 15, and 25°C) on the growth and photosynthesis of seedlings of the Japanese larch (Larix kaempferi) and its hybrid larch (L. gmelinii × L. kaempferi) to simulate early stages of regeneration after disturbance. At a soil temperature of 7°C, the root length per unit root biomass, chlorophyll concentration, and photosynthetic nitrogen-use efficiency (PNUE) were markedly lower in the Japanese larch than in the hybrid larch, which may indicate that the hybrid larch is better at acquiring water and nutrients. At ambient temperatures of 17–25°C, the light-saturated photosynthesis rate (P _sat) of both seedlings grown at a soil temperature of 7°C was lower than at 15 or 25°C. By the 16th week, the needle area, root area, and biomass in seedlings of both types were lower at a soil temperature of 7°C than at soil temperatures of 15 or 25°C. At a soil temperature of 25°C, P _sat and nitrogen uptake were lower in both larch species than at 15°C. The growth of the Japanese larch declined sharply from 15 to 25°C; however, the growth of the hybrid larch decreased only slightly from 15 to 25°C. We conclude that an increased soil temperature may retard larch growth in cold regions, especially in the case of the Japanese larch.     

Neurotensin and bombesin: differential effects on body temperature of mice after intracisternal administration

Intracisternal administration of neurotensin or bombesin produces a significant hypothermic response in rodents in an ambient temperature of 23°C or below; bombesin has been reported to produce a significant hyperthermic response in rats at 36°C, but no change in colonic temperature at ambient temperatures between 31 and 33°C. In this study we compared the effects of the two neuropeptides on colonic temperature of mice exposed to different ambient temperatures to determine whether neurotensin also produces a poikilothermic state. From a series of experiments conducted at ambient temperatures of 4, 23, 26, 30, 34 and 38°C, in which mice received an intracisternal injection of an equimolar dose (0.6 nmol) of neurotensin or bombesin (or vehicle), we noted that the two neuropeptides produce different effects on colonic temperature. At ambient temperatures of 26°C and below, both neurotensin and bombesin produce a significant hypothermic response; however, at higher temperatures bombesin has no effect (30°C) or produces hyperthermia (34°C). In contrast, neurotensin produces hypothermia at 30°C and no significant effect at 34 and 38°C. In addition, a wide range of doses of neurotensin failed to produce the poikilothermic effects characteristic of centrally administered bombesin.     

Bark cells and xylem cells in Japanese white birch twigs initiate deacclimation at different temperatures

Appropriate timing of cold deacclimation is an important component of winter survival of perennial plants, such as trees, in temperate and boreal zones. Recently, concerns about predicted global climate change disturbing deacclimation timing have been increasing. The relationship between ambient temperatures and the manner by which cells' freezing resistance changes is essential for forecasting the timing of deacclimation. In this study, Japanese white birch twigs that underwent deacclimation treatment at a constant temperature of −2, 0, 4, 10, or 20 °C were separated into bark in which cells adapted to subfreezing temperatures by extracellular freezing and xylem in which cells adapted to subfreezing temperatures by deep supercooling, and the freezing resistance of cells in each tissue type was investigated by measuring percentage electrolyte leakage. Birch cells deacclimated in a different manner according to tissue type. Within 7 days under deacclimation treatment, xylem cells decreased their freezing resistance significantly at a high subfreezing temperature (−2 °C). In contrast, bark cells required a temperature of 10 or 20 °C for a detectable decrease in freezing resistance to occur within the same period. At a temperature lower than 0 °C, bark cells did not decrease their freezing resistance, even after 28 days of treatment. The difference in freezing behavior of cells might involve the difference in how deacclimation occurred in bark and xylem cells.     

Effect of ambient temperature on female endurance performance

Ambient temperature can affect physical performance, and an ambient temperature range of −4 °C to 11 °C is optimal for endurance performance in male athletes. The few similar studies of female athletes appear to have found differences in response to cold between the genders. This study investigated whether ambient temperature affects female endurance performance. Nine athletes performed six tests while running on a treadmill in a climatic chamber at different ambient temperatures: 20, 10, 1, −4, −9 and −14 °C and a wind speed of 5 m s⁻¹. The exercise protocol consisted of a 10-min warm-up, followed by four 5-min intervals at increasing intensities at 76%, 81%, 85%, and 89% of maximal oxygen consumption. This was followed by an incremental test to exhaustion. Although peak heart rate, body mass loss, and blood lactate concentration after the incremental test to exhaustion increased as the ambient temperature rose, no changes in time to exhaustion, running economy, running speed at lactate threshold or maximal oxygen consumption were found between the different ambient temperature conditions. Endurance performance during one hour of incremental exercise was not affected by ambient temperature in female endurance athletes.     

Human thermoregulatory responses during prolonged walking in water at 25, 30 and 35°C

Eight healthy and physically well-trained male students exercised on a treadmill for 60 min while being immersed in water to the middle of the chest in a laboratory flowmill. The water velocity was adjusted so that the intensity of exercise correspond to 50% maximal oxygen uptake of each subject, and experiments were performed once at each of three water temperatures: 25, 30, 35°C, following a 30-min control period in air at 25°C, and on a treadmill in air at an ambient temperature of 25°C. Thermal states during rest and exercise were determined by measuring rectal and skin temperatures at various points, and mean skin temperatures were calculated. The intensity of exercise was monitored by measuring oxygen consumption, and heart rate was monitored as an indicator for cardiovascular function. At each water temperature, identical oxygen consumption levels were attained during exercise, indicating that no extra heat was produced by shivering at the lowest water temperature. The slight rise in rectal temperature during exercise was not influenced by the water temperature. The temperatures of skin exposed to air rose slightly during exercise at 25°C and 30°C water temperature and markedly at 35°C. The loss of body mass increased with water temperature indicating that both skin blood flow and sweating during exercise increased with the rise in water temperature. The rise in body temperature provided the thermoregulatory drive for the loss of the heat generated during exercise. Heart rate increased most during exercise in water at 35°C, most likely due to enhanced requirements for skin blood flow. Although such requirements were certainly smallest at 25°C water temperature, heart rate at this temperature was slightly higher than at 30°C suggesting reflex activation of sympathetic control by cold signals from the skin. There was a significantly greater increase in mean skin and rectal temperatures in subjects exercising on the treadmill in air, compared to those exercising in water at 25°C. Accepted: 22 May 1998     

Temperature regulation in the echidna (Tachyglossus aculeatus)

The echidna (Tachyglossus aculeatus) maintained a body temperature of 30.7°C ± 1.03 s.d. (N = 23) at ambient temperatures (T_A) between 0 and 25°C. It may, however, also become hypothermic at low T_A. At T_A = 30°C or above the echidna became hyperthermic. The thermoneutral range was about 20–30°C. At low T_A the metabolic rate might be increased several fold. The thermal conductance was at a minimum at T_A = 20°C, and was not further reduced at lower T_A. At higher T_A the thermal conductance increased up to five-fold. The evaporation showed little change with increasing T_A. At the highest T_A we used (33°C) the evaporation on the average accounted for the dissipation of only about one-third of the metabolic heat produced. These findings suggest that the echidna, although it can maintain its body temperature at low ambient temperature, cannot rely upon evaporation as the major avenue for heat loss at high ambient temperature.     

Effect of temperature on growth and macromolecular biosynthesis in cryptococcus species

Cryptococcus neoformans, a pathogenic yeast, grows at temperatures between 25 and 37°C. However, the closely related non-pathogen C. albidus exhibits restricted growth at temperatures above ambient with little or no growth at 37°C. The inhibition of growth of the non-pathogen, as measured by turbidity, cell number, and per cent budding, is reversible after 48 hr at the non-permissive temperature (37°C). Growth cessation at 37°C is accompanied by a corresponding decrease in DNA synthesis, which is not observed in C. neoformans. RNA and protein synthesis in C. albidus and C. neoformans are only slightly affected at the elevated temperature. Degradation by nucleases does not seem to account for the differences found in this cumulative DNA synthesis in C. albidus at 25 and 37°C. These facts suggest that C. albidus may possess a thermo-sensitive defect in the machinery responsible for the initiation of DNA replication.     

Temperature-induced changes in treatment efficiency and microbial structure of aerobic granules treating landfill leachate

This paper investigates the effect of temperature on nitrogen and carbon removal by aerobic granules from landfill leachate with a high ammonium concentration and low concentration of biodegradable organics. The study was conducted in three stages; firstly the operating temperature of the batch reactor with aerobic granules was maintained at 29 °C, then at 25 °C, and finally at 20 °C. It was found that a gradual decrease in operational temperature allowed the nitrogen-converting community in the granules to acclimate, ensuring efficient nitrification even at ambient temperature (20 °C). Ammonium was fully removed from leachate regardless of the temperature, but higher operational temperatures resulted in higher ammonium removal rates [up to 44.2 mg/(L h) at 29 °C]. Lowering the operational temperature from 29 to 20 °C decreased nitrite accumulation in the GSBR cycle. The highest efficiency of total nitrogen removal was achieved at 25 °C (36.8 ± 10.9 %). The COD removal efficiency did not exceed 50 %. Granules constituted 77, 80 and 83 % of the biomass at 29, 25 and 20 °C, respectively. Ammonium was oxidized by both aerobic and anaerobic ammonium-oxidizing bacteria. Accumulibacter sp., Thauera sp., cultured Tetrasphaera PAO and Azoarcus–Thauera cluster occurred in granules independent of the temperature. Lower temperatures favored the occurrence of denitrifiers of Zooglea lineage (not Z. resiniphila), bacteria related to Comamonadaceae, Curvibacter sp., Azoarcus cluster, Rhodobacter sp., Roseobacter sp. and Acidovorax spp. At lower temperatures, the increased abundance of denitrifiers compensated for the lowered enzymatic activity of the biomass and ensured that nitrogen removal at 20 °C was similar to that at 25 °C and significantly higher than removal at 29 °C.