The succinic dehydrogenase activity of eptocephalus dichotomus Baird

Summary The succinic dehydrogenase activity in Streptocephalus dichotomus in the entire animals as well as in the different regions of the body, increased with increase in temperature up to 30°C and at 33°C it decreased.In both males and females there exists a linear relationship between body weight and enzyme activity.Analyses of covariance revealed that the F ratios are not significant in the case of rate of succinic dehydrogenase activity between the two sexes or when the comparison is made within the sexes at the different temperatures.The succinic dehydrogenase activity in the thoracic region is higher than in the head and abdominal regions.This work formed a part of a thesis submitted for the Degree of Doctor of Phylosophy to the University of Madras in 1970.     

Amber mutations in the structural gene for RNA polymerase sigma factor of Escherichia coli

Summary Amber mutants of Escherichia coli K-12 affected in the structural gene (rpoD) for th subunit of RNA polymerase have been obtained from a strain harboring a temperature-sensitive amber suppressor (supF-Ts6) which is active only at low temperatures. These mutants grow normally at low temperature (30°C) but do not grow at high temperature (42°C) due to the inability to synthesize factor. In one mutant studied in detail (rpoD40), the rate of -factor synthesis at 30°C is about half that of the wild type and is decreased to 10%–15% within 1 h of incubation at 42°C. The synthesis of core polymerase subunits or bulk protein is virtually unaffected at least for 2 h. The defect of the mutant in synthesis and growth at high temperature can be suppressed by any of the amber suppressors tested (supD, supE or supF). RNA-polymerase holoenzymes prepared from the mutant cells carrying each of the suppressors (grown at 42°C) exhibit different thermostabilities attributable to alterations in the factor. The reduced synthesis in the mutant is accompanied by the synthesis of polypeptide tentatively identified as amber fragment. These results as well as the genetic mapping data indicate that the amber mutation (rpoD40) resides within the structural gene for the factor and directly affects synthesis upon inactivation of the suppressor at high temperature.     

Soybean seedling emergence at high temperatures

Bragg and Cobb soybean [Glycine max (L.) Merr.] seeds were germinated in sand at temperatures ranging from 25 to 40°C. Emergence decreased with increasing temperature above 37°C, with virtually no emergence at 40°C. Emergence of 12 other cultivars at 38°C ranged from 25 to 95%. Foster and Coker 338 were more sensitive to high temperature than the other cultivars.     

Oxygen isotope fractionation during respiration for different temperatures ofT. utilis andE. coli K12

Summary The temperature dependence of the oxygen isotope fractionation factor during respiration has been examined for two different microorganisms, namelyTorulopsis utilis andEscherichia coli K12 representing a yeast and a bacterium, respectively. The investigation covered a temperature range of 18° C, that is from 16° C to 34° C forT. utilis and from 19° C to 37° C forE. coli K12. Within this temperature range the fractionation factor ofT. utilis increases by 0.18; an insignificant change ( _{10° C} = 0.063;r = 0.067), whereas withE. coli K 12 an increase of 1.12; has been observed ( _{10° C} = 0.6;r = 0.55).     

Characterization of thermostable α-glucosidase from Clostridium thermohydrosulfuricum 39E

Summary Clostridium thermohydrosulfuricum 39E produced a cell-bound -glucosidase. It was partially purified 140-fold by solubilizing with Triton X-100, ammonium sulfate treatment, DEAE-Sepharose CL-6B, octyl-Sepharose and acarbose-Sepharose affinity chromatography. The optimum temperature for the action of the enzyme was at 75°C. It had a half-life of 35 min at 75°C, 110 min at 70°C and 46 h at 60°C. The enzyme was stable at pH 5.0–6.0 and had an optimum pH at 5.0–5.5. It hydrolyzed the -1,4-linkages in maltose, maltotriose, maltotetraose and maltohexaose, the rate decreasing in order of higher-sized oligosaccharides. The enzyme preparation also hydrolyzed the -1,6 linkages in isomaltose and isomaltotriose. It rapidly hydrolyzed p-nitrophenyl -d-glucoside (pNPG). The K _m values for maltose, isomaltose, panose, maltotriose, and pNPG were 1.85, 2.95, 1.72, 0.58, and 0.31 mm, respectively, at pH 5.5 and 60°C. The enzyme produced glucose from all these substrates. The enzyme preparation did not require any metal ion for activity. The -glucosidase activity was inhibited by acarbose. Offprint requests to: B. C. Saha     

Timing of diapause induction outside the natural distribution range of a species: an outdoor experiment with the bean bug Riptortus clavatus

The phytophagous bug Riptortus clavatus (Thunberg) (Heteroptera: Alydidae) produces two or three generations per year in Central Japan and overwinters in the adult stage. In bugs from the Kyoto population (35°00 N, 135°45 E), we studied (1) the effects of day-length on the nymphal and preoviposition periods under constant photoperiod at 20.5 °C, and (2) photoperiodic induction of adult diapause at 20.5 °C and under a combination of constant photoperiod and natural daily rhythm of temperature in the forest-steppe zone of Russia (50°38 N, 35°58 E). Then, we examined (3) the timing of diapause induction under quasi-natural conditions in the same region, far outside the species' natural geographical range. At 20.5 °C, the nymphal period in both males and females was significantly longer under regimes with shorter photophases than under those with longer photophases. The preoviposition period in females was significantly longer under the near-critical long-day regime L14:D10 than under typical long-day regimes (L15:D9, L16:D8, and L17:D7). The critical day-length for diapause induction was shorter under conditions of natural daily rhythm of temperature than those reported at constant 20, 25, and 30 °C. Under quasi-natural conditions in the forest-steppe zone, R. clavatus entered diapause in September, much later than the local populations of true bugs studied to date. This experiment showed that R. clavatus was maladapted to new environmental conditions: diapause was induced too late with the result that all or most nymphs hatched in late August or early September will die.     

Low temperatures stabilize interferon α-2 against proteolysis in Methylophilus methylotrophus and Escherichia coli

Summary The accumulation of interferon (IFN) -2 in transformed strains of Escherichia coli and Methylophilus methylotrophus was greater at 25° C than at 37° C. Interferon -2 catabolism was followed by measuring the change in IFN titre (measured immunoreactively) with time at temperatures between 25° C and 37° C in chloramphenicol-treated cells. The IFN -2 titre remained constant at 29° C and below, while at higher temperatures the titres declined. The t _1/2 values for IFN -2 decreased with increasing incubation temperature. Pulse-chase studies using [³⁵S]methionine, sodium dodecyl sulphate-gel electrophoresis and autoradiography demonstrated that IFN -2 was subjected to degradation at 37° C while at 25° C it was stable. It is proposed that the susceptibility of IFN -2 to degradation in both E. coli and M. methylotrophus is affected by incubation temperature and 30° C may be a transition temperature above which the conformation of the molecule is recognised by the bacterial proteases.     

Characterization of a new Bacillus stearothermophilus isolate: a highly thermostable α-amylase-producing strain

A novel strain of Bacillus stearothermophilus was isolated from samples of a potato-processing industry. Compared to known -amylases from other B. stearothermophilus strains, the isolate was found to produce a highly thermostable -amylase. The half-time of inactivation of this -amylase was 5.1 h at 80°C and 2.4 h at 90°C. The temperature optimum for activity of the -amylase was 70°C; the pH optimum for activity was relatively low, in the range 5.5–6.0. -Amylase synthesis was regulated by induction and repression mechanisms. An inverse relationship was found between growth rate and -amylase production. Low starch concentrations and low growth temperatures were favourable for enzyme production by the organism. At the optimal temperature for growth, 65°C, the -amylase was a growth-associated enzyme. The optimal temperature for -amylase production, however, was 40°C, with -amylase increasing from 3.9 units (U)/ml to 143 U/ml when lowering the growth temperature from 65°C to 40°C. Maximal -amylase production in a batch fermentor run at 65°C was 102 U/ml, which was 26-fold higher than in erlenmeyer flasks at 65°C. The dissolved O₂ concentration was found to be a critical factor in production of the -amylase.     

Effect of hydration,photoperiod and temperature on diapause termination in eggs ofPetrobia (Tetranychina) harti (Acari: Tetranychidae)

Petrobia harti (Ewing) displays a facultative summer diapause in the egg stage. An adult female will lay only either diapause or non-diapause eggs throughout her life. In the laboratory, diapause eggs are laid by females which develop on detachedOxalis articulata leaves under long-day photoperiods and a relatively low temperature of 19±1°C.Diapause occurs in a stage of advanced embryonic development, in which the embryo appears U-shaped when observed from the egg's ventral side. Embryonic development ceased at this stage, and no further growth occurred when the eggs were kept under a relative humidity of about 70% in various photoperiod and temperature conditions. However, when the eggs were hydrated by placing them on wet cotton wool, development in some embryos (apparently in those which had completed their diapause development) proceeded beyond the U-stage at a rate similar to that in non-diapause embryos and the eggs hatched.Under LD 168 and 19±1°C or 26±1°C, the later from oviposition the period of egg hydration started, the higher the percentage of diapause termination. Under LD 168 and 26±1°C, diapause termination occurred mostly during the first week of hydration, while at 19±1°C mostly during the second and third week.At 26±1°C, in eggs hydrated 15 days but not 30 days from oviposition, the percentage of diapause termination was higher under a long-day than under a short-day photoperiod.Under LD 168, when the eggs were hydrated continuously from oviposition or starting 15, 30 and 45 days from it, the percentage of diapause termination was higher at 26±1°C than at 19±1°C.The percentage of diapause-laying adult females and the intensity of egg diapause were higher when the pre-imaginal mites grew at LD 1212 and 19±1°C, than when they grew at LD 168 and 26±1°C. This maternal effect on egg diapause intensity was expressed when the eggs were maintained at LD 1212 and 19±1°C but not at LD 168 and 26±1°C.     

Effect of the dnaN mutation on the growth of small DNA phages

Summary The effect of the dnaN mutation on the growth of single-stranded DNA phages was studied by burst experiments. In HC138 dnaN cells exposed to 42.5° C at 5 min before infection, growth of spherical (microvirid or isometric) phages such as 3, Kh-1 and X174 was partially reduced at the nonpermissive temperature. When infection was performed at 30 min after temperature shift-up, viral replication was completely inhibited at 42.5° C in the dnaN strain but not in a dna ⁺ revertant. At 41° C, multiplication of filamentous (inovirid) phages M13 and fd was restricted specifically in HC138 F⁺ dnaN bacteria. When dnaN cells lysogenic for i²¹ were grown at 42.5° C for 60 min and then shifted down to 33° C, a burst of i²¹ occurred with concomitant cellular lysis, manifesting induction of the prophage development.     

Involvement of polyamines in cytoplasmic male sterility of stem mustard (Brassica juncea var. tsatsai)

Changes in carbon isotope composition(¹³C) and leaf morphology associated withvegetative phase change were monitored in Metrosiderosexcelsa Sol. ex Gaertn. (family Myrtaceae). Plants of threeontogenetic states were used: juvenile seedlings, micropropagated plants in arejuvenated state, and reproductively mature plants bearing leaves with adultcharacteristics. The effects of temperature regime (32/24 °C,24/16 °C, and 16/8 °C day/night) and plantarchitecture (branched and single-stemmed plants) were studied in two separateexperiments. Although both juvenile and rejuvenated plants exhibited juvenileleaf morphology at the start of the experiments, there was no differencebetweenleaf ¹³C in these plants and that in adultplantsat this time (mean ca. –27%). Vegetative phase change occurred injuvenileand rejuvenated plants grown at 24/16 °C, and there was acorresponding increase in leaf ¹³C (from ca.–27% to –23%) in these two groups of plants. Leaf¹³C in adult plants remained relatively constant(ca. –26%) at 24/16 °C. There was little change in leaf¹³C in all plant states maintained at 32/24°C or 16/8 °C, and vegetative phase change didnot occur in juvenile and rejuvenated plants grown under these two temperatureregimes. Rejuvenated plants grown in a greenhouse also exhibited a progressivedevelopment of adult leaf morphology, accompanied by an increase in leaf¹³C, an effect that was more pronounced insingle-stemmed (from –26.4% to ca. –24%) than in branched plants. Itis suggested that increasing ¹³C in juvenile andrejuvenated plants undergoing phase change is a result of reduced sink strengthin single-stemmed plants, and to a lesser extent within each branch of branchedplants, causing reduced stomatal conductance and photosynthesis.     

Intraspecific variation for CO2 compensation point and differential growth among variants in a C3−C4 intermediate plant

CO₂ compenstation point (), the concentration of CO₂ at which photosynthesis and respiration are at equilibrium, is a commonly used diagnostic for the C₄ photosynthetic pathway, since it reflects the reduced photorespiration that is a property of C₄ photosynthesis. Geographic variation for was examined within Flaveria linearis, a C₃–C₄ intermediate species. Collections from four widely separated Floridian populations were propagated in a greenhouse and measured for . Little differentiation among populations was found, but significant within-population variation was present. Temperature is a hypothesized selective agent for the C₄ photosynthetic pathway. To test this hypothesis, plants exhibiting a range of were cloned and placed in growth chambers at 25°C and 40°C. After 7 weeks, valves were remeasured and plants were harvested and weighed. There was a poor correlation between initial and final measures of for a given genotype (r=0.38, P>0.1). Broad sense heritability for was computed to be 0.10. At 25°C, there was no relationship between final size and . At 40°C, more C₄-like plants, as indicated by their low , had grown larger. Differences in relative growth rate were attributable more to differences in net assimilation rate than in leaf area ratio. Taken together, these results demonstrate that although significant plasticity exists in the amount of photorespiration in this C₃–C₄ species, high temperature appears to be an effective selective agent for the reduction of photorespiration and the enhancement of C₄-like traits.     

Contribution to the rotifer fauna of subarctic Greenland (Kangerlussuaq and Ammassalik area)

Six water bodies in the region of Kangerlussuaq, West Greenland (67° 30 N, 50° 46 W), and four near Ammassalik, East Greenland (65° 36 N, 37° 38 W) were sampled. Sixty-nine taxa (2 Bdelloidea, 67 Monogononta) are reported, forty-six of which represent new records for Greenland. Proales pejleri n. sp. is described.     

Proteolytic digestion of α-lactalbumin: Physiological implications

The kinetics of the partial digestion of bovine -lactalbumin (-LA) by trypsin, -chymotrypsin, and pepsin was monitored by lactose synthase activity, HPLC, and difference spectrophotometry. The relative stabilities of the various metal-bound states of -LA to trypsin and chymotrypsin at 37 and 5°C decrease in the following order: Ca(II)--LA>Zn(II), Ca(II)--LA>apo--LA. The HPLC digestion patterns of Ca(II)--LA and Zn(II), Ca(II)--LA at 5 and 37°C were similar, while the corresponding digestion patterns for apo--LA were quite different, reflecting the existence of the thermally induced denaturation states of apo--LA within this temperature region. Occupation of the first Zn(II)-binding site in Ca(II)-loaded -LA slightly alters the HPLC digestion patterns at both temperatures and accelerates the digestion at 37°C due to Zn(II)-induced shift of the thermal transition of -LA, exposing some portion of thermally denatured protein. The results suggest that the binding of Zn(II) to the first Zn(II)- (or Cu(II))-specific site does not cause any drastic changes in the overall structure of -LA. The acidic form of -LA (atpH 2.2 and 37°C) was digested by pepsin at rates similar to that for the apo- or Cu(II), Ca(II)-loaded forms by trypsin or -chymotrypsin at neutralpH. Complexation of -LA with bis-ANS affords protection against pepsin cleavage. It is suggested that the protective effects of similar small lipophilic compounds to -LA may have physiological significance (e.g., for nutritional transport).On leave from the Institute of Biological Physics, USSR Academy of Sciences, Pushchino, Moscow Region, 142292, USSR.     

Temperature effects on self incompatibility in Lilium longiflorum

Summary Detached pistils of the clonal variety, Lilium longiflorum Aral No. 5, were submerged before pollination in 50°C water for 0, 1, 2, 3, 4, 5, 6 or 7 min and then immediately compatibly and incompatibly pollinated. Incompatibility, as indicated by pollen tube length after 48 h at 23.5°C, was eliminated by a 1–2 min submersion while compatibility was removed by a 4–5 min one. The window of incubation temperatures at which incompatible and compatible pollen tubes are clearly differentiated occurred between 15 and 30°C.     

Toxigenic fungi and the deterioration of Nigerian poultry feeds

Growth of toxigenic strains of Aspergillus clavatus Des. and Aspergillus flavus Link at 30°C on milled poultry feeds led to a considerable decrease in the protein, oil and crude fibre contents of the feed substrate. A corresponding increase in the free fatty acid fractions of the feeds due to the activities of these microbes was also recorded. Rapid degradation of the feedstuff by both species was recorded at a temperature of 25°C and 30°C and a pH range of 4.8–6.4. When grown on feed infusion broth at 30°C, the highest amounts of mycelial production with sporulation of both fungal species occurred within the 8-day incubation period. A determination of their extra-cellular enzyme profile showed the production of amylases, pectate lyase, cellulases, proteases, lipases, xyalanases, DNase and RNase.All the carbon and nitrogen sources used (except L-sorbose and DL-tryptophan), supported good mycelial growth with sporulation. An optimal CN ratio of 5.04.5 and 7.53.0 was recorded for growth and sporulation of A. clavatus. For A. flavus, a CN ratio of 7.54.5 was found best for growth and 5.03.0 for sporulation.     

Heat-sensitive DNA-binding activity of thecI product of bacteriophage lambda

Summary The binding of genecI product to DNA was studied at temperatures from 0°C to 46° C. Binding activity of the products ofcIts mutants was higher at 22° C than at 0° C, 26° C or 30° C. BothcI⁺ andcIts products lost DNA-binding activity at 46° C, but after subsequent cooling to 22° C, they regained 50–100% of their activity.     

Replicon properties of chromosomal DNA fibers and the duration of DNA synthesis of sunflower root-tip meristem cells at different temperatures

Chromosomal DNA fiber autoradiography was used to examine the replicon properties of root-tip meristem cells of Helianthus annuus intact seedlings grown at temperatures from 10 to 38° C and those of root-tip cells grown in vitro at 23°. The average replicon size was approximately 22 m and it did not change with temperature nor when the roots were grown in culture. The average fork rate was 6 m/h at 10° and it rose gradually to 12 m/h at 38°. The responses of replication fork movement and of the duration of S to temperature were of three types: those in which change in fork rate was primarily (more than 90%) responsible for change in the duration of S, those in which the fork rate remained constant while S increased nearly twofold, and those in which the duration of S increased even though the replication forks were moving faster. The first type of response listed was observed at temperatures from 20 to 35°, the second type listed was observed at 10 to 15°, and the third, was produced at 38°.     

Photoperiodism and thermoperiodism in the predatory mite Amblyseius potentillae are probably based on the same mechanism

Summary A comparative study was made of the photoperiodic and thermoperiodic induction of diapause in the phytoseiid mite Amblyseius potentillae. Sensitivity to thermoperiod was found to be highest during the protonymphal and deutonymphal stages, with some sensitivity still being present in the young adult. Summation of both photoperiodic and thermoperiodic cycles was shown to take place, which demonstrated the presence of a photoperiodic counter as well as a thermoperiodic counter in these mites. Vitamin A appeared to be necessary for some early step in the physiological mechanism of diapause induction and not just for the expression of the diapause response. The light sensitivity threshold for photoperiodic induction of diapause was found to be extremely low, viz. less than 0.02 W/cm². Moreover, the light sensitivity threshold appeared to be strongly temperature dependent in A. potentillae. Experiments in which the mites experienced various sequences of short-day photoperiods and short-day thermoperiods, applied either concurrently or in succession, showed that the information collected by the photoperiodic counter and the thermoperiodic counter is integrated into one induction sum. These results strongly suggest that photoperiodic and thermoperiodic induction of diapause in these mites is based on the same physiological mechanism.Abbreviations DD continuous darkness - LL continuous light - LD light-dark cycle (e.g. LD 16:8 is a cycle of 16 h of light and 8 h of darkness) - TC thermoperiodic cycle (e.g. TC 16:8 (27°: 15°) is a thermoperiod with a 16 h thermophase of 27 °C and an 18 h cryophase of 15°C)     

Trehalose synthesis from maltose by a thermostable trehalose synthase from Thermus caldophilus

Purified trehalose synthase from Thermus caldophilus GK24 produced 18–86% trehalose from 10 mM–1 M maltose. The enzyme also catalyzed the conversion of ,-trehalose into maltose but did not act on other disaccharides. The yield of trehalose from maltose by this enzyme increased 30% more at 40°C than at 80°C and was independent of the substrate concentration. The maximum yield of ,-trehalose from 10 mM maltose reached 86% at 40°C. In addition, ,-trehalose was also formed from maltose or ,-trehalose at 3.5% yield at 80°C. © Rapid Science Ltd. 1998