Activity and Thermostability of Acid Phosphatase in Amoebae Amoeba proteus Cultured at Different Temperatures

Activity and thermostability of total, tartrate-resistant (TR), and tartrate-sensitive (TS) acid phosphatases (APh) was determined by spectrophotometric and electrophoretic methods, using 1-naphtyl phosphate (1-NPh) as substrate in supernatant of homogenates of amoebae Amoeba proteus acclimated to 10 and 25°C. A decrease of the APh activity in the pH range from 3.5 to 5.8 is revealed in the amoebae cultured at 10°C (cold) in comparison with the cells cultured at 25°C (warm). The activity and thermostability both of total APh detected at pH 4.0 and of TS-APh detected at pH 5.5 are lower in cold amoebae, than in warm cells, while the activity and the heat resistance of TR-APh (pH 4.0) are identical at both temperatures of cultivation of the amoebae. Thus, acclimation of amoebae to cold is accompanied by a decrease of the activity and of the heat resistance of TS-APh. A decrease of the activity and the thermostability of this APh in cold amoebae correlate with a decrease of their primary cellular thermostability and phagocytic activity.     

Narrow- and Broad-Host-Range Symbiotic Plasmids of Rhizobium spp. Strains That Nodulate Phaseolus vulgaris

Agrobacterium transconjugants containing symbiotic plasmids from different Rhizobium spp. strains that nodulate Phaseolus vulgaris were obtained. All transconjugants conserved the parental nodulation host range. Symbiotic (Sym) plasmids of Rhizobium strains isolated originally from P. vulgaris nodules, which had a broad nodulation host range, and single-copy nitrogenase genes conferred a Fix⁺ phenotype to the Agrobacterium transconjugants. A Fix⁻ phenotype was obtained with Sym plasmids of strains isolated from P. vulgaris nodules that had a narrow host range and reiterated nif genes, as well as with Sym plasmids of strains isolated from other legumes that presented single nif genes and a broad nodulation host range. This indicates that different types of Sym plasmids can confer the ability to establish an effective symbiosis with P. vulgaris.     

不同光温条件下紫背浮萍叶肉细胞和叶绿体超微结构的研究

以浮萍科紫萍属紫背浮萍为试验材料,利用透射电子显微镜研究了紫背浮萍叶肉细胞和叶绿体的超微结构。结果发现:强光下,紫背浮萍叶肉细胞内的叶绿体数明显增加;弱光时虽然叶绿体数减少,但叶绿体基粒片层结构变厚,增加了光合作用反应面积。与25℃适温条件相比,10℃低温和35℃高温下,紫背浮萍细胞均出现一定程度的逆境胁迫作用。表现在低温时部分叶绿体皱缩成带状,叶肉细胞之间出现较大空隙;高温时叶绿体外膜溶解,基质外渗,脂质小球数量增多。紫背浮萍通过改变细胞内部形态结构的方式来适应不同光强和温度环境条件,对逆境光温条件具有一定的耐受性。     

Acute Toxicity of Arsenic under Different Temperatures and Salinity Conditions on the White Shrimp Litopenaeus vannamei

The aim of this study was to determine acute toxicity in the post larvae of the white shrimp Litopenaeus vannamei after 96 h of exposure to dissolved arsenic under three different temperatures and salinity conditions. Recent reports have shown an increase in the presence of this metalloid in coastal waters, estuaries, and lagoons along the Mexican coast. The white shrimp stands out for its adaptability to temperature and salinity changes and for being the main product for many commercial fisheries; it has the highest volume of oceanic capture and production in Mexican shrimp farms. Lethal concentrations (LC₅₀–96 h) were obtained at nine different combinations (3?×?3 combinations in total) of temperature (20, 25, and 30 °C) and salinity (17, 25, and 33) showing mean LC₅₀–96 h values (±standard error) of 9.13?±?0.76, 9.17?±?0.56, and 6.23?±?0.57 mgAs?L^?1(at 20 °C and 17, 25, and 33 salinity); 12.29?±?2.09, 8.70?±?0.82, and 8.03?±?0.59 mgAs?L^?1 (at 25 °C and 17, 25, and 33 salinity); and 7.84?±?1.30, 8.49?±?1.40, and 7.54?±?0.51 mgAs?L^?1 (at 30 °C and 17, 25, and 33 salinity), respectively. No significant differences were observed for the optimal temperature and isosmotic point of maintenance (25 °C–S 25) for the species, with respect to the other experimental conditions tested, except for at 20 °C–S 33, which was the most toxic. Toxicity under 20 °C–S 33 conditions was also higher than 25 °C–S 17 and 20 °C (S 17 or 25). The least toxic condition was 25 °C–S 17. All this suggests that the toxic effect of arsenic is not affected by temperature changes; it depends on the osmoregulatory pattern developed by the shrimp, either hyperosmotic at low salinity or hiposmotic at high salinity, as observed at least on the extreme salinity conditions here tested (17 and 33). However, further studies testing salinities near the isosmotic point (between 20 and 30 salinities) are needed to clarify these mechanisms.     

不同光照和营养条件下两种不同寿命热带先锋种的对比研究

探讨了热带次生演替早期阶段短命先锋种山黄麻(Trema tomentosa)和长命先锋种中平树(Macaranga denticulata)在两种光照(4%和20%的全光照)和营养梯度(低肥和高肥)下,叶片和细根营养物质含量、非结构性碳水化合物含量、生物量分配模式以及形态结构特征的差异.结果表明:(1)两种先锋种叶片和细根氮、磷含量随着光照和营养的增强显著上升,并且山黄麻叶片和细根氮、磷含量要显著高于中平树.(2)山黄麻各器官淀粉和总非结构性碳水化合物(TNC)浓度在高光下低于中平树,但在低光下高于中平树.(3)山黄麻和中平树的叶片都是可溶性糖的主要存储器官,而淀粉和TNC则主要储存在根中,并且淀粉都是二者TNC库最主要的组成形态和成分.(4)山黄麻拥有更高的根生物量比、细根生物量比、根冠比、比叶面积、叶面积比、比细根长、比细根表面积及更小的细根直径等更强大的资源捕获能力的结构和生物量分配特征.总之,与长命先锋种中平树相比,短命先锋种山黄麻有着更适合快速生长的结构和生物量分配特征、更高的组织营养物质含量、更低的非结构性碳水化合物浓度,因而具有更高的生长速率,能够在次生演替的早期阶段占领统治地位,为以后的次生演替创造条件.     

Effect of Gibberellic Acid on Dark and Light Germination at Different Temperatures of Calluna, Ledum andRhododendron Seeds

The aim of the experiments was to study the effects of gibberellic acid (GAs) on the germination of Calluna vulgaris L., Ledum palustre L. and Rhododendron lapponicum (L.) Wahlenb. seeds under different environmental conditions. Under continuous light from white fluorescense tubes (3000 lux), untreated seeds of Calluna were partly dormant at all temperatures studied (9, 15, 21, 27, 27/9, 8/16 hours). Percentage of dormant seeds increased, however, with decreasing temperature, and it varied also from seed lot to seed lot. Untreated seeds of Ledum were dormant in light at 9° and 15°C but not at higher temperatures. Untreated seeds of Rhododendron were completely dormant in light at temperatures from 13° to 24°C. Seeds of all species were completely dormant in darkness both at 15° and 27°C. GA₃ stimulated greatly the germination of all species under all studied environmental conditions. The used concentrations (0.2–3.2 mM) gave nearly 100% germination in most cases. At 9°C the dormancy in some seed lots of Calluna and Ledum was only partly broken by the used concentrations of GA₃.     

不同温度处理对虎耳草叶片气体交换及叶肉结构的影响

在人工气候箱中对盆栽虎耳草进行处理,测定不同温度条件下虎耳草叶片光合特征、叶绿素含量、抗氧化酶活性、叶肉结构等生理形态指标。结果表明：低温处理后,虎耳草叶片净光合速率、气孔导度下降迅速,叶绿素含量最少,SOD、CAT活性最低,MDA含量最高,栅栏组织排列更紧密,移置正常温度下,光合速率能在短时间内恢复;高温处理的净光合速率下降速度不及低温处理,但叶片海绵组织显著增加,光合速率恢复较慢。     

Light Effects in Yeast: Evidence for Participation of Cytochromes in Photoinhibition of Growth and Transport in Saccharomyces cerevisiae Cultured at Low Temperatures

Visible light of moderate intensity inhibits growth, respiration, protein synthesis, and membrane transport in bakers' yeast and has a deleterious effect on membrane integrity. The results of this study indicate that these effects require the presence of cytochromes b and a/a(3). The light sensitivities of growth rate and [(14)C]histidine uptake in wild-type rho(+) Y185 and D225-5A strains of Saccharomyces cerevisiae were compared with those in a variety of mutants lacking cytochrome b or a/a(3) or both; a close correlation was found between the presence of these respiratory pigments and photosensitivity. Thus, strain TL5-3C, a nuclear petite lacking cytochromes b, a, and a(3), was resistant to light; strain GL5-6A, another nuclear petite having reduced amounts of cytochromes a and a(3), was partially resistant; strains MB127-20C and MB1-6C, nuclear petites lacking only cytochrome b, were also only partially resistant to light; whereas mutants containing all three cytochromes but having their respiratory chain either nonfunctional (strain ZK3-6B) or uncoupled (strain 18-27/t12) were fully sensitive to light. Finally, an equal-energy, broad-band action spectrum for the light inhibition of growth and transport indicated that blue light (408 nm) was most effective; these wavelengths correspond to the Soret region of the cytochrome absorption spectrum. The results suggest, therefore, that the yeast cytochromes b, a, and a(3) are the primary photoreceptors for the inhibitory effects of light and, perhaps, for other processes, such as the entrainment of biological rhythms in this species.     

Metabolomic Profiling and Lipid Composition of Arctic and Antarctic Strains of Micromycetes Geomyces pannorum and Thelebolus microsporus Grown at Different Temperatures

Microbiology - Adaptive reactions of Arctic and Antarctic strains of psychrophilic micromycetes Geomyces pannorum and Thelebolus microsporus to growth within a broad temperature range were studied....     

SERS Properties of Different Sized and Shaped Gold Nanoparticles Biosynthesized under Different Environmental Conditions by Neurospora crassa Extract

Surface-enhanced Raman scattering (SERS) is a surface-sensitive technique that enhances Raman scattering by molecules adsorbed on rough metal surfaces. It is known that metal nanoparticles, especially gold and silver nanoparticles, exhibit great SERS properties, which make them very attractive for the development of biosensors and biocatalysts. On the other hand, the development of ecofriendly methods for the synthesis of metallic nanostructures has become the focus of research in several countries, and many microorganisms and plants have already been used to biosynthesize metallic nanostructures. However, the majority of these are pathogenic to plants or humans. Here, we report gold nanoparticles with good SERS properties, biosynthesized by Neurospora crassa extract under different environmental conditions, increasing Raman signals up to 40 times using methylene blue as a target molecule. Incubation of tetrachloroauric acid solution with the fungal extract at 60°C and a pH value of a) 3, b) 5.5, and c) 10 resulted in the formation of gold nanoparticles of a) different shapes like triangles, hexagons, pentagons etc. in a broad size range of about 10-200 nm, b) mostly quasi-spheres with some different shapes in a main size range of 6-23 nm, and c) only quasi-spheres of 3-12 nm. Analyses included TEM, HRTEM, and EDS in order to corroborate the shape and the elemental character of the gold nanoparticles, respectively. The results presented here show that these ‘green’ synthesized gold nanoparticles might have potential applicability in the field of biological sensing.     

Levels of (+/-) Abscisic Acid and Xanthoxin in Spinach under Different Environmental Conditions

Kinetin-induced changes in dry weight, soluble protein content, δ-aminolevulinic acid dehydratase activity, and chlorophyll content of two clones of Nicotiana tabacum L. callus were studied. Kinetin brought about a marked increase in the δ-aminolevulinic acid dehydratase activity of nongreen tissue just before induction of greening. The experimental data suggested a possible induction of specific chloroplast protein(s) during the kinetin-induced greening of nongreen tobacco tissue. Kinetin caused a decline in the δ-aminolevulinic acid dehydratase activity and chlorophyll content of the green callus used in the present study.     

Polygalacturonase, Pectate Lyase and Pectin Methylesterase Activity in Pathogenic Strains of Phytophthora capsici Incubated under Different Conditions

Pectolytic enzymes are found mainly in fungi and bacteria. The most widely occurring enzymes are polygalacturonase (PGs), pectin methylesterase (PMEs) and pectate lyase (PLs) produced during the infection process and during culturing. The secretion of these enzymes results in the disorganization of the plant cell walls, which is responsible for the pathogenicity of the pathogens. These enzymes degrade the pectin of plants causing maceration of plant tissues and the enzyme activity increases under favourable environmental conditions. We have found that Phytophthora capsici , a pathogenic oomycete, produces levels of these three enzymes equal to those produced by soft-rotting Erwinia chrysanthemi . The activity of PGs, PLs and PMEs was investigated at the optimum temperature, pH and ionic strength in highly pathogenic P. capsici strains cultivated in two kinds of liquid medium containing either crude pepper extracts plus pectin or pectin as the carbon source. Virulence tests and enzymes activity showed that there was a high correlation between the enzyme activity and the pathogenicity of P. capsici . The effects of different carbon sources on the enzyme activity showed that pepper extract plus pectin was the best source for the carbon source.     

虎耳草不同光温条件下光合特性及有效成分含量的相关性分析

对盆栽的虎耳草进行不同光照和温度处理,测定其叶片光合特性及重要有效成分,分析虎耳草有效成分与光合速率的相关性。结果表明：虎耳草光合速率在透光率50%的条件下最高,透光率100%下最低;100%光照下的岩白菜素和没食子酸的含量最高。光合速率在20℃/16℃（12 h昼/12 h夜）适温下最高,此时岩白菜素和没食子酸的含量也最高。相关性分析表明,温度处理条件下的岩白菜素和没食子酸含量与光合速率、气孔张开面积等呈正相关,其中没食子酸含量与光合速率及蒸腾速率的正相关达极显著;不同光照条件下,没食子酸含量与光合有效辐射呈显著正相关。     

Optimum Initial Inoculum Levels for Evaluation of Resistance in Tomato to Meloidogyne spp. at Two Different Soil Temperatures

The effects of Meloidogyne incognita or M. javanica at five initial inoculum levels of 20, 100, 200, 1,000, and 2,000 eggs and infective juveniles per seedling on ''Floradade,'' ''Nemarex,'' ''Patriot,'' and ''PI 129149-2(sib)-5'' tomatoes maintained at 25 or 32.5 C were studied. The number of egg masses on roots of the susceptible cultivar Floradade was similar for both species of root-knot nematodes at either 2.5 or 32.5 C soil temperatures. At 25 C, very low numbers of egg masses were produced by both species of root-knot nematodes on Nematex, Patriot, and Lycopersicon peruvianum PI 129149-2(sib)-5. At 32.5 C, the best inoculum level for assessing resistance in these tomato genotypes was 200 eggs and infective juveniles per seedling. With 28 days of incubation, this temperature and inoculum level produced quantitative differences in resistance for both species of Meloidogyne.     

Regulatory Effect of Exogenous Vasopressinon Autonomous Functions and Higher Nervous Activity in Hedgehogs Erinateus auritus under Conditions of High Environmental Temperatures

The role of vasopressin (arginine–vasopressin) in animal adaptation to the effect of high environmental temperatures as well as a possibility to prevent development of thermal stress by use of vasopressin was studied under conditions of chronic experiments in hedgehogs. The experiments were carried out on a model of feeding behavior with objective recording of motor and autonomous components of the higher nervous activity and body temperature as well as the basal gas exchange. It is established that exposure of hedgehogs to a heat chamber at 40°C for 35 min is accompanied by a disturbance of autonomous functions and suppression of conditional reflex activity of the brain. The body temperature and oxygen consumption rise considerably on the background of the heat exposure. A preliminary injection of vasopressin at low dosages was found to prevent functional disorders and disturbances of the higher nervous activity in the hedgehogs exposed to high temperatures and to promote a better adaptation to heat exposure. The question of vasopressin as a specific antipyretic agent and of its possible clinical use is discussed.     

Cell Cycle Dynamics of Cultured Coral Endosymbiotic Microalgae (Symbiodinium) Across Different Types (Species) Under Alternate Light and Temperature Conditions

Dinoflagellates of the genus Symbiodinium live in symbiosis with many invertebrates, including reef‐building corals. Hosts maintain this symbiosis through continuous regulation of Symbiodinium cell density via expulsion and degradation (postmitotic) and/or constraining cell growth and division through manipulation of the symbiont cell cycle (premitotic). Importance of premitotic regulation is unknown since little data exists on cell cycles for the immense genetic diversity of Symbiodinium. We therefore examined cell cycle progression for several distinct SymbiodiniumITS2‐types (B1, C1, D1a). All types exhibited typical microalgal cell cycle progression, G₁ phase through to S phase during the light period, and S phase to G₂/M phase during the dark period. However, the proportion of cells in these phases differed between strains and reflected differences in growth rates. Undivided larger cells with 3n DNA content were observed especially in type D1a, which exhibited a distinct cell cycle pattern. We further compared cell cycle patterns under different growth light intensities and thermal regimes. Whilst light intensity did not affect cell cycle patterns, heat stress inhibited cell cycle progression and arrested all strains in G₁ phase. We discuss the importance of understanding Symbiodinium functional diversity and how our findings apply to clarify stability of host‐Symbiodinium symbioses.     

Growth of Octopine-Catabolizing Pseudomonas spp. under Octopine Limitation in Chemostats and Their Potential To Compete with Agrobacterium tumefaciens

The growth characteristics of five octopine-catabolizing pseudomonads have been determined in batch and continuous cultures. All five strains belonged to rRNA homology group I and showed a more psychrotrophic growth pattern than did Agrobacterium tumefaciens B6 and ATCC 15955. In chemostats limited by octopine, either as the source of carbon and nitrogen or the sole source of nitrogen, maximum specific growth rates and substrate affinities were lower than those in chemostats limited by glutamate. These growth dynamics were similar to those observed for Agrobacterium strains B6 and ATCC 15955 even though the catabolic genes and pathways are believed to be different in the two genera. An analysis of the yields in octopine-limited chemostats indicated that the use of octopine as the sole source of carbon and nitrogen was grossly inefficient. Octopine and presumably lysopine and octopinic acid provided a better source of nitrogen than of carbon. One of the Pseudomonas fluorescens strains, E175D, was able to produce its highest yield on octopine as a nitrogen source. Competition models formulated on pure culture parameters indicated that two of the Pseudomonas spp. would dominate A. tumefaciens B6 and ATCC 15955 when in simple competition for octopine as a limiting substrate.     

不同光强下红松幼树光合作用和营养物质含量的季节模式

一、前言原始红松林下幼树生长缓慢,死亡率高,若干文献通过与桦木林光照和水热条件的对比观察,认为光是影响生长的主要原因。但同时也发现,在植物一切代谢活动最旺盛的生长季(6—9月),上述二种林下的光强(lx)