不同水分条件下坚韧胶衣固氮活性对冻融的响应

坚韧胶衣Collema tenax是干旱和半干旱生态系统中生物土壤结皮的重要组分,其固氮作用对生态系统氮素循环具有重要影响。该地衣生长于温度和水分条件变化剧烈的土壤表面,但在我国北方其固氮活性对冻融的响应尚不清楚。采用乙炔还原法研究了坚韧胶衣固氮活性在不同水分条件下(湿冻组:地衣体含水量200%干重;干冻组:地衣体含水量20%干重)和4次冻融处理之间的差异。坚韧胶衣固氮活性为2,371.0-8,701.8nmolC2H4/m2·h,湿冻组固氮活性低于干冻组,对照组固氮活性最高,湿冻组和干冻组的固氮活性(对照的百分比)均与冻融次数呈显著的线性负相关关系(干冻组:R2=0.916,p0.001;湿冻组:R2=0.965,p0.001),但湿冻组的斜率绝对值(25.05)明显高于干冻组斜率绝对值(7.60)。结果表明低温对坚韧胶衣固氮活性具有显著抑制作用,干燥条件下坚韧胶衣固氮活性对于低温胁迫的敏感性比地衣体湿润条件下更低,这种较低的敏感性可能是该地衣对我国北方干燥和冷热变化剧烈的气候特点的生理适应策略。     

A multiple extraction--centrifugation method for the recovery of viruses from waste water treatment plant effluents and sludges

Absorption of 14C-labelled poliovirus-2 to sedimentable solids of primary sludge samples collected from a secondary treatment facility during a 6-month period averaged 94%; for anaerobically digested sludge, 99%. The extent of virus adsorption was influenced by the amount of solids. Maximal adsorption occurred at or above 0.5% solids with sludge diluted with deionized water and above 1.5% solids when diluted with the respective particle-free sludge supernatants. A Tris-HCl buffer containing NaCl, glycerol, and serum was found to efficiently elute poliovirus-2 from primary sludge solids. By means of re-extraction and concentration by centrifugation (the TEC procedure), the average recoveries of poliovirus-2 were 92-94% based upon either infectivity or radioactivity analyses. Similarly, recoveries were 90-92% for poliovirus-2 in digested sludge. Maximum elution was dependent upon all four TEC buffer components and the restriction of solids to less than or equal to 1.0%. The procedure was found to be more efficient than glycine-NaOH and Freon procedures or elution with beef embryo extract. As adapted for effluents the procedure increased the yield and improved the consistency of virus recovery. The arithmetic mean titers and obtained during a monitoring study for primary and digested sludge were 4.2 X 10(5) and 5.1 X 10(3) plaque-forming units (pfu)/L; for primary, secondary, and final effluents 2.3 X 10(5), 4.7 X 10(3), and 4.7 X 10(2) pfu/L, respectively.     

不同水分条件下两种叶状地衣的光合活性对冻融交替的响应

冻融交替是我国北方常见气候现象,其对地衣光合作用的影响尚不清楚。研究了采自雾灵山的卷叶点黄梅Flavopunctelia soredica和平盘软地卷Peltigera elisabethae的光合活性(以净光合速率表示,net photosynthetic rate,Pn)对冻融处理的响应及其与地衣体含水量(干冻组:含水量<20%干重;湿冻组:含水量>200%)和物种的关系。结果显示卷叶点黄梅的干冻组Pn经5次冻融后下降至对照的21%,湿冻组经3次冻融后下降至负值,平盘软地卷的干冻组和湿冻组在5次冻融后Pn均为负值;相对净光合速率(relative net photosynthetic rate,Rpn)与冻融次数的线性回归分析表明,卷叶点黄梅湿冻组的斜率绝对值(58.06)>平盘软地卷湿冻组(41.01)>平盘软地卷干冻组(32.27)>卷叶点黄梅干冻组(11.44)。结果表明冻融胁迫可显著抑制两种地衣的光合活性,这种抑制作用具有物种差异且和地衣体内水分含量有关:水分含量的增高将增强冻融胁迫对地衣光合活性的抑制作用;干燥状态下,卷叶点黄梅的低温耐性远高于平盘软地卷,但在湿润状态下则低于后者。两种地衣对冻融循环的光合响应的物种差异与其微生境气候有关:生长于较干燥开阔地带的卷叶点黄梅与生于阴湿生境中的平盘软地卷相比,可能已形成了更强的低温干燥适应能力,其低温湿润适应能力则较弱。全球气候变化可能会通过冻融事件的时空格局的改变而对地衣的光合作用和分布造成负面影响。     

Novel Chlamydiales strains isolated from a water treatment plant

Chlamydiae are obligate intracellular bacteria infecting free-living amoebae, vertebrates and some invertebrates. Novel members are regularly discovered, and there is accumulating evidence supporting a very important diversity of chlamydiae in the environment. In this study, we investigated the presence of chlamydiae in a drinking water treatment plant. Samples were used to inoculate Acanthamoeba monolayers ( Acanthamoeba co-culture), and to recover autochthonous amoebae onto non-nutritive agar. Chlamydiae were searched for by a pan-chlamydia 16S rRNA gene PCR from both Acanthamoeba co-cultures and autochthonous amoebae, and phylotypes determined by 16S rRNA gene sequencing. Autochthonous amoebae also were identified by 18S rRNA gene amplification and sequencing. From a total of 79 samples, we recovered eight chlamydial strains by Acanthamoeba co-culture, but only one of 28 amoebae harboured a chlamydia. Sequencing results and phylogenetic analysis showed our strains belonging to four distinct chlamydial lineages. Four strains, including the strain recovered within its natural host, belonged to the Parachlamydiaceae ; two closely related strains belonged to the Criblamydiaceae ; two distinct strains clustered with Rhabdochlamydia spp.; one strain clustered only with uncultured environmental clones. Our results confirmed the usefulness of amoeba co-culture to recover novel chlamydial strains from complex samples and demonstrated the huge diversity of chlamydiae in the environment, by identifying several new species including one representing the first strain of a new family.     

Ozone treatment of process water from a dry-mill ethanol plant

Fuel ethanol production in corn dry milling plants is a rapidly expanding industrial sector. Whole stillage, the residue from the distillation of the fermented corn, is centrifuged and the concentrate, thin stillage, is found to have a chemical oxygen demand (COD) of approximately 75,000 mg/L. This thin stillage is partly recycled, but much of it needs to be evaporated to concentrate the solubles for addition to the animal feed coproduct from corn dry milling. This research is an exploration into lowering COD from thin stillage using ozonation as a simple single-step unit process to facilitate a larger reusable fraction. The ozonation would usually be a pretreatment before additional flocculation or biological treatment. Also, COD removal by ozonation with and without a catalyst has been studied. Three different application rates of ozone O(3,1)=7 mg/min, O(3,2)=21 mg/min, and O(3,3)=33 mg/min were used for 8h into samples of 2L each of three dilutions 20x, 30x and 40x. COD removal of 85% was observed with an ozone dosage of 4000 mg/L into a 40x-diluted sample. This would correspond to about 0.5 mg COD removed per mg ozone dosed. However, at lower dosages and smaller dilutions, more than 1mg COD removal was achieved per mg ozone dosed. Two different catalysts, Fe(II) and Fe(III), were used and the samples were ozonated for 4 h. Five different dosages of each of the two catalysts were used and better COD removal was observed compared to ozonation alone with all 5 dosages. COD removal rate was increased from 45% to 74% with Fe(III) and was increased to 77% with Fe(II). Up to 10mg/L COD was removed per mg O(3) dosed well below the maximum dosage. Both the catalysts resulted in almost the same improved COD removal rates when compared to ozonation alone.     

Growth of phototrophic biofilms from limestone monuments under laboratory conditions

In the current study, five phototrophic biofilms from different Southern Europe limestone monuments were characterised by molecular techniques and cultivated under laboratory conditions. Phototrophic biofilms were collected from Orologio Tower in Martano (Italy), Santa Clara-a-Velha Monastery and Ajuda National Palace, both in Portugal, and Seville and Granada Cathedrals from Spain. The biofilms were grown under laboratory conditions and periodically sampled in order to monitor their evolution over a three-month period. Prokaryotic communities from natural samples and cultivated biofilms were monitored using denaturing gradient gel electrophoresis (DGGE) of PCR-amplified 16S rRNA gene fragments in conjunction with clone sequencing and phylogenetic analysis. DNA-based molecular analysis of 16S rRNA gene fragments from the natural green biofilms revealed complex and different communities composition with respect to phototrophic microorganisms. The biofilms from Orologio Tower (Martano, Italy) and Santa Clara-a-Velha Monastery (Coimbra, Portugal) were dominated by the microalga Chlorella. The cyanobacterium Chroococcidiopsis was the dominating genus from Ajuda National Palace biofilm (Lisbon, Portugal). The biofilms from Seville and Granada Cathedrals (Spain) were both dominated by the cyanobacterium Pleurocapsa. The DGGE analysis of the cultivated biofilms showed that the communities developed differently in terms of species establishment and community composition during the three-month incubation period. The biofilm culture from Coimbra (Portugal) showed a remarkable stability of the microbial components of the natural community in laboratory conditions. With this work, a multiple-species community assemblage was obtained for further stone colonisation experiments.     

Isolation of viruses from drinking water at the Point-Viau water treatment plant

Viruses were isolated from every sample of raw (100 L) and treated (1000 L) water collected at a water treatment plant drawing sewage-contaminated river water. Few plaque-forming isolates were formed but cytopathogenic viruses were isolated as frequently in drinking water as in raw water. In drinking water some samples contained more than 1 cytopathogenic unit per litre, but most contained 1-10/100 L. These viruses had not been inactivated or removed by prechlorination, flocculation, filtration, ozonation, and postchlorination. There were no coliforms present and a residual chlorine level had been maintained. Poliovirus type 1 was a frequent isolate but many isolates were nonpoliovirus. The presence of these viruses in drinking water raises questions about the efficacy of some water treatment processes to remove viruses from polluted water.     

Anaerobic treatment of low-strength municipal wastewater by a two-stage pilot plant under psychrophilic conditions

A two-stage anaerobic treatment pilot plant was tested for the treatment of raw domestic wastewater under temperatures ranging from 21 to 14 degrees C. The plant consisted of a hydrolytic upflow sludge bed (HUSB) digester (25.5m3) followed by an upflow anaerobic sludge blanket (UASB) digester (20.36m3). The hydraulic retention time (HRT) varied from 5.7 to 2.8h for the first stage (HUSB digester) and from 13.9 to 6.5h for the second stage (UASB digester). Total suspended solids (TSS), total chemical oxygen demand (TCOD), and biochemical oxygen demand (BOD) removals ranged from 76% to 89%, from 49% to 65%, and from 50% to 77%, respectively, for the overall system. The percentage of influent COD converted to methane was 36.1%, the hydrolysis of influent volatile suspended solids (VSS) reached 59.7% and excess biomass was 21.6% of the incoming VSS. Plant performance was influenced by the wastewater concentration and temperature, yet better results were obtained for influent COD higher than 250mg/l.     

Physiological and biochemical changes during the larval development of a brachyuran crab reared under constant conditions in the laboratory

Larvae of the spider crabHyas araneus were reared in the laboratory at constant conditions (12°C; 32‰S), and their feeding rate (F), oxygen consumption (R), nitrogen excretion (U), and growth were measured in regular intervals of time during development from hatching to metamorphosis. Growth was measured as dry weight (W), carbon (C), nitrogen (N), hydrogen (H) protein, and lipid. All these physiological and biochemical traits revealed significant changes both from instar to instar and during individual larval moult cycles. AverageF was low in the zoea I, reached a maximum in the zoea II, and decreased again in the megalopa. In the zoeal instars, it showed a bell-shaped pattern, with a maximum in the middle (zoea I) or during the first half of the moult cycle (zoea II). MaximumF in the megalopa was observed still earlier, during postmoult. Respiration (R) increased in the zoeal instars as a linear function of time, whereas it showed a sinusoidal pattern in the megalopa. These findings on variation inF andR during larval development confirm results obtained in previous studies onH. araneus and other decapod species. Excretion (U) was measured for the first time with a high temporal resolution in crab larvae. It showed in all three larval instars a bell-shaped variation pattern, with a maximum near the middle of the moult cycle, and significantly increasing average values from instar to instar. The atomicO/N ratio followed an inverse pattern, suggesting a maximum utilization of protein as a metabolic substrate during intermoult. Growth data from the present study and from a number of previous studies were compiled, showing consistency of growth patterns, but a considerable degree of variability between larvae from different hatches reared under identical conditions. The data show the following consistent tendencies: during the first part of each larval moult cycle (in postmoult, partly in intermoult), lipids are accumulated at a higher rate than protein, whereas an inverse growth patterns is typical of the later (premoult) stages. These two different growth phases are interpreted as periods dominated by reserve accumulation in the hepatopancreas, and epidermal growth and reconstruction (morphogenesis), respectively. Differences between individual larval instars in average biochemical composition and growth patterns may be related to different strategies: the zoeal instars and the early megalopa are pelagic feeding stages, accumulating energy reserves (principally lipids) necessary for the completion of larval development, whereas the later (premoult) megalopa is a semibenthic settling stage that converts a significant part of this energy to epidermal protein. The megalopa shifts in behaviour and energy partitioning from intense feeding activity and body growth to habitat selection and morphogenesis, preparing itself for metamorphosis, i.e. it shows an increasing degree of lecithotrophy. Data from numerous parallel elemental and biochemical analyses are compiled to show quantitative relationships betweenW, C, N, H, lipid, and protein. These regressions may be used as empirical conversion equations for estimates of single chemical components in larvalHyas araneus, and, possibly, other decapods.     

Occurrence of ammonia-oxidizing Archaea in activated sludges of a laboratory scale reactor and two wastewater treatment plants

Aims:  Characterization of the ammonia-oxidizing archaea (AOA) community in activated sludge from a nitrogen removal bioreactor and wastewater treatment plants (WWTPs).
Methods and Results:  Three primer sets specific for ammonia mono-oxygenase α -subunit ( amoA ) were used to construct clone libraries for activated sludge sample from a nitrogen removal bioreactor. One primer set resulted in strong nonspecific PCR products. The other two clone libraries retrieved both shared and unique AOA amoA sequences. One primer set was chosen to study the AOA communities of activated sludge samples from Shatin and Stanley WWTPs. In total, 18 AOA amoA sequences were recovered and compared to the previous reported sequences. A phylogenetic analysis indicated that sequences found in this study fell into three clusters.
Conclusions:  Different primers resulted in varied AOA communities from the same sample. The AOA found from Hong Kong WWTPs were closely similar to those from sediment and soil, but distinct from those from activated sludge in other places. A comparison of clone libraries between Shatin WWTP and bioreactor indicated the AOA community significantly shifted only after 30-day enrichment.
Significance and Impact of the Study:  This study confirmed the occurrence of AOA in a laboratory scale nitrogen removal bioreactor and Hong Kong WWTPs treating saline or freshwater wastewater. AOA communities found in this study were significantly different from those found in other places. To retrieve diverse AOA communities from environmental samples, a combination of different primers for the amoA gene is needed.     

Maintenance of previously uncultured freshwater archaea from anoxic waters under laboratory conditions

Culture conditions for the maintenance of previously uncultured members of the Archaea thriving in anoxic water layers of stratified freshwater lakes are described. The proposed enrichment conditions, based on the use of defined medium composition and the maintenance of anoxia, have been proven effective for the maintenance of the archaeal community with virtually no changes over time for periods up to 6 months as revealed by a PCR-DGGE analysis. Phylotypes belonging to groups poorly represented in culture collections such as the Deep-Sea Hydrothermal Vent Euryarchaeota (DHVE) and the Miscellaneous Crenarchaeotic Group (MCG) were maintained and selectively enriched when compared to the correspondent indigenous planktonic archaeal community.     

Solar disinfection of poliovirus and Acanthamoeba polyphaga cysts in water - a laboratory study using simulated sunlight

AIMS: To determine the efficacy of solar disinfection (SODIS) in disinfecting water contaminated with poliovirus and Acanthamoeba polyphaga cysts. METHODS AND RESULTS: Organisms were subjected to a simulated global solar irradiance of 850 Wm(-2) in water temperatures between 25 and 55 degrees C. SODIS at 25 degrees C totally inactivated poliovirus after 6-h exposure (reduction of 4.4 log units). No SODIS-induced reduction in A. polyphaga cyst viability was observed for sample temperatures below 45 degrees C. Total cyst inactivation was only observed after 6-h SODIS exposure at 50 degrees C (3.6 log unit reduction) and after 4 h at 55 degrees C (3.3 log unit reduction). CONCLUSIONS: SODIS is an effective means of disinfecting water contaminated with poliovirus and A. polyphaga cysts, provided water temperatures of 50-55 degrees C are attained in the latter case. SIGNIFICANCE AND IMPACT OF THE STUDY: This research presents the first SODIS inactivation curve for poliovirus and provides further evidence that batch SODIS provides effective protection against waterborne protozoan cysts.     

Conserving genetic variability of a wild insect population under laboratory conditions

Drosophila melanogaster (Meigen) was used to test the power of isofemale lines in preserving genetic variability. We performed experiments in two ways. One series consisted of measuring the genetic variability for three enzymatic loci in 32 isofemale lines, in the first and 23^rd generations of culture. In the second series, we tested the capacity of the larvae to eliminate a parasitoid by encapsulation after eight years of laboratory breeding. In general, individual isofemale lines appeared to change during the 23 generations of the study, but the global frequency of these alleles among the 32 isofemale lines stayed relatively unchanged. The only rare allele observed was also conserved. Changes in allozyme frequencies at any one locus were independent of those at other loci. Genetic variation of a biological trait, the capacity of the larvae to encapsulate a parasitoid, also changed, but it could be restored to a level close to that of the starting population by mass hybridizing together individuals of each line.

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Résumé D. melanogaster (Meigen) a été utilisé pour tester la capacité des lignées isofemelles à conserver la variabilité génétique d'une population naturelle. Deux types d'expériences ont été réalisées. L'une a consisté à déterminer la variabilité génétique de 3 locus enzymatiques pour 32 lignées isofemelles à la première et à la 23^ème génération d'élevage au laboratoire. L'autre a consisté à tester la capacité des larves à éliminer un parasito?de par le processus d'encapsulation après 8 années d'élevage au laboratoire. D'une fa?on générale, certaines lignées isofemelles perdent de la variabilité durant les 23 générations de l'étude. Mais la fréquence globale des allèles reste inchangée si l'on considère l'ensemble des 32 lignées. Le seul allèle rare observé a également été conservé. Les modifications des fréquences allèliques à chacun des locus ont lieu de fa?on indépendante les unes des autres. La variabilité génétique d'un caractère biologique, la capacité des larves à encapsuler le parasito?de, a également varié, mais elle a pu être restaurée à un niveau proche de la population initiale en rassemblant plusieurs individus de chacune des lignées.

     

Survivorship characteristics of the mosquito Aedes caspius adults from southern France under laboratory conditions

The survivorship characteristics of two populations of Aedes caspius (Pallas) (Diptera: Culicidae) were compared in the laboratory. One population was sourced from Mourgues, where larvicides have been used continuously for approximately 40 years, and the other from Pont de Gau, where there has been no consistent mosquito control. The aims of the study were to ascertain the basic life history profiles of adults and to determine whether continuous larviciding affects inherent adult survivorship. Life tables were constructed to calculate the following life expectancy parameters: mean lifetime (tau(ad)); maximum lifetime (tau(max)), and daily survival rate (p(ad)). All three parameters were higher for females than for males (paired t-test, P < or = 0.001); male mean lifetime, maximum lifetime and daily survival rate were 4.95 +/- 0.94 days, 20.50 +/- 6.66 days and 0.79 +/- 0.05, respectively; female values were 14.74 +/- 3.68 days, 49.69 +/- 16.55 days and 0.93 +/- 0.02, respectively. No differences were found between the two populations, and no correlations were found between initial adult densities and their respective survival rates. The survivorship curves for Ae. caspius were type IV for males (mortality rates higher for young adults) and type III for females (mortality rates constant).     

Performance evaluation of a 1 m modified, fixed-dome Deenbandhu biogas plant under hilly conditions

The performance of a 1 m³ daily gas-production-capacity, modified, Deenbandhu biogas plant was evaluated under hilly conditions. The modified plant had a digester volume of 2·65 m³ with 55 days hydraulic retention time (HRT) as against a volume of 2·45 m³ with 50·96 days HRT of the Action for Food Production (AFPRO) design. All the constructional items used in the modified plant were in accordance with the recommendations of AFPRO except the number of bricks, i.e. 625 in the modified design as against 800 in the AFPRO design. The rates of biogas production in October 1993 and January 1994 were 0·0357 and 0·0282 m³/kg feed (wet weight of dung); respectively. Thus the modified plant had a gas production efficiency of 70·5–89·4% of its rated capacity. All other functional parameters were within the optimum limits recommended for successful operation of any anaerobic digester.     

Secretion of phytase from the roots of several plant species under phosphorus-deficient conditions

Phosphorus (P) deficiency increased the secretion of phytases from roots of various plant species. The secretory phytases were collected with a dialysis membrane tube for 24 hours from roots of sixteen plant species grown with low or adequate supply of P in nutrient solutions. The activity of not only secretory phytase, but also acid phosphatase, increased with the low P treatment in all of the plant species examined. Secretion of phytase by the roots under P-deficient conditions was highest in Brachiaria decumbens CIAT 606, Stylosanthes guianensis CIAT 184 and tomato, moderate in Brachiaria brizantha CIAT6780, Stylosanthes guianensis CIAT 2950, alfalfa, white clover and orchard grass, and lowest in Andropgon gayanus CIAT 621, Stylosanthes capitata CIAT 10280, upland rice, timothy, redtop, alsike clover, red clover and white lupin plants. An immunoreactive protein band that reacted with a polyclonal antibody raised against wheat bran phytase, corresponding to molecular weight 35–40 kD, could be detected in seven of the species tested. These results indicate that the secretory phytase may provide an efficient mechanism for certain plants to utilize inositol hexaphosphate in soil.     

Energy balance of a plant under normal and unfavourable conditions

Two main components of plant energy balance are analyzed--photosynthesis and dark respiration. Different plant species, growing in optimal conditions and differing in photosynthetic metabolism, productivity and potential resistance to stress, have constant ratio between total dark respiration and grossphotosynthesis. The ratio about 38-40% at the phase of active growth. This value reflect plant state, when income (assimilation) is maximized, and expense (total oxidation) is minimized. Intensities of dark respiration of plants in darkness and light are similar despite the fact that the plants have considerable differences: 1) different carbon sources--young assimilates in light and reserve ones in the dark; 2) biochemical modifications (or inhibition) of some stages of dark respiration in light; 3) intensification of alternative respiration in unfavourable conditions differing in dark and light variants. Ratio between intensity of dark respiration and photosynthesis increases in plants growing in unfavourable conditions. This increase is more considerable in plants that are less resistant to the given stress. Characters of energy balance can be used for estimation of physiological status of plants, prediction of resistance and potential productivity at seedling stage.