Isolation and characterization of Dehalococcoides sp. strain FL2, a trichloroethene (TCE)- and 1,2-dichloroethene-respiring anaerobe

A strictly anaerobic bacterium was isolated from tetrachloroethene (PCE)-to-ethene dechlorinating microcosms established with river sediment without prior exposure to chlorinated solvents. The isolation procedure included the addition of 2-bromoethanesulfonate to select against methanogenic archaea, >50 consecutive 1-2% (v/v) transfers to reduced mineral salts medium amended with trichloroethene (TCE), acetate, and hydrogen, the addition of ampicillin, and the dilution-to-extinction principle. Culture-dependent and 16S rRNA gene-targeted approaches suggested culture purity. Microscopic examination revealed a homogeneous culture of an organism with a distinct, disc-shaped morphology. The isolate shared >99% 16S rRNA gene sequence similarity with members of the Pinellas group of the Dehalococcoides cluster, and was designated Dehalococcoides sp. strain FL2. Strain FL2 could be propagated with TCE, cis-1,2-dichloroethene (cis-DCE), or trans-DCE as the electron acceptors, acetate as the carbon source, and hydrogen as the electron donor in defined, completely synthetic medium. No other growth-supporting redox couples were identified. Trichloroethene, cis-DCE and trans-DCE were dechlorinated at rates of 27.5, 30.4 and 18.8 micromol l-1 day-1 respectively. Quantitative real-time polymerase chain reaction (PCR) with a fluorescently labelled linear hybridization probe confirmed growth with these electron acceptors, and suggested that strain FL2 captures energy from both the TCE-to-cis-DCE and 1,2-DCE-to-VC dechlorination steps. Tetrachloroethene and vinyl chloride (VC) were slowly and cometabolically dechlorinated in the presence of a growth-supporting chloroethene, but ethene formation was incomplete, even after prolonged incubation. At room temperature, strain FL2 grew with a doubling time of 2.4 days, and yielded 166.1+/-10.2 mg of protein per mole of chloride released. In the presence of excess electron acceptor, strain FL2 consumed hydrogen to a concentration of 0.061+/-0.016 nM. Dechlorination ceased following the addition of 0.5 mM sulfite, whereas sulfate (10 mM) and nitrate (5 mM) had no inhibitory effects.     

电子受体和光照对土壤CH4排放相关微生物功能基因丰度的影响

为探究光照条件下添加不同电子受体对土壤甲烷排放的影响及微生物的响应,本研究在土壤中添加3种电子受体(Fe3+、NO3-、SO42-)共设计8个处理,即黑暗+ Fe3+(DF)、黑暗+NO3-(DN)、黑暗+SO42-(DS)、黑暗+蒸馏水(DCK)、光照+Fe3+(LF)、光照+NO3-(LN)、光照+SO42-(LS...     

Landscape effects on large scale abundance patterns of turtle doves Streptopelia turtur in Portugal

The European turtle dove is both a highly valued game species and a species of conservation concern, which is declining due probably to a combination of habitat degradation and unsustainable hunting. Although declines seem to be less severe in the Mediterranean region, it remains uncertain the extent to which ongoing land use changes will negatively affect this species. This study examined this issue, by estimating the effects of landscape composition on the broad scale abundance pattern of breeding turtle doves in continental Portugal. Turtle doves were surveyed in the breeding seasons of 2002 and 2003, from 3160 point counts spaced at about 1-km intervals along 158 transects of about 20 km, evenly covering the country. The frequency of occurrence of turtle doves at each transect was used as a proxy of species abundance, and related using GAM modelling to 21 variables describing land cover and woody linear features (e.g., hedgerows and riparian galleries). Turtle doves were most abundant in north- and central-eastern Portugal, with high abundances also recorded in the regions around Lisbon and along the Guadiana valley. Abundances were positively related to forest cover, particularly by broadleaved forests and by pine stands without woody understory, to cover by permanent crops, and to the density of woody linear habitats. Results suggest that conservation of Mediterranean turtle doves requires policies and management strategies reversing the pervasive trends of forest management neglect and agricultural abandonment, while preserving hedgerows and riparian galleries in more intensive agricultural landscapes.     

Herbivory: effects on plant abundance, distribution and population growth

Plants are attacked by many different consumers. A critical question is how often, and under what conditions, common reductions in growth, fecundity or even survival that occur due to herbivory translate to meaningful impacts on abundance, distribution or dynamics of plant populations. Here, we review population-level studies of the effects of consumers on plant dynamics and evaluate: (i) whether particular consumers have predictably more or less influence on plant abundance, (ii) whether particular plant life-history types are predictably more vulnerable to herbivory at the population level, (iii) whether the strength of plant-consumer interactions shifts predictably across environmental gradients and (iv) the role of consumers in influencing plant distributional limits. Existing studies demonstrate numerous examples of consumers limiting local plant abundance and distribution. We found larger effects of consumers on grassland than woodland forbs, stronger effects of herbivory in areas with high versus low disturbance, but no systematic or unambiguous differences in the impact of consumers based on plant life-history or herbivore feeding mode. However, our ability to evaluate these and other patterns is limited by the small (but growing) number of studies in this area. As an impetus for further study, we review strengths and challenges of population-level studies, such as interpreting net impacts of consumers in the presence of density dependence and seed bank dynamics.     

Strong positive effects of termites on savanna bird abundance and diversity are amplified by large herbivore exclusion

Vast areas of the African savanna landscapes are characterized by tree‐covered Macrotermes termite mounds embedded within a relatively open savanna matrix. In concert with termites, large herbivores are important determinants of savanna woody vegetation cover. The relative cover of woody species has considerable effects on savanna function. Despite the potentially important ecological relationships between termite mounds, woody plants, large herbivores, and birds, these associations have previously received surprisingly little attention. We experimentally studied the effects of termites and large herbivores on the avian community in Lake Mburo National Park, Uganda, where woody vegetation is essentially limited to termite mounds. Our experiment comprised of four treatments in nine replicates; unfenced termite mounds, fenced mounds (excluding large mammals), unfenced adjacent savanna, and fenced savanna. We recorded species identity, abundance, and behavior of all birds observed on these plots over a two‐month period, from late dry until wet season. Birds used termite mounds almost exclusively, with only 3.5% of observations occurring in the treeless intermound savanna matrix. Mean abundance and species richness of birds doubled on fenced (large herbivores excluded) compared to unfenced mounds. Feeding behavior increased when large mammals were excluded from mounds, both in absolute number of observed individuals, and relative to other behaviors. This study documents the fundamental positive impact of Macrotermes termites on bird abundance and diversity in an African savanna. Birds play crucial functional roles in savanna ecosystems, for example, by dispersing fruits or regulating herbivorous insect populations. Thus, the role of birds in savanna dynamics depends on the distribution and abundance of termite mounds.     

Productivity and abundance of large sponge populations on Flinders Reef flats,Coral Sea

Large populations of flattened sponges with cyanobacterial symbionts were observed on the shallow reef-flats of the Flinders Reefs, Coral Sea. Estimates of these populations indicated as many as 60 individuals with a total wet biomass of 1.2 kg per m² in some areas. Along a metre wide transect across 1.3 km of reef flat the population was estimated at 530 kg wet weight sponge (mean 411 g m^-2). The four prominent species had instantaneous P/R ratios between 1.3 and 1.8 at optimum light such that photosynthetic productivity was calculated to provide between 61 and 80% of sponge energy requirements in summer and 48 to 64% in winter. While such sponge beds are a prominent feature of these reefs, they appear to contribute less than 10% of gross reef-flat productivity.Contribution no. 352 from the Australian Institute of Marine Science     

Beneficial effects of alternate dietary regimen on liver inflammation, atherosclerosis and renal activation

Background

Alternate day calorie restriction (CR) has been shown to be almost as beneficial as daily CR. The question arises whether this concept is also applicable to alternating dietary composition.

Objective

To seek evidence that alternating high cholesterol (HC) - cholesterol-free (CON) Western diet can effectively diminish hepatic and renal inflammation and cardiovascular risk factors as compared with daily HC-supplemented Western diet.

Design

Four groups of ApoE*3Leiden mice, a humanized model for atherosclerosis, were subjected to different feeding treatments for 16 weeks. Mice were fed CON diet; CON diet with 1% w/w cholesterol (HC); alternate (ALT) diet regimen of CON (4 days) and HC (3 days); or CON diet supplemented with 0.43% (w/w) cholesterol (MC), with overall dietary cholesterol intake equal to ALT. Plasma was analyzed for cardiovascular risk factors, aorta for atherosclerotic lesion formation, and liver and kidney for inflammation.

Results

ALT diet but not MC was almost as effective as daily CON feeding in preventing disease development. Compared to HC, the ALT group showed 62% lower hepatic nuclear factor kappa B (NF-κB) activity (P<0.001), a reduction of the circulating inflammatory markers E-selectin (−20%; P<0.05), vascular cell adhesion molecule 1 (VCAM-1; −15%; P<0.05) and Serum Amyloid A (SAA; −31%; P<0.05), smaller atherosclerotic lesion sizes (−51%; 46497±10791 µm² vs. 94664±16470 µm²; P<0.05) and diminished renal expression of specific inflammation and activation markers (VCAM-1, −27%; P<0.05; monocyte chemotactic protein-1 (MCP-1); −37%; P<0.01).

Conclusion

Alternate HC-CON feeding reproduced most of the beneficial effects of daily cholesterol-free diet, including strongly diminished hepatic, vascular and renal activation and inflammation; also atherosclerosis was reduced by half as compared to HC, albeit still higher compared to the CON group.     

Relative influence of temperature and electron donor and electron acceptor concentrations on bacterial sulfate reduction in saltmarsh sediment

The relative importance of three environmental variables known to influence the rate of bacterial sulfate reduction was examined using sediment from a saltmarsh pan. The variables investigated were temperature, electron donor concentration, and electron acceptor concentration. Their relative influence on the rate of bacterial sulfate reduction was examined with multiple replicate sediment samples in which the variables were experimentally adjusted. Sulfate reduction rates were measured with³⁵SO ₄ ^2– .The relative importance of each variable to sulfate reduction rate was assessed with multiple regression analysis by calculating the standardized partial regression coefficients, and the results were compared with the ranges of the three variables encountered in the natural sediment. Temperature proved to have the greatest influence, followed by electron donor and electron acceptor concentrations, in that order. The sulfate concentration was shown to have little influence on sulfate reduction rate at seawater concentrations of sulfate, but its effect increased if sulfate concentrations were diminished compared to those of seawater.     

Models for scopolamine,atropine and amphetamine effects on an alternate bar pressing paradigm

A hypothetical neural network is presented to account for errors made by food-deprived albino-rats in a bar-pressing situation (Carlton, 1964). The rats were required to press alternately on two bars in order to activate a device that releases milk to them. When-ever an animal pressed consecutively on the same bar, no milk was released and the animal was scored as having committed an error. In the first part of the paper, a time-independent neural network, part of which is equivalent to the psychophysical discrimination network of H. D. Landahl (1938), is used to interpret the effects on the animals’ performances of the drugs amphetamine, scopolamine and atropine. Suggestions for further experiments are made on the basis of the initial form to the model. In the second part of the paper, certain parameters of the initial form of the model are assumed to be time-dependent and a further generalization occurs through the introduction of the interresponse time distribution. It is shown that, under specified conditions, the second form of the model reduces to the first. The time-dependent form of the model allows certain features to be discussed that could not be discussed in the time-independent form [e.g. P. Dew’s (1961) notion of a possible mode of action for a variety of the behavioral effects of amphetamine]. Furthermore, experiments of an essentially different type from those discussed in the first part can be proposed to aid in the development of a theory for this kind of behavioral situation.     

Spatial, bottom-up, and top-down effects on the abundance of a leaf miner

Many plant and animal species have higher densities at the centre of their distribution, with a gradual decline in abundance towards the edge of the range, though reasons for this pattern is not well known. We examined the abundance of the leaf miner Cameraria sp. nova over the range of its host plant Quercus myrtifolia in Florida and addressed how bottom-up and top-down factors varied over its whole distribution. Leaf miner densities, plant quality and natural enemy effects on mine survivorship were evaluated in 40 sites and spatially structured models were used to determine the effects of spatial location on the abundance of Cameraria and effects of both bottom-up (tannin concentration, foliar nitrogen, soil nitrogen, and leaf area) and top-down factors (larval parasitism and predation) on abundance and survivorship. Cameraria mines were, on average, three times more abundant on edge/coastal sites compared to centre/inland sites and did not support the hypothesis of higher abundance on the centre of the distribution. Differences in plant quality, larval parasitism and successful emergence of mines on edge versus central sites might be partially responsible for this finding. A trend surface equation with latitude and longitude combined explained almost 52% of the variation in Cameraria density and a trend surface map also revealed peaks of Cameraria abundance on the edges of the plant distribution. Correlograms also indicated a significant spatial structure of Cameraria as mines were positively spatially autocorrelated at small distances (≈122 km). Partial regression analyses indicated that 69% of the variation in Cameraria abundance was explained by the effects of latitude, longitude, elevation and percentage of foliar nitrogen. Our results indicated that variation in Cameraria abundance was mostly explained by spatial position and significant effects of bottom-up and top-down factors were not detected in our large-scale study.     

Photophosphorylation in intact algae: Effects of inhibitors, intensity of light, electron acceptor and donors

The luciferin-luciferase method was used to determine ATP extractedfrom darkmaintained and light-exposed samples of the green algaChlorella pyrenoidosa and of the blue-green alga Anacystis nidulans.A few measurements on Synechococcus lividus (a bluegreen thermophile,clone 65?C) are also reported.

1. The light-minus-dark ATP levels (ATP) from aerobic cells ofChlorella and Anacystis were negative; however, ATP from Synechococcuswas positive. Large positive ATP was obtained in regularly grown(RG: moderate light) Chlorella treated with oligomycin; darklevels were reduced, light levels remained essentially unaffected.In high-light exposed (HLE) Chlorella, oligomycin reduced bothlight and dark ATP levels, but positive ATP was still obtained.However, in Anacystis, which has a different organization ofthylakoid membrane, oligomycin severely reduced both the lightand the dark ATP levels and the ATP remained negative.
2. Theoligomycin (12 µM) treated Chlorella and the untreatedAnacystis and Synechococcus show the presence of cyclic photophosphorylationunder conditions in which the non-cyclic electron flow fromphotosystem II to photosystem I is blocked by 10 µM 3-(3,4-dichlorophenyl)-l,l-dimethylurea(DCMU), or not allowed to operate by the absence of CO₂. Cyclicphotophosphorylation ranged from 10–30% of the maximumATP in RG, to 40–50% in HLE Chlorella. In RG Chlorella,cyclic and non-cyclic (in the absence of DCMU) photophosphorylation(ATP) saturate at about 10³ ergs cm^–2 sec^–1 and10⁴ ergs cm^–2 sec^–1 and 10⁴ ergs cm^–2 sec^–1red (>640 nm) light, respectively; a lag was observed inthe light curve.
3. In Chlorella, the addition of the photosystemI electron acceptormethyl viologen (MV; 1 mM) increased ATPby twofold. Furtheraddition of DCMU (25 µm) reduced thisto the level observedwith DCMU alone. If 1 mM reduced dichlorophenolindophenol orphenazine methosulphate (DCPIPH₂ or PMSH₂, respectively)wasadded along with DCMU, the ATP level was 30–40% ofthecontrol. Further addition of MV increased the JATP to be70–80%of that of the control. These and other resultsconfirm thepresence of both non-cyclic and cyclic photophosphorylationin vivo, the former predominating in Chlorella, and the latterin Anacystis and Synechococcus.

(Received May 1, 1973; )     

Deuteration effects on the in vivo EPR spectrum of the reduced secondary photosystem I electron acceptor A1 in cyanobacteria

The photoreduction of the secondary PSI electron acceptor A1 in vivo has recently been detected via X-band EPR spectroscopy in intact spinach chloroplasts and in marine cyanobacteria Synechococcus PCC 7002 [Klughammer, C., and Pace, R. J. (1997) Biochim. Biophys. Acta 1318, 133-144]. A further study of the A1- EPR spectrum of Synechococcus PCC 7002 at room temperature with higher-field resolution revealed partially resolved hyperfine structure which was dominated by 0.4 mT splittings of three equivalent protons. The hyperfine splitting was not significantly affected by incubation of the cyanobacteria in 2H2O medium for 20 h, but was absent in fully deuterated cyanobacteria that were grown in 2H2O medium. Anisotropic g-factors consistent with a phylloquinone radical were derived by spectra simulation. Biosynthetic protonation of quinones via the CH3 donor L-methionine in deuterated cells maintained hyperfine structure in the A1- spectrum, indicating the incorporation of CH3 groups in 60% of the deuterated, photoactive A1 molecules. Conversely, biosynthetic quinone deuteration via L-[methyl-d3]methionine in protonated cells led to the loss of the 0. 4 mT splittings in 54% of the A1 molecules. These observations confirm the conclusion of Heathcote et al. [(1996) Biochemistry 35, 6644-6650] of the identity of EPR-detected, photoreduced A1- in vivo with a phylloquinone (vitamin K1) radical in PSI. The partially resolved hyperfine structure of the A1- spectrum indicates an altered spin distribution in the bound vitamin K1- radical in vivo compared to that of unbound vitamin K1- in vitro.     

The interaction of methanol dehydrogenase and its electron acceptor, cytochrome cL in methylotrophic bacteria.

The interactions of methanol dehydrogenase (MDH, EC1.1.99.8) with its specific electron acceptor cytochrome cL has been investigated in Methylobacterium extorquens and Methylophilus methylotrophus. The MDHs of these two very different methylotrophs have the same alpha 2 beta 2 structure; the interaction of these MDHs with their specific electron acceptor, cytochrome cL, has been studied using a novel assay system. Electrostatic reactions are involved in 'docking' of the two proteins. EDTA inhibits the reaction by a process involving neither metal chelation nor the 'docking' process. Chemical modification studies showed that the two proteins interact by a 'docking' process involving interactions of lysyl residues on MDH and carboxyl residues on cytochrome cL. When 'zero length', two stage cross-linking was done (with proteins from both bacteria), the alpha-subunits of MDH cross-linked with cytochrome cL by way of lysyl groups on MDH and carboxyl groups on the cytochrome. Tuna mitochondrial cytochrome c provided a model for cytochrome cH which is the electron acceptor for cytochrome cL in the 'methanol oxidase' electron transport chain. Tuna cytochrome c was shown to form crosslinked products with carboxyl-modified cytochrome cL. MDH and tuna cytochrome c competed for the same domain on cytochrome cL. It was concluded that MDH reacts with cytochrome cL by an electrostatic reaction which involves carboxyl groups on cytochrome cL and amino groups on the alpha-subunit of MDH. The same domain on cytochrome cL is involved in subsequent 'docking' with its electron acceptor.     

The influence of energy-level fluctuation and acceptor local diffusion on electron transport in biological systems

The present work is a modification of nonadiabatic electron transfer theory for fixed electron exchanging groups. We attempt to account for the role of the relative motion of exchanging groups on electron transfer processes. We also show how the fluctuation of the potential surfaces of the initial and final states of solute molecules (here, the donor-acceptor pari) affect electron transfer.     

Management strategy, shade, and landscape composition effects on urban landscape plant quality and arthropod abundance

Intensity and type of management, the cultural variable shade, and the combination of woody and herbaceous annual and perennial plants were evaluated for their effect on key landscape arthropod pests. Azalea lace bugs, Stephanitis pyrioides (Scott), and twolined spittlebugs, Prosapia bicincta (Say), were most effectively suppressed in landscape designed with resistant plant species of woody ornamentals and turf. Landscapes containing susceptible plant counterparts were heavily infested by these two insect species in untreated control plots. A traditional management program of prescribed herbicide, insecticide, and fungicide applications effectively suppressed azalea lace bug and produced a high-quality landscape. Targeted integrated pest management with solely horticultural oils resulted in intermediate levels of azalea lace bug. Neither program completely controlled twolined spittlebug on hollies or turf. Carabidae, Staphylinidae, Formicidae, and Araneae were not reduced by any management strategy. Lace bugs (Stephanitis) were more common in plots with 50% shade than those in full sun. Spittlebugs (Prosapia) were more common in the shade during 1996 and in the sun during 1997. Spiders and ants were more often collected in full sun plots. Carabids, staphylinids, and spiders were more commonly collected from pitfall traps in turf than in wood-chip mulched plant beds, whereas ants were equally common in both locations. The addition of herbaceous plants to the landscape beds had little effect on pest insect abundance.