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1.
[1,5-14C]-citrate was employed to indicate complete five carbon incorporation into the chlorophylls from the labelling pattern to be found in degraded chlorophylls and the maleimides. This provides additional evidence that there may be an alternative pathway to that involving δ-aminolaevulinic acid (δ-ALA) synthetase in higher plants.  相似文献   

2.
δ-Amino [4-14C]laevulinate added to reticulocytes incubated in vitro is incorporated into haem. Exogenous δ-aminolaevulinate restores the incorporation of 59Fe into haem in reticulocytes which had been treated with isonicotinic acid hydrazide (INH) or penicillamine and were hence unable to synthesize δ-aminolaevulinate. On the other hand, the addition of δ-aminolaevulinate does not restore the incorporation of Fe into reticulocytes incubated with haemin. The inhibition of the incorporation of iron is neither restored by δ-aminolaevulinate in reticulocytes incubated with cycloheximide (which inhibits globin synthesis and thus elevates the free intracellular haem pool). These results suggest that in intact reticulocytes haemin does not inhibit δ-aminolaevulinate synthetase. This conclusion is further supported by the finding that the pattern of incorporation of [2-14C]glycine and δ-amino[4-14C]-laevulinate into haem differs in reticulocytes incubated with an inhibitor of δ-aminolaevulinate synthetase (INH) and in reticulocytes incubated with haemin and cycloheximide.  相似文献   

3.
Cytochrome segregation at cell division was studied in an Escherichia coli mutant requiring δ-amino-laevulinic acid (δ-ALA) for cytochrome synthesis and oxidative growth. Approximately three generations after transfer to δ-ALA-deficient medium, two sub-populations of cells were distinguishable by their ampicillin sensitivity in a medium supporting growth only of cytochrome-containing cells. The sub-populations were separable on Percoll gradients: ampicillin-sensitive cells contained higher cytochrome concentrations than insensitive cells. The results support a model that describes localized growing zones of membrane, which are conserved in successive cell cycles.  相似文献   

4.
The seasonal changes of pigments and stable carbon isotope composition (δ13C values) were investigated in needles of Qilian juniper (Sabina przewalskii Kom.) from two typical sites, one drier and the other wetter, in the Qilian Mountains, China. The anthocyanins and rhodoxanthin content from both sites were much higher in winter than in summer. Plant needles contained more carotenoids and xanthophylls in winter at the wetter site, while no seasonal difference appeared at the drier site. However, lower chlorophyll content and higher proline and δ13C were observed at the drier site. Average tree height was shorter at the drier site trees than at the wetter site. Our results suggested that under natural conditions, pigmentation in S. przewalskii may serve to improve the energy balance of the photosynthetic apparatus under cold and drought stresses. Proline and δ13C could be used as drought indicators for S. przewalskii.  相似文献   

5.
The chlorophyll repair potential of mature Cucumis chloroplasts incubated in a simple Tris-HCI/sucrose medium is described. The chloroplasts were isolated from green, fully expanded Cucumis cotyledons which were capable of chlorophyll repair. This was evidenced by a functional chlorophyll biosynthetic pathway in the mature tissue. The biosynthesis of protochlorophyllide from exogenous δ-aminolevulinic acid was used as a marker for the operation of the chlorophyll biosynthetic chain between δ-aminolevulinic acid and protochlorophyllide. The conversion of exogenous protochlorophyllide into chlorophyll a was used as a marker for the operation of the chlorophyll pathway beyond protochlorophyllide. It appeared from these studies that contrary to published reports, unfortified fully developed Cucumis chloroplasts incubated in Tris-HCl/sucrose without the addition of cofactors exhibited a partial and limited chlorophyll repair capability. Their net tetrapyrrole biosynthetic competence from δ-aminolevulinic acid was confined to the accumulation of coproporphyrin. No net tetrapyrrole biosynthesis beyond coproporphyrin was observed. However, the plastids were capable of incorporating small amounts of δ-amino-[4-14C]levulinic acid into [14C] protochlorophyllide but were incapable of converting exogenous protochlorophyllide into chlorophyll. After prolonged incubation of the unfortified chloroplasts in the dark, a fluorescent protochlorophyllide-like compound accumulated. This compound [Cp (E430-F631)] exhibited a soret excitation maximum at 430 nm (E430) and a fluorescence emission maximum at 631 nm (F631) in methanol/acetone (4 : 1, v/v). Cp (E430-F631) was shown to be neither protochlorophyllide nor zinc-protochlorophyllide but an enzymatic degradation product of chlorophyll. The exact chemical identity of this compound has not yet been determined.  相似文献   

6.
Addition of hemin (5–200 μM) to a rabbit reticulocyte iron-free incubation medium, resulted in a progressive inhibition of heme synthesis as measured by incorporation of (14C)-glycine. In contrast when (14C) δ-aminolevulinic acid incorporation into heme was studied, significant inhibition below that of the (14C)-glycine control only occurred with hemin concentrations greater than 100 μM. Hemin progressively inhibited cellular and mitochondrialδ-aminolevulinic acid synthetase activity, as well as cellular δ-aminolevulinic acid dehydratase activity. The results indicated that elevated levels of hemin initially control heme synthesis by feedback inhibition at the rate-limiting enzyme of heme synthesis, δ-aminolevulinic acid synthetase. Hemin inhibition of δ-aminolevulinic acid dehydratase is only significant for the entrire heme synthetic pathway when greater than one-third of this enzyme's activity is inhibited.  相似文献   

7.
River discharge supplies nearshore communities with a terrestrial carbon source that is often reflected in invertebrate and fish consumers. Recent studies in the Beaufort Sea have documented widespread terrestrial carbon use among invertebrates, but only limited use among nearshore fish consumers. Here, we examine the carbon source and diet of rapidly growing young-of-year Arctic cisco (Coregonus autumnalis) using stable isotope values (δ13C and δ15N) from muscle and diet analysis (stomach contents) during a critical and previously unsampled life stage. Stable isotope values (δ15N and δ13C) may differentiate between terrestrial and marine sources and integrate over longer time frames (weeks). Diet analysis provides species-specific information, but only from recent foraging (days). Average δ13C for all individuals was ?25.7 ‰, with the smallest individuals possessing significantly depleted δ13C values indicative of a stronger reliance of terrestrial carbon sources as compared to larger individuals. Average δ15N for all individuals was 10.4 ‰, with little variation among individuals. As fish length increased, the proportion of offshore Calanus prey and neritic Mysis prey increased. Rapid young-of-year growth in Arctic cisco appears to use terrestrial carbon sources obtained by consuming a mixture of neritic and offshore zooplankton. Shifts in the magnitude or phenology of river discharge and the delivery of terrestrial carbon may alter the ecology of nearshore fish consumers.  相似文献   

8.
Bats are important ecosystem service providers, and therefore most relevant for both lowland and highland habitats, particularly in the tropics. Yet, it is poorly understood to what extent they perform large-scale movements, especially movements along mountain slopes. Here, we studied the movement ecology of the potentially migratory species Miniopterus natalensis at Mount Kilimanjaro in Tanzania. We analysed stable isotope ratios of C (δ13C), N (δ15N) and H (δ2H) in keratin of sedentary frugivorous and insectivorous bats captured between 800 and 2,400 m above sea level to establish elevational gradients of stable isotope ratios in consumer tissues. We expected correlations between stable isotope ratios of the non-exchangeable portion of H in fur keratin and the elevation of capture site, but not necessarily for δ13C and δ15N. Yet, in bats of both feeding ensembles, we found δ15N of fur keratin to correlate positively with the elevation of capture sites but not δ2H. In frugivorous bats, δ13C increased with increasing capture elevation as well. By looking at intra-individual variation of δ13C and δ15N in fur keratin and wing membrane tissues of sedentary Rhinolophus cf. clivosus and of the potentially migratory species M. natalensis, we gathered evidence that M. natalensis migrates seasonally between low and high elevations along the slopes of Mount Kilimanjaro. Finally, based on an isoscape origin model we estimated that M. natalensis captured before and after the cold period at around 1,800 m above sea level originated from around 1,400 m a.s.l. or lower. Thus, we received convergent results in support of seasonal elevational movements of M. natalensis, probably in search for cold hibernacula at higher elevations of Mount Kilimanjaro.  相似文献   

9.
《Mammalian Biology》2014,79(2):110-116
Nitrogen stable isotope analysis studies have become a useful tool in dietary studies to quantify differences in diet composition among species or individuals. However, laboratory studies have revealed several factors that influence the nitrogen isotope ratios (δ15N) in animal tissues (e.g. habitat, amount of ingested food, and metabolic rate). The influence of these factors has not been validated for free-ranging bat species, which is important for interpreting nitrogen isotope data in field studies. In this study, we measured δ15N from wing membranes (δ15Nw) and habitat samples (δ15Nh; soil and leaf, or sediment) to test for effects of diet, age, and individual energy demand in three free-living bat species (Myotis daubentonii, Nyctalus noctula and Nyctalus leisleri). We hypothesised that based on differences in diet composition δ15Nw values should increase in the sequence M. daubentonii, N. leisleri, and highest N. noctula. Furthermore, juveniles should have significantly lower δ15Nw compared to their mothers. Thirdly, the δ15Nw values of reproductively active individuals should be significantly higher than those of non-reproductive individuals. Values of δ15Nw were significantly influenced by differences in feeding ecology among species and individual reproductive status, but not by animal age. Our results show that species feeding on primary consumers have lower δ15Nw values than species feeding on secondary and tertiary consumers. Further, independent young did not differ in their δ15Nw values from adults suggesting that their tissues already reflect the insect diet. The effect of reproductive status varied among species which might reflect intra-specific differences in foraging behaviour of generalist vs. specialist species. In this study, we demonstrated that δ15N can provide information on the dietary range of bats, but researchers should account for variation owing to reproductive status, habitat, and species.  相似文献   

10.
Among the mechanisms that allow competing species to coexist are resource partitioning and dietary segregation. The current study uses multiple stable isotopes, carbon (δ13C), nitrogen (δ15N) and sulphur (δ34S), to test the hypothesis that dietary segregation in cohabiting invasive mysids (Limnomysis benedeni and Katamysis warpachowskyi) and gammarids (Dikerogammarus villosus and Gammarus roeselii) will be reflected by differences in isotope values. Furthermore, IsoError mixing models were used to estimate the relative contributions of periphyton and seston to the invaders’ diets. Whole tissue δ13C, δ15N and δ34S analysis in L. benedeni and K. warpachowskyi imply that these sympatric, non-native mysids maintain differentiated feeding niches or resource partitioning by feeding on distinct components of the available food resources (predominantly seston by L. benedeni and periphyton by K. warpachowskyi). By contrast, the gammarids D. villosus (‘killer shrimp’) and G. roeselii exhibited no significant difference in δ13C and δ15N, indicating a considerable overlap between the dietary sources of these sympatric invaders. Feeding niche differentiation, irrespective of season or the nature of habitat invaded (lake or river), might facilitate the coexistence of invasive mysids in their ‘new’ environment by minimizing direct resource competition. The mutual interaction by the invasive gammarids, coupled with voracious behavior, could assist their success at co-invasion with serious implications for local biodiversity including the potential extinction of native species.  相似文献   

11.
The farming of shrimp is developing quickly worldwide, and recently, ingredients such as seaweeds in low proportion (25 to 4 %), incorporated into the commercial food, have been shown to improve the shrimp productive variables. The change of commercial foods to commercial feed with a proportion of natural food, and finally, to natural food has been little and simultaneously evaluated. The aim of our study was to determine the relative contribution of dietary carbon to the growth of Litopenaeus vannamei fed with a proportion of 4 % Sargassum13C = ?20.9?±?0.05?‰), 4 % Ulva13C = ?20.6?±?0.6?‰) meal, and a control diet (δ13C?=??22.6?±?0.2?‰) in 60-L tanks for 30 days, and finally, with the green seaweed Ulva spp. (δ13C = ?13.2?±?0.25?‰) and Ulva meal (δ13C = ?14.5?±?0.6?‰) in open-air ponds for 120 days, by measuring δ13C for each of the foods and in the muscle of shrimp. After 15 days, the rates of metabolic turnover (Δ13C = δ13Cshrimp ? δ13Cfood) were constant until the end of the experiment in the tanks. The muscle of shrimp assimilated carbon from all diets, which demonstrated the potential use of combined diets and the optimization of their use in diets containing seaweed. Our data will be useful in future interpretations of field and laboratory isotopic values for this species.  相似文献   

12.
This study contrasted the influence of tertiary treated municipal wastewater effluent (MWWE) exposure on the abundance, food selection (stomach contents), and carbon (δ13C) and nitrogen (δ15N) stable isotope signatures of Rainbow Darter (Etheostoma caeruleum) and Greenside Darter (Etheostoma blennioides) in a small receiving stream in southern Ontario, Canada. Despite tertiary treatment resulting in relatively high effluent quality, there is continued concern for environmental degradation downstream of the effluent outfall because of the relatively small size of the receiving environment and recent studies that have indicated changes occurring in relative fish abundance and stable isotope signatures. In July and August of 2009 fish and benthic invertebrate communities were examined along with analysis of δ13C and δ15N of the most common species to determine the effects of effluent exposure on the food web. Rainbow Darter increased in abundance and their δ15N values were enriched immediately downstream of the effluent outfall throughout the summer (July and August). In contrast, while δ15N of Greenside Darter followed a similar pattern in July, they were not enriched in August. The benthic community was changed immediately downstream of the outfall and the δ15N of invertebrates was enriched, similar to that observed in Rainbow Darter. Stomach contents of the two darter species diverged the most in the summer possibly explaining some of the changes in δ13C and δ15N among sites. It is possible that Greenside Darter fed on less enriched food downstream of the outfall, or fed outside of the effluent plume during the summer. Rainbow Darter may be able to exploit the changes in habitat and prey composition, resulting in differences in relative abundance of darters immediately downstream of the effluent outfall.  相似文献   

13.
Based on the relationship between salinity and δ18O and δ13C of modern shells in the Lake Nakaumi-Shinji lagoon system (southwestern Japan), where the salinity changes regularly from ca. 1 PSU to 34 PSU, a paleosalinity record for Nakaumi Lagoon during the Holocene has been derived from bulk mollusk shell δ18O and δ13C data. The robust relationships between the salinity and modern shell δ18Oar and δ13Car (aragonite) were used to calibrate the paleosalinity reconstruction. The salinity relationships are expressed by the regressions:
Salinity (PSU)=3.86 δ18Oar(‰ VPDB)+33.9 (n=18, r=0.978)  相似文献   

14.
Wild-type cells of the unicellular rhodophyte, Cyanidium caldarium, synthesize chlorophyll a, phycobiliproteins, and heme from δ-aminolevulinic acid during light-dependent chloroplast development but are unable to make photosynthetic pigments in the dark. C. caldarium, mutant GGB-Y, is an obligate heterotroph which, in the light, produces a chloroplast devoid of photosynthetic pigments. The present investigation has shown that δ-aminolevulinic acid is synthesized in cells of mutant GGB-Y incubated with levulinic acid, a competitive inhibitor of δ-aminolevulinic acid dehydrase (the second enzyme in the porphyrin biosynthetic pathway). In vivo, cells of mutant GGB-Y preferentially incorporated C1 of glutamate and α-ketoglutarate into the C5 fragment (formaldehyde) of δ-aminolevulinic acid after alkaline periodate degradation. This suggested that δ-aminolevulinic acid arises directly from the carbon skeleton of glutamate and α-ketoglutaric acid. The pattern of incorporation of C3, C4, and C5 of α-ketoglutarate into the C1–C4 (succinic acid) fragment of δ-aminolevulinic acid after alkaline periodate degradation was consistent with the origin of δ-aminolevulinic acid from a five-carbon precursor. C1 and C2 of glycine and C2 and C3 of succinate were incorporated into both the formaldehyde and succinate fragments of δ-aminolevulinic acid in a manner inconsistent with condensation of glycine and succinyl CoA by δ-aminolevulinic acid synthetase, the rate-limiting enzyme in the porphyrin pathway in animals and bacteria. Extracts of the soluble protein from cells of mutant GGB-Y displayed a Soret band at 410 nm indicating the presence of hemoproteins. This shows that mutant GGB-Y cells synthesize heme. The respiration of radiolabeled glutamate, α-ketoglutarate, and glycine to 14CO2 is consistent with the existence of mitochondrial cytochromes in cells of mutant GGB-Y and with the ability of the mutant to synthesize δ-aminolevulinic acid. The present results suggest that δ-aminolevulinic acid is synthesized directly from glutamate or α-ketoglutarate and that this is the only process by which the rate-limiting intermediate in the porphyrin pathway is synthesized in C. caldarium. If correct, the rate-limiting, regulative enzyme in the biosynthetic pathway for synthesis of chlorophyll a, bile pigment (phycocyanobilin), and heme must have been completely different in the evolutionary antecedents of modern-day plants and animals.  相似文献   

15.
Understanding the response of long-lived species to natural climatic variability at multiple scales is a prerequisite for forecasting ecosystem responses to global climate change. This study investigated the response of piñon pine (Pinus edulis) to natural climatic variability using information on physiology and growth as recorded in leaves and tree rings. δ13C of annual leaf cohorts (δ13Cleaf) and tree rings (δ13Cring) were measured at an ecotonal/xeric site and a mid-range/mesic site. Ring width indices (RWI) were used to estimate annual growth of individual trees. Relationships between seasonal and annual climate parameters and δ13C and growth were investigated. δ13C–climate relationships were stronger for δ13Cleaf than for δ13Cring especially at the xeric site. The mean monthly maximum summer temperatures over May through September (summer T max) had the strongest influence on δ13Cleaf. There was a strong negative relationship between RWI with summer T max and a strong positive relationship between RWI with October to October precipitation (water–year PPN) at both sites. This suggests that piñon pine populations could be vulnerable to decreased growth and, perhaps mortality, in response to warmer, drier conditions predicted by models of global climate change.  相似文献   

16.
A chlorophyll-deficient xantha mutant of cotton (Gossypium hirsutum L.) was examined with respect to development and structural organization of the chloroplast membrane system as affected by disruption of early stages of chlorophyll biosynthesis in the light. The analysis of early chlorophyll precursors showed that the mutant is unable to synthesize 5-aminolevulinic acid (5-ALA) in the light. The disorders in early stages of chlorophyll biosynthesis arrested the development of chloroplast membrane system at the stage of vesicles and single thylakoids. The accumulation of 2–5% chlorophyll in the mutant was related to the formation of light-harvesting chlorophyll-a/b-protein complexes I and II, whereas pigment-protein complexes composing reaction centers of photosystem I and photosystem II were lacking. It is concluded that the chloroplast membrane system in the mutant with impaired 5-ALA synthesis is incapable of development and is even reduced upon long-term growing under light.  相似文献   

17.
The stable carbon (δ13C) and nitrogen (δ15N) isotope values of bone collagen are frequently used in paleodietary studies to assess the marine contribution to an individual's diet. Surprisingly, the relationship between stable isotope these values characteristics and the percentage of marine foods in diet has never been effectively demonstrated. To clarify this relationship, the stable isotope values and radiocarbon dates of nine humans and one sheep from Herculaneum, all who perished simultaneously during the AD 79 eruption of Vesuvius, were determined. Significant differences were found in the radiocarbon dates which are attributable to the incorporation of “old” carbon from the marine reservoir. The magnitude of the observed differences was linearly correlated with both δ13C and δ15N values allowing the response of each isotope to increasing marine carbon in collagen to be independently verified. Regression analyses showed that for every 1‰ enrichment in δ13C and δ15N, 56 years and 34 years were added to the radiocarbon age, respectively. Predictions of the maximum marine reservoir age differed considerably depending on which stable isotope was considered. This discrepancy is attributed to some degree of macronutrient scrambling whereby nitrogen from marine protein is preferentially incorporated in collagen over marine carbon. It is suggested that the macronutrient scrambling explains the observed relationship between δ13C and δ15N from Roman coastal sites and should be considered when interpreting any diet which is not dominated by protein. Nevertheless, without knowing the degree of macronutrient scrambling in different dietary scenarios, the accuracy of dietary reconstructions is severely compromised. Am J Phys Anthropol 152:345–352, 2013. © 2013 Wiley Periodicals, Inc.  相似文献   

18.
Using both oxygen isotope ratios of leaf water (δ18OL) and cellulose (δ18OC) of Tillandsia usneoides in situ, this paper examined how short‐ and long‐term responses to environmental variation and model parameterization affected the reconstruction of the atmospheric water vapour (δ18Oa). During sample‐intensive field campaigns, predictions of δ18OL matched observations well using a non‐steady‐state model, but the model required data‐rich parameterization. Predictions from the more easily parameterized maximum enrichment model (δ18OL–M) matched observed δ18OL and observed δ18Oa when leaf water turnover was less than 3.5 d. Using the δ18OL–M model and weekly samples of δ18OL across two growing seasons in Florida, USA, reconstructed δ18Oa was ?12.6 ± 0.3‰. This is compared with δ18Oa of ?12.4 ± 0.2‰ resolved from the growing‐season‐weighted δ18OC. Both of these values were similar to δ18Oa in equilibrium with precipitation, ?12.9‰. δ18Oa was also reconstructed through a large‐scale transect with δ18OL and the growing‐season‐integrated δ18OC across the southeastern United States. There was considerable large‐scale variation, but there was regional, weather‐induced coherence in δ18Oa when using δ18OL. The reconstruction of δ18Oa with δ18OC generally supported the assumption of δ18Oa being in equilibrium with precipitation δ18O (δ18Oppt), but the pool of δ18Oppt with which δ18Oa was in equilibrium – growing season versus annual δ18Oppt – changed with latitude.  相似文献   

19.
The nitrogen isotope ratio (δ15N) in tissues of native macroalgae was evaluated as a means of indicating the intensity and spatial extent of organic contamination due to disposal of waste from land-based marine fish farms (LBMFFs). Three species of macroalgae from the genus Fucus and the green macroalgae Codium tomentosum were selected for study. The study was carried out at seven flat marine fish farms located in Galicia (NW Spain). Tests were carried out to determine the intra-annual variation in δ15N values and any differences between selected macroalgae. The δ15N values enrichment was observed close to the disposal point, and δ15N values varied more widely throughout the year (±5.57 ‰) at sites affected by the marine fish farm effluent compared to natural conditions (±2 ‰). No significant differences in the isotopic signals were observed in the different species studied (standard major axis). The δ15N values of macroalgae may be an ideal means of detecting the presence of LBMFFs effluents.  相似文献   

20.
Carbon, nitrogen and sulfur stable isotope ratios (δ13C, δ15N and δ34S) were measured from water column sulfate, sediments, particulate organic matter (POM), macrophytes, periphyton, macroinvertebrates and fish, sampled from the littoral, open water and macrophyte zones of Lake Biwa. In most of the littoral zones, the δ13C and δ15N values of organisms indicated that POM and periphyton support the consumers. However, in the dysoxic interior macrophyte (IM) zone, the δ13C values of Sinotaia quadrata histrica, Propsilocerus akamusi and Anodonta woodiana were lower than that of all resources. The δ15N values of S. quadrata histrica were lower than those of P. akamusi and A. woodiana. δ13C and δ15N values thus failed to distinguish the foods of these consumers. The δ34S values of sediment and S. quadrata histrica were lower than those of water column sulfate, suggesting that this consumer incorporated reduced sulfur derived from sulfate reduction in the sediment by ingesting detritus. In contrast, the δ34S values of P. akamusi and A. woodiana were higher than that of S. quadrata histrica, suggesting that they incorporated sulfur derived from water column sulfate by ingesting POM. Consequently, δ13C, δ15N and δ34S signatures provide complementary estimates of foods for consumers in this freshwater lake.  相似文献   

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