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1.
The yeast Schizosaccharomyces malidevorans utilizes l-malate when grown on glucose as the carbon source. A mutant of this yeast has been isolated which is dependent on the presence of both l-malate and glucose for growth. The mutant utilizes l-malate as rapidly as the wildtype and the utilization of glucose is greatly reduced. Other TCA cycle intermediates do not relieve the malate dependence.To John Ingraham whose pioneering work with malolactic bucteria made me curious enough about the field of nine microbiology to enter it and whose intense instruction in scientific method has made my continued pursuit of physiological and genetic questions a joy 相似文献
2.
Seviour RJ Kragelund C Kong Y Eales K Nielsen JL Nielsen PH 《Antonie van Leeuwenhoek》2008,94(1):21-33
This review considers what is known about the Actinobacteria in activated sludge systems, their abundance and their functional roles there. Participation in processes leading to the microbiological removal of phosphate and in the operational problems of bulking and foaming are discussed in terms of their ecophysiological traits. We consider critically whether elucidation of their nutritional requirements and other physiological properties allow us to understand better what might affect their survival capabilities in these highly competitive systems. Furthermore, how this information might allow us to improve how these processes work is discussed. 相似文献
3.
Lee N Nielsen PH Aspegren H Henze M Schleifer KH la Cour Jansen J 《Systematic and applied microbiology》2003,26(2):211-227
Quantitative fluorescence in situ hybridization (FISH) and the combination of FISH with microautoradiography (MAR) were used in order to study the long-term population dynamics (2.5 years) and the in situ physiology in two parallel activated sludge pilot systems with enhanced biological phosphorus removal (EBPR). The two systems received the same influent wastewater, but were differently operated (with and without nitrogen removal, respectively). Both systems showed a significant P removal that increased when different substrates (phosphorus (P), acetate and glucose, respectively) were added to the influent wastewater. Rhodocyclus-related bacteria were present in both systems in significant numbers (ranging from 4 to 28%) throughout the whole period. This supports the hypothesis that these bacteria occur in significant numbers in different types of well-operating EBPR activated sludge processes. However, we observed a lower correlation (< 0.5) for the amount of Rhodocyclus-related bacteria to the P content in activated sludge than previous studies (> 0.9). The Actinobacteria were the only additional group of bacteria which showed a similar degree of correlation to the P content in activated sludge as the Rhodocyclus-related bacteria--but only for the system without nitrogen removal. Significant amounts (< or = 12%) of glycogen-accumulating bacteria (GAOs) were detected in the system with nitrogen removal (but not in the other system), but had no, in contrast to previous observations, apparent negative effect on the overall EBPR performance. FISH-MAR indicated that a significant part of the Betaproteobacteria (part of them identified as Rhodocyclus-related bacteria) as well as the Actinobacteria were able to take up 33Pi, [3H]-acetate and [3H]-glucose under anaerobic-aerobic conditions. The contribution of anoxic 33Pi uptake under alternating anaerobic-anoxic conditions was significantly lower. Interestingly, not all Rhodocyclus-related bacteria showed uptake of these three radioactive substrates. This may be due to differences in metabolic state, physiological potential or genotype, not detectable by the present probe set for Rhodocyclus-related bacteria. Comparison of the 33Pi, [3H]-acetate and [3H]-glucose uptake by activated sludge after different fixation and incubation procedures showed that a part of the observed 33Pi uptake may have been caused by a combination of a biological and chemical or biologically induced chemical P adsorption. 相似文献
4.
Most investigations on the effects of and responses to stress exposures have been performed on a limited number of model organisms
in the laboratory. Here much progress has been made in terms of identifying and describing beneficial and detrimental effects
of stress, responses to stress and the mechanisms behind stress tolerance. However, to gain further understanding of which
genes are involved in stress resistance and how the responses are regulated from an ecological and evolutionary perspective
there is a need to combine studies on multiple levels of biological organization from DNA to phenotypes. Furthermore, we emphasize
the importance of studying ecologically relevant traits and natural or semi-natural conditions to verify whether the results
obtained are representative of the ecological and evolutionary processes in the field. Here, we will review what we currently
know about thermal adaptation and the role of different stress responses to thermal challenges in insects, particularly Drosophila. Furthermore, we address some key questions that require future attention. 相似文献
5.
Unlike predators, which immediately consume their prey, parasitoid wasps incapacitate their prey to provide a food supply for their offspring. We have examined the effects of the venom of the parasitoid wasp Ampulex compressa on the metabolism of its cockroach prey. This wasp stings into the brain of the cockroach causing hypokinesia. We first established that larval development, from egg laying to pupation, lasts about 8 days. During this period, the metabolism of the stung cockroach slows down, as measured by a decrease in oxygen consumption. Similar decreases in oxygen consumption occurred after pharmacologically induced paralysis or after removing descending input from the head ganglia by severing the neck connectives. However, neither of these two groups of cockroaches survived more than six days, while 90% of stung cockroaches survived at least this long. In addition, cockroaches with severed neck connectives lost significantly more body mass, mainly due to dehydration. Hence, the sting of A. compressa not only renders the cockroach prey helplessly submissive, but also changes its metabolism to sustain more nutrients for the developing larva. This metabolic manipulation is subtler than the complete removal of descending input from the head ganglia, since it leaves some physiological processes, such as water retention, intact. 相似文献
6.
Edge effects in a tropical montane forest mosaic: experimental tests of post-dispersal acorn removal
Forest edges created by scattered-patch clear-cutting have become common in tropical montane cloud forests in the highlands of Chiapas, Mexico. It was hypothesised that forest edges may influence regeneration of oak species, which are canopy dominants in these forests, by affecting the activities of small mammal species. Acorns of different oak species varying in germination timing were offered to predators and/or dispersers at different positions along replicated forest edges during 2 consecutive years. We investigated the effects of (1) edge type (hard and soft), (2) distance from the edge (0, 15, 30, 45 and 60 m inside forest fragments) and (3) oak species, on the rate of acorn removal mainly by small mammals. During a non-masting year, acorn removal was affected by the interaction of edge type and distance from the edge (P<0.05), with acorn removal being highest near hard edges compared to adjacent forest interiors. As predicted, acorn removal was greater along soft (100%) than along hard edges (82%), but this pattern was recorded only during the non-masting year. This study partly supports previous studies of rodents preferentially consuming acorns with early germination rather than acorns exhibiting dormancy, however these patterns may change with variation in acorn abundance. These results suggest that patch clear-cutting affects regeneration processes within forest fragments by influencing the activities of small mammals, but the nature of this effect also depends on acorn abundance and the characteristics of the forest edge created. 相似文献
7.
A sharply defined white line in vitro forms between the pathogenic form of Pseudomonas tolaasii and another Pseudomonas bacterium, referred to as "reactans". This interaction has been considered as highly specific. However, results presented in this study rise doubt about the strict specificity of this interaction, as some other pseudomonads, associated with the cultivated mushroom Agaricus bisporus, also yielded a white line precipitate when they were streaked towards Pseudomonas tolaasii LMG 2342T. Moreover, some Finnish isolates inducing brown blotch symptoms on mushrooms like P. tolaasii(T), produced a typical white precipitate when streaked towards P. "reactans" LMG5329, even though phenotypical and genotypical features exclude these isolates from the species P. tolaasii. We propose that the white-line-in-agar (WLA) test should no longer be considered as an unequivocal diagnostic trait of P. tolaasii. 相似文献
8.
Ferreira ME Marques Edos R Malavazi I Torres I Restrepo A Nunes LR de Oliveira RC Goldman MH Goldman GH 《Molecular genetics and genomics : MGG》2006,276(5):450-463
The dimorphic pathogenic fungus Paracoccidioides brasiliensis can grow as a prototroph for organic sulfur as a mycelial (non-pathogenic) form, but it is unable to assimilate inorganic sulfur as a yeast (pathogenic) form. Temperature and the inability to assimilate inorganic sulfur are the single conditions known to affect P. brasiliensis mycelium-to-yeast (M-Y) dimorphic transition. For a comprehensive evaluation of genes that have their expression modulated during the M-Y transition in different culture media, we performed a large-scale analysis of gene expression using a microarray hybridization approach. The results of the present work demonstrate the use of microarray hybridization analysis to examine gene expression during the M-Y transition in minimal medium and compare these results with the M-Y transition in complete medium. Our results showed that about 95% of the genes in our microarray are mainly responding to the temperature trigger, independently of the media where the M-Y transition took place. As a preliminary step to understand the inorganic sulfur inability in P. brasiliensis yeast form, we decided to characterize the mRNA accumulation of several genes involved in different aspects of both organic and inorganic sulfur assimilation. Our results suggest that although P. brasiliensis cannot use inorganic sulfur as a single sulfur source to initiate both M-Y transition and Y growth, the fungus can somehow use both organic and inorganic pathways during these growth processes. 相似文献
9.
Pollination success of plants is highly susceptible to the frequency of visits and foraging behavior of pollinators. Pollination
of the nectarless flowers of Pedicularis species depends on bumblebee workers collecting pollen by vibrating the anthers (buzz pollination). However, little is known
about the efficiency of the pollination system. Foraging behavior, pollen removal from anthers and pollen deposition on stigmas
of P. chamissonis were studied to assess the effectiveness of buzz pollination in an alpine snowbed population of northern Japan. Although
bumblebees tended to visit most of the flowers open at a given time within inflorescences during a single visit, pollen removal
rate at the first visit was about 20%, and buzzing period decreased with increasing number of previous visits, resulting in
a decreasing proportion of pollen removed per visit as the number of visits increased. These trends enable plants to provide
pollen for more pollinators. The number of pollen grains deposited on stigmas was not saturated during the first visit and
increased with additional visits. Irrespective of weak self-compatibility, evidence of interference between self and outcross
pollen was lacking for seed production. Therefore, buzz pollination in P. chamissonis acts as a mechanism that improves the chance of cross-pollination upon multiple visits if pollinator visitation is frequent. 相似文献
10.
The molecular mechanisms that control P element transposition and determine its tissue specificity remain incompletely understood, although much information has been compiled about this element in the last decade. This review summarizes the currently available information about P element transposition, P-M hybrid dysgenesis and P cytotype features, P element-encoded repressors, and regulation of transposition. 相似文献
11.
Molecular ecology of hydrothermal vent microbial communities 总被引:6,自引:0,他引:6
Jeanthon C 《Antonie van Leeuwenhoek》2000,77(2):117-133
12.
Selenium uptake,translocation, assimilation and metabolic fate in plants 总被引:24,自引:0,他引:24
The chemical and physical resemblance between selenium (Se) and sulfur (S) establishes that both these elements share common
metabolic pathways in plants. The presence of isologous Se and S compounds indicates that these elements compete in biochemical
processes that affect uptake, translocation and assimilation throughout plant development. Yet, minor but crucial differences
in reactivity and other metabolic interactions infer that some biochemical processes involving Se may be excluded from those
relating to S. This review examines the current understanding of physiological and biochemical relationships between S and
Se metabolism by highlighting their similarities and differences in relation to uptake, transport and assimilation pathways
as observed in Se hyperaccumulator and non-accumulator plant species. The exploitation of genetic resources used in bioengineering
strategies of plants is illuminating the function of sulfate transporters and key enzymes of the S assimilatory pathway in
relation to Se accumulation and final metabolic fate. These strategies are providing the basic framework by which to resolve
questions relating to the essentiality of Se in plants and the mechanisms utilized by Se hyperaccumulators to circumvent toxicity.
In addition, such approaches may assist in the future application of genetically engineered Se accumulating plants for environmental
renewal and human health objectives. 相似文献
13.
P. B. Vose 《Plant and Soil》1983,72(2-3):351-364
Genetic effects are obtainable for any aspect of transport, accumulation, and efficiency of nutrient use by plants, and for virtually any element. Some of the important characters are: tolerance to acid soils (18% of soils or 2.4 billion ha), tolerance to high pH induced Fe-chlorosis, and tolerance to salinity (about 1,000 m ha). Genotypes which made better use of N and P would be the means of saving fertilizers, especially important to developing countries. A 10% economy of fertilizer use represents a minimum world saving of US$6 billion annually.
Phaseolus vulgaris is taken as a model to show that although we know quite a lot about the extent of its nutritional variation, e.g. adaptability to acid soils, and the crop's utilization of N and P, we are handicapped in exploiting this because of lack of genetic information. This in turn depends on knowledge of specific mechanisms, and investigating these must be a priority.IAEA Project BRA/5/009 相似文献
14.
The evolution of the nervous system is one of the most fascinating, but also most nebulous fields of homology research. We do not know for example whether the last common ancestors of human, squid, and fly already possessed an elaborate brain and eyes, or rather had a simple, diffuse nervous system. Nevertheless, in the past decade molecular data has greatly advanced our understanding of bilaterian nervous system evolution. In this methodological review, I explain the four levels on which molecular genetic studies advance the quest for homologies between animal nervous systems. (I) Bioinformatic homology research elucidates the evolutionary history of gene families relevant for nervous system evolution such as the opsin superfamily. It tells us when and in what order genes and their functions have emerged. Based on this, we can (II) infer the organismal complexity of some remote ancestor from the functional diversity of its reconstructed proteome. (III) Most common in molecular homology research has been the comparison of expression patterns of developmental control genes. This approach matches and aligns embryonic regions along the body axes, between remote bilaterians. It does not tell us much, however, about the complexity of structures that developed from these regions in Urbilateria. (IV) This is overcome by a novel variant of molecular homology research, the comparison of cell types. Here, a similar “molecular fingerprint” of cells is taken as indication of cross-bilaterian homology. This approach makes it possible to reconstruct the cell-type repertoire of the urbilaterian nervous system. 相似文献
15.
Weller SC Baer RD Garcia de Alba Garcia J Salcedo Rocha AL 《Culture, medicine and psychiatry》2008,32(3):406-420
Folk illnesses that are cultural constructions of psychological distress offer a vehicle for the cross-cultural study of stress and stress-related morbidity. This study explores the relationship between the Latin American folk illnesses susto and nervios and mental health. We hypothesize that these folk illnesses are distinct and that there is a stronger association between current levels of stress and depressive symptoms with past experience of nervios than with susto, because the cultural constructions of these folk illnesses reflect chronic and acute concepts of distress, respectively. Interviews were conducted in Guadalajara, Mexico, where participants responded to questions about their socio-demographic characteristics, stress, depressive symptoms, and whether they had experienced susto or nervios. Susto and nervios are very prevalent and occur across sociodemographic subgroups, with the exception that nervios occurred more often in women (p < 0.05). Susto was significantly associated with stress and depressive symptoms (p < 0.05), but nervios had a much stronger association (p < 0.0001), even after controlling for gender. Susto and nervios were expressions of psychological distress; most of those with depression reported susto and/or nervios. This study validates the link between these folk illnesses and stress and depression and may, ultimately, facilitate cross-cultural research on stress. 相似文献
16.
Microsphaeropsis amaranthi and Phomopsis amaranthicola are potential biological control agents for several Amaranthus species. In an effort to understand the initial infection processes with these pathogens, a study was conducted of the conidial germination and germ tube length (μm) on the weed leaf surfaces at 21 °C and 28 °C. Weeds included Amaranthus rudis, A. palmeri, A. powellii, A. retroflexus, A. spinosus, A. hybridus, and A. albus. For P. amaranthicola, conidial germination and germ tube length varied among the seven weed species at both temperatures, while for M. amaranthi the differences in germ tube lengths were significant among weed species only at 21 °C. While the conidia of M. amaranthi and P. amaranthicola germinated on the leaf surfaces of all seven weed species, temperature appeared to impact the number and length of germ tubes on the leaf surfaces. The percentage of germinated conidia and the length of germ tubes at both temperatures were often greater for M. amaranthi than for P. amaranthicola. In order for the fungal pathogen to successfully infect and kill a weedy host, conidia must germinate and form a germ tube, two processes that vary with host species and temperature for M. amaranthi and P. amaranthicola. The extent to which successive infection processes, e.g., penetration, invasion and colonization, contribute to host specificity warrants study. 相似文献
17.
Kinorhyncha from the stomach of the shrimp Pleoticus muelleri (Bate, 1888) from Comodoro Rivadavia, Argentina 总被引:1,自引:0,他引:1
Six kinorhynchs were found in the stomachs of the Argentine red shrimp, Pleoticus mulleri (Bate, 1888) from the Argentine coast of Patagonia. Three new species are described: Condyloderes storchi n. sp., Pycnophyes argentinensis n. sp. and P. neuhausi n. sp. A fourth species, Kinorhynchus anomalus Lang, 1953 was previously known only from the coast of Chile. This is the third known record of kinorhynchs documented as a food source. Condyloderes storchi, n. sp. is the fourth new species in this genus. It is distinguished by its paradorsal cuspidate spines on segments 7 and 9, lateral accessory and ventrolateral spines on segments 3, 6, 7, 10 and 11. P. argentinensis, n. sp. has nearly equal sternal width for segments 3–11 (about 7% of the trunk length), episternal plates with three distinct areas along the anterior margin, mid-sternal plate with even margin, mid-dorsal spinose protrusions along the terminal borders of segments 11 and 12, and lateral terminal spines 176 μm long, about 21% of trunk length. P. neuhausi, n. sp.has a prominent posterior elongation of the tergal plate of segment 3, uneven lateral margins of the mid-sternal plate, a maximum sternal width at segment 3, no mid-dorsal spinose processes and mid-ventral thickenings on segments 10–12. 相似文献
18.
The caudal fin represents the posteriormost region of the vertebrate axis and is one location where forces are exerted to the surrounding medium. The evolutionary changes of its skeleton have been well analyzed in gnathostomes and revealed transitions from heterocercal to diphycercal and homocercal tails. In contrast, we only know little about the evolutionary transformations of the muscular system of the caudalis and about possible ways of force transmission from anterior myomeres to the caudal fin. The goals of this study are to gain insight into evolutionary transformations of the musculoskeletal system in the four basal actinopterygian groups (Cladistia, Chondrostei, Ginglymodi, and Halecomorphi) and to identify likely pathways of force transmission to the tail. In this context, the connective tissue of the myosepta is considered to be an essential part of the musculoskeletal system. For the first time, this system is analyzed for the whole postanal region. The use of microdissection techniques and polarized light microscopy revealed the collagen fiber architecture and the insertions of all postanal myosepta from cleared and stained specimens. The collagen fiber architecture is similar in all investigated specimens and thus represents the primary actinopterygian condition. All parts of postanal myosepta are dominated by longitudinally arranged myoseptal tendons (lateral and myorhabdoid tendons) that span several vertebral segments. This architecture supports the view that posterior myosepta are well designed to transfer muscular forces that are generated in anterior myomeres. In contrast to the uniform myoseptal architecture, the musculoskeletal system differs between the four basal actinopterygian groups. Among them, chondrosteans have retained the plesiomorphic condition of actinopterygian tails. For the remaining taxa several evolutionary novelties in the musculoskeletal system of the tail are revealed. Most of these have evolved independently in the cladistian and neopterygian stem lineage. In these groups extensions of all epaxial and hypaxial parts of myosepta are present that insert on caudal fin rays. This remarkable contribution of epaxial muscle masses to the caudal fin organization is in contrast to the skeletal organization, that largely derives from hypaxial material only. In contrast to former studies the hypochordal longitudinalis muscle is shown to be a synapomorphy of Halecostomi (Halecomorphi + Teleostei). The morphological framework presented here allows to generate new hypotheses on the function of caudal fins that can be tested experimentally. 相似文献
19.
Although monandry (single mating) is the ancestral state in social hymenopteran insects, effective mating frequencies greater
than 2 have been confirmed for a fair amount of ant species: Cataglyphis cursor, the leaf-cutters of the genera Atta and Acromyrmex, army ants of the genera Eciton, Dorylus, Aenictus and Neivamyrmex, and some North American seed harvester species of the genus Pogonomyrmex. This last genus spreads throughout open arid habitats from Patagonia to southwestern Canada. Whereas some North American
Pogonomyrmex species are thoroughly studied, we know much less about these ants in South America. The objective of this study was to estimate
the effective mating frequency of Pogonomyrmex inermis and P. pronotalis, two Pogonomyrmex sensu stricto species from the central Monte desert of Argentina. A total of 477 P. pronotalis workers from 24 colonies and 402 P. inermis workers from 20 colonies were analyzed using six and four highly polymorphic microsatellites, respectively. The multilocus
analysis revealed that all colonies were monogynous and all queens multiply-mated. The effective mating frequency was 8.75
and 6.52 for queens of P. pronotalis and P. inermis, respectively; those values increased up to 15.66 and 9.78, respectively, when corrected for sampling errors. This is the
first demonstration that queens in at least some members of the South American Pogonomyrmex sensu stricto are strictly polyandrous, with mating numbers per queen at least as high as those previously found for North American species.
We suggest that multiple mating probably arose early in the evolution of the genus Pogonomyrmex and may be the basis of its ecological success and wide distribution.
Received 11 October 2006; revised 10 August 2007 and 19 November 2007; accepted 21 November 2007. 相似文献
20.
We tested if subalpine heath vegetation in northern Italy recovered after experimental perturbation of soil nutrient availability
(fertilization) and species composition (removal of co-dominant dwarf shrubs). Species cover was assessed non-destructively
before the start of the treatments (1995), at the end of the treatments (1999) and 4 years after the treatments ended (2003).
Shrub removal had rather modest effects on heath vegetation, except for mosses which decreased significantly in removal plots.
Fertilization decreased the cover of shrubs, mosses, and some graminoids but increased the cover of Festuca rubra. Fertilization converted heath to grassland, but the response of graminoid species was individualistic. Fertilization decreased
vascular species richness and evenness, probably through negative effects of shading and litter accumulation on plant growth
or recruitment. The vegetation had not recovered completely 4 years after the perturbations had stopped. This suggests that,
in contrast to rapid responses to species removal and fertilization, recovery from these perturbations was rather slow, presumably
because recovery was affected by long-term biotic interactions and species controls on ecosystem properties. 相似文献