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  • 1
    ISSN: 1573-5036
    Keywords: Acetobacter ; Herbaspirillum ; growth ; identification ; PCR ; sugarcane
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Nitrogen-fixing Acetobacter diazotrophicus, Herbaspirillum seropedicae and Herbaspirillum rubrisubalbicans colonize sugar cane, and are thought to be capable of supplying high levels of fixed nitrogen to this plant. Eight A. diazotrophicus, two H. seropedicae and four H. rubrisubalbicans isolates were identified and compared by complementary biochemical and genetic methods. Utilization of carbon sources and antibiotic resistance patterns allowed differentiation of A. diazotrophicus from Herbaspirillum species. In order to distinguish strains within A. diazotrophicus species, the polymerase chain reaction was employed, using a Rhizobium meliloti dctA primer under low stringency hybridization conditions.
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  • 2
    ISSN: 1573-5117
    Keywords: toxicity ; cultures ; oligochaetes ; T. tubifex ; growth ; reproduction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Reproduction in Tubifex tubifex is being used as part of a suite of indicators of sediment toxicity in Canada and Spain, and reproduction of T. tubifex is being considered as a component of sediment objectives for environmental regulation and clean-up in the Canadian Great Lakes. The data being used to set these reproductive targets have been developed from a single culture of T. tubifex from Lake Erie. The plasticity of this particular species is well known and before it can be adopted widely as a test organism it is necessary to determine whether a single culture source should be used or if cultures derived from different populations respond similarly. A series of experiments with two cultures, one from Lake Erie the second from a small mountain stream in Northern Spain have shown that the Spanish worms appear to produce fewer cocoons per adult (mean 8.6 S.D. 1.0) than those from Lake Erie (mean 10.4 S.D. 0.3) at 22.5 °C, a standard test temperature. The number of young produced per adult by the Spanish culture is also lower (mean 19.0 S.D. 4.6) than the L. Erie population (mean 30.6 S.D. 2.3), however, the Spanish population has higher reproductions rates at a lower temperature. The Spanish worms also have lower and more variable growth rates than the Canadian population. There also appear to be slight differences in the sensitivities to toxicants, with the Canadian worms having higher LC50s for copper, chromium and cadmium. While there are differences in the responses in the two cultures these are not considered to be sufficient to invalidate the use of either population in a standard bioassay protocol as long as appropriate calibration and validation are undertaken.
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  • 3
    ISSN: 1573-5117
    Keywords: β-carotene ; baker's yeast ; growth ; survival
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Coloration of phyllopods varies from place to place and from one life stage to another. It ranges from translucent or whitish through gray, blue, green, orange, and reddish. Here, we present experimental evidence for a food- dependent color pattern inThamnocephalus platyurus Packard. The presence or absence of the synthetic pigment trans — β — carotene in a baker's yeast diet was the controlling factor. All the 24 old larvae used in the experiment were whitish in color. From day 6 until the end the experiment (day 11), 100% of the shrimps under a diet with synthetic trans — β — carotene (treatment 1) exhibited a characteristic color pattern which consisted of an orange color in the cercopods, and in all theracopods; the rest of the body exhibited no particular color. In comparison, 100% of the shrimps under a diet without synthetic trans — β — carotene (treatment 2) were whitish throughout the body. In females from treatment 1, the ovaries and oocytes were green-bluish, while in females from treatment 2 the ovaries and oocytes were whitish. No significant differences in survival and growth were found, except that at day 9, there was a significant difference in growth, the females with the synthetic trans — β — carotene group growing faster.
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  • 4
    ISSN: 1573-5117
    Keywords: Thamnocephalus ; Branchinecta ; growth ; filter-feeders ; feeding ; clay ; silicium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We designed and standardized a culture method for freshwater anostracans using diets free of live algae.Thamnocephalus platyurus andBranchinecta lindahli were used as test organisms. We used baker's yeast as basic food and added inert particles (clay or amorphic silicium dioxide) to improve the digestion of the yeast. A flow-through culture system was used, according to a fixed feeding schedule, to supply separately, culture medium (tap water), food, and inert particle suspensions. Three variants with baker's yeast as basic, food were compared for survival, growth, and reproduction. A diet of solely baker's yeast (diet 1) or baker's yeast supplemented with vegetal oil containing ß-carotene (diet 2) was unsuitable for reproduction ofT. platyurus. Cyst production was only achieved when diet 2 was supplemented with fish oil andSpirulina powder (diet 3). This suggests that not only a digestibility problem, but also nutritional deficiencies are present in baker's yeast.
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  • 5
    ISSN: 1573-3017
    Keywords: Tubifex tubifex ; sediment bioassay ; hormesis ; growth ; reproduction ; egestion rates
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Toxicity assessment based on sediment chronic bioassays with the aquatic worm Tubifex tubifex was performed at ten contaminated sites in the industrial area of Bilbao (Northern Spain). One control and three reference sites were also included. Tubifex bioassay measures both survival and reproduction impairment. These endpoints have been contrasted and discussed in relation to somatic growth and both individual and total biomass of cocoons. Survival was only affected at one site which was heavily contaminated by organic compounds, mainly PAHs. A group of four severely ecotoxic sediments was characterised by a drastic reduction in number and size of cocoons, and adult somatic growth. In other group of sediments, some significant increases were found for these variables. It is suggested that these increases represent an effect of hormesis. An index of reproductive effort was used to integrate the relationship between somatic growth and reproduction. Values of reproductive effort at the test sediments were lower than those at the control sediment, suggesting a conservative strategy of oligochaete worms which consisted in an investment into somatic line (growth) at the expenses of offspring. Rates of food consumption which were estimated from egestion rates, were low at the contaminated sites. This fact could be related to the low production levels found at these sites and may reflect avoidance feeding behaviour of the oligochaete worms within the sediments. At some reference sites, high production could have resulted from high nutritional quality of sediments, or to an hormetic effect due to low concentration of some chemicals. Results are discussed in relation to toxicity data from sediment three-brood bioassay with Daphnia magna Straus performed separately on the same sediments.
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  • 6
    ISSN: 1573-5176
    Keywords: agar ; Gracilaria tenuistipitata ; growth ; salinity ; seawater pH
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Acclimation responses of the red alga Gracilaria tenuistipitata var. liui collected on the northwest coast of Philippines were determined in laboratory setups and outdoor cultivation tanks in Haifa, Israel. Growth under laboratory conditions was influenced by all three variables studied, namely, temperature (20 or 30 °C), salinity (20, 30 or39‰) and seawater pH (6.5, 7.0, 8.0 or ≥ 9.0). In 250 mL flasks lacking pH control growth was influenced by temperature only at 20 ‰, whereas at 39 ‰, growth rates were similar at 20 or 30 °C. In 500 mL cylinders in which pH was controlled, growth rates were significantly different at a pH of 6.5 and 7.0 for all salinities, with maximal rates occurring in 39 ‰. At pH 8.0, and above, growth rates between salinities were similar and reduced to approximately 50% at a pH of 9.0 compared to rates at a pH of 6.5. Photosynthesis responses generally resembled growth responses both, in 250 mL and 500 mL cultures. In 40-L outdoor tanks, weekly growth and agar yields were apparently enhanced by increasing light intensities (up to full sunlight) and nutrient concentrations (up to 0.2 mM PO3 2- and 2.0 mM NH4 +), and rates averaged four times higher than rates determined in the smaller flask cultures. This study shows broad salinity tolerance of G. tenuistipitata var. liui and its ability to sustain growth rates that are among the highest measured for Gracilaria spp. in outdoor cultures.
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Yeast 14 (1998), S. 501-515 
    ISSN: 0749-503X
    Keywords: Saccharomyces cerevisiae ; bakers' yeast ; pH homeostasis ; cytoplasmic pH ; vacuolar pH ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: The effects of monovalent cations on the internal pH of yeast were studied. Our former procedure was modified, inducing maximal alkalinization of the cells with 100 mM-NH4OH instead of Tris base. The pH values were lower than reported before (Peña et al., J. Bacteriol. 1995 177, 1017-1022). With glucose as substrate, the internal cytoplasmic pH reached higher values when incubating at an external pH of 6·0, as compared to pH 4·0. Monovalent cations added approximately 5 min after glucose produced a further increase in the internal pH, which was higher at a previous incubation pH of 4·0 than that observed at pH 6·0. The selectivity of the changes followed a similar order to that of the transport system for monovalent cations.When incubating cells with glucose for more than 30 min, the initial changes of the internal pH appeared to be regulated by the cell. However, under the fluorescence microscope, it was observed that pyranine, which was confined to the cytoplasm during the first 15 min, was progressively concentrated in the vacuole. By studying the fluorescence changes of cells electroporated and then incubated with glucose or glucose plus potassium, we could follow the internal pH of this organelle, obtaining values within the range reported by other authors. Also, in cells preincubated with glucose for 60 min, and electroporated afterwards, the fluorescence of pyranine, which only entered the cytoplasm, allowed us to measure the pH of this compartment, showing that it was more alkaline than the vacuole. Moreover, the cytoplasmic pH increased upon addition of glucose or potassium. The vacuolar pH, on the other hand, increased upon addition of potassium after glucose, but decreased upon addition of glucose. In addition, incubation of the cells with glucose with or without pyranine produced vesiculation of the vacuole. © 1998 John Wiley & Sons, Ltd.
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Yeast 11 (1995), S. 1399-1411 
    ISSN: 0749-503X
    Keywords: flor yeast ; Sherry wine ; flor formation ; DNA polymorphism ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Yeast strains which form velum on the surface of Sherry wine during the aging process have been isolated and characterized. According to their metabolic and molecular features most of the yeasts that were isolated belong to different races of Saccharomyces cerevisiae (beticus, cheresiensis, montuliensis and rouxii). Due to the conditions under which these yeasts were isolated, all strains have in common the capacity to develop a film as an adaptive mechanism which allows them to grow and survive in 15·5% vol. ethanol. All strains were prototrophs for amino acids and most vitamins but they gave different responses to the killer factor. However, whereas their physiological features were similar, they showed a great heterogeneity with regards to the nuclear and mitochondrial genome (mtDNA): DNA content per cell was quite variable (1·3 to 2n), electrophoretic karyotypes of nuclear genomes indicated a main pattern with some variations, and polymorphism shown by the mtDNA was very high. Under extreme conditions such as Sherry wine with 15·5% vol. ethanol, no fermentable sugar and an exclusively oxidative metabolism, cells hardly grow and the maintenance of a live population depends on survival and respiration, which in turn depend on the mtDNA. At the same time these environmental conditions are mutagenic for the mtDNA, causing an increase in variation. Thus, the polymorphism observed might reflect the enormous variability induced by the ethanol followed by the selection of those mtDNA sequences which make the mitochondria metabolically active under these conditions.
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Yeast 11 (1995), S. 137-144 
    ISSN: 0749-503X
    Keywords: Saccharomyces cerevisiae ; HXK1 ; HXK2 ; GLK1 ; mRNA ; transcriptional control ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: In Saccharomyces cerevisiae, the transcriptional regulation of most glycolytic genes has been extensively studied. By contrast, little is known about the transcriptional control of the three glucose-phosphorylating enzymes, although this catalytic reaction has an important role in the regulation of cell metabolism. In this paper, we describe the transcriptional regulation of the HXK1, HXK2 and GLK1 genes in the hope of revealing differences in the steady-state levels of mRNA associated with a particular carbon source used in the culture medium. Our results provide evidence supporting a differential expression of the three genes depending on the carbon source used for growth. We have also studied the induction and repression kinetics of mRNA expression for the HXK1, HXK2 and GLK1 genes.
    Additional Material: 4 Ill.
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  • 10
    ISSN: 0749-503X
    Keywords: Candida albicans ; heat-shock (stress) proteins ; nucleotide sequence ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: We have cloned and sequenced a Candida albicans gene (SSB1) encoding a potential member of the heat-shock protein seventy (hsp70) family. The protein encoded by this gene contains 613 amino acids and shows a high degree (85%) of sequence identity to the ssb subfamily (ssb1 and ssb2) of the Saccharomyces cerevisiae hsp70 family. The transcribed mRNA (2·1 kb) is present in similar amounts both in yeast and germ tube cells of C. albicans. The sequence data has been deposited in the GenBank data library under the Accession Number X97723. © John Wiley & Sons, Ltd.
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