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Water from several oligotrophic reservoirs of the North West Water Authority at Longridge, Lancashire, supported only sparse growth of streptomycetes isolated from the reservoirs. Growth was enhanced by nutrient-amendment of the water and one common isolate, identified as Streptomyces albidoflavus , produced geosmin in water which was supplemented with sufficient concentrations of available carbon, nitrogen and phosphorus. The minimum concentrations required for geosmin production were higher than those recorded in natural reservoir water. Synthesis of geosmin in water also required a minimum temperature of about 15dEC. Sterilized samples of reservoir sediment, sediment extract, plant debris from banks and surrounding soil also supported geosmin production by S. albidoflavus. Both bank debris and exposed sediment developed earthy odours without inoculation. The structure of reservoir banks influenced the quantity of plant growth and accumulation of litter, and therefore also the potential for contamination of reservoir water by geosmin. The potential of these various sites of geosmin production to contaminate reservoir water is assessed. 相似文献
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LARSSON MARIE; LARSSON CARL-MAGNUS; GUERRERO MIGUEL G. 《Journal of experimental botany》1985,36(9):1373-1386
Larsson, M., Larsson, C.-M. and Guerrero, M. G. 1985. Photosyntheticnitrogen metabolism in high and low CO2-adapted Scenedesmus.I. Inorganic carbon-dependent O2 evolution, nitrate utilizationand nitrogen recycling.J. exp Bot. 36: 13731386 Scenedesmus obtusiusculus Chod. was grown on an inorganic mediumflushed with either air or air supplemented with 3% CO2. Inair-grown cells, O2 evolution dependent on low, but not high,HCO3 concentrations was strongly inhibited by the carbonicanhydrase inhibitor acetazolamide. Cells grown with 3% CO2 exhibitedlow rates of O2 evolution at low external inorganic C; however,after 30 min in air O2 evolution rates at low inorganic C approachedthose of air-grown cells. These results are compatible withthe view that Scenedesmus develops a CO2 concentratingmechanism in air, with carbonic anhydrase as an importantconstituent When 3% CO2-grown cells were subjected to air-level of CO2,just a transient decline in NO3 utilization was observed,but in the presence of acetazolamide the rate of the processdecreased drastically in response to the decrease in the CO2level. In CO2-free air NO3 was taken up at high ratesbut in a deregulated manner, leading to release of NH4+. A portionof the NO3 taken up in the absence of CO2 was apparentlyassimilated Cellular nitrate reductase (NR) activity initially decreasedbut subsequently recovered after a transition from 3% CO2 toair. In the presence of acetazolamide, a persistent decreasein NR activity was observed. Cellular glutamine synthetase (GS)activity increased after transition from 3% CO2 to air, theactivity increase being unaffected by acetazolamide. NH4+ releaseto the medium in the presence of L-methionine-D, L-sulphoximine(MSO) transiently increased in 3% CO2-grown cells in responseto a transfer to air. MSO-induced NH4+ release was in fact higherin air-grown cells than in 3% CO2-grown cells. Glycollate wasinitially released after transition from 3% CO2 to air, butthere was no difference in glycollate release between MSO-treatedand untreated cells. In air-adapted Scenedesmus, N recyclingseems to be of minor importance in comparison to primary N assimilation Key words: CO2-fixation, N recycling, nitrate uptake, Scenedesmus 相似文献
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LARSSON CARL-MAGNUS; LARSSON MARIE; GUERRERO MIGUEL G. 《Journal of experimental botany》1985,36(9):1387-1395
Larsson, C.-M., Larsson, M. and Guerrero, M. G. 1985. Photosyntheticnitrogen metabolism in high and low CO2-adapted Scenedesmus.II. Effect of ammonium and methionine sulphoximine on nitrateutilization.J. exp. Bot. 36: 13871395 In 3% CO2-grown Scenedesmus obtusiusculus Chod. utilizing NO3J as the N source, NH4+ addition caused a prompt inhibitionof NO3 utilization. Nitrate reductase (NR) activity declinedrapidly in response to the presence of NO4+, but the cessationof NO3 utilization was too rapid to be accounted forby the loss in NR activity. The first site of NO4+ inhibitionin these cells seems to be the entrance of NO3 into thecells. Upon exhaustion of NO4+ from the medium, NO3 utilizationwas rapidly restored and NR activity increased. Air-grown cellswere much less sensitive to the effect of NO4+, more than 30min being required for added NO4+ to cause complete inhibitionof NO3 utilization. In these cells, NO3 uptakeand NR activity decreased in parallel in response to NO4+ addition.In 3% CO2-grown cells simultaneously subjected to NO4+ and air-levelof CO2, NO4+ initially inhibited NO3 utilization completely,but a slight recovery took place after approximately 20 min The glutamine synthetase (GS) inhibitor L-methionine D, L-sulphoximine(MSO) behaved as a potent inhibitor of NO3 uptake in3% CO2-grown cells, but had considerably less effect in air-growncells, although the time-course of the MSO-induced inhibitionof GS was the same in both cases Key words: Ammonium, nitrate utilization, Scenedesmus 相似文献
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Antigens of the Ii System on Lymphocytes 总被引:8,自引:0,他引:8
K. H. SHUMAK ROSE A. RACHKEWICH MARIE C. CROOKSTON J. H. CROOKSTON 《Nature: New biology》1971,231(22):148-149
USUALLY Ii specificity is assigned to cold agglutinins on the basis of their reactions with the red cells of human adults (adult red cells) and newborn infants (cord red cells). Those which react more strongly with adult red cells are said to detect I antigen and are designated anti-I; those which react more strongly with cord red cells are said to detect i antigen and are designated anti-i1,2. We have now found that I and i antigens can be easily detected on lymphocytes. 相似文献
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'Spicules' in halysitids: a reply 总被引:1,自引:0,他引:1
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The Biology of the Tospoviruses 总被引:1,自引:0,他引:1
The tospoviruses are a diverse, cosmopolitan and economically important genus of plant viruses. In the recent past, interest in the tospoviruses has been rekindled with the resurgence and expansion of tomato spotted wilt virus and the appearance of new tospoviruses, including impatiens necrotic spot. This renewed interest in the tospoviruses, accompanied with the many recent advances in plant virology techniques, particularly those utilising molecular biology, have resulted in a rapid growth of our understanding of these viruses. This paper provides a review of the tospoviruses, encompassing all the major aspects of their biology, including the recent changes in the classification of the genus and current knowledge on molecular biology, vector relations, control and diagnosis. 相似文献
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