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  • 1
    Electronic Resource
    Electronic Resource
    Amino acid uptake and respiration by marine heterotrophs (1976)
    Springer
    Marine biology 35 (1976), S. 41-47 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The concentration and turnover of dissolved free amino acids were measured in samples from 25 and 100 m on three occasions at a station 6 miles off the California (USA) coast. Individual amino acid concentrations varied from undetectable (〈0.05 μg/l) to 3 μg/l, the total amino acid concentration from 1.8 to 8.5 μg/l. The greater concentration of total amino acids was always found at 25 m. The predominant amino acids were serine, lysine, aspartate, glutamate and alanine; reliable analyses could not be made for glycine because of a high blank. For the 10 individual amino acids studied, the rate of heterotrophic turnover ranged from undetectable to 1.2 μg/l day-1; serine, aspartate, alanine and glutamate showed the highest rates. In samples from 25 m, the rates were 15 to 20 times higher than those taken from 100 m. The total calculated flux of the amino acids studied varied from 0.015 to 3.2 μg/l day-1 and amounted to 1–10% of photosynthetic carbon dioxide fixation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00386673
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  • 2
    Electronic Resource
    Electronic Resource
    Release of photoassimilated carbon as dissolved organic matter by marine phytoplankton (1974)
    Springer
    Marine biology 28 (1974), S. 305-310 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The release of photoassimilated carbon as dissolved organic matter was studied in situ in oligotrophic and eutrophic marine waters and in axenic laboratory cultures. Percentage extracellular release (PER), integrated for the trophogenic zone, ranged from 6 to 12% in eutrophic waters and from 17 to 27% in oligotrophic seas. Most of the algal cultures released low amounts of dissolved organic matter (∼5%) during exponential growth. The highest levels of PER were observed in surface and deep samples, possibly as a result of elevated photorespiration and senescent cells. The generally lower values for extracellular release reported in this work as compared to other studies may be partly due to improved experimental techniques which minimized previously encountered artifacts.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00388498
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  • 3
    Electronic Resource
    Electronic Resource
    Size fractionation of natural aquatic populations associated with autotrophic and heterotrophic carbon uptake (1975)
    Springer
    Marine biology 33 (1975), S. 215-220 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Natural phytoplankton samples from the Gulf of California were incubated with radioactive bicarbonate or glucose, with or without the addition of gentamycin, a broad spectrum antibiotic which inhibits bacterial activity but has little effect on many algae. The relative distribution of chlorophyll and radioactivity in particles retained by filters of 3 and 0.45 μ mean pore size was measured. From 13 to 83% of the 14C-bicarbonate assimilated by natural populations appeared to be associated with organisms having a smallest dimension less than 3 μ. These were probably algae, since the distribution of chlorophyll on the filters was similar to that of the radioactivity. Furthermore, gentamycin treatment did not change the distribution of radioactivity from 14C-bicarbonate. In these waters, considerable photosynthesis may be carried out by ultra-nannoplankton (3 to 1 μ). Glucose was assimilated mainly by bacteria, of which more than 90% passed through 3 μ filters. Gentamycin significantly reduced glucose uptake in most cases. Although this method cannot be adopted uncritically for the estimation of carbon flux from photoautotrophs to heterotrophs, differential filtration can be used to elucidate the size distribution of various metabolic groups in the plankton.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00390925
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  • 4
    Electronic Resource
    Electronic Resource
    Autoradiographic screening for potential heterotrophs in natural algal populations of Lake Kinneret (1975)
    Springer
    Microbial ecology 2 (1975), S. 252-260 
    Details
    ISSN: 1432-184X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Microautoradiography was used to screen natural phytoplankton populations from Lake Kinneret for their ability to take up radioactive organic substrates (glucose, acetic acid, amino acids, and glycollic acid. Several of the important Chlorophyta (Pediastrum spp.,Actinastrum hantzschii, Kirchncriella spp.,Coelastrum spp.,Scenedesmus spp., andTetraëdron spp.) and Cyanophyta (Microcystis spp.,Merismopedia sp.,Chroococcus spp., andAnabaena spp.) showed consistent organic uptake. However, the principal bloom former, the dinoflagellatePeridinium cinctum fawestii and most of the pelagic algae observed, never assimilated any of the above substrates. Autoradiographic surveys permit rapid screening of algal populations for species which are capable of taking up organic matter and can indicate potential facultative heterotrophs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02011646
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  • 5
    Electronic Resource
    Electronic Resource
    Natural populations of bacteria in Lake Kinneret: Observations with scanning electron and epifluorescence microscopy (1987)
    Springer
    Microbial ecology 13 (1987), S. 1-12 
    Details
    ISSN: 1432-184X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The bacterioplankton assemblage in Lake Kinneret, Israel, sampled on 6 occasions representative of different seasonal conditions was studied with scanning electron microscopy (SEM) and epifluorescence microscopy after acridine-orange staining. In near-surface (1–3 m) samples taken in October 1981 and March 1983, several unusual types of budding, appendaged, and filamentous cells were found. During lake stratification, typical large anaerobic forms (including photosynthetic green sulphur bacteria) were observed in samples from the metalimnion and deep (40 m) hypolimnion. Epifluorescence counts indicated that bacteria in the water column ranged from 0.55 to 2.67 × 106 cells ml−1.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02014959
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  • 6
    Electronic Resource
    Electronic Resource
    High performance liquid chromatography detection of phototrophic bacterial pigments in aquatic environments (1990)
    Springer
    Microbial ecology 19 (1990), S. 127-136 
    Details
    ISSN: 1432-184X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Pigment extracts of phototrophic bacteria isolated from Lake Kinneret (Rhodopseudomonas palustris, Thiocapsa roseopersicina, Prosthecochloris aestuaris andChlorobium phaeobacteroides) were studied by means of high performance liquid chromatography (HPLC). An absorption wavelength of 360 nm provided the best resolution among the pigments of the species tested and between them and chlorophylla. Signature pigments were identified for each of these species, and their presence was thereby monitored in lake water samples.C. phaeobacteroides, which was observed in the anaerobic hypolimnion and predominated in the metalimnion, was recognized by a characteristic cluster of major chlorophyllous pigment peaks. The spectral qualities of these pigments were close but not identical to published data on bacteriochlorophylle, presumably due to the use of different solvents for extraction. The intensity of these pigment peaks was employed to determine the depth of the greatest phototrophic bacterial biomass, which was not related to that of algae.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02012094
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  • 7
    Electronic Resource
    Electronic Resource
    Effects of iron and chelation on Lake Kinneret bacteria (1993)
    Springer
    Microbial ecology 26 (1993), S. 1-8 
    Details
    ISSN: 1432-184X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The response of natural populations of bacteria (prepared by passing Lake Kinneret water through 1 μm filters) to additions of Fe2+ and/or the chelator ethylenediaminetetraacetic acid (EDTA) was followed by measuring the incorporation of 3H-thymidine into 〉0.2 μm particulates, and also by determining the increments in cell numbers after 24 h. In most cases, a stimulation of 3H-thymidine incorporation was observed in supplemented samples relative to untreated controls after 3 and 24 h incubation. The increase in bacterial numbers was also enhanced by these supplements. Generally, EDTA alone evoked a greater stimulation than Fe2+; combined supplements gave no further increase. This response pattern appeared consistently throughout the year in samples taken from near-surface lake waters. These results suggest that the availability of iron or chelators may play an important role in regulating bacterial metabolism and growth even in aquatic ecosystems like Lake Kinneret where ambient concentrations of total Fe are relatively high.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00166024
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  • 8
    Electronic Resource
    Electronic Resource
    Simultaneous measurement of phosphorus and carbon uptake in Lake Kinneret by multiple isotopic labeling and differential filtration (1977)
    Springer
    Microbial ecology 3 (1977), S. 279-288 
    Details
    ISSN: 1432-184X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Differential filtration and multiple isotopic labeling were combined to study the uptake of [14C]bicarbonate, [14C]glucose, and [32P]orthophosphate by microplakton in Lake Kinneret, Israel. Short-term (4 hr) uptake experiments showed seasonal changes in the size distributions of organisms taking up inorganic carbon, glucose carbon, and orthophosphate in the lake water. In a time-course experiment of 48 hr (Jan 1976) most, but not all, of the photosynthetic activity (average 72%) and a similar fraction of chlorophyll (72%) were associated with organisms retained on 3-μm Nuclepore filters (retention on 0.4-μm filters was 100%). About 90% of the organisms that assimilated glucose passed through 3-μm filters. Photosynthetic carbon fixation, dark carbon uptake, and heterotrophic uptake of glucose carbon accounted for 99%, 1%, and 1%, respectively, of the total net carbon assimilated during the first 6 hours. Radioactive phosphorus showed an initial rapid uptake into particles, which was not affected by light or dark. We suggest that this methodology has a wide potential for elucidating the flux of nutrients into various components of the microplankton and in characterizing different aquatic environments.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02010736
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  • 9
    Electronic Resource
    Electronic Resource
    Differential filtration studies of carbon flux from living algae to microheterotrophs, microplankton size distribution and respiration in Lake Kinneret (1980)
    Springer
    Microbial ecology 6 (1980), S. 189-198 
    Details
    ISSN: 1432-184X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The flux of newly photosynthetically fixed, dissolved organic carbon (PDOC) from phototrophs to microheterotrophs in Lake Kinneret was examined by differential (3 and 0.4μm) filtration after samples were incubated with14C-bicarbonate for 3 hours (in the light) and subsequently for 21 hours (in darkness). Only a small proportion (average about 10%) of the carbon fixed from14C-bicarbonate in the light was associated with particulate matter 〈3μm. In 14 out of 16 experiments there was no significant decrease in the relative proportion of radioactivity associated with larger (〉3μm) organisms after the dark period, suggesting that the amount of PDOC taken up by unclumped, single bacteria (〈3μm) was not very great. Respiration rates, estimated by the decrease in14C particulate counts in the dark period, ranged from 3.4 to 21.2% of daylight net photosynthesis. In almost all cases, parallel experiments with additions of radioactive glucose or amino acids indicated that the majority of active heterotrophs passed through 3μm filters. Apparent residence times for glucose and amino acids were 20 to 168 hours and 20 to 152 hours, respectively.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02010384
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  • 10
    Electronic Resource
    Electronic Resource
    Dinoflagellate ribosomal RNA; an evolutionary relic? (1975)
    Springer
    Journal of molecular evolution 5 (1975), S. 307-313 
    Details
    ISSN: 1432-1432
    Keywords: rRNA Evolution ; Dinoflagellate Phylogeny ; Dinoflagellate rRNA
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The apparent molecular weights of the rRNA subunits of the dinoflagellatePeridinium cinctum fa.westii were determined by polyacrylamide gel electrophoresis to obtain an indication of its evolutionary status. The apparent molecular weights of thePeridinium light and heavy rRNA subunits were 0.7 and 1.23 × 106 respectively. The light rRNA is therefore typically eukaryotic but the heavy rRNA has a significantly lower MW than previously reported for higher eukaryotes which range from 1.3 to 1.75 × 106 depending on their evolutionary position. Thus by this criterionPeridinium is similar to red algae and may represent a eukaryotic stage, lower than fungi or green plants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01732217
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