de Beer, D, Glud, AN, Epping, E & Kuhl, M 1997, 'A fast-responding CO, microelectrode for profiling sediments, microbial mats, and biofilms', Limnology and Oceanography, vol. 42, no. 7, pp. 1590-1600.
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de Beer, D, Schramm, A, Santegoeds, CM & Kuhl, M 1997, 'A nitrite microsensor for profiling environmental biofilms', Applied and Environmental Microbiology, vol. 63, no. 3, pp. 973-977.
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A highly selective liquid membrane nitrite microsensor based on the hydrophobic ion-carrier aquocyanocobalt(III)-hepta(2-phenylethyl)-cobrynate is described. The sensor has a tip diameter of 10 to 15 (mu)m. The response is log-linear in freshwater down to 1 (mu)M NO(inf2)(sup-) and in seawater to 10 (mu)M NO(inf2)(sup-). A method is described for preparation of relatively large polyvinyl chloride (PVC)-gelled liquid membrane microsensors with a tip diameter of 5 to 15 (mu)m, having a hydrophilic coating on the tip. The coating and increased tip diameter resulted in more sturdy sensors, with a lower detection limit and a more stable signal than uncoated nitrite sensors with a tip diameter of 1 to 3 (mu)m. The coating protects the sensor membrane from detrimental direct contact with biomass and can be used for all PVC-gelled liquid membrane sensors meant for profiling microbial mats, biofilms, and sediments. Thanks to these improvements, liquid membrane sensors can now be used in complex environmental samples and in situ, e.g., in operating bioreactors. Examples of measurements in denitrifying, nitrifying, and nitrifying/denitrifying biofilms from wastewater treatment plants are shown. In all of these biofilms high nitrite concentrations were found in narrow zones of less than 1 mm.
Franklin, LA & Larkum, AWD 1997, 'Multiple strategies for a high light existence in a tropical marine macroalga', Photosynthesis Research, vol. 53, no. 2-3, pp. 149-159.
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Acclimation to high light conditions on the top of coral reefs was examined in the coenocytic, filamentous green macroalga Chlorodesmis fastigiata (C. Ag.) Ducker. Despite having a pool of violaxanthin, high light does not induce formation of zeaxanthin in this macroalga. Exposure to 11 and 33% of surface irradiance resulted in parallel, reversible declines in F(v)/F(m) and in the number of functional PSII centers. The quantum requirement for PSII inactivation was calculated to be approx. 2 x 107 photons. Recovery of PSII activity after low photon exposures did not depend on protein synthesis, unlike at higher photon exposures, where recovery was inhibited by 50% in the presence of lincomycin. Accumulation of inactive, quenching PSII centers is proposed as a mechanism of energy dissipation; only some of these centers require protein synthesis for reactivation. In natural-sized populations, midday photoinhibition was greater in filament tips than in bases, but the number of inactive PSII centers within entire filaments did not significantly change over the course of the day. It is proposed that the higher chlorophyll concentration in the tips provides protective shading to chloroplasts in lower regions, and that cytoplasmic streaming of chloroplasts within this siphonous alga limits the cumulative exposure to high light, thereby providing another level of protection from high light stress.
Fukshansky-Kazarinova, N, Fukshansky, L, Kuhl, M & Jørgensen, BB 1997, 'General theory of three-dimensional radiance measurements with optical microprobes', Applied Optics, vol. 36, no. 25, pp. 6520-6528.
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Measurements of the radiance distribution and ?uence rate within turbid samples with ?ber-optic radiance microprobes contain a large variable instrumental error caused by the nonuniform directional sensitivity of the microprobes. A general theory of three-dimensional radiance measurements is presented that provides correction for this error by using the independently obtained function of the angular sensitivity of the microprobes
Holst, G, Glud, RN, Kuhl, M & Klimant, I 1997, 'A microoptode array for fine-scale measurement of oxygen distribution', Sensors and Actuators B: Chemical, vol. 38-39, pp. 122-129.
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Klimant, I, Holst, G & Kuhl, M 1997, 'A simple fiberoptic sensor to detect the penetration of microsensors into sediments and other biogeochemical systems', Limnology and Oceanography, vol. 42, no. 7, pp. 1638-1643.
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Kuehl, M 1997, 'Microenvironmental controls of micro-phytobenthos', PHYCOLOGIA, vol. 36, no. 4, pp. 56-56.
Kuhl, M, Lassen, C & Revsbech, NP 1997, 'A simple light meter for measurements of PAR (400 to 700 nm) with fiber-optic microprobes: application for P vs E0 (PAR) measurements', Aquatic Microbial Ecology, vol. 13, pp. 197-207.
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A simple portable light meter for use with fiber-optic microprobes was developed. The meter has a flat spectral quantum responsivity for 400 to 700 nm light (photosynthetically available radiation, PAR). With scalar irradiance microprobes connected to the meter, it was possible to directly measure photosynthetically available quantum scalar irradiance, E0(PAR), at <100 µm spatial resolution and over a dynamic range from <1 to >1300 µmol photons m-2 s-1. We used the new instrument for scalar irradiance measurements in microbial mats from a freshwater lake (Lake Stigsholm, Denmark) and from a hypersaline pond (Eilat, Israel). Combined measurements of quantum scalar irradiance by fiber-optic microprobes and oxygenic photosynthesis by oxygen microelectrodes made it possible to measure gross photosynthesis as a function of the prevailing scalar irradiance (P vs E0 curves) at distinct depths within an undisturbed hypersaline microbial mat of immotile unicellular cyanobacteria (Aphanothece spp.).
La Roche, J, Van Der Staay, GWM, Partensky, F, Ducret, A, Aebersold, R, Li, R, Golden, SS, Hiller, RG, Wrench, PM, Larkum, AWD & Green, BR 1997, 'Evolution of chlorophyll-binding proteins', Trends in Plant Science, vol. 2, no. 4, p. 123.
Noll, T, Desponds, C, Belli, SI, Glaser, T & Fasel, N 1997, 'Histone H1 Expression Varies During The Leishmania Major Life Cycle', Molecular And Biochemical Parasitology, vol. 84, no. 2, pp. 215-227.
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The deduced amino acid sequence of Leishmania major sw3 cDNA reveals the presence of characteristic histone H1 amino acid motifs. However, the open reading frame is of an unusually small size for histone H1 (105 amino acids) because it lacks the coding p
O'MEARA, TJ, NESA, M & SANDEMAN, RM 1997, 'Antibody responses to Lucilia cuprina in sheep selected for resistance or susceptibility to L. cuprina', Parasite Immunology, vol. 19, no. 12, pp. 535-543.
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Ploug, H, Kuhl, M, Buchholz-Cleven, B & Jorgensen, BB 1997, 'Anoxic aggregates - an ephemeral phenomenon in the pelagic environment?', Aquatic Microbial Ecology, vol. 13, pp. 285-294.
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Radial microscale distributions of oxygen and pH were studied in ca 1.5 mm large laboratory-made aggregates composed of phytoplankton detritus and fecal pellets. Microsensor measurements were done at spatial increments down to 0.05 mm in a vertical flow system in which the individual aggregates stabilized their position in the water phase according to the upward flow velocity. The aggregates were surrounded by a diffusive boundary layer with steep gradients of oxygen and pH. They were highly heterotrophic communities both under natural light conditions and in darkness. pH was lowered from 8.2 in the surrounding water to 7.4 in the center of an anoxic aggregate. Sulfide was not detectable by use of sulfide microelectrodes in anoxic aggregates, and methanogenic bacteria could not be detected after PCR (polymerase chain reaction) amplification using archaebacterial-specific primers. The oxygen respiration rate decreased exponentially over time with a T1/2 of 2.3 d. Theoretical calculations of the volumetric oxygen respiration rate needed to deplete oxygen inside aggregates was compared to the density of organic matter in natural marine aggregates. These calculations showed that carbon limitation of heterotrophic processes would limit anoxic conditions to occurring only over a few hours, depending on the size of the aggregates. Therefore slow-growing obligate anaerobic microorganisms such as sulfate reducing bacteria and methanogenic bacteria may be limited by the relatively short persistence of anoxia in marine aggregates.
Ritchie, RJ, Trautman, DA & Larkum, AWD 1997, 'Phosphate Uptake in the Cyanobacterium Synechococcus R-2 PCC 7942', Plant and Cell Physiology, vol. 38, no. 11, pp. 1232-1241.
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Phosphate uptake rates in Synechococcus R-2 in BG-11 media (a nitrate-based medium, not phosphate limited) were measured using cells grown semi-continuously and in continuous culture. Net uptake of phosphate is proportional to external concentration. Growing cells at pHo 10 have a net uptake rate of about 600 pmol m-2s-1 phosphate, but the isotopic flux for 32P phosphate was about 4 nmol m-2 s-1. There appears to be a constitutive over-capacity for phosphate uptake. The Km and Vmax of the saturable component were not significantly different at pHo 7.5 and 10, hence the transport system probably recognizes both H2PO4- and HPO42-. The intracellular inorganic phosphate concentration is about 3 to 10 mol m-3, but there is an intracellular polyphosphate store of about 400 mol m-3. Intracellular inorganic phosphate is 25 to 50 kJ mol-1 from electrochemical equilibrium in both the light and dark and at pHo 7.5 and 10. Phosphate uptake is very slow in the dark (≈100 pmol m-2s-1) and is light-activated (pHo 7.5 ≈1.3 nmol m-2 s-1, PHo 10≈600 pmol m-2S-1). Uptake has an irreversible requirement for Mg2+ in the medium. Uptake in the light is strongly Na+-dependent. Phosphate uptake was negatively electrogenic (net negative charge taken up when transporting phosphate) at pHo 7.5, but positively electrogenic at pHo 10. This seems to exclude a sodium motive force driven mechanism. An ATP-driven phosphate uptake mechanism needs to have a stoichiometry of one phosphate taken up per ATP (1 PO4 in /ATP) to be thermodynamically possible under all the conditions tested in the present study.
Schreiber, U, Gademann, R, Ralph, PJ & Larkum, A 1997, 'Assessment of photosynthetic performance of Prochloron in Lissoclinum patella in hospite by chlorophyll fluorescence measurements', Plant And Cell Physiology, vol. 38, no. 8, pp. 945-951.
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Two new PAM fluorometers (pulse amplitude modulated) were used in an investigation of photosynthetic performance of Prochloron resident as a symbiont in the ascidian Lissoclinum patella, growing in a coral reef of Heron Island on the Great Barrier Reef.
Holst, G, Kuhl, M, Klimant, I, Liebsch, G & Kohls, O 1997, 'Characterization and application of temperature microoptodes for use in aquatic biology', ADVANCES IN FLUORESCENCE SENSING TECHNOLOGY III, Conference on Advances in Fluorescence Sensing Technology III, SPIE - INT SOC OPTICAL ENGINEERING, SAN JOSE, CA, pp. 164-170.
Klimant, I, Kuhl, M, Glud, RN & Holst, G 1996, 'Optical measurement of oxygen and temperature in microscale: strategies and biological applications', SENSORS AND ACTUATORS B-CHEMICAL, 3rd European Conference on Optical Chemical Sensors and Biosensors (EUROPT(R)ODE III), ELSEVIER SCIENCE SA LAUSANNE, ZURICH, SWITZERLAND, pp. 29-37.
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Kohls, O, Klimant, I, Holst, G & Kuhl, M 1997, 'Development and comparision of pH microoptodes for use in marine systems', MICRO- AND NANOFABRICATED ELECTRO-OPTICAL MECHANICAL SYSTEMS FOR BIOMEDICAL AND ENVIRONMENTAL APPLICATIONS, PROCEEDINGS OF, 1st SPIE Conference on Microfabricated and Nanofabricated Electro-Optical Mechanical Systems for Biomedical and Environmental Applications, SPIE - INT SOC OPTICAL ENGINEERING, SAN JOSE, CA, pp. 82-91.
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Pritchard, TR, Lee, RS & Ajani, PA 1997, 'Oceanic and anthropogenic nutrients and the phytoplankton response: Preliminary Findings', Pacific Coasts and Ports Conference Proceedings, Pacific Coasts and Ports '97, CAE University of Cantebury, Christchurch, New Zealand.
Pritchard, TR, Lee, RS & Ajani, PA 1997, 'Oceanic and Anthropogenic Nutrients and the Phytoplankton Response: Preliminary Findings (Oral Presentation). Pacific Coasts and Ports Conference 1997, New Zealand.', T. R.
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Oral Presentation