caa a22 4500 39755284X CHVBK 20180308164755.0 cr unu---uuuuu 161202e199610 xx s 000 0 eng 10.1111/j.1574-6941.1996.tb00336.x doi (NATIONALLICENCE)oxford-10.1111/j.1574-6941.1996.tb00336.x Microflora of a subalpine lake: bacterial populations, size and DNA distributions, and their dependence on phosphate [Elektronische Daten] [D.K. Button, B.R. Robertson, Friedrich Jüttner] In Lake Zürich, a deep subalpine mesotrophic lake, phosphate was low or limiting at 0.2 to 1 μM relative to combined nitrogen at 50 μM. Heterotrophic bacteria were responsible for 53% of the observed microbial wet biomass in our depth profile while phytoplankton, largely Planktothrix (Oscillatoria) rubescens, contributed most of the remainder. Most cell carbon was contributed by this carbon-sufficient cyanobacterium. A material balance indicated that most of the phosphate was sequestered by the bacteria due to a higher phosphate content and specific affinity for this nutrient. Size distributions of the heterotrophic bacteria were narrow; 90% of organisms were from 0.06 to 0.06 μ3 in volume. Several subpopulations of bacteria were resolved by flow cytometry, and bivariate fluorescence (DAPI-DNA) and light scatter (cell-size) histogram profiles varied with depth. One or two of these subpopulations appeared to be bacteria with sufficient cytoplasmic constituents to produce a normal light-scatter signal but retained only a small amount of DNA; an apparent content of 200 kbp or 5% of a usual oligobacterial genome. These helped increase the oligobacterial population to 6 × 106 ml−1. Application of published specific affinities and measured nutrient concentrations to formulations of system kinetics led to the conclusion that growth rates of the heterotrophic bacterial fraction were carbon limited with cell size, and thus populations were controlled by grazing. The depth profile indicated that phototrophs affected concentrations in a significant way. Considerations of nutrient uptake kinetics suggested that much potential capacity remained in the dissolved phosphate pool to support additional phytoplanktonic biomass. Computations led to the conclusion that, if phosphate is generally limiting in lakes, then additional mechanisms exist which limit populations of phytoplankton to sufficiently small values to allow phosphate accumulation to observed levels. Bacterial biomass then depends on the organic carbon from these phosphate-controlled organisms. © 1996 Federation of European Microbiological Societies. Published by Elsevier Science B.V. Bacterial biomass nationallicence Subalpine lake nationallicence Phosphate nationallicence Button D.K. Institute of Marine Science, University of Alaska, Fairbanks, Alaska 99775, USA aut Robertson B.R. Institute of Marine Science, University of Alaska, Fairbanks, Alaska 99775, USA aut Jüttner Friedrich Institut für Pflanzenbiologie, Limnologische Station, Seestrasse 187, Kilchberg, Switzerland aut FEMS Microbiology Ecology Blackwell Publishing Ltd 21/2(1996-10), 87-101 21:2<87 1996 21 femsec https://doi.org/10.1111/j.1574-6941.1996.tb00336.x text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1111/j.1574-6941.1996.tb00336.x text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Button D.K. Institute of Marine Science, University of Alaska, Fairbanks, Alaska 99775, USA aut NATIONALLICENCE 700 1- Robertson B.R. Institute of Marine Science, University of Alaska, Fairbanks, Alaska 99775, USA aut NATIONALLICENCE 700 1- Jüttner Friedrich Institut für Pflanzenbiologie, Limnologische Station, Seestrasse 187, Kilchberg, Switzerland aut NATIONALLICENCE 773 0- FEMS Microbiology Ecology Blackwell Publishing Ltd 21/2(1996-10), 87-101 21:2<87 1996 21 femsec Metadata rights reserved CC BY-NC-4.0 http://creativecommons.org/licenses/by-nc/4.0 nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-oxford