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Appl Environ Microbiol, February 1998, p. 688-694, Vol. 64, No. 2
Institute of Zoology and Limnology,
University of Innsbruck, A-6020 Innsbruck, Austria
Received 7 July 1997/Accepted 17 November 1997
We applied transmission electron microscopy and densitometric image
analysis to measure the cell volume (V) and dry weight (DW)
of single bacterial cells. The system was applied to measure the DW of
Escherichia coli DSM 613 at different growth phases and of
natural bacterial assemblages of two lakes, Piburger See and
Gossenköllesee. We found a functional allometric relationship between DW (in femtograms) and V (in cubic micrometers) of
bacteria (DW = 435 · V0.86); i.e.,
smaller bacteria had a higher ratio of DW to V than larger cells. The measured DW of E. coli cells ranged from 83 to
1,172 fg, and V ranged from 0.1 to 3.5 µm3
(n = 678). Bacterial cells from Piburger See and
Gossenköllesee (n = 465) had DWs from 3 fg
(V = 0.003 µm3) to 1,177 fg
(V = 3.5 µm3). Between 40 and 50% of
the cells had a DW of less than 20 fg. By assuming that carbon
comprises 50% of the DW, the ratio of carbon content to V
of individual cells varied from 466 fg of C µm
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Copyright © 1998, American Society for Microbiology. All rights reserved.
Determination of Bacterial Cell Dry Mass by
Transmission Electron Microscopy and Densitometric Image
Analysis
3 for
Vs of 0.001 to 0.01 µm3 to 397 fg of C
µm
3 (0.01 to 0.1 µm3) and 288 fg of C
µm
3 (0.1 to 1 µm3). Exponentially growing
and stationary cells of E. coli DSM 613 showed conversion
factors of 254 fg of C µm
3 (0.1 to 1 µm3)
and 211 fg of C µm
3 (1 to 4 µm3),
respectively. Our data suggest that bacterial biomass in aquatic environments is higher and more variable than previously assumed from
volume-based measurements.
*
Corresponding author. Mailing address: Institut fur
Zoologie und Limnologie, Universitat Innsbruck Technikerstr. 25, A-6020 Innsbruck, Austria. Phone: 43 512 507 6130. Fax: 43 512 507 2930. E-mail: roland.psenner{at}uibk.ac.at.
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