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Appl. Environ. Microbiol., Dec 1996, 4521-4528, Vol 62, No. 12
A Heissenberger, GG Leppard and GJ Herndl
The integrity of the intracellular structures and the presence and
dimension of the capsular envelope were investigated in marine
snow-associated and marine free-living bacteria by transmission electron
microscopy and special fixation techniques. Three categories depending on
the presence of internal structures were differentiated. In marine snow,
51% of the marine snow-associated bacterial community was considered
intact, 26% had a partly degraded internal structure, and 23% were empty
with only the cell wall remaining. For the free-living bacterial community,
34% were intact cells, 42% exhibited damage, and 24% of the cells were
lacking any internal structure. We also investigated the morphology and the
extent of the bacterial capsular envelope. More than 95% of all intact
marine snow-associated bacteria were surrounded by a capsule while
(apprx=)55% of empty marine snow-associated bacteria had no capsule. For
free-living bacteria, (apprx=)65% of the intact cells had a capsule while
(apprx=)80% of the empty free-living bacteria lacked a capsule. Thus there
is a clear trend from intact cells which are commonly surrounded by a
capsular envelope to empty bacteria for which only the cell wall is
remaining. Since bacterioplankton represent the largest living surface in
the ocean, it is concluded that the release of intracellular material from
bacteria into the environment as well as the release of extracellular
capsular material might fuel the dissolved organic matter pool of the
ocean.
Copyright © 1996, American Society for Microbiology
Relationship between the Intracellular Integrity and the Morphology of the Capsular Envelope in Attached and Free-Living Marine Bacteria
Institute of Zoology, University of Vienna, A-1090 Vienna, Austria, and Aquatic Ecosystem Protection Branch, National Water Research Institute, Environment Canada, Burlington, Ontario, Canada L7R 4A6, and Department of Biology, McMaster University, Hamilton, Ontario, Canada L8S 4K1
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