Sie können Bookmarks mittels Listen verwalten, loggen Sie sich dafür bitte in Ihr SLUB Benutzerkonto ein.
Medientyp:
E-Artikel
Titel:
Morphological and Compositional Changes in a Planktonic Bacterial Community in Response to Enhanced Protozoan Grazing
Beteiligte:
Jürgens, Klaus;
Pernthaler, Jakob;
Schalla, Sven;
Amann, Rudolf
Erschienen:
American Society for Microbiology, 1999
Erschienen in:
Applied and Environmental Microbiology, 65 (1999) 3, Seite 1241-1250
Sprache:
Englisch
DOI:
10.1128/aem.65.3.1241-1250.1999
ISSN:
1098-5336;
0099-2240
Entstehung:
Anmerkungen:
Beschreibung:
ABSTRACTWe analyzed changes in bacterioplankton morphology and composition during enhanced protozoan grazing by image analysis and fluorescent in situ hybridization with group-specific rRNA-targeted oligonucleotide probes. Enclosure experiments were conducted in a small, fishless freshwater pond which was dominated by the cladoceranDaphnia magna. The removal of metazooplankton enhanced protozoan grazing pressure and triggered a microbial succession from fast-growing small bacteria to larger grazing-resistant morphotypes. These were mainly different types of filamentous bacteria which correlated in biomass with the population development of heterotrophic nanoflagellates (HNF). Small bacterial rods and cocci, which showed increased proportion after removal ofDaphniaand doubling times of 6 to 11 h, belonged nearly exclusively to the beta subdivision of the classProteobacteriaand theCytophaga-Flavobacteriumcluster. The majority of this newly produced bacterial biomass was rapidly consumed by HNF. In contrast, the proportion of bacteria belonging to the gamma and alpha subdivisions of theProteobacteriaincreased throughout the experiment. The alpha subdivision consisted mainly of rods that were 3 to 6 μm in length, which probably exceeded the size range of bacteria edible by protozoa. Initially, these organisms accounted for less than 1% of total bacteria, but after 72 h they became the predominant group of the bacterial assemblage. Other types of grazing-resistant, filamentous bacteria were also found within the beta subdivision ofProteobacteriaand theCytophaga-Flavobacteriumcluster. We conclude that the predation regimen is a major structuring force for the bacterial community composition in this system. Protozoan grazing resulted in shifts of the morphological as well as the taxonomic composition of the bacterial assemblage. Grazing-resistant filamentous bacteria can develop within different phylogenetic groups of bacteria, and formerly underepresented taxa might become a dominant group when protozoan predation is the major selective pressure.