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Grazing resistant freshwater bacteria profit from chitin and cell‐wall‐derived organic carbon
Author(s) -
Eckert Ester M.,
Baumgartner Michael,
Huber Iris M.,
Pernthaler Jakob
Publication year - 2013
Publication title -
environmental microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.954
H-Index - 188
eISSN - 1462-2920
pISSN - 1462-2912
DOI - 10.1111/1462-2920.12083
Subject(s) - biology , microbial food web , bacterioplankton , bacteria , phytoplankton , grazing , flagellate , ecology , lysin , chitin , bacterivore , peptidoglycan , predation , nutrient , botany , escherichia coli , bacteriophage , biochemistry , genetics , chitosan , gene
Summary The rise of grazing resistant planktonic bacteria in freshwater lakes during vernal phytoplankton blooms is favoured by predation of heterotrophic nanoflagellates ( HNF ). The spring period is also characterized by increased availability of organic carbon species that are in parts derived from cellular debris generated during bacterivory or viral lysis, such as peptidoglycan, chitin and their subunit N ‐ acetylglucosamine ( NAG ). We tested the hypothesis that two dominant grazing resistant bacterial taxa, the ac1 tribe of A ctinobacteria (ac1) and filamentous bacteria from the LD 2 lineage ( S aprospiraceae ), profit from such carbon sources during periods of intense HNF predation. The abundances of ac1 and LD 2 rose in parallel with HNF , and disproportionally high fractions of cells from both lineages were involved in NAG uptake. Members of ac1 and LD 2 were significantly more enriched after NAG addition to lake water. However, highest growth rates of both bacterial lineages were found on chitin and peptidoglycan. Moreover, the direct or indirect transfer of organic carbon from peptidoglycan to LD 2 filaments could be demonstrated. We thus provide evidence that these taxa may benefit twofold from protistan predation: by removal of their competitors, and by specific physiological adaptations to utilize carbon sources that are released during grazing or viral lysis.