Summary While mechanisms of different carbon dioxide (CO 2 ) assimilation pathways in chemolithoautotrohic prokaryotes are well understood for many isolates under laboratory conditions, the ecological significance of diverse CO 2 fixation strategies in the environment is mostly unexplored. Six stratified freshwater lakes were chosen to study the distribution and diversity of the Calvin‐Benson‐Bassham (CBB) cycle, the reductive...

Summary The ecological relevance and factors shaping dynamics of Limnohabitans sp. have been largely studied by fluorescence in situ hybridization with a 16S rRNA probe targeting the R‐BT group (lineages LimBCDE), but not lineage LimA. Consequently, ecology and distribution of LimA remained unknown. We developed a double hybridization strategy using a novel 23S rRNA probe specifically targeting LimA and LimE that in combinatio...

Wheat production will be impacted by increasing concentration of atmospheric CO 2 [ CO 2 ], which is expected to rise from about 400 μmol mol −1 in 2015 to 550 μmol mol −1 by 2050. Changes to plant physiology and crop responses from elevated [ CO 2 ] (e[ CO 2 ]) are well documented for some environments, but field‐level responses in dryland Mediterranean environments with terminal drought and heat waves are scarce. The Austral...

Summary We studied the seasonal growth potential of opportunistic bacterial populations in L ake Z urich ( S witzerland) by a series of grazer‐free dilution culture assays. Pronounced shifts in the composition of the bacterial assemblages were observed within one doubling of total cell numbers, from initially abundant A ctinobacteria to other fast‐growing microbial lineages. Small populations with growth potentials far above c...

Summary The vernal successions of phytoplankton, heterotrophic nanoflagellates (HNF) and viruses in temperate lakes result in alternating dominance of top‐down and bottom‐up factors on the bacterial community. This may lead to asynchronous blooms of bacteria with different life strategies and affect the channelling of particular components of the dissolved organic matter (DOM) through microbial food webs. We followed the dynam...

The pelagic zone of large, deep freshwater lakes features pronounced horizontal and vertical gradients of physicochemical parameters, which in turn might allow for a nonuniform occurrence of specifically adapted bacterial taxa. We, therefore, studied the spatial distribution patterns of different heterotrophic bacteria, picocyanobacteria, and the dominant primary producer, the filamentous cyanobacterium Planktothrix rubescens...

The spatiotemporal changes in abundance and biomass of heterotrophic bacteria, of three major bacterial phylogenetic groups, and of picocyanobacteria in the upper 20 m of a deep prealpine lake (Lake Zurich, Switzerland) were monitored during a seasonally persistent bloom of the toxigenic filamentous cyanobacterium Planktothrix rubescens . In addition, bacterial 16S ribosomal deoxyribonucleic acid (rDNA) sequences were collecte...

We explored the seasonal and vertical patterns of cell numbers, biomass, and amino acid incorporation of three major phylogenetic groups of the bacterioplankton in an oligomesotrophic alpine lake. Throughout the year the numerically dominant bacteria in the oxygenated epilimnion were small Actinobacteria . The timing and vertical location of their spring peak coincided with that of the heterotrophic flagellates (HNF). A second...

Summary We investigated the diversity of planktonic Betaproteobacteria and the seasonal population changes of betaproteobacterial taxa in an oligo‐mesotrophic lake (Piburger See, Austria). Focus was put on the vertical distribution of the investigated populations and on differences between their respective cell fractions with apparent amino acid incorporation. On average, 66% of betaproteobacterial cells and 73% of their diver...