Maximum growth rates and possible life strategies of different bacterioplankton groups in relation to phosphorus availability in a freshwater reservoir

Abstract

We investigated net growth rates of distinct bacterioplankton groups and heterotrophic nanoflagellate (HNF) communities in relation to phosphorus availability by analysing eight in situ manipulation experiments, conducted between 1997 and 2003, in the canyon-shaped Rímov reservoir (Czech Republic). Water samples were size-fractionated and incubated in dialysis bags at the sampling site or transplanted into an area of the reservoir, which differed in phosphorus limitation (range of soluble reactive phosphorus concentrations--SRP, 0.7-96 microg l-1). Using five different rRNA-targeted oligonucleotide probes, net growth rates of the probe-defined bacterial groups and HNF assemblages were estimated and related to SRP using Monod kinetics, yielding growth rate constants specific for each bacterial group. We found highly significant differences among their maximum growth rates while insignificant differences were detected in the saturation constants. However, the latter constants represent only tentative estimates mainly due to insufficient sensitivity of the method used at low in situ SRP concentrations. Interestingly, in these same experiments HNF assemblages grew significantly faster than any bacterial group studied except for a small, but abundant cluster of Betaproteobacteria (targeted by the R-BT065 probe). Potential ecological implications of different growth capabilities for possible life strategies of different bacterial phylogenetic lineages are discussed.

A Guide to the Natural History of Freshwater Lake Bacteria

“…The Algor tribe (Algoriphagus-like) of the bacIII lineage was represented by the most sequences among all Bacteroidetes tribes. The Flecto (Flectobacillus-like) tribe is known to be filamentous and is targeted by the frequently used probe R-FL615 (188,192). The two bacVI tribes (Muci for Mucilaginibacterlike and Pedo for Pedobacter-like) were not recovered frequently in our database.…”

“…This disadvantage does not seemingly stem from an inability to assimilate common substrates, as the Actinobacteria have been shown to be capable of incorporating arginine, leucine, and thymidine at rates similar to those of other common freshwater lake taxa (23) or as the most active bacterial fraction for amino acid uptake (174). However, the growth rates for the freshwater Actinobacteria often do not match their capability for substrate uptake; generally, this group exhibits growth rates that are average to below average compared to those of other phyla or the bulk freshwater lake bacterioplankton community (188). The various growth and substrate incorporation rates observed for the freshwater Actinobacteria may be due to the preferences of individual tribes for different substrate sources.…”

“…Substantial evidence for both top-down and bottom-up controls on their abundances is available based on both field observations and experiments. The R-BT065 bacteria are known for their relatively short population turnover times and ability to respond rapidly to changing environmental conditions (6,187,188,192). They grow quickly when exposed to nutrient pulses in mesocosms (187,188), and their abundance was positively associated with watercolor metrics that are proxies for low-molecular-weight alga-derived substrates (190).…”

Climate‐related changes of soil characteristics affect bacterial community composition and function of high altitude and latitude lakes

“…This agrees with previous observations from field (Crump et al ., 2003; Roiha et al ., 2011) and laboratory experiments (Logue et al ., 2016) showing that rapid shifts in community composition take place upon soil organic matter input. The loss and prevalence of the taxa determined in our study may be explained by their different functional adaptability, including differences in resource affinities (Cottrell & Kirchman, 2000; Salcher et al ., 2011; Heinrich et al ., 2013), physiological characteristics (Hahn & Pöckl, 2005; Šimek et al ., 2006) and genetic composition (Bauer et al ., 2006; Gómez‐Pereira et al ., 2012; Teeling et al ., 2012; Tveit et al ., 2013). Further, changes in lake bacterial community composition have been attributed not only to the differential response of individual bacterial taxa to DOM inputs, but also to the introduction of soil bacteria with allochthonous sources or to incubation effects (Crump et al ., 2003; Logue et al ., 2016).…”

Susceptibility of bacterioplankton to nutrient enrichment of oligotrophic and ultraoligotrophic lake waters

“…The dominant subclass β-Proteobacteria has opportunistic strategies and grew significantly faster than the bulk bacterioplankton (Burkert et al 2003;Šimek et al 2006), reacting very quickly to our experimental +CP enhancement, in particular in summer in Lake Maggiore. Nevertheless, we were able to observe differences in the relative contribution of the other bacterial groups in both seasons and lakes.…”