Influence of Top-Down and Bottom-Up Manipulations on the R-BT065 Subcluster of β-Proteobacteria, an Abundant Group in Bacterioplankton of a Freshwater Reservoir

Abstract

We studied the effects of nutrient availability and protistan grazing on bacterial dynamics and community composition (BCC) in different parts of the canyon-shaped Ř ímov reservoir (Czech Republic). The effects of protistan grazing on BCC were examined using a size fractionation approach. Water from the dam area with only bacteria (<0.8 m), bacteria and heterotrophic nanoflagellates (<5 m), or whole water were incubated in situ inside dialysis bags. Top-down or predator manipulations (size fractionation) were also combined with bottom-up or resource manipulations, i.e., transplantation of samples to the middle and upper inflow parts of the reservoir with increased phosphorus availability. Significant genotypic shifts in BCC occurred with transplantation as indicated by denaturing gradient gel electrophoresis. Using different probes for fluorescence in situ hybridization, we found that 10 to 50% of total bacteria were members of the phylogenetically small cluster of ␤-proteobacteria (targeted with the probe R-BT065). These rod-shaped cells of very uniform size were vulnerable to predation but very fast growing and responded markedly to the different experimental manipulations. In all the grazer-free treatments, the members of the R-BT065 cluster showed the highest net growth rates of all studied bacterial groups. Moreover, their relative abundance was highly correlated with bacterial bulk parameters and proportions of bacteria with high nucleic acid (HNA) content. In contrast, increasing protistan bacterivory yielded lower proportions of R-BT065-positive and HNA bacteria substituted by increasing proportions of the class Actinobacteria, which profited from the enhanced protistan bacterivory.

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

“…2011). These results are particularly relevant because the contribution of different taxa to the uptake of C and P substrates greatly affects the energy and nutrient supply to aquatic food webs (Šimek et al ., 2005; Salcher et al ., 2007). Our findings agree with a recent study showing that in grazer‐free incubations, and particularly during periods of high organic matter loadings, rare taxa dominated bacterial community composition (Neuenschwander et al ., 2015).…”

“…2011). In turn, bacterial communities have been shown to respond quickly to variation in substrate availability and concentration, often favouring opportunistic bacteria such as members of Betaproteobacteria (Burkert et al ., 2003; Šimek et al ., 2005; Hornák et al ., 2006; Posch et al ., 2007) or Bacteroidetes (Cottrell & Kirchman, 2000; Battin et al ., 2001; Eiler et al ., 2003; Zeder et al ., 2009). Besides the critical role of heterotrophic bacteria in processing soil‐derived organic matter in inland waters, knowledge on covarying factors, such as the release from nutrient limitation during pulses of soil run off in high altitude and latitude lakes remains limited (Pérez & Sommaruga, 2006).…”

The impact of physico-chemical water quality parameters on bacterial diversity in the Vaal River, South Africa

“…Members of Betaproteobacteria respond rapidly to organic and inorganic nutrient enrichment (Hahn, 2003;Simek et al, 2005) and have been isolated from various polluted and unpolluted freshwater bodies (De Figueiredo et al, 2011;Haller et al, 2011). Two important genera of this subphylum include Dechlorosomonas and Variovorax.…”

Bacterial degradation of dissolved organic matter released by Planktothrix agardhii (Cyanobacteria)

“…The Betaproteobacteria, on the other hand, are a dominant group in a wide variety of aquatic environments (Liu et al, 2012;Newton et al, 2006;Šimek et al, 2005) and thus, bands representing this group were found during the whole experiment, although dominated only in the first days of degradation, together with Gammaproteobacteria. The large distribution of Betaproteobacteria in freshwater environments is usually associated to their high capacity of adaptation to different environments, and fast response of growth (Burkert et al, 2003;Šimek et al, 2005).…”

“…The large distribution of Betaproteobacteria in freshwater environments is usually associated to their high capacity of adaptation to different environments, and fast response of growth (Burkert et al, 2003;Šimek et al, 2005). Langenheder et al (2004) suggested that Gammaproteobacteria may be fast growing opportunists dominating at high nutrient levels, whereas in low nutrient concentrations they may be out-competed by Alphaproteobacteria.…”